Aerodrome design manuel part 5 electrical systems 1983 doc 9157 an 901 part 5 by cabledatasheet

AERODROME DESIGN MANUAL

PART 5 ELECTRICAL SYSTEMS FIRST EDITION - 1983

Approved by the Secretary General and published under his authority

INTERNATIONAL CIVIL -4VI-ATIONORGANIZATION

Aerodrome Design Manual (Doc 9157-AN/901)

Part 5 Electrical Systems First Edition - 1983

AMENDMENTS Amendments are announced in the supplelnenfs to the Catalogue of ICAO Publications; the Catalogue and its supplements are available on the ICAO website at www.icao.int. The space below is provided to keep a record of such amendments.

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Proper d e s i g n , i n s t a l l a t i o n and m a i n t e n a n c e of e l e c t r i c a l s y s t e m s f o r n a v i g a t i o n a i d s , b o t h v i s u a l and n o n v i s u a l , a r e p r e r e q u i s i t e s f o r t h e s a f e t y , r e g u l a r i t y , and e f f i c i e n c y of c i v i l a v i a t i o n . To t h i s e n d , t h i s manual p r o v i d e s g u i d a n c e on t h e d e s i g n and i n s t a l l a t i o n of e l e c t r i c a l s y s t e m s f o r aerodrome l i g h t i n g and r a d i o n a v i g a tion aids. The e l e c t r i c a l s y s t e m s f o r aerodrome l i g h t i n g and r a d i o n a v i g a t i o n a i d s i n c l u d e f e a t u r e s which a r e n o t u s u a l l y i n v o l v e d i n o t h e r e l e c t r i c a l i n s t a l l a t i o n s . This manual t h e r e f o r e d i s c u s s e s n o t o n l y t h e g e n e r a l f e a t u r e s of e l e c t r i c a l p r a c t i c e s and i n s t a l l a t i o n s b u t a l s o t h o s e f e a t u r e s which a r e of s p e c i a l s i g n i f i c a n c e f o r aerodrome It i s assumed t h a t r e a d e r s of t h e manual w i l l be f a m i l i a r w i t h e l e c installations. t r i c a l c i r c u i t s and g e n e r a l d e s i g n c o n c e p t s , b u t may n o t be knowledgeable of c e r t a i n f e a t u r e s of aerodrome i n s t a l l a t i o n s which a r e l e s s f r e q u e n t l y e n c o u n t e r e d i n o t h e r installations. It i s i m p o r t a n t t o n o t e t h a t t h e m a t e r i a l p r e s e n t e d i n t h i s manual i s i n t e n d e d t o complement n a t i o n a l s a f e t y c o d e s r e l a t e d t o e l e c t r i c a l i n s t a l l a t i o n s . The manual d o e s n o t d i s c u s s e l e c t r i c a l s y s t e m s f o r b u i l d i n g s l o c a t e d on a n a i r p o r t o t h e r t h a n t h e e f f e c t of s u c h b u i l d i n g s on t o t a l power r e q u i r e m e n t s f o r p r i m a r y and s e c o n d a r y power s u p p l i e s . S i m i l a r l y , t h e manual d o e s n o t d e a l w i t h t h e m a i n t e n a n c e o f e l e c t r i c a l s y s t e m s . F o r g u i d a n c e on t h i s l a t t e r i s s u e t h e r e a d e r i s a d v i s e d t o r e f e r t o t h e A i r p o r t S e r v i c e s Manual, (Doc 9 1 3 7 ) , P a r t 9, A i r p o r t Maintenance P r a c t i c e s . F u t u r e e d i t i o n s of t h i s manual w i l l be improved on t h e b a s i s of e x p e r i e n c e g a i n e d and of comments and s u g g e s t i o n s r e c e i v e d from u s e r s of t h i s manual. Readers of t h i s manual a r e i n v i t e d t o g i v e t h e i r v i e w s , comments and s u g g e s t i o n s t o t h e S e c r e t a r y G e n e r a l of ICAO.

....................................................5-1 Purpose ............................................................5-1 O r g a n i z a t i o n o f t h e manual ............................................ 5-1 2. E l e c t r i c i t y S u p p l i e s ............................................5-2 Sources of power ......................... ~ ~ P O O O O O O O O i O O O 2.1.1 G e n e r a l .....................................................5-2 2.1.2 Primary power s o u r c e s .......................................5-2 Secondary power s o u r c e s .....................................5-2 2.1.3 2.1.4 D i s t r i b u t i o n o f i n t e r m e d i a t e power ..........................5-3 Power t r a n s f e r c h a r a c t e r i s t i c s ...................................... -3 2.2.1 T r a n s f e r ( s w i t c h - o v e r ) t i m e r e q u i r e m e n t s ....................5-3 2.2.2 Continuous power s o u r c e s ....................................5-3 2.2.3 Methods of t r a n s f e r .........................................5-5 Secondary power equipment ..........................................5-7 2.3.1 Components ..................................................5-7 2.3.2 Engine-generator s e t s .......................................5-9 2.3.3 Power t r a n s f e r s w i t c h i n g ....................................5-10 2.3.4 U n i n t e r r u p t i b l e power s u p p l i e s ..............................5-10 2.3.5 S p e c i a l s e c o n d a r y power d e v i c e s .............................5-11 V a u l t s and s h e l t e r s f o r e l e c t r i c a l equipment .......................5-11 2.4.1 S h e l t e r s ....................................................5-11 2.4.2 L a c a t i o n ....................................................5-13 2.4.3 S p e c i a l p r o v i s i o n s ..........................................5-13 D i s t r i b u t i o n of power ..............................................5-14 2s5sl General .....................................................5-14 2.5.2 Primary power f e e d e r c i r c u i t s ...............................5-15 .

Chapter 1

1.1 1.2 Chapter

2'1

2.2

2.3

2.4

2.5

Introduction

2.5.3 2.5.4 2.5.5 2.5.6 2.5.7 2.5.8 2.5.9 2.5.10 2.5.11 2.5.12 2.5.13 2.5.14 2.5.15

~ e ~

Above-ground ( o v e r h e a d ) p r i m a r y d i s t r i b u t i o n s y s t e m s .......=5-- 1 5 Line-voltage r e g u l a t o r s 6(r(r(r(r(r(r(rOsDDDD55i5 Power l i n e s 5-16 Conductors 5-16 Insulators 5-17 Lacknuts 5-18 Transformers 5-18 Capacitors 5-19 Circuit interruption devices 5-19 Lightning p r o t e c t i o n 5-20 Clearances 5-20 Grounding 5-20 Underground d i s t r i b u t i o n s y s t e m s 5-21

....................... ................................................. .................................................. .................................................. .................................................... ................................................ .................................................. ................................ ........................................ .................................................. ................................................... ............................

E l e c t r i c a l C i r c u i t s f o r Aerodrome L i g h t i n g and Radio Chapter 3 N a v i g a t i o n Aids

...........................................................5-23 Types of e l e c t r i c a l c i r c u i t s .......................................5-23 3.1.1 E l e c t r i c a l c h a r a c t e r i s t i c s ..................................5-23 3.1.2 S e r i e s c i r c u i t s .............................................5-23 3. 1.3 P a r a l l e l c i r c u i t s ...........................................5-24 3.1.4 Comparison of s e r i e s and p a r a l l e l l i g h t i n g c i r c u i t s .........5-25 S e r i e s c i r c u i t r y f o r aerodrome l i g h t i n g ............................5-25 3.2.1 F a c t o r s t o be c o n s i d e r e d ....................................5-25 P a r a l l e l ( m u l t i p l e ) c i r c u i t r y ......................................5-41 Use of p a r a l l e l ( m u l t i p l e ) c i r c u i t r y i n aerodrome l i g h t i n g ..5-41 3.3.1 C o n t r o l of aerodrome l i g h t i n g s y s t e m s ..............................5-42 3.4.1 C o n t r o l c i r c u i t r y ...........................................5-42 C o n t r o l p a n e l s ..............................................5-43 3.4.2 Use of r e l a y s ...............................................5-44 3.4.3 3.4.4 I n t e r c o n n e c t i o n of c o n t r o l s .................................5-45 Automatic c o n t r o l s ..........................................5-45 3.4.5 Radio remote c o n t r o l s .......................................5-46 3.4.6 Lamps ..............................................................5-46 C h a r a c t e r i s t i c s of i n c a n d e s c e n t lamps .......................5-46 3.5.1 3.5.2 C h a r a c t e r i s t i c s of g a s e o u s d i s c h a r g e lamps ..................5-48 Methods of o b t a i n i n g i n t e g r i t y and r e l i a b i l i t y f o r aerodrome l i g h t i n g .........................................................5-49 3.6.1 D e f i n i t i o n of terms .........................................5-49 3.6.2

Summary of means of improving e l e c t r i c a l i n t e g r i t y and r e l i a b i l i t y M f n i t o r i n g of aerodrome l i g h t i n g c i r c u i t s 3.7.1 Methods of m o n i t o r i n g 3.7.2 Design of m o n i t o r i n g d e v i c e s 3.7.3 C l a s s e s of m o n i t o r s 3.7.4 Monitor o v e r r i d e c o n t r o l s E l e c t r i c a l c i r c u i t s f o r radio navigation aids 3.8.1 Types of r a d i o n a v i g a t i o n a i d s 3.8.2 Electrical characteristics 3.8.3 Control c i r c u i t s f o r r a d i o navigation a i d s 3.8.4 R e l i a b i l i t y and i n t e g r i t y of r a d i o n a v i g a t i o n a i d s Monitoring of r a d i o n a v i g a t i o n a i d s 3.8.5 Acceptance t e s t i n g of aerodrome e l e c t r i c a l c i r c u i t s 3.9.1 Application 3.9.2 Guarantee p e r i o d 3.9.3 Inspection procedures 3.9.4 E l e c t r i c a l t e s t of s e r i e s - c i r c u i t equipment 3.9.5 E l e c t r i c a l t e s t s of o t h e r c a b l e s 3.9.6 E l e c t r i c a l t e s t s of r e g u l a t o r s 3.9.7 Troubleshooting t e s t s E l e c t r i c a l t e s t s of o t h e r equipment 3.9.8 3.9.9 T e s t s of m o n i t o r s

...........................................5-50 .......................... 5-51 5-51 ................................ .......................................a.5-51 ...................................5-52 ..................a.e. 5-52 ..............................5-52 ....................C*...... eeaOO05-52 .................. ..........5-53 5-54 .........................5-54 ................5-54 .................................................5-54 ............................................5-55 .......................................5-55 .................5-57 ............................ .............................. 5-59 5-60 .......................................5-61 .........*...........*...5-62 ...........................................5-62 .

~ t -e*

3-3"

T a b l e of C o n t e n t s

4.1

4.2

4.3

4.4

4.5

Underground E l e c t r i c a l Systems

405.6 4.5.7 Chapter 5.

5.1

5.2

........................I..*......5-63 G e n e r a l r e q u i r e m e n t s ...............................................5-63 4.1.1 I n i t i a l c o n s i d e r a t i o n s ........................................5-63 4.1.2 P r e c o n s t r u c t i o n a r r a n g e m e n t s ................................5-63 4.1.3 Methods o f i n s t a l l a t i o n .....................................5-63 D i r e c t b u r i a l of c a b l e .............................................5-63 4.2.1 S t e p s of i n s t a l l i n g .........................................5-63 4.2.2 T r e n c h i n g ...................................................5-63 4.2.3 S e p a r a t i o n between c a b l e s ...................................5-64 4.2.4 I n s t a l l a t i o n of d i r e c t - b u r i a l c a b l e s ........................5-65 I n s t a l l a t i o n o f d u c t s ( c o n d u i t ) ....................................5-66 4.3.1 I n s t a l l a t i o n t e c h n i q u e s and p r o c e d u r e s ......................5-66 Manholes and h a n d h o l e s .............................................5-67 4.4.1 S e l e c t i o n ...................................................5-67 4.4.2 b c a t i o n ....................................................5-69 Stubs ....................................................... 5-69 4.4.3 4.4.4 Hardware ....................................................5-69 4.4.5 T w o s e c t i o n manholes ........................................5-69 I n s t a l l a t i o n of underground c a b l e s .................................5-69 4.5.1 P r e p a r a t i o n of d u c t s ........................................5-69 4.5.2 Cable p u l l i n g i n d u c t s ......................................5-69 4.5.3 I n s t a l l a t i o n of c a b l e i n manholes and h a n d h o l e s .............5-71 4.5.4 P r e s s u r i z e d t y p e c o a x i a l c a b l e s .............................5-72 4.5.5 Cable i n s t a l l a t i o n i n saw c u t s .............................5-73

Chapter 4

(vii

Cable marking . . ~ . e . . . . . . . . e . . . . . e . ~ e . . . . . . Enclosures f o r connections

Cables f o r Underground

~eDii5ei66ieee~aee5-74

..................................5-75 S e r v i c e a t Aerodromes ....................5-77

...........5-77 5-77 .......................................... ......................................5-79 5-80 .................................................. ...............................................5-82 5-82 ........................................a.....e 5-83 .......................5-85 .............................................. ....................................5-85 5-88

F e a t u r e s of t h e c a b l e s . . . . . . e . . . . . . . . . . . . . . . e C e . . a e a e . O . I ) . . . . . . . . . . . . C h a r a c t e r i s t i c s of c a b l e s f o r underground s e r v i c e 5.1.1 5.1.2 C l a s s e s of s e r v i c e Causes of c a b l e damage 5.1.3 Cable c o n n e c t i o n s 5.2.1 Cable s p l i c e s 5.2.2 Taped s p l i c e s Connector k i t s f o r aerodrome l i g h t i n g 5.2.3 5.2.4 Coaxial c a b l e s 5.2.5 Connection of c o n d u c t o r s

1.1

PURPOSE

1.1.1 To e n s u r e t h e r e g u l a r i t y and s a f e t y of a v i a t i o n , i t i s n e c e s s a r y t h a t a e r o It i s drome l i g h t i n g and r a d i o n a v i g a t i o n a l a i d s have h i g h i n t e g r i t y and r e l i a b i l i t y . c o n s i d e r e d t h a t t h e p r o b a b i l i t y of f a i l u r e of w e l l d e s i g n e d and m a i n t a i n e d l i g h t i n g and r a d i o a i d s a t a c r i t i c a l moment i s e x t r e m e l y low, 1.1.2 The f o l l o w i n g m a t e r i a l i s i n t e n d e d as a g u i d e t o t h e recommended e l e c t r i c a l e n g i n e e r i n g p r a c t i c e s f o r d e s i g n and i n s t a l l a t i o n of new systems and t h e m o d i f i c a t i o n of e x i s t i n g s y s t e m s of aerodrome f i x e d l i g h t i n g and of d i s t r i b u t i o n of power t o r a d i o navigation aids. It does n o t imply t h a t e x i s t i n g i n s t a l l a t i o n s , i f d i f f e r e n t , a r e wrong It d o e s mean t h a t some of t h e e a r l i e r d e s i g n s and s h o u l d be changed a u t o m a t i c a l l y . a d o p t e d a r e n o t recommended f o r r e p e t i t i o n s i n c e t h e y have been s u p e r s e d e d by l a t e r thinking. Because of t h e d i f f e r e n c e s i n e n g i n e e r i n g s t y l e and equipment i n d i f f e r e n t c o u n t r i e s , t h i s material e s t a b l i s h e s only b a s i c design principles. It i s n o t i n t e n d e d t o i l l u s t r a t e d e t a i l e d d e s i g n o r p a r t i c u l a r p i e c e s of equipment o r s y s t e m s u n i q u e t o any one S t a t e . 1.1.3 The e l e c t r i c a l s y s t e m s f o r aerodrome v i s u a l a i d s and n a v i g a t i o n s y s t e m s r e q u i r e good q u a l i t y i n s t a l l a t i o n s and c o n s i d e r a t i o n f o r f e a t u r e s which a r e n o t u s u a l l y involved i n other e l e c t r i c a l i n s t a l l a t i o n s . T h i s manual d i s c u s s e s t h e g e n e r a l f e a t u r e s o f e l e c t r i c a l p r a c t i c e s and i n s t a l l a t i o n s w i t h emphasis on t h o s e f e a t u r e s which a r e l e s s commonly i n v o l v e d o r have s p e c i a l s i g n i f i c a n c e f o r aerodrome o p e r a t i o n s . It i s assumed t h a t t h o s e u s i n g t h i s manual w i l l be f a m i l i a r w i t h e l e c t r i c a l c i r c u i t s and g e n e r a l p r a c t i c e s b u t may n o t b e knowledgeable of c e r t a i n f e a t u r e s of aerodrome i n s t a l l a t i o n s which a r e l e s s f r e q u e n t l y e n c o u n t e r e d i n o t h e r e l e c t r i c a l s y s t e m s . Some o f t h e s e f e a t u r e s a r e t h a t most e l e c t r i c a l c i r c u i t s a r e i n s t a l l e d underground, s e r i e s c i r c u i t s a r e u s e d f o r most l i g h t i n g s y s t e m s , h i g h e r r e l i a b i l i t y i s r e q u i r e d o f t h e i n p u t power s o u r c e s , and r a p i d , a u t o m a t i c t r a n s f e r t o s e c o n d a r y power i n c a s e of power f a i l u r e s . Each aerodrome i s u n i q u e , and i t s e l e c t r i c a l i n s t a l l a t i o n s h o u l d be d e s i g n e d t o p r o v i d e e c o n o m i c a l l y power and c o n t r o l which i s s a f e , r e l i a b l e , and e a s i l y m a i n t a i n e d .

1.2

ORGANIZATION OF THE :NNUAL

1.2.1 T h i s manual p r o v i d e s i n f o r m a t i o n on t h e E l e c t r i c i t y S u p p l i e s i n Chapter 2, E l e c t r i c a l C i r c u i t s f o r Aerodrome L i g h t i n g and N a v i g a t i o n Aids i n C h a p t e r 3, Underground E l e c t r i c a l Systems i n Chapter 4 , and C a b l e s f o r Underground S e r v i c e a t Aerodromes i n C h a p t e r 5.

2.1 2.1.1

SOURCES OF POWER

General

2.1.1.1 The p r i m a r y s o u r c e s of power f o r aerodromes s h o u l d be d e t e r m i n e d b e f o r e t h e d e s i g n s of t h e aerodrome l i g h t i n g i n s t a l l a t i o n s and t h e r a d i o n a v i g a t i o n a i d s are initiated. The e l e c t r i c a l power f o r t h e s e i n s t a l l a t i o n s i s u s u a l l y o n l y a s m a l l p a r t o f t h e e l e c t r i c a l power u s e d by t h e aerodrome. Whether t h e v i s u a l and r a d i o n a v i g a t i o n a i d s b e i n g i n s t a l l e d a r e f o r a new aerodrome o r f o r m o d e r n i z a t i o n and e x p a n s i o n of a n e x i s t i n g aerodrome, t h e s o u r c e s of power s h o u l d be a n a l y z e d f o r a v a i l a b i l i t y , c a p a c i t y , r e l i a b i l i t y , p r a c t i c a l i t y f o r t h e p r o p o s e d i n s t a l l a t i o n , and f o r f u t u r e e x p a n s i o n . T h i s a n a l y s i s s h o u l d i n c l u d e b o t h t h e p r i m a r y power s o u r c e and t h e s e c o n d a r y power s o u r c e r e q u i r e d by Annex 1 0 , Volume I, 2.9 and Annex 1 4 , 8.1 f o r u s e i n c a s e s of f a i l u r e o r m a l f u n c t i o n of t h e p r i m a r y power s o u r c e . Primary power s o u r c e s

2.1.2.1 The p r i m a r y s o u r c e s o f power f o r most aerodromes a r e f e e d e r s f r o m a w i d e l y i n t e r c o n n e c t e d e l e c t r i c i t y network o u t s i d e t h e aerodrome, u s u a l l y f r o m e i t h e r a commerc i a l o r a p u b l i c mains s u p p l y . I n some c a s e s t h e power may come f r o m a l o c a l g e n e r a t i n g p l a n t o r f r o m a l i m i t e d d i s t r i b u t i o n system. Two i n d e p e n d e n t incoming power s o u r c e s a r e d e s i r a b l e f o r major aerodromes, i n s t e a d of a s i n g l e p r i m a r y power s o u r c e . They s h o u l d come f r o m w i d e l y s e p a r a t e d s e c t i o n s of t h e e l e c t r i c i t y network beyond t h e aerodrome w i t h e a c h s u p p l y i n g s e p a r a t e c i r c u i t s t h a t would p r o v i d e i n t e g r i t y of f a c i l i t i e s if o n e failed. P r e f e r a b l y , t h e s e s o u r c e s w i l l have s e p a r a t e f e e d e r s f r o m s e p a r a t e s u b s t a t i o n s Other s u p p l y a r r a n g e m e n t s may b e u s e d and w i l l a l s o be from d i f f e r e n t g e n e r a t o r s . d e p e n d i n g on t h e security, r e l i a b i l i t y , s t a t i s t i c s , o r economics a p p l i c a b l e t o a p a r t i c u l a r situation, 2,1.2.2 T h i s power i s u s u a l l y s u p p l i e d a t h i g h e r v o l t a g e ( o v e r 5 0 0 0 v o l t s ) t o t h e aerodrome main power s u b s t a t i o n . 2.1.3

Secondary power s o u r c e s

2.1.3.1 Most aerodromes w i t h aerodrome l i g h t i n g and r a d i o n a v i g a t i o n a i d s s h o u l d b e p r o v i d e d w i t h s e c o n d a r y e l e c t r i c a l power f o r t h e a i d s r e q u i r e d a s a minimum f o r o p e r a t i o n s . The c i r c u i t s and f a c i l i t i e s t o be p r o v i d e d w i t h s e c o n d a r y power v a r y w i t h t h e most c r i t i c a l c l a s s o r c a t e g o r y of f l i g h t o p e r a t i o n s . The aerodrome f a c i l i t i e s f o r which a s e c o n d a r y power s u p p l y i s recommended a r e i n d i c a t e d i n Annex 1 4 , C h a p t e r 8 f o r v i s u a l a i d s and i n Annex 1 0 , Volume I , P a r t I, C h a p t e r 2 f o r r a d i o n a v i g a t i o n a i d s . Those f a c i l i t i e s f o r which s e c o n d a r y power i s r e q u i r e d s h o u l d b e a r r a n g e d t o a u t o m a t i c a l l y c o n n e c t t o t h e s e c o n d a r y power s u p p l y on f a i l u r e of t h e p r i m a r y s o u r c e power. 2.1.3.2 Sources of s e c o n d a r y power. As recommended i n Annex 1 4 , C h a p t e r 8, s o a r c e s o f s e c o n d a r y power may be i n d e p e n d e n t p u b l i c power s o u r c e s o r stand-by power u n i t s .

For a e r o d r o m e s w i t h t h e 2.1.3.3 primary supp dependent e l e c t r i c a l t r a n s m i s s i o n power l i n e s may be u s e d t o p r o v i d e s e c o n d a r y power. These i n d e p e n d e n t power s o u r c e s a r e n o t u s u a l l y c o n n e c t e d t o t h e aerodrome l i g h t i n g and r a d i o n a v i g a t i o n a i d s l o a d s b u t c a n be a u t o m a t i c a l l y c o n n e c t e d t o t h e s e l o a d s i n c a s e of f a i l u r e of t h e p r i m a r y power s o u r c e . T h e s e i n d e p e n d e n t power s o u r c e s may be i n a r e s e r v e s t a t u s o n l y An o r may be s u p p l y i n g e l e c t r i c a l power t o o t h e r f a c i l i t i e s on t h e aerodrome. i n d e p e n d e n t s o u r c e s u p p l y i n g power t o o t h e r f a c i l i t i e s s h o u l d have a d e q u a t e c a p a c i t y t o p r o v i d e t h e power f o r t h e more e s s e n t i a l aerodrome l i g h t i n g a n d r a d i o n a v i g a t i o n a i d s i n a d d i t i o n t o t h e u s u a l l o a d o r s w i t c h i n g a r r a n g e m e n t s s h o u l d be p r o v i d e d t o d i s c o n n e c t from i t s u s u a l l o a d a s i t i s connected t o t h e l i g h t i n g and r a d i o a i d s l o a d . The improvement i n i n t e g r i t y of o p e r a t i o n s p r o v i d e d by i n d e p e n d e n t power s o u r c e s depends on I f t h e two t h e s e p a r a t i o n and i n d e p e n d e n c e of t h i s s o u r c e from t h e p r i m a r y s o u r c e . s o u r c e s come f r o m i n t e r c o n n e c t e d d i s t r i b u t i o n n e t w o r k s , a f a i l u r e i n t h e n e t w o r k may c a u s e b o t h s o u r c e s t o f a i l . An i n d e p e n d e n t power s o u r c e may be u s e d as a s e c o n d a r y power s o u r c e i f i t h a s t h e c a p a c i t y t o s u p p l y i t s own l o a d p l u s t h e aerodrome l i g h t i n g and r a d i o a i d s l o a d and i s s o s e p a r a t e d t h a t any s i n g l e c a u s e of power f a i l u r e of t h e p r i m a r y s o u r c e w i l l n o t i n t e r f e r e w i t h power from t h e o t h e r s o u r c e . Unless t h e i n d e p e n d e n t s o u r c e Is c o m p l e t e l y i s o l a t e d f r o m t h e p r i m a r y s o u r c e and w i l l n o t be o v e r l o a d e d upon f a i l u r e of t h e p r i m a r y s o u r c e , l o c a l s e c o n d a r y power s h o u l d be p r o v i d e d f o r t h e v i s u a l and r a d i o n a v i g a t i o n a i d s e s s e n t i a l t o t h e o p e r a t i o n s of t h e aerodrome. 2.1.3.4 Independent l o c a l power s o u r c e . Some aerodromes may have t u r b o - a l t e r n a t o r motor u n i t s which a r e u s e d t o s u p p l y power t o n o n - c r i t i c a l f a c i l i t i e s . These l o c a l power s o u r c e s may be u s e d a s t h e s e c o n d a r y s o u r c e of power f o r c r i t i c a l aerodrome l i g h t i n g and r a d i o n a v i g a t i o n a l a i d s . I f t h e p r i m a r y power f a i l s , t h e c r i t i c a l l i g h t i n g and r a d i o a i d s a r e t r a n s f e r r e d a u t o m a t i c a l l y t o t h e l o c a l power s o u r c e . I f t h e l o c a l power s o u r c e h a s a d e q u a t e c a p a c i t y , t h e l i g h t i n g and r a d i o a i d s l o a d may be i n a d d i t i o n t o t h e u s u a l load. I f t h e c a p a c i t y of t h e l o c a l power s o u r c e i s l i m i t e d , t h e l o c a l power s o u r c e may need t o d i s c o n n e c t some of t h e n o n - c r i t i c a l l o a d b e f o r e c o n n e c t i n g t o t h e c r i t i c a l l i g h t i n g and r a d i o a i d s l o a d .

Another a r r a n g e m e n t i s t o s u p p l y t h e power 2.1.3.5 f o r t h e aerodrome l i g h t i n g - and r a d i o n a v i g - a t i o n a l a i d s from t u r b o - a l t e r n a t o r motor u n i t s which may a l s o be s u p p l y i n g power t o o t h e r f a c i l i t i e s . I f t h i s s o u r c e of power f a i l s , t h e c r i t i c a l l i g h t i n g and r a d i o a i d s l o a d may be t r a n s f e r r e d a u t o m a t i c a l l y t o t h e p r i m a r y power s o u r c e f o r t h e aerodrome. 2.1.3.6 Stand-by power s o u r c e s . Secondary power s o u r c e s may be e n g i n e - g e n e r a t o r s e t s , o r t u r b i n e g e n e r a t o r s f r o m which e l e c t r i c a l power can be o b t a i n e d a n d which can be The maximum l o a d a u t o m a t i c a l l y c o n n e c t e d t o t h e f a c i l i t i e s r e q u i r i n g s e c o n d a r y power. which c a n be c o n n e c t e d s h o u l d be w i t h i n t h e c a p a c i t y of t h e stand-by u n i t s . Stand-by u n i t s w i t h c a p a c i t i e s r a n g i n g f r o m 5 0 t o more t h a n 1 000 k i l o v o l t - a m p e r e s a r e u s e d a s s e c o n d a r y power s o u r c e s f o r a i r p o r t s . The s e c o n d a r y power s o u r c e s h o u l d be c a p a b l e of s u p p l y i n g power f o r a t i m e p e r i o d t h a t e x c e e d s t h e maximum t i m e needed t o r e s t o r e power E n g i n e - g e n e r a t o r s e t s a r e o f t e n e x p e c t e d t o o p e r a t e f o r 24 t o from t h e primary source. 72 hours without r e f u e l l i n g . Other s e c o n d a r y power s o u r c e s , u s u a l l y f o r s m a l l l o a d s , may be b a t t e r y u n i t s , f u e l c e l l s , e t c .

2.1.4.1 T1e v o l t a g e f r o m t h e p r i m a r y power s o u r c e i s u s u a l l y r e d u c e d a t t h e a e r o drome s u b s t a t i o a t o a n i n t e r m e d t a t e v o l t a g e ( 2 000 t o 5 500 v o l t s ) f o r d i s t r i b u t i o n

5-4

A e r o d r o l l l e D e s i g n Manual

Table 2-1.

ry Pawer Supply ( b m &X

AidsdRBdioAlds

14 and

10)

P-

WO Aids

V i s u a l aids requiring F r

C l a s s lfication

r tine

Noll-in%trurnent

time

Visual approach slope i d i c a t o r s a

W edge RLmway threshold e d

Obstaclea

Noqmcision

Approach Lighting s y s t w Visual approach slope indicatorsa

m dge m y threshold

b a y end Obstaclea

Precision approach category I

Approach lighting systan

~~ RLmwq threshold -Y

Kurway ad Essential taxiway Obstaclea Precision approach c a t e p r y II

Approach lighting systan Y&S Runway t h r e i b l d Ihlmq oentre line Runwrny mchdown zone Stop bars at taxi-holding pcxsitions Esserltial taxiway including stop bars other than those at taxl-holdiq p i t ions Obstaclea

(%me as category I1 excepl-

stop bars

m m D/F facility

15 seconds l5 seconds 15 seconds 15 seconds

15 seconds 15 seconds 15 seconds l5 &S 15 sec&

IIS locallzer ILS glide path IIS middle marker ILS outer nrucker PAR

10 seconds 10 secords 10 seconds 10 secords 10 seconds

MDB

15 secorads

Rumay erd

Precision approach c a t e r p r y I11

15 seconds 15 seconds 15 seconds 15 seconds 15 secarads L5 seconds

1 second 15 s e d s 1s e d 1 second l &cord l sfxotki

IIS locallzer

ILS glide path

m Inns ~ ~ l i l l h ILs middle m outer llm-ka

1 secorad

15 seconds

all

I second)

%ppLif?d w i t h s e a m p e r when tlleir operatim is essential to tk safety of f 1igt-s operations.

0s e d 0 seconds 1 second 1 second 10 seconds

w i t h i n t h e aerodrome. This power i s u s u a l l y d i s t r i b u t e d by a " p a r a l l e l " s y s t e m t o t h e v a r i o u s t r a n s f o r m e r s t a t i o n s f o r f u r t h e r step-down of v o l t a g e t o w t c h t h e i n p u t v o l t a g e of t h e equipment. Two i n d e p e n d e n t incoming e l e c t r i c a l s u p p l i e s t a k e n f r o m w i d e l y s e p a r a t e d s e c t i o n s of t h e e l e c t r i c i t y network beyond t h e aerodrome a r e recommended. W i t h i n t h e aerodrome, r e l i a b i l i t y i n t h e s u p p l y of power t o t h e i n d i v i d u a l s t a t i o n s c a n be improved by u s i n g a c l o s e d r i n g h i g h v o l t a g e i n p u t c i r c u i t w i t h b a l a n c e d v o l t a g e p r o t e c t i o n on t h e d i s t r i b u t i o n t r a n s f o r m e r s o r by u s i n g a d o u b l e l o o p s y s t e m f r o m i n d e p e n d e n t p r i m a r y s o u r c e s o p e r a t i n g a s open r i n g s f e e d i n g two t r a n s f o r m e r s a t e a c h s t a t i o n . T h i s l a t t e r s y s t e m i s i l l u s t r a t e d i n F i g u r e 2-1. I f a c e n t r a l i z e d monitoring s y s t e m of t h e l o o p s w i t c h e s a t e a c h s t a t i o n and of f a u l t c u r r e n t s l i k e l y t o o c c u r i n e a c h s e c t i o n a r e u s e d p r a c t i c a l l y c o m p l e t e e l i m i n a t i o n of power f a i l u r e s t o t h e t r a n s f o r m e r s t a t i o n s c a n be a c h i e v e d . Simpler arrangements p r o v i d i n g l e s s e r r e l i a b i l i t y may be u s e d a t s m a l l e r a i r p o r t s .

2.2

2.2.1

POWER TRANSFER CHARACTERISTIC S

T r a n s f e r (switch-over) time requirements

2.2.1.1 When t h e p r i m a r y power s u p p l y t o t h e more c r i t i c a l v i s u a l a i d s , f a c i l i t i e s , and r a d i o n a v i g a t i o n a i d s f a i l s , t h e l o a d must be t r a n s f e r r e d t o t h e s e c o n d a r y power s o u r c e . The s e c o n d a r y power s o u r c e must be s t a r t e d and s p e e d and v o l t a g e s t a b i l i z e d b e f o r e t h e load i s t r a n s f e r r e d . 2.2.1.2 The t r a n s f e r , o r s w i t c h - o v e r , t i m e s p e r m i t t e d depend on t h e most c r i t i c a l i n s t r u m e n t c l a s s i f i c a t i o n of t h e aerodromes o p e r a t i o n . Annex 14, C h a p t e r 8, and Annex 10, Volume I , P a r t I , Attachment C l i s t t h e maximum p e r m i s s i b l e t r a n s f e r t i m e s f o r t h e components of aerodrome l i g h t i n g s y s t e m s and r a d i o a i d s a s s o c i a t e d w i t h n o n - i n s t r u m e n t , n o n - p r e c i s i o n , and p r e c i s i o n a p p r o a c h runway c a t e g o r i e s I , I T , and III; (See T a b l e 2-1.

Continuous power s o u r c e s 2.2.2.1 C e r t a i n t y p e s of lamps c a n n o t be r e s t a r t e d f o r s e v e r a l m i n u t e s i f t h e r e i s a b r e a k i n t h e c u r r e n t t h r o u g h t h e lamp of more t h a n a few t e n t h s of a s e c o n d . Some t y p e s It i s n e c e s of r a d i o n a v i g a t i o n and computer d e v i c e s a l l o w no i n t e r r u p t i o n of power, s a r y t o p r o v i d e a n u n i n t e r r u p t i b l e o r n e a r c o n t i n u o u s s o u r c e of power when t h e p r i m a r y power s o u r c e f a i l s t o c a t e r t o s u c h equipment. Some d e v i c e s , s u c h a s some computers, a r e c a p a b l e of accommodating o n l y v e r y l i m i t e d f l u c t u a t i o n s of f r e q u e n c y o r v o l t a g e and r e q u i r e a t r u l y u n i n t e r r u p t i b l e power s u p p l y . 2.2.3

Methods of t r a n s f e r

2.2.3.1 The f o l l o w i n g methods a r e s u g g e s t e d a s p o s s i b l e ways t o r e s t o r e t h e power s u p p l y w i t h i n t h e s p e c i f i e d maximum t r a n s f e r t i m e s . It i s a d v a n t a g e o u s t o g r o u p l o a d s w i t h s i m i l a r l i m i t i n g t r a n s f e r t i m e s s o t h a t t h e y may be c o n t r o l l e d a t t h e t r a n s f o r m e r s u p p l y o r a t t h e f e e d e r d i s t r i b u t i o n c o n n e c t i o n s f r o m t h e same s e c o n d a r y s o u r c e . - I

2 ~ i n u t et r a n s f e r t i m . m - e r e a 2 - m i n u t e t r a n s f e r t i m e i s p e r m i s s i b l e , l o c a l g a s o l i n e o r d i e s e l engine-generator o r gas turbine-generator s e t s In w i t h a u t o m a t i c o r remote s t a r t i n g and s w i t c h i n g are s a t i s f a c t o r y . t h i s 2--minute p e r i o d t h e e n g i n e o r t u r b i n e c a n be s t a r t e d and t h e s p e e d and v o l t a g e r e g u l a t i o a can be s t a b i l i z e d .

o LC. i g u ~ e2-1,

Example of a d o u b l e - l o o p o p e n - r i n g i n t e r - m e d i a t e v o l t a g e d i s t r i b u t i o x network

P a r t 5.-

E l e c t r i c a l Systems

5-7

15-second t r a n s f e r t i m e . Where a 15-second t r a n s f e r t i m e i s r e q u i r e d , s t a n d b y d i e s e l and g a s o l i n e e n g i n e - g e n e r a t o r s e t s w i t h r a p i d - s t a r t c a p a b i l i t y and f a s t - a c t i n g a u t o m a t i c s w i t c h i n g o r an i n d e p e n d e n t s o u r c e w i t h a u t o m a t i c t r a n s f e r s w i t c h i n g can be used.

10-second t r a n s f e r t i m e . Where a 10-second t r a n s f e r t i m e i s r e q u i r e d , s e c o n d a r y power u n i t s w i t h s u i t a b l e s t a r t i n g and s w i t c h - o v e r c a p a b i l i t y can be used.

One-second t r a n s f e r t i m e . Where a one s e c o n d s w i t c h - o v e r time i s r e q u i r e d , one of t h e f o l l o w i n g two methods a r e u s u a l l y used f o r t h i s r a p i d t r a n s f e r of power. One method i s t o s t a r t t h e stand-by d i e s e l e n g i n e o r gas t u r b i n e - g e n e r a t o r s e t a s soon a s t h e RVR i s of t h e o r d e r of 600 m and o p e r a t e t h e more c r i t i c a l l i g h t i n g and r a d i o a i d s from t h i s g e n e r a t o r s e t w i t h a u t o m a t i c t r a n s f e r t o t h e p r i m a r y power s o u r c e i n c a s e t h e s e c o n d a r y power f a i l s . The c r i t i c a l l o a d power s h o u l d c o n t i n u e t o be f u r n i s h e d by t h e s e c o n d a r y power s o u r c e u n t i l an RVR of 800 m i s reached on a f i r m t r e n d of improvements. The second method i s t o a u t o m a t i c a l l y switch-over t o a s a t i s f a c t o r y i n d e p e n d e n t power s u p p l y .

Near z e r o t r a n s f e r t i m e . Very f a s t - a c t i n g ( s w i t c h i n g i n 0.3 second o r l e s s ) a u t o m a t i c t r a n s f e r d e v i c e s which can s w i t c h t h e l o a d from t h e o p e r a t i n g stand-by g e n e r a t o r t o t h e p r i m a r y s o u r c e a r e r e q u i r e d f o r l i g h t s u s i n g some t y p e s of d i s c h a r g e lamps i n o r d e r t o m a i n t a i n t h e d i s c h a r g e . Another method of o b t a i n i n g a n e a r - z e r o t r a n s f e r time i s t o u s e an i n e r t i a f l y w h e e l - d r i v e n g e n e r a t o r which i s c a p a b l e of m a i n t a i n i n g t h e power s u p p l y d u r i n g t h e s t a r t - u p of t h e s e c o n d a r y power s o u r c e .

Zero t r a n s f e r t i m e . For t h o s e f a c i l i t i e s r e q u i r i n g u n i n t e r r u p t i b l e power and a c c e p t i n g o n l y l i m i t e d v a r i a t i o n s of v o l t a g e o r f r e q u e n c y , b a t t e r y - d r i v e n s t a t i c i n v e r t e r ( s ) o r g e n e r a t o r ( s ) ( s e e F i g u r e 2-2) may be used. Although t h e s e c o n d a r y power t r a n s f e r s h o u l d u s u a l l y be accomplished i n o n l y s e v e r a l s e c o n d s , t h e b a t t e r y s e t ( s ) s h o u l d be c a p a b l e of o p e r a t i n g t h e f a c i l i t i e s f o r a minimum of 15 m i n u t e s w i t h o u t recharging.

2.3

SECONDARY POWER EQUIPMENT

Component S

2.3. 1.1 Secondary e l e c t r i c a l power s h o u l d be of s u c h q u a l i t y t h a t it w i l l p r o v i d e t h e r e l i a b i l i t y , a v a i l a b i l i t y , and v o l t a g e s and f r e q u e n c i e s needed by t h e f a c i l i t y . The majo r i t e m s of s e c o n d a r y power equipment commonly used f o r aerodrome l i g h t i n g and r a d i o n a v i g a t i o n a i d s a r e engine-generator s e t s , power-transfer s w i t c h i n g d e v i c e s , b a t t e r i e s , and b a t t e r y c h a r g e r s t o f u r n i s h power f o r s t a r c i n g t h e e n g i n e g e n e r a t o r s , and v a u l t s o r s h e l t e r s f o r t h i s equipment. Less o f t e n u s e d , u s u a l l y f o r s p e c i a l f a c i l i t i e s , a r e u n i n t e r r u p t i b l e power (UPS) s y s t e m s , s t a n d b y battery-power s y s t e m s , s o l a r o r wind g e n e r a t o r s with b a t t e r y systems, independent g e n e r a t i n g devices such a s t h e s m e l e c t r l c , n u c l e a r , o r f u e l c e l l s . The s e c o n d a r y power equipment s h o u l d be l o c a t e d a s c l o s e a s i s p r a c t i c a l t o t h e i n p u t of t h e f a e i l i t h e a s e r v e d .

UPS MODULE

I I I I l I

STATIC

P S OUTPUT TO mITICAL BUS

*UPS

( U n i n t e r r u p t i b l e Power Supply)

-. rlgure

2-2,

T y p i c a l n o n r e d u n d a n t uninterruptibfe power s u p p l y

2.3,2.1 The b a s i c s e c o n d a r y power e n g i n e - g e n e r a t o r s e t c o n s i s t s of a p r i m e mover, a g e n e r a t o r o r a l t e r n a t o r , a s t a r t i n g d e v i c e , s t a r t i n g c o n t r o l s , and a f u e l t a n k o r E n g i n e - g e n e r a t o r s e t s f o r s e c o n d a r y power u n i t s a r e u s u a l l y i n 1 0 0 t o supply. 500 k i l o v o l t - a m p e r e s c a p a c i t i e s b u t may r a n g e f r o m 50 t o 1 000 k i l o v o l t - a m p e r e s i n capacity

Prime movers. The prime movers f o r most s e c o n d a r y power u n i t s a r e g a s o l i n e , d i e s e l , o r g a s e n g i n e s o r t u r b i n e s , t h e c h o i c e b e i n g b a s e d on c o s t and a v a i l a b i l i t y of f u e l s . These prime movers a r e u s u a l l y a v a i l a b l e i n s t a n d a r d i z e d s i z e s w i t h a d e q u a t e power t o h a n d l e t h e k i l o v o l t - a m p e r e r a t i n g of t h e g e n e r a t o r . The prime movers f o r most major aerodromes a r e r a p i d - s t a r t t y p e s which can s t a r t a u t o m a t i c a l l y , s t a b i l i z e t h e s p e e d , and be c o n n e c t e d t o t h e l o a d w i t h i n 1 0 s e c o n d s .

Generators. The g e n e r a t o r , u s u a l l y a n a l t e r n a t o r , i s m e c h a n i c a l l y c o u p l e d t o t h e prime mover and p r o v i d e s s e c o n d a r y e l e c t r i c a l power a t t h e f r e q u e n c y , v o l t a g e , and power r a t i n g of t h e u n i t . These g e n e r a t o r s may be e i t h e r s i n g l e p h a s e o r t h r e e phase. They s h o u l d h a v e h i g h e f f i c i e n c y i n c o n v e r t i n g mechanical energy t o e l e c t r i c a l energy.

S t a r t i n g d e v i c e s . Most s e c o n d a r y power e n g i n e - g e n e r a t o r s e t s u s e b a t t e r y packs t o s t o r e energy f o r s t a r t i n g . Because o f t h e i n f r e q u e n t u s e , s h o r t o p e r a t i n g p e r i o d s , h i g h s t a r t i n g c u r r e n t demands, and c o s t , l e a d - a c i d t y p e b a t t e r i e s a r e used most f r e q u e n t l y f o r s t a r t i n g t h e s e units. The b a t t e r y pack ( o f t e n a s e t of b a t t e r i e s c o n n e c t e d i n s e r i e s a n d / o r p a r a l l e l ) must be c a p a b l e of p r o v i d i n g t h e v o l t a g e and c u r r e n t needed t o s t a r t t h e e n g i n e w i t h i n t h e r e q u i r e d t i m e l i m i t s and u n d e r t h e most s e v e r e c o n d i t i o n s ( u s u a l l y a low t e m p e r a t u r e of -7째C) a t which t h e s e c o n d a r y power u n l t i s e x p e c t e d t o o p e r a t e . A b a t t e r y c h a r g e r w i t h o v e r - c u r r e n t and over-charge c o n t r o l i s p e r m a n e n t l y c o n n e c t e d t o t h e e l c t r i c a l power t o m a i n t a i n t h e s t o r e d e n e r g y i n t h e b a t t e r i e s . The b a t t e r y pack s h o u l d b e w e l l v e n t i l a t e d t o p r e v e n t a c c u m u l a t i o n of hydrogen g a s and s h o u l d be p r o t e c t e d f r o m a r c s , s p a r k s , o r f l a m e s which c o u l d c a u s e a n e x p l o s i o n of any accumulated g a s . Nickel-cadmium b a t t e r i e s may b e u s e d where s p e c i a l c o n d i t i o n s w a r r a n t t h e i r h i g h i n i t i a l cost. Flywheels, pneumatic-pressure v e s s e l s , other-than-battery stored-energy devices a r e used i n f r e q u e n t l y f o r engine s t a r t i n g because of u n r e l i a b i l i t y o r c o s t .

S t a r t i n g c o n t r o l s . The c o n t r o l s f o r t h e e n g i n e - g e n e r a t o r s e t a r e u s u a l l y a u t o m a t i c s t a r t w i t h t h e s e n s o r f o r primary power f a i l u r e a s p a r t of t h e t r a n f e r s w i t c h i n g d e v i c e . Manual o r r e m o t e c o n t r o l s a r e sometimes u s e d f o r f a c i l i t i e s w i t h low c r i t i c a l r e q u i r e m e n t s . Once i t i s s t a r t e d , s p e e d and power a r e a u t o m a t i c a l l y r e g u l a t e d by t h e e n g i n e and t h e e l e c t r i c a l l o a d i s c o n n e c t e d by t h e t r a n s f e r s w i t c h . The e n g i n e generator should o p e r a t e automatically without adjustment o r o t h e r a t t e n t i o n . T r a n s f e r of power back t o t h e p r i m a r y s o u r c e a n d s t o p p i n g t h e e n g i n e may be a u t o m a t i c o r by remote c o n t r o l .

L i q u i d f u e l f o r s e c o n d a r y power i s u s u a l l y s t o r e d i n t a n k s The c a p a c i t y of t h e f u e l t a n k s near t h e engine generator location. s h o u l d be a d e q u a t e f o r t h e m a x i m u m o p e r a t i n g t i m e e x p e c t e d of t h e

Some a u t h o r i t i e s r e q u i r e a minimum of 72 h o u r s engine-generator. supply. Others d e s i g n f o r a l e s s e r time p e r i o d , but t h e t i m e period u s u a l l y s h o u l d be a t l e a s t t w i c e t h e maximum d u r a t i o n e x p e c t e d of c o n d i t i o n s t h a t c o u l d r e q u i r e t h e u s e of s e c o n d a r y power. Fuel tanks and c o n n e c t i o n s s h o u l d meet a l l s a f e t y r e q u i r e m e n t s and s h o u l d p r o v i d e convenient access f o r r e f u e l l i n g . These t a n k s s h o u l d a l s o p r o v i d e a r r a n g e m e n t s f o r t e s t i n g f o r c o n t a m i n a t i o n of t h e f u e l , e s p e c i a l l y t h e a c c u m u l a t i o n of w a t e r i n t h e t a n k . Power t r a n s f e r s w i t c h i n g A s u i t a b l e t r a n s f e r d e v i c e i s needed f o r t r a n s f e r r i n g power f r o m t h e p r i m a r y s o u r c e t o t h e s e c o n d a r y s o u r c e . F o r manual s t a r t i n g and c o n t r o l t h i s may be a s i m p l e s w i t c h o r r e l a y t h a t d i s c o n n e c t s t h e l o a d f r o m one power s o u r c e and c o n n e c t s i t t o t h e o t h e r . A d d i t i o n a l c o n t r o l s a r e needed f o r a u t o m a t i c t r a n s f e r . These a r e u s u a l l y combined i n t o a s i n g l e c o n t r o l u n i t o r c u b i c l e . Such a u n i t s h o u l d be c a p a b l e o f s e n s i n g t h e f a i l u r e of p r i m a r y power, i n i t i a t i n g t h e s t a r t i n g of t h e prime mover of t h e s e c o n d a r y g e n e r a t o r s e t , d e t e r m i n i n g t h a t t h e v o l t a g e and f r e q u e n c y of t h e g e n e r a t o r T h i s u n i t may h a v e s t a b i l i z e d a d e q u a t e l y , and c o n n e c t i n g t h e l o a d t o t h e g e n e r a t o r . a l s o d i s c o n n e c t n o n - e s s e n t i a l l o a d s and f a c i l i t i e s which a r e n o t t o be e n e r g i z e d by t h e s e c o n d a r y s o u r c e and t r a n s f e r t h e s e l o a d s back t o t h e p r i m a r y s o u r c e a f t e r t h a t power has been r e s t o r e d . The s w i t c h e s o r r e l a y s f o r d i s c o n n e c t i n g and c o n n e c t i n g t h e l o a d s h o u l d have t h e c a p a c i t y t o h a n d l e t h e r a t e d l o a d of t h e g e n e r a t o r . The f u n c t i o n i n g of these switches o r relays i s similar f o r e i t h e r 2arinute, 15second, o r l s e c o n d t r a n s f e r t i m e s , a l t h o u g h more r a p i d - a c t i n g r e l a y s may be needed f o r t h e s h o r t e s t t r a n s f e r t i m e . For a 2-minute t r a n s f e r , t h e power f a i l u r e s e n s o r s may d e l a y a few s e c o n d s i n d e t e r mining i f t h e p r i m a r y power h a s f a i l e d o r i s o n l y f l u c t u a t i n g and a l s o t o d e t e r m i n e i f t h e s e c o n d a r y power h a s s t a b i l i z e d . For a 1 5 s e c o n d t r a n s f e r , t h e s e n s o r s must r e s p o n d i n l e s s t h a n 3 s e c o n d s e a c h b e c a u s e t h e q u i c k s t a r t i n g e n g i n e s need 1 0 s e c o n d s t o s t a r t For t r a n s f e r t i m e s of 1 second o r l e s s , t i m e i s t o o s h o r t t o s t a r t and t o s t a b i l i z e . t h e e n g i n e , b u t t h e l o a d c a n be s w i t c h e d f r o m one power s o u r c e t o a n o t h e r o p e r a t i n g s o u r c e w i r h i n t h i s t i m e l i m i t ; however, t h e power f a i l u r e s e n s o r ~ a s rt e s p ~ n dw i t h d n a few c y c l e s .

2.3.3.1

2.3.4

U n i n t e r r u p t i b l e power s u p p l i e s (UPS) s y s t e m s

2.3.4.1 An u n i n t e r r u p t i b l e e l e c t r i c power s u p p l y i s n e c e s s a r y f o r e l e c t r o n i c o r o t h e r equipment t h a t performs a c r i t i c a l f u n c t i o n and r e q u i r e s c o n t i n u o u s , d i s t u r b a n c e f r e e e l e c t r i c power t o o p e r a t e p r o p e r l y . 2.3.4.2 UPS equipment. The u n i n t e r r u p t i b l e power s u p p l y (UPS) s y s t e m c o n s i s t s of one o r more UPS modules, a n e n e r g y - s t o r a g e b a t t e r y , and a c c e s s o r i e s a s r e q u i r e d t o p r o v i d e a r e l i a b l e arid h i g h q u a l i t y power s u p p l y . The UPS s y s t e m i s o l a t e s t h e l o a d f r o m t h e p r i m a r y and s e c o n d a r y s o u r c e s and i n t h e e v e n t of a power i n t e r r u p t i o n p r o v i d e s r e g u l a t e d power t o t h e c r i t i c a l l o a d f o r a s p e c i f i e d p e r i o d . (The b a t t e r y t y p i c a l l y h a s (See F i g u r e 2-2.) a 15-minute c a p a c i t y when o p e r a t i n g a t f u l l l o a d . ) a)

UPS module. A UPS module i s t h e s t a t i c power c o n v e r s i o n p o r t i o n of t h e UPS s y s t e m and c o n s i s t s of a r e c t i f i e r , an i n v e r t e r , and a s s o d a t e d c o n t r o l s a l o n g w i t h s y n c h r o ~ ~ i z i n gp, r o t e c t i v e , and a u x i l i a r y d e v i c e s . UPS modules may be d e s i g n e d t o o p e r a t e e i t h e r i n d i v i d u a l l y o r i n parallel.

A n o n r e d u n d a n t UPS s y s t e m i s s u i t a b l e f o r m o s t o p e r a t i o n s . However, i f t h e e x p e n s e i s j u s t i f i e d , a r e d u n d a n t UPS c o n f i g u r a t i o n ( s e e F i g u r e 2-3) may be u s e d t o p r o t e c t a g a i n s t module f a i l u r e o r v e r y f r e q u e n t p r i m a r y power f a i l u r e s .

The b a t t e r y s h o u l d b e a h e a v y - d u t y i n d u s t r i a l u n i t of t h e lead-cadmium t y p e h a v i n g a n ampere-hour r a t i n g s u f f i c i e n t t o s u p p l y d i r e c t c u r r e n t t o t h e i n v e r t e r as r e q u i r e d by t h e UPS s y s t e m manufacturer's i n s t a l l a t i o n instructions. The b a t t e r y i s u s u a l l y f u r n i s h e d w i t h t w o - t i e r r a c k s ; however, w h e r e s p a c e i s l i m i t e d t h r e e t i e r r a c k s may b e n e c e s s a r y .

Remote a l a r m s . The UPS e q u i p m e n t s h o u l d b e s u p p l i e d w i t h a r e m o t e - a l a r m p a n e l t o b e i n s t a l l e d i n t h e o p e r a t i n g s p a c e s e r v e d by t h e UPS u n i t o r Since i n a n o t h e r c o n t i n u o u s l y o c c u p i e d room, s u c h as a g u a r d o f f i c e . UPS e q u i p m e n t rooms a r e u s u a l l y u n a t t e n d e d , a d d i t i o n a l r e m o t e i n d i c a t i n g d e v i c e s s h o u l d be provided t o monitor t h e e n v i r o n m e n t a l c o n t r o l and f i r e a l a r m s y s t e m o f UPS module and b a t t e r y rooms.

UPS a n d b a t t e r y room r e q u i r e m e n t s . The UPS modules a n d t h e i r a s s o c i a t e d Construction should b a t t e r y s e t s h o u l d b e i n s t a l l e d i n s e p a r a t e rooms. The w a l l s e p a r a t i n g t h e UPS module room f r o m be of a p e r m a n e n t t y p e . t h e b a t t e r y room s h o u l d b e f i r e p r o o f ( l - h o u r r a t i n g ) . When f e a s i b l e , s p a c e s h o u l d b e p r o v i d e d i n t h e UPS module a n d b a t t e r y rooms f o r t h e a d d i t i o n o f f u t u r e UPS e q u i p m e n t .

Environmental c o n t r o l . Both t h e UPS module a n d b a t t e r y rooms s h o u l d b e provided with an environmental c o n t r o l system t o maintain t h e prescribed room c o n d i t i o n s . Each e n v i r o n m e n t a l c o n t r o l s y s t e m s h o u l d c o n s i s t o f a primary system with a secondary system c a p a b i l i t y . Upon f a i l u r e o f t h e primary environmental c o n t r o l system, a u t o m a t i c t r a n s f e r t o t h e secsnda r y s y s t e r n s h o u l d o c c u r and s h o u l d sound a n a l a r m i n d i c a t i n g t h e need f o r maintenance.

2.3.5.1 O t h e r s e c o n d a r y power d e v i c e s which may be u s e d f o r s p e c i a l f a c i l i t i e s a r e s t a n d b y b a t t e r y power s y s t e m s , w i t h o r w i t h o u t d c t o a c i n v e r t e r s ; p h o t o v o l t a i c o r wind g e n e r a t o r s w i t h b a t t e r y systems and w i t h o r without d c t o a c i n v e r t e r s ; i n d e p e n d e n t g e n e r a t i n g d e v i c e s , s u c h as t h e r m o e l e c t r i c , n u c l e a r , o r c h e m i c a l f u e l c e l l s ; a n d inertia-flywheel generators. The m a n u f a c t u r e r ' s i n f o r m a t i o n s h o u l d e x p l a i n t h e f u n c t i o n i n g and i n s t a l l a t i o n s f o r u s i n g t h e s e d e v i c e s .

2.4

2.4.1

VAULTS A N D SHELTEKS F O K ELECTRICAL EQUIPMENT

Shelters

2.4.1.1 Host e l e c t r i c a l e q u i p m e n t f o r a i r p o r t L i g h t i n g a n d o t h e r f a c i l i t i e s i s l o c a t e d i n v a u i c s o r s p e c i a i s h e l t e r s f o r p r o t e c t i o n from t h e weather and f o r b e t t e r security. S u b s t a t i o n s f o r h i g h v o l t a g e a r e u s u a l l y o u t d o o r s , and medium v o l t a g e d i s t r i h ~ f i o nt r a n s f o r m e r % a r e o f t e n p o l e mounted o r p l a c e d o n f e n c e d t r a n s f o r m e r p a d s . Host e l e c t r i c a l v a u l t s & r e a b o v e ground aad made of f i r e ~ r o ~materials. f Peinforced

5-1 2

Aerodrome D e s i n n I?lanual

UPS NoDVLE

m.1

UPS MODULE NO. 2

BATTERY PACK

NONAUTOMATIC CIRCUIT BREAKER UPS OUTPUT T CRITICAL BUS

F i g u r e 2-3-

i y p i c a i dP5 stana-by

redunnant configuration

c o n c r e t e f o r t h e f l o o r s and c o n c r e t e , c o n c r e t e o r c i n d e r b l o c k , a n d / o r b r i c k f o r t h e The u s e of s u c h m a t e r i a l s r e d u c e t h e w a l l s a r e m a t e r i a l s commonly used i n t h e s e v a u l t s . h a z a r d of e l e c t r i c s h o c k , s h o r t i n g of e l e c t r i c a l c i r c u i t s , and f i r e h a z a r d s . Prefabric a t e d m e t a l s t r u c t u r e s a r e o c c a s i o n a l l y u s e d a s s h e l t e r s f o r t r a n s f o r m e r s and e n g i n e g e n e r a t o r s e t s . These v a u l t s a r e u s e d t o h o u s e t h e power d i s t r i b u t i o n and c o n t r o l equipment, s e c o n d a r y power equipment, and t h e v a r i o u s d e v i c e s u s e d t o p r o v i d e power and c o n t r o l f o r t h e a i r p o r t l i g h t i n g s y s t e m s . These v a u l t s s h o u l d be of a d e q u a t e s i z e t o c o n t a i n t h e n e c e s s a r y equipment w i t h o u t crowding. These v a u l t s may be d i v i d e d i n t o rooms f o r b e t t e r s e g r e g a t i o n of equipment and a c t i v i t i e s . 2.4.2

Location

2.4.2.1 E l e c t r i c a l v a u l t s s h o u l d n o t be l o c a t e d where t h e y would i n f r i n g e on o b s t a c l e l i m i t a t i o n s u r f a c e s . The d i s t a n c e s f r o m t h e c o n t r o l tower t o t h e v a u l t s s h o u l d be The p e r m i s s i b l e s h o r t enough t o a v o i d e x c e s s i v e v o l t a g e d r o p i n t h e c o n t r o l c a b l e s . l e n g t h of t h e s e c a b l e s v a r i e s w i t h t h e s i z e of t h e c a b l e , t h e c o n t r o l v o l t a g e , and t h e t y p e s of c o n t r o l r e l a y s u s e d , b u t some of t h e l o n g e r c o n t r o l s y s t e m s l i m i t t h e l e n g t h o f c o n t r o l c a b l e s t o a b o u t 2 250 m e t r e s . V e h i c u l a r a c c e s s t o t h e v a u l t s i n a l l t y p e s of w e a t h e r c o n d i t i o n s i s n e c e s s a r y and minimum c o n f l i c t w i t h a i r c r a f t t r a f f i c i s d e s i r a b l e . The l o c a t i o n s h o u l d be c o n v e n i e n t f o r c o n n e c t i n g t o t h e a p p r o p r i a t e l i g h t i n g c i r c u i t s and f a c i l i t i e s t o k e e p f e e d e r c a b l e l e n g t h s a s s h o r t a s i s p r a c t i c a l . The v a u l t s s h o u l d b e i s o l a t e d f r o m o t h e r b u i l d i n g s and f a c i l i t i e s t o p r e v e n t t h e s p r e a d of f i r e s o r e x p l o s i o n s , e x c e p t t h e s h e l t e r s f o r s e c o n d a r y e n g i n e - g e n e r a t o r s e t s may b e n e a r t h e e l e c t r i c a l v a u l t t o r e d u c e c a b l e l e n g t h and s i z e and t o s i m p l i f y t h e power t r a n s f e r Aerodromes w i t h a p p r o a c h l i g h t i n g s y s t e m s may n e e d s e p a r a t e a p p r o a c h l i g h t i n g system. v a u l t s f o r e a c h a p p r o a c h l i g h t i n g system. F o r major a e r o d r o m e s , some a u t h o r i t i e s u s e a v a u l t n e a r e a c h end of t h e runway o r a p p r o a c h l i g h t i n g s y s t e m t o more e a s i l y a r r a n g e f o r i n t e r l e a v i n g o f t h e l i g h t i n g c i r c u i t s and t o improve i n t e g r i t y of t h e s y s t e m s . 2.4.3

Special provisions

2=4+3.1 A s s p e c i a l p u r p o s e b u i l d i n g s , e l e c t r i c a l v a u l t s may r e q u i r e s p e c i a l f e a t u r e s t o p r o v i d e s a f e t y and r e l i a b l e performance of t h e equipment. Some of t h e s e f e a t u r e s a r e a s follows: a)

Ventilation. Provide adequate v e n t i l a t i o n t o p r e v e n t t r a n s f o r m e r t e m p e r a t u r e s e x c e e d i n g t h e v a l u e s p r e s c r i b e d by t h e m a n u f a c t u r e . Most of t h e e l e c t r i c a l h e a t l o s s e s must be removed by v e n t i l a t i o n ; o n l y a minor p a r t c a n be d i s s i p a t e d by t h e v a u l t w a l l s . Some e l e c t r i c a l codes recommend 20 s q u a r e c e n t i m e t r e s of c l e a r g r a t i n g a r e a p e r k i l o v o l t ampere of t r a n s f o r m e r c a p a c i t y . I n l o c a l i t i e s w i t h above-average temperatures, such a s t r o p i c a l o r s u b t r o p i c a l a r e a s , t h e g r a t i n g a r e a s h o u l d be i n c r e a s e d o r supplemented by f o r c e d v e n t i l a t i o n .

Access. Adequate a c c e s s s h o u l d be p r o v i d e d f o r r e p a i r s , m a i n t e n a n c e , i n s t a l l a t i o n , and removal of equipment.

A l l v a u l t s s h o u l d be p r o v i d e d w i t h d r a i n a g e . When normal Drainage. d r a i n a g e i s n o t p o s s i b l e , p r o v i d e a sump p i t t o p e r m i t t h e u s e of a p o r t a b l e pump.

S e c u r i t y . Each e l e c ~ r i c a lv a u i c s h o u l d b e e q u i p p e d t o d e t e r i n a d v e r t e n t o r p r e m e d i t a t e d a c c e s s by u n a u t h o r i z e d p e r s o n s . T h i s s e c u r i t y i s n e c e s s a r y t o p r e v e n t i n t e r f e r e n c e w i t h equipmeat o p e r a t i o n and t o p r o t s c t t h o s s persGns f r o m p ~ s s i b l ee l e c t r i c s h ~ c k . Some rnerhods u s e d

a r e b a r r e d and s c r e e n e d windows, heavy-duty m e t a l d o o r s w i t h p a d l o c k s , and s e c u r i t y fencing. e

E l e c t r i c a l v a u l t s s h o u l d be w e l l i l l u m i n a t e d f o r u s e e i t h e r day o r n i g h t . T h i s l i g h t i n g i s u s u a l l y p r o v i d e d by i n t e r i o r l i g h t s of a s i z e , t y p e , and l o c a t i o n t o p r o v i d e good v i s i b i l i t y i n a l l a r e a s . Poor v i s i b i l i t y c a n i n c r e a s e t h e p o t e n t i a l f o r a c c i d e n t s r e s u l t i n g i n e l e c t r i c a l shock o r improper c o n t r o l and a d j u s t m e n t s .

Local communications. Most e l e c t r i c a l v a u l t s s h o u l d be p r o v i d e d w i t h c o n v e n i e n t and r e l i a b l e communications t o t h e c o n t r o l t o w e r , o t h e r v a u l t s , and p e r h a p s o t h e r f a c i l i t i e s o r o f f i c e s . Special telephone o r i n t e r c o m m u n i c a t i o n s y s t e m s may a v o i d o u t s i d e i n t e r f e r e n c e w i t h t h e s e c i r c u i t s , b u t o t h e r dependable arrangements can be used.

E l e c t r i c a l conduits. E l e c t r i c a l v a u l t s s h o u l d be p r o v i d e d w i t h a s u f f i c i e n t number of c o n d u i t s and c a b l e e n t r a n c e a c c e s s e s t o a v o i d l a t e r m o d i f i c a t i o n of t h e s t r u c t u r e t o p e r m i t t h e i n s t a l l a t i o n of a d d i t i o n a l i n p u t o r o u t p u t c i r c u i t s . These c a b l e s e n t r a n c e s a r e u s u a l l y t h r o u g h underground c o n d u i t s which may be c o n n e c t e d t o e x i s t i n g c a b l e d u c t s , d i r e c t - b u r i a l c a b l e s , o r unused c o n d u i t s a v a i l a b l e f o r f u t u r e e x p a n s i o n . Unused c o n d u i t s s h o u l d be p l u g g e d , and c o n d u i t s w i t h c a b l e s s h o u l d be sealed.

I n s t a l l a t i o n s of equipment. Arrange t h e equipment, e s p e c i a l l y t h e l a r g e r items such a s r e g u l a t o r s , d i s t r i b u t i o n transformers, c o n t r o l p a n e l s , and c i r c u i t s e l e c t o r o r c o n t r o l d e v i c e s , t o p r o v i d e a s i m p l e , u n c l u t t e r e d , uncrowded p l a n . This arrangement should c o n s i d e r s a f e t y , e s p e c i a l l y p r o t e c t i o n from h i g h v o l t a g e e l e c t r i c a l c o n n e c t i o n s , a s w e l l a s a c c e s s t o t h e equipment and c o n t r o l s . The e l e c t r i c a l c i r c u i t s s h o u l d a i s o be a r r a n g e d i n a s i m p l e p a t t e r n wherever p o s s i b l e . Follow t h e a p p l i c a b l e e l e c t r i c s a f e t y codes f o r i n s t a l l i n g a l l e l e c t r i c a l c i r c u i t s and c o n t r o l s .

2.5 2.5.1

DISTRIBUTION OF POWER

General

2.5.1.1 The equipment d i s c u s s e d i n t h i s s e c t i o n r e l a t e s o n l y t o t h a t u s e d i n t r a n s m i t t i n g e l e c t r i c a l power f o r t h e aerodrome l i g h t i n g and r a d i o n a v i g a t i o n a i d s between t h e main aerodrome s u b s t a t i o n ( s ) and t h e l i g h t i n g v a u l t s o r t h e l o c a l s i t e d i s t r i b u t i o n transformers. D e s c r i p t i o n s of equipment a r e i n g e n e r a l t e r m s o f c h a r a c t e r i s t i c s and n e e d s and u s u a l l y a r e n o t r e l a t e d t o s p e c i f i c t y p e s o r i t e m s of e q u i p m e n t s . Types of equipment and number of d e v i c e s w i l l v a r y g r e a t l y w i t h t h e s i z e and c o m p l e x i t y of t h e aerodrome. Economics i s a n i m p o r t a n t p a r t of i n s t a l l a t i o n s , and o n l y equipment which c o n t r i b u t e s t o p e r f o r m a n c e , s a f e t y , r e l i a b i l i t y , and i n t e g r i t y s h o u l d b e used. The c i r c u i t s and equipment used s h o u l d p r o v i d e f o r a r e a s o n a b l e e x p a n s i o n of f a c i l i t i e s w E f f i c i e n t u s e of e l e c t r i c a l power i s always a d e s i r a b l e g o a l , b u t t h e power c o s t f o r aerodrome l i g h t i n g and r a d i o navigation a i d s i s u s u a l l y a r a t h e r s m a i i p a r t o f t h e t o t a l aerodrome e n e r g y c o s t and s h o u l d n o t be emphasized t o t h e p o i n t of o v e r l y i n c r e a s i n g l r i s t a l l a t i o n c o s t s 01- of d i m i n i s h i n g p e r f o r m a ~ l c e , s a f e t y , o r r e l i a b l l i t y i Follow r h e l o c a l e l e c t r i c a l s a f e c y codes.

Primary power i s u s u a l l y r e d u c e d i n v o l t a g e a t t h e main aerodrome s u b s t a t i o n 2.5.2.1 f o r d i s t r i b u t i o n on t h e aerodrome. F o r major a e r o d r o m e s , t h i s power a t t h e f i r s t s t a g e may be a t a n i n t e r m e d i a t e v o l t a g e ( u s u a l l y 5 000 t o 20 000 v o l t s ) , b u t f o r s m a l l e r , l e s s complex aerodromes, t h i s power may be d i s t r i b u t e d a t a medium v o l t a g e ( u s u a l l y 1 000 t o 5 000 v o l t s ) . The d i s t a n c e and t o t a l l o a d on t h e c i r c u i t a r e i m p o r t a n t f a c t o r s i n determining t h e v o l t a g e l e v e l of transmission. For an intermediate-voltage d i s t r i b u t i o n s y s t e m , power i s o f t e n r u n t o s u b s t a t i o n s n e a r l a r g e power u s a g e a r e a s where i t i s r e d u c e d t o medium v o l t a g e f o r l o c a l d i s t r i b u t i o n . A c o m b i n a t i o n of t h e s e v o l t a g e Primary power i s t r a n s m i t t e d f r o m t h e main s u b s t a t i o n d i s t r i b u t i o n s y s t e m s may b e u s e d . t o t h e l o c a l s u b s t a t i o n o r d i s t r i b u t i o n s i t e s u s u a l l y as m u l t i - p h a s e c i r c u i t s by above ground ( o v e r h e a d ) c i r c u i t s , u n d e r g r o u n d c i r c u i t s , o r a c o m b i n a t i o n of t h e s e c i r c u i t s . Above ground c i r c u i t s a r e l e s s e x p e n s i v e t o i n s t a l l and a r e u s u a l l y u s e d i f f e a s i b l e , b u t t h e s e c i r c u i t s may be more exposed t o damage and i n some a r e a s a r e a h a z a r d t o a i r c r a f t and c r e a t e e l e c t r o m a g n e t i c i n t e r f e r e n c e f o r o t h e r equipment. Underground Each f e e d e r c a b l e s a r e u s u a l l y i n s t a l l e d i n d u c t s , b u t sometimes d i r e c t b u r i a l i s u s e d . t y p e of c i r c u i t , w h e t h e r o v e r h e a d o r underground, i n v o l v e s s p e c i f i c t y p e s o f equipment and d e s i g n . 2.5.3

Above-ground

(overhead) primary d i s t r i b u t i o n systems

2.5.3.1 The f o l l o w i n g f a c t o r s s h o u l d be c o n s i d e r e d i n t h e d e s i g n of a n o v e r h e a d power d i s t r i b u t i o n system:

2.5.4

Application. Use o v e r h e a d d i s t r i b u t i o n i n l i e u of u n d e r g r o u n d d i s t r i b u t i o n wherever f e a s i b l e .

Capacity. P r o v i d e f o r s p a r e c a p a c i t y i n e a c h p o r t i o n of t h e c i r c u i t . Peak l o a d s do n o t r e l a t e d i r e c t l y t o s p a r e c a p a c i t y .

Wire s i z e . Select t h e wire s i z e i n accordance with t h e current-carrying c a p a c i t y r e q u i r e d a n d , where a p p l i c a b l e , t h e v o l t a g e - d r o p l i m i t a t i o n .

Linevoltage regulators

2.5.4.1 R e g u l a t o r s a r e u s e d f o r c o r r e c t i o n of 1 i n e v o Z t a g e v a r i a t i o n s r e s u l t i n g f r o m c h a n g i n g l o a d s o r u t i l i t y company i n p u t v o l t a g e changes. Do n o t u s e t h e s e r e g u l a t o r s t o c o r r e c t f o r excessive voltage drops. B o o s t e r t r a n s f o r m e r s which c o r r e c t f o r v o l t a g e d r o p s h o u l d be used o n l y i n r a r e i n s t a n c e s a s , i n most c a s e s , c o r r e c t d e s i g n e l i m i n a t e s e x c e s s i v e v o l t a g e drop. a)

Rating. Choose t h e r a t i n g of t h e r e g u l a t i n g d e v i c e s i n a c c o r d a n c e w i t h t h e amount of r e b w l a t i o n r e q u i r e d .

Selection. Choose t h e t y p e of r e g u l a t o r s f r o m f i x e d c a p a c i t o r s , s w i t c h e d c a p a c i t o r s , m u l t i s t e p (motor-driven t a p c h a n g i n g ) r e g u l a t o r s , and i n d u c t i o n ( s t e p l e s s v o l t a g e c h a n g e ) r e g u l a t o r s .

Multistep o r induction regulators. Provide l i n e d r o p compensation f o r a u t o m a t i c o p e r a t i o n when t h e s e r e g u l a t o r s a r e used on more t h a n one s o u r c e o r when more t h a n one r e g u l a t o r i s used on a s i n g l e c i r c u i t .

Power l i n e s 2.5.5.1 S e l e c t t h e t y p e of power l i n e s i n a c c o r d a n c e w i t h t h e t y p e o f c i r c u i t i n v o l v e d and t h e c o n d i t i o n s t o which i t i s s u b j e c t e d f r o m t h e f o l l o w i n g : a)

Open w i r e ( b a r e o r w e a t h e r p r o o f ) on i n s u l a t o r s .

A e r i a l c a b l e , s e l f s u p p o r t e d o r s u p p o r t e d by a h i g h s t r e n g t h s t e e l ( m e s s e n g e r ) c a b l e , c o n s i s t i n g of i n s u l a t e d , b u n d l e d , s i n g l e - c o n d u c t o r cable o r multiple-conductor cable.

2.5.6

Poles. Wood, c o n c r e t e ( r e i n f o r c e d w i t h p r e s t r e s s i n g o r p o s t t e n s i o n i n g ) , o r m e t a l ( s t e e l o r aluminum) may be used. Concrete or m e t a l p o l e s s h o u l d b e u s e d o n l y where t h e y a r e more e c o n o m i c a l o r s p e c i a l considerations warrant t h e i r use.

Footings. P r o v i d e f o o t i n g s , o r r e i n f o r c e m e n t s of t h e p o l e b u t t - e n d , a s r e q u i r e d by f o u n d a t i o n c o n d i t i o n s .

C o n f i g u r a t i o n . Armless c o n s t r u c t i o n f o r a e r i a l l i n e s i s u s u a l l y l e s s c o s t l y t h a n c r o s s a r m c o n s t r u c t i o n and i t s u s e i s p r e f e r r e d , as i s m u l t i corlductor s e c o n d a r y c a b l e w i t h a l a r g e n e u t r a l c o n d u c t o r a s t h e s u p p o r t i n g member o v e r i n d i v i d u a l s u p p o r t e d c o n d u c t o r s . Use c r o s s a r m s mainly f o r equipment s u p p o r t .

Guys and a n c h o r s . P r o v i d e guys and a n c h o r s t o s u p p o r t p o l e s o r l i n e t o w e r s a g a i n s t h o r i z o n t a l u n b a l a n c e d l o a d s c a u s e d by a n g l e s , c o r n e r s , and t e r m i n a t i o n s of l i n e s and where r e q u i r e d b e c a u s e of e x t r e m e wind loadings. Consult manufacturers7 c a t a l o g u e s f o r t y p e s of eareh anchors S e l e c t equipment s u i t a b l e f o r t h e p a r t i c u l a r s o i l and d e s i g n d a t a . c o n d i t i o n s and t h e c o n s t r u c t i o n m t h o d t o be used.

Conductors

2.5.6.1 S i z e l i m i t a t i o n s . L i m i t t h e u s e of p o l e - l i n e c o n d u c t o r s i n a c c o r d a n c e w i t h T a b l e 2-2 f o r an econom%cal s y s t e m f r o m t h e i n s t a l l a t i o n , o p e r a t i o n a l , and m a i n t e n a n c e p o i n t s of view. S p e c i a l i r l s t a n c e s may r e q u i r e l a r g e r c o n d u c t o r s . I n a l l i n s t a n c e s be s u r e t h a t t h e t y p e and s i z e of c o n d u c t o r s u s e d p r o v i d e s a d e q u a t e s t r e n g t h f o r t h e s p a n l e n g t h s and l o a d i n g c o n d i t i o n s . T a b l e 2-2

Conductor t y p e

2.5.6.2 Base w i r e s i z e on t h e r a n g e s shown i n Table 2-2. Primary w i r e For primary s i z e s u s u a l l y s h o u l d n o t be l e s s t h a n 13.0 mm2 copper o r 33.0 mm2 aluminum. c o n d u c t o r s , s e l e c t from t h e f o l l o w i n g :

Bare c o p p e r c o n d u c t o r , s t r a n d e d o r s o l i d c o p p e r .

Bare aluminum-alloy

Bare aluminum c o n d u c t o r , s t e e l r e i n f o r c e d .

Bare h i g h s t r e n g t h all-aluminum a l l o y c o n d u c t o r .

c o n d u c t o r , s t r a n d e d o r s o l i d aluminum-alloy.

I n s p e c i a l i n s t a n c e s , u s e of t h e f o l l o w i n g c o n d u c t o r s 2.5.6.3 Special conductors. may be a p p r o p r i a t e f o r p r i m a r y c o n d u c t o r s : a)

I n s u l a t e d c o n d u c t o r , c o p p e r o r aluminum, p r e a s s e m b l e d n o n - m e t a l l i c sheathed o r metallic-sheathed, steel-cable-supported (messengers u p p o r t e d ) a e r i a l c a b l e i s u s e d where n e c e s s a r y t o a v o i d e x p o s u r e t o open w i r e h a z a r d s , f o r example, h i g h r e l i a b i l i t y s e r v i c e i n heavy s t o r m areas.

Compound c o n d u c t o r m a t e r i a l s s u c h a s c o p p e r - c l a d s t e e l , aluminum-clad s t e e l , g a l v a n i z e d s t e e l , o r b r o n z e a r e u s e d t o p r o v i d e h i g h s t r e n g t h and corrosion resistance.

2.5.6.4 D i s s i m i l a r c o n d u c t o r s . Where i t i s n e c e s s a r y t o c o n n e c t aluminum c o n d u c t o r s t o copper conductors, a p p r o p r i a t e connectors s p e c i f i c a l l y designed f o r such u s e should be i n s t a l l e d i n a c c o r d a n c e w i t h t h e i n s t r u c t i o n s of t h e m a n u f a c t u r e r . 2.5.7

Insulators

2,5,7,1 Types of i n s u l a t o r s - Select from t h e f o l l o w i n g l i s t t h e t y p e of i n s u l a t o r t o support b a r e o r weatherproof i n s u l a t e d conductors. a)

Suspension t y p e , s i n g l e o r m u l t i p l e .

Spool t y p e .

L i n e - p o s t t y p e ( o n e - p i e c e p o r c e l a i n on a b o l t f o r mounting on c r o s s a r m s o r on a s a d d l e on t h e s i d e of a p o l e ) .

S t r a i n type (suspension u n i t s with s t r e n g t h e q u a l o r exceeding t e n s i l e s t r e n g t h of t h e c o n d u c t o r u s u a l l y h a v i n g one t o t h r e e e x t r a d i s k s e c t i o n s and a r c i n g h o r n s o r r i n g s ) .

P i n t y p e ( p o r c e l a i n , u s u a l l y two o r more s e p a r a t e s h e l l s cemented t o g e t h e r , w i t h a n i n t e r n a l t h r e a d f o r s c r e w i n g o n t o a wood o r m e t a l pin).

Combinations. V a r i o u s t y p e s of i n s u l a t o r s may be combined; f o r example, s t r a i n t y p e f o r anchor p o l e s o r t e r m i n a t i o n s w i t h e i t h e r p i n o r l i n e post types f o r l i n e insulation. Line-post types a r e considered t o be b o t h l e s s e x p e n s i v e and s u p e r i o r t o p i n t y p e s .

2.5.7.2 I f overhead l i n e s a r e used i n l o c a t i o n s e n s i t i v e t o e l e c t r o m a g n e t i c i n t e r f e r e n c e , t h e i n s u l a t o r s s h o u l d b e of a s t a t i c - f r e e t y p e . 2.5.8

Locknuts

2.5.8.1 Hardware components s h o u l d be p r o v i d e d w i t h l o c k n u t s t o a v o i d l o o s e c o n n e c t i o n s which c o u l d c a u s e s t a t i c . Locknuts must be t h r e a d e d and of a t y p e w h i c h w i l l p r e v e n t l o o s e n i n g of t h e c o n n e c t i o n when wood members s h r i n k . 2.5.9

Transformers

2.5.9.1 Mount t r a n s f o r m e r s on p o l e s o r a t g r o u n d l e v e l . When s h e e t m e t a l e n c l o s u r e s a r e n o t t a m p e r p r o o f , ground mounted u n i t s s h o u l d b e p r o v i d e d A c o n c r e t e o r b r i c k s t r u c t u r e s h o u l d be u s e d where a d v e r s e with a fenced enclosure. w e a t h e r c o n d i t i o n s make s u c h a n i n s t a l l a t i o n a d v i s a b l e . a1 single-phase

For s i n g l e - p o l e mounting, l i m i t t h e s i z e o f o r three-phase u n i t s i n accordance w i t h approved p r a c t i c e s .

P o l e - p l a t f o r m mounting. P o l e - p l a t f o r m mounting (two-pole s t r u c t u r e s ) s h o u l d n o t be u s e d , e x c e p t i n i n s t a n c e s where o t h e r methods a r e n o t satisfactory. For i n s t a l l a t i o n s of 225 o r 500 k i l o v o l t - a m p e r s , pad-mounted compartmental-type t r a n s f o r m e r s become an a t t r a c t i v e economic a l t e r n a t i v e t o pole-mounted u n i t s *

Ground m o u n t i n g For ground mounting on a c o n c r e t e b a s e , t h e r e i s n o k i l o v o l t - a m p e r e l i m i t . U s u a l l y tamperproof t r a n s f o r m e r s ( c l a s s i f i e d a s gad-mounted compartmental-type u n i t s ) s h o u l d n o t b e s p e c i f i e d f o r r a t i n g s of o v e r 500 k i l o v o l t - a m p e r e s .

2.5.9.2 Ratings. S e l e c t t r a n s f o r m e r s w i t h s t a n d a r d k i l o v o l t - a m p e r e r a t i n g s and i n p u t and o u t p u t v o l t a g e as single-phase o r three-phase u n i t s , Transformers w i t h i n p u t v o l t a g e t a p s f o r s e l e c t i n g t h e most s u i t a b l e i n p u t v o l t a g e l e v e l may be d e s i r a b l e f o r some i n s t a l l a t i o n s . 2.5.9.3 Indoor i n s t a l l a t i o n s . Oil-immersed ( f l a m m a b l e ) t r a n s f o r m e r s s h o u l d n o t be i n s t a l l e d i n d o o r s e x c e p t i n v a u l t s conforming t o t h e r e q u i r e m e n t s of t h e a p p l i c a b l e e l e c t r i c code. Such v a u l t s s h o u l d b e p r o v i d e d o n l y when o t h e r t y p e s of t r a n s f o r m e r s a r e l e s s e c o n o m i c a l o r a r e p r o h i b i t e d by s p e c i a l c o n s i d e r a t i o n s . Where s u c h a v a u l t i s n o t p r o v i d e d , s e l e c t t r a n s f o r m e r s f o r i n d o o r i n s t a l l a t i o n from t h e f o l l o w i n g : a)

high-fire-point,

dry-type

dry-type,

nonhazardous g a s - i n s u l a t e d .

liquid-immersed;

ventilated; s e a l e d t a n k ; and

2.5.9.4 T o x i c i n s u l a t i o n f l u i d s . The t r a n s f o r m e r s s h o u l d n o t u s e p o l y - c h l o r i n a t e d b i p h e n y l (PCB) o r o t h e r h i g h l y t o x i c i n s u l a t i o n f l u i d s . Leakage o r m i s h a n d l i n g of t h e s e c h e m i c a l s d u r i n g m a i n t e n a n c e t e s t i n g c a n be h a z a r d o u s t o p e r s o n n e l .

2.5.10

Capacitors Use s h u n t c a p a c i t o r s t o improve t h e power f a c t o r o f In applying capacitors, consider t h e following:

2,5.10.1 t h e l o a d c a r r i e d by t h e c i r c u i t . a)

Fixed c a p a c i t a n c e . Fixed c a p a c i t a n c e i s t h e amount of c a p a c i t a n c e t h a t c a n be a p p l i e d c o n t i n u o u s l y w i t h o u t e x c e s s i v e v o l t a g e rise a t r e d u c e d load.

Switched c a p a c i t a n c e . Switched c a p a c i t a n c e i s a n a d d i t i o n a l amount o f c a p a c i t a n c e t h a t c a n be a p p l i e d , i f p r o v i s i o n i s made t o s w i t c h o f f t h i s a d d i t i o n a l amount a t r e d u c e d demand.

Capacitor switching. S e l e c t a t y p e of c a p a c i t o r s w i t c h i n g t h a t i s s u i t a b l e f o r t h e c o n d i t i o n a t hand. P o s s i b l e c h o i c e s i n c l u d e remote c o n t r o l of t h e c a p a c i t o r s w i t c h i n g d e v i c e , time-clock c o n t r o l , powerfactor relay control o r voltage-sensitive relay control.

2.5.10.2 L o c a t i o n of c a p a c i t o r s . I n s t a l l c a p a c i t o r s i n banks on p o l e s , a t ground l e v e l , o r i n a s u b s t a t i o n a s n e a r l y a s p o s s i b l e t o t h e c e n t r o i d of t h e a r e a where c o r r e c t i o n i s required. 2.5.11

Circuit interruption devices

2.5.11.1 F u s e s . A f t e r c o n s i d e r a t i o n of t h e n e c e s s a r y c u r r e n t - c a r r y i n g c a p a c i t i e s , i n t e r r u p t i n g d u t i e s , and t i m e - c u r r e n t m e l t i n g and c l e a r i n g c h a r a c t e r i s t i c s , s e l e c t f u s e s from t h e f o l l o w i n g t y p e s : a)

open f u s i b l e l i n k ;

expulsion type;

b o r i c - a c i d t y p e ; and

current-limiting

type.

2.5.11.2 C i r c u i t breakers. Co-ordinate t h e c i r c u i t breaker r a t i n g w i t h t h e load i n t e r r u p t i n g d u t y and w i t h c i r c u i t b r e a k e r s and f u s e s ahead of o r a f t e r t h e c i r c u i t breaker. 2.5.11.3 Automatic c i r c u i t r e c l o s e r s . Use of a u t o m a t i c r e c l o s e r s f o r o t h e r t h a n I f an a u t o o v e r h e a d l i n e l o a d s may c a u s e problems from h i g h - r e s i s t a n c e ground f a u l t s . m a t i c c i r c u i t r e c l o s e r i s u s e d , c o n s i d e r t h e r e l i a b i l i t y and c o n t i n u i t y r e q u i r e m e n t s of the service. R e c l o s e r s may c o n s i s t of a c i r c u i t - b r e a k e r o r m u l t i p l e s w i t c h i n g d e v i c e s . R e c l o s e r s o p e r a t e s o t h a t a f a u l t e d c i r c u i t may be opened and t h e n , e i t h e r i n s t a n t a n e o u s l y o r w i t h d e l i b e r a t e time d e l a y , reclosed. Up t o t h r e e r e c l o s u r e s w i t h v a r y i n g t i m e i n t e r v a l s may be u s e d . Co-ordinate automatic c i r c u i t r e c l o s e r s with f u s e s o r c i r c u i t b r e a k e r s on t h e same c i r c u i t . 2.5.11.4 S w i t c h e s . Use s w i t c h e s t o l o c a l i z e d e f e c t i v e p o r t i o n s of a e r i a l and underground c i r c u i t s and t o a c c o m p l i s h d e a d - c i r c u i t work. S e l e c t from one of t h e f o l l o w i n g p r i n c i p a l types:

Nonload-break

switches.

Use nonload-break s w i t c h e s o n l y f o r t h e i n t e r t c a r r y no a p p r e c i a b l e l o a d . S e l e c t t h e type a p p l i c a b l e , d e p e n d i n g on c i r c u i t i m p o r t a n c e , l o a d , v o l t a g e , a n d f a u l t c i r c u i t d u t y . The t y p e s a v a i l a b l e a r e p o r c e l a i n d i s c o n n e c t f u s e c u t o u t s , p l a i n o r f u s e d s i n g l e - p o l e a i r disconnect s w i t c h e s , and d i s c o n n e c t f u s e c u t o u t s of v a r i o u s t y p e s . D i s c o n n e c t i n g and horn-gap s w i t c h e s may a l s o be u s e d a s nonload-break s w i t c h e s ,

Load-break s w i t c h e s . b a d - b r e a k switches a r e provided w i t h a n i n t e r r u p t i n g d e v i c e capable of d i s c o n n e c t i n g c i r c u i t s under load. Fuse c u t o u t s , which a r e d e s i g n e d t o be l o a d - b r e a k and l o a d - i n t e r r u p t e r switches, are a v a i l a b l e . Vacuum s w i t c h e s a l s o p r o v i d e l o a d - b r e a k capability.

2.5.12.1 To d e t e r m i n e t h e r e q u i r e m e n t s f o r l i g h t n i n g p r o t e c t i o n , c o n s i d e r o v e r h e a d ground w i r e , open o r e x p u l s i o n g a p s , and d i s t r i b u t i o n - t y p e s u r g e ( l i g h t n i n g ) a r r e s t e r s . P r o t e c t i o n f o r l i g h t n i n g - i n d u c e d s u r g e s may be The w e a t h e r s h o u l d a l s o be c o n s i d e r e d . u n n e c e s s a r y i n a r e a s where a n n u a l l i g h t n i n g s t o r m s a r e few. A d m i n i s t r a t i v e p o l i c y o r l o c a l e l e c t r i c power company p r a c t i c e s h o u l d u s u a l l y be f o l l o w e d . Select t h e proper a r r e s t e r i n a c c o r d a n c e w i t h t h e c h o s e n b a s i c i m p u l s e i n s u l a t i o n l e v e l f o r which t h e c i r c u i t must be b u i l t . 2.5.13

Clearances

2.5.13.1 P r o v i d e t h e n e c e s s a r y h o r i z o n t a l and v e r t i c a l c l e a r a n c e s f r o m a d j a c e n t p h y s i c a l o b j e c t s , s u c h a s b u i l d i n g s , s t r u c t u r e s , and o t h e r e l e c t r i c l i n e s , a s r e q u i r e d by t h e a p p l i c a b l e e l e c t r i c a l s a f e t y code. Provide a g a i n s t contingency i n t e r f e r e n c e s , s u c h as b r o k e n p o l e s , b r o k e n c r o s s a r m s , and b r o k e n c i r c u i t c o n d u c t o r s . Provide f o r c l e a r a n c e c o n d i t i o n s a r i s i n g f r o m mu.ltipurpose j o i n t u s e of p o l e s . !%e t h e a p p l i c a b l e e l e c t r i c a l s a f e t y code f o r c l i m b i n g s p a c e c l e a r a n c e s , j o i n t u s e , and s u p p l y c o n d u c t o r protection. 2.5.14

Grounding

2.5.14.1 For i n f o r m a t i o n on g r o u n d i n g of o v e r h e a d d i s t r i b u t i o n s y s t e m s , u s e t h e For s a f e t y p r o v i d e grnunda p p l i c a b l e e l e c t r i c a l s a f e t y code o r A d m i n i s t r a t j v e p o l i c y . i n g f o r a l l equipment and s t r u c t u r e s a s s o c i a t e d w i t h e l e c t r i c a l s y s t e m s t o p r e v e n t s h o c k Maximum ground r e s i s t a n c e s h o u l d n o t e x c e e d v a l u e s f r o m s t a t i c o r dynamic v o l t a g e s . s p e c i f i e d i n t h e a p p l i c a b l e e l e c t r i c a l s a f e t y code. C o n s i d e r t h e s o u r c e of e l e c t r i c power, c a p a c i t y , magnitude of f a u l t c u r r e n t , and method of s y s t e m g r o u n d i n g , a s t h e y affect t h i s resistance. 2.5.14.2 Ground r o d s . Ground r o d s may be u s e d e i t h e r s i n g l y o r i n c l u s t e r s . Drive t h e ground r o d s t o ground w a t e r l e v e l f o r a n e f f e c t i v e and permanent i n s t a l l a t i o n . P r o v i d e f o r c o r r o s i o n p r e v e n t i o n by a p r o p e r c h o i c e of m e t a l s o r by c a t h o d i c p r o t e c t i o n . Where ground w a t e r c a n n o t be r e a c h e d , c h e m i c a l s s u c h a s magnesium s u l p h a t e (MgS04) o r c o p p e r s u l p h a t e (CuSO,+) may be u s e d t o improve s o i l c o n d u c t i v i t y where n e c e s s a r y . Manuf a c t u r e r s of ground r o d s c a n p r o v i d e d a t a on s u c h t r e a t m e n t . P r o v i d e f o r e a s y mainteAlthough d r i v i n g ground r o d s d e e p e r ( s e c t i o n a l t y p e ) may b e nance and p e r i o d i c t e s t i n g . more e f f e c t i v e t h a n m u l t i p l e r o d s , i n many c a s e s , s o i i v a r i a t i o n s and p o s s i b l e bedrock may make p r o v i s i o n of a d d i t i o n a l r o d s l e s s e x p e n s i v e .

2.5.14.3 A b u r i e d network of ground c o n d u c t o r s w i l l a s s u r e a n e f f e c t i v e s a f e t y ground i n p o o r s o i l and w i l l e l i m i n a t e l a r g e v o l t a g e g r a d i e n t s a t s u b s t a t i o n s f o r u t i l i t y aerodrome i n t e r c o n n e c t i o n s . Mesh s p a c i n g s of 3 t o 3.5 m e t r e s a r e commonly u s e d and u s u a l l y s u c h s p a c i n g s c a n c o n t r o l s u r f a c e v o l t a g e g r a d i e n t s even t h o u g h t h e ground r e s i s t a n c e may be r e l a t i v e l y h i g h . The e l e c t r i c a l s y s t e m may b e g r o u n d e d t o a w a t e r Water p i p e c o n n e c t i o n s . 2.5.14.4 s u p p l y s y s t e m e x c e p t where n o n m e t a l l i c p i p e s , c a t h o d i c a l l y p r o t e c t e d m e t a l l i c p i p e s , o r i n s u l a t i n g c o u p l i n g s a r e i n c o r p o r a t e d i n t h e w a t e r p i p e s y s t e m . The w a t e r p i p e connect i o n s h o u l d be supplemented by o t h e r g r o u n d i n g e l e c t r o d e s where r e q u i r e d by t h e a p p l i c a b l e e l e c t r i c a l s a f e t y code. 2.5.14.5 Combination of g r o u n d i n g methods. Where t h e ground r e s i s t a n c e i n a n e x i s t i n g s y s t e m i s h i g h , two o r more of t h e a f o r e m e n t i o n e d methods may be combined t o e f f e c t improvement. 2.5.14.6 Ground c o n n e c t i o n s . Wires r u n n i n g f r o m p r o t e c t i v e d e v i c e s ( f o r example, g a p s , g r a d i n g r i n g s , e x p u l s i o n o r p r o t e c t i o n t u b e s , and s u r g e a r r e s t e r s ) t o ground Where bends a r e n e c e s s a r y t h e y s h o u l d s h o u l d be k e p t a s s t r a i g h t and s h o r t a s p o s s i b l e . b e of l a r g e r a d i i t o k e e p t h e s u r g e impedance a s low a s p o s s i b l e . 2.5.14.7 Overhead ground w i r e s . Where o v e r h e a d ground w i r e s a r e u s e d f o r p r o t e c t i o n o f e l e c t r i c l i n e s , a ground c o n n e c t i o n s h o u l d be p r o v i d e d a t t h e b a s e of e a c h p o l e from t h e o v e r h e a d ground w i r e t o a w i r e l o o p o r a ground p l a t e o r t o a d r i v e n r o d , d e p e n d i n g on t h e e x i s t i n g s o i l c o n d i t i o n s . Use of w i r e wraps o r p o l e b u t t p l a t e s i s a l l o w e d o n l y i n a r e a s of v e r y low s o i l r e s i s t i v i t y . 2.5.14.8 Measurement of ground r e s i s t a n c e . resistance are:

Two methods of m e a s u r i n g g r o u n d

T h r e e - e l e c t r o d e method. I n t h e t h r e e - e l e c t r o d e method, two t e s t e l e c t r o d e s a r e u s e d t o measure r e s i s t a n c e of t h e t h i r d e l e c t r o d e , t h e ground p o i n t . A s e l f - c o n t a i n e d s o u r c e of a l t e r n a t i n g c u r r e n t and a b a t t e r y o p e r a t e d v i b r a t o r s o u r c e equipment p r o v i d i n g d i r e c t r e a d i n g s a r e a v a i l able.

F a l l - o f - p o t e n t i a l method. The f a l l - o f - p o t e n t i a l method i n v o l v e s a n ungrounded a l t e r n a t i n g c u r r e n t s o u r c e which c i r c u l a t e s a measured c u r r e n t t o ground. Voltage r e a d i n g s t a k e n , of t h e c o n n e c t i o n t o a u x i l i a r y g r o u n d s , a l l o w u s e of Ohm's law t o d e t e r m i n e t h e ground resistance.

Underground d i s t r i b u t i o n s y s t e m s 2.5.15.1 Primary power d i s t r i b u t i o n c i r c u i t s i n c e r t a i n a r e a s o n and n e a r aerodromes must be i n s t a l l e d underground. Although underground i n s t a l l a t i o n s c o s t more t h a n overhead s y s t e m s , r a d i o i n t e r f e r e n c e problems o r t h e p r o x i m i t y of t h e l i g h t i n g f a c i l i t i e s t o a r e a s of a i r c r a f t o p e r a t i o n s o f t e n r e q u i r e s t h e u s e of underground d i s t r i b u t i o n s y s t e m s . Underground c i r c u i t s may be i n s t a l l e d by d i r e c t b u r i a l o r by t h e p u l l - i n method ( p u l l i n g t h e cables through conduits). D i r e c t b u r i a l of d i s t r i b u t i o n c i r c u i t s i s u s u a l l y l e s s c o s t l y t h a n i n s t a l l a t i o n i n d u c t s ( p u l l i n method), b u t b e c a u s e of t h e p o o r e r p r o t e c t i o n , d i r e c t b u r i a l i s u s u a l l y u s e d o n l y f o r s m a l l l o a d s where r e i i a b i i i i y r e q u i r e m e n t s

a r e low. M e d i u m v o l t a g e d i r e c t b u r i a l c a b l e s h o u l d be p r o v i d e d w i t h a m e t a l armor c o v e r i n g o r s h i e l d f o r p r o t e c t i o n a g a i n s t m e c h a n i c a l i n j u r y . Where c o r r o s i o n r e s i s t a n c e i s i m p o r t a n t , armored c a b l e s may r e q u i r e a p l a s t i c o r s y n t h e t i c - r u b b e r j a c k e t o v e r t h e armor. The underground d i s t r i b u t i o n c i r c u i t s u s e d f o r aerodrome l i g h t i n g a n d r a d i o navigation f a c i l i t i e s a r e pull-in c i r c u i t s .

2.5.15.2 D e t a i l s of t h e i n s t a l l a t i o n of underground d i s t r i b u t i o n s y s t e m s a r e g i v e n i n C h a p t e r 4 , and c h a r a c t e r i s t i c s of c a b l e s u i t a b l e f o r underground s e r v i c e a r e g i v e n i n C h a p t e r 5.

EUeTRZGBL CIRCUITS FOR AEBO

3.1

3.1.1

L I G H T W m W I O WIGBTZON B I D S

TYPES OF ELECTRICAL CIRCUITS

Electrical characteristics

E l e c t r i c a l power f o r a e r o d r o m e l i g h t i n g a i d s i s a l m o s t e n t i r e l y a l t e r n a t i n g 3.1.1.1 current (ac). (Some c o n t r o l c i r c u i t s are d i r e c t c u r r e n t ( d c ) a n d e n e r g y f o r s t a r t i n g s e c o n d a r y power e n g i n e s o r f o r some u n i n t e r r u p t i b l e power s y s t e m s i s s t o r e d i n b a t t e r Both s e r i e s a n d p a r a l l e l ies.) T h i s a l t e r n a t i n g c u r r e n t i s u s u a l l y 50 t o 60 h e r t z . c i r c u i t s a r e u s e d i n t h e s e l i g h t i n g i n s t a l l a t i o n s . Most o f t h e a e r o d r o m e l i g h t s a r e e n e r g i z e d by s e r i e s c i r c u i t s , b u t t h e i n c o m i n g power i s d i s t r i b u t e d by p a r a l l e l circ u i t s , a n d some s i n g l e u n i t s o r s h o r t e r c i r c u i t s o f l i g h t s may b e e n e r g i z e d by p a r a l l e l circuits. S e q u e n c e - f l a s h i n g l i g h t s o f a p p r o a c h l i g h t i n g s y s t e m s , some f l o o d l i g h t s , a n d some o b s t a c l e l i g h t s a r e t h e more i m p o r t a n t l i g h t i n g s y s t e m s u s i n g p a r a l l e l c i r c u i t s . 3.1.2

Series c i r c u i t s

3.1.2.1 The c i r c u i t e l e m e n t s o f s e r i e s c i r c u i t s a r e c o n n e c t e d i n a s t r i n g w i t h t h e same c u r r e n t f l o w i n g i n e a c h e l e m e n t . The c i r c u i t i s o n e c o n t i n u o u s l o o p s t a r t i n g a n d e n d i n g a t t h e i n p u t power s o u r c e . I f a f i x e d i n p u t v o l t a g e were c o n n e c t e d t o t h e l o a d , t h e c u r r e n t i n t h e c i r c u i t would v a r y w i t h t h e c o n n e c t e d l o a d ; however, c o n s t a n t - c u r r e n t r e g u l a t o r s w i l l maintain a constant c u r r e n t independent of t h e load on t h e c i r c u i t . Thus t h e same c u r r e n t w i l l f l o w i n a l o n g c i r c u i t a s i n a s h o r t e r c i r c u i t a n d w i l l r e m a i n t h e same e v e n i f some o f t h e lamps f a i l . T h i s c o n s t a n t c u r r e n t means t h a t a s h o r t - c i r c u i t a c r o s s t h e o u t p u t of a c o n s t a n t - c u r r e n t r e g u l a t o r i s a no-load c o n d i t i o n and a n open-circuit i s an overload. I n a s i m p l e d i r e c t - c o n n e c t e d series c i r c u i t , a lamp f a i l u r e c a u s e s a n o p e n - c i r u i t ; h e n c e , i t i t n e c e s s a r y t o p r o v i d e a by-pass d e v i c e , s u c h as a f u s e d f i l m c u t o u t o r a n i s o l a t i n g t r a n s f o r m e r , as p a r t o f e a c h l i g h t i n g f i x t u r e . I s o l a t i n g t r a n s f o r m e r s a r e p r e f e r r e d f o r aerodrome l i g h t i n g c i r c u i t s . 3.1.2.2 c i r c u i t s f o r aerodrome l i g h t i n g a r e :

Some o f t h e a d v a n t a g e s o f s e r i e s

a l l lamps a r e o p e r a t i n g a t t h e same c u r r e n t a n d t h u s a t t h e same i n t e n s i t y . T h i s u n i f o r m i n t e n s i t y a n d a p p e a r a n c e o f t h e l a m p s are h e l p f u l ;

a single-conductor c a b l e of one conductor s i z e and i n s u l a t i o n v o l t a g e r a t i n g can be used throughout the c i r c u i t ;

i n t e n s i t y c o n t r o l of t h e l i g h t s can be o b t a i n e d o v e r a wide r a n g e ;

t h e c i r c u i t may h a v e a s i n g l e g r o u n d f a u l t a t a n y p o i n t a l o n g t h e c i r c u i t without a f f e c t i n g t h e o p e r a t i o n of t h e l i g h t s ; and

ground f a u l t s a r e e a s y t o l o c a t e .

3,1.2.3 Disadvantages of s e r i e s l i g h t i n g c i r c u i t s . s e r i e s c i r c u i t s when u s e d f o r l i g h t i n g a r e :

The m a j o r d i s a d v a n t a g e s o f

3.1.3

i n s t a l l a t i o n c o s t s a r e h i g h - t h e c o n s t a n t - c u r r e n t r e g u l a t o r and t h e i s o l a t i n g t r a n s f o r m e r s o r by-pass d e v i c e s add a p p r e c i a b l y t o t h i s c o s t ;

poor e f f i c i e n c y , p r i m a r i l y of t h e moving-coil t y p e c o n s t a n t - c u r r e n t r e g u l a t o r , i n u s e of e l e c t r i c a l power;

a l l components - c a b l e , i s o l a t i n g t r a n s f o r m e r s and lamp s o c k e t s - must be i n s u l a t e d f o r f u l l v o l t a g e i f i s o l a t i n g t r a n s f o r m e r s a r e n o t u s e d ;

a n o p e n - - c i r c u i t f a u l t anywhere i n t h e c i r c u i t makes t h e e n t i r e c i r c u i t i n o p e r a t i v e and p o s s i b l y may damage t h e c a b l e i n s u l a t i o n o r t h e c o n s t a n t - c u r r e n t r e g u l a t o r ; and

l o c a t i o n of f a u l t s , e s p e c i a l l y o p e n - c i r c u i t f a u l t s , may b e d i f f i c u l t .

Parallel circuits

3.1.3.1 The c i r c u i t e l e m e n t s of p a r a l l e l ( m u l t i p l e ) c i r c u i t s a r e c o n n e c t e d i n p a r a l l e l a c r o s s t h e c o n d u c t o r s t o which t h e i n p u t v o l t a g e i s a p p l i e d . In theory the same v o l t a g e i s a p p l i e d t o e a c h l i g h t ; however, t h e c u r r e n t t h r o u g h t h e c o n d u c t o r s c a u s e s a d e c r e a s e i n v o l t a g e ( l i n e d r o p ) which f o r l o n g e r c i r c u i t s may r e d u c e a p p r e c i a b l y t h e v o l t a g e t o , and c o n s e q u e n t l y t h e i n t e n s i t y o f , t h e l i g h t s a t t h e f a r e n d of t h e circuit. In d i s t r i b u t i o n c i r c u i t s where t h e v o l t a g e may be h i g h and t h e c u r r e n t low, t h e v o l t a g e d r o p i n t h e l i n e s i s l e s s i m p o r t a n t , and p a r a l l e l c i r c u i t s a r e o f t e n u s e d f o r such c i r c u i t s . If i n t e n s i t y c o n t r o l of t h e l i g h t s i s required, tapped transformers of i n d u c t i o n - v o l t a g e r e g u l a t o r s may be u s e d , b u t t h e s e i n c r e a s e t h e c o s t of t h e i n s t a l l a t i o n and r e d u c e t h e e f f i c i e n c y of t h e c i r c u i t . 3.1.3.2 p a r a l l e l c i r c u i t s f o r aerodrome l i g h t i n g a r e :

Some of t h e a d v a n t a g e s o f

l o w e r c o s t of t h e i n s t a l l a t i o n , e s p e c i a l l y i f v ~ l t a g er e g u l a t i o n a n d i n t e n s i t y c o n t r o l a r e not required;

more e f f i c i e n t u t i l i z a t i o n of e l e c t r i c a l power;

e a s y t o add t o o r r e d u c e a n e x i s t i n g c i r c u i t ;

t h e c i r c u i t s a r e more f a m i l i a r t o most p e o p l e ;

cable f a u l t s , especi.ally open-circuit

an open-circuit

t h e s e c i r c u i t s do n o t need b y - p a s s d e v i c e s and may n o t need i s o l a t i n g transformers.

f a u l t s , may be e a s i e r t o l o c a t e ;

may n o t d i s a b l e t h e e n t i r e c i r c u i t ; a n d

3.1.3.3 D i s a d v a n t a g e s of p a r a l l e l l i g h t i n g c i r c u i t s . a g e s of p a r a l l e l c i r c u i t s f o r aerodrome l i g h t i n g a r e : a)

Some of t h e m a j o r d i s a d v a n t -

t h e i n t e n s i t y of t h e l i g h t s d e c r e a s e s w i t h l i n e d r o p a l o n g t h e c i r c u i t . T h i s may be m i s i n t e r p r e t e d i f i t i s n o t i c e a b l e i n a p a t t e r n o f l i g h t s ;

two c o n d u c t o r s a r e r e q u i r e d a l o n g t h e c o m p l e t e c i r c u i t , a n d l a r g e r c o n d u c t o r s may be needed t o r e d u c e t h e l i n e v o l t a g e d r o p ;

lamp f i l a m e n t s a r e u s u a l l y l o n g e r which may r e q u i r e l a r g e r o p t i c s a n d larger l i g h t Eixtures;

i n t e n s i t y c o n t r o l , e s p e c i a l l y a t t h e l o w e r i n t e n s i t i e s , i s more d i f f i c u l t t o f u r n i s h a c c u r a t e l y , o r t h e equipment c o s t a d d s a p p r e c i a b l y t o t h e i n s t a l l a t i o n cos t ;

a s i n g l e ground f a u l t on t h e h i g h - v o l t a g e f e e d e r w i l l d i s a b l e t h e c i r c u i t s ; and

ground f a u l t s a r e d i f f i c u l t t o l o c a t e .

Comparison of s e r i e s and p a r a l l e l l i g h t i n g c i r c u i t s 3.1.4.1 Often a c c e p t a b l e l i g h t i n g can be p r o v i d e d by e i t h e r s e r i e s o r p a r a l l e l circuits. S e r i e s c i r c u i t s a r e u s u a l l y u s e d f o r aerodrome l i g h t i n g s y s t e m s where t h e p a t t e r n p r o v i d e s g u i d a n c e i n f o r m a t i o n b e c a u s e of t h e more u n i f o r m i n t e n s i t y of t h e l i g h t s and b e t t e r i n t e n s i t y c o n t r o l . Such s y s t e m s i n c l u d e most runway and t a x i w a y l i g h t s and most s t e a d y - b u r n i n g l i g h t s o f a p p r o a c h l i g h t i n g s y s t e m s . Parallel circuits a r e u s e d f o r most a r e a i l l u m i n a t i o n , i n d i v i d u a l o r s m a l l numbers of v i s u a l a i d s , and power d i s t r i b u t i o n . Aerodrome l i g h t i n g s y s t e m s u s u a l l y u s i n g p a r a l l e l c i r c u i t s a r e apron f l o o d l i g h t i n g , o t h e r apron l i g h t s , sequence-flashing l i g h t s , s p e c i a l purpose v i s u a l a i d s s u c h a s beacons and wind d i r e c t i o n i n d i c a t o r s , some o b s t a c l e l i g h t s and electrical distribution circuits.

3.2

S E R I E S CIRCUITRY FOR AERODROME LIGHTING

F a c t o r s t o be c o n s i d e r e d 3.2.1.1 If a s e r i e s c i r c u i t i s t o be u s e d , c e r t a i n o p t i o n s on t h e equipment t o b e u s e d s h o u l d be e v a l u a t e d . O f t e n when one c h o i c e i s made i t r e d u c e s t h e o p t i o n s of o t h e r F i r s t , t h e c o m p l e t e c i r c u i t s h o u l d be a n a l y s e d f o r c r i t i c a l p e r f o r m a n c e , equipment. r e l i a b i l i t y , economy of i n s t a l l a t i o n s and o p e r a t i o n s , e a s e of m a i n t e n a n c e , and how t h e s e v e r a l t y p e s of equipment a r e i n t e r r e l a t e d . Some o p t i o n a l f a c t o r s a r e t h e f o l l o w i n g items. 3.2.1.2 Choice of c u r r e n t . Equipment development h a s l i m i t e d t h e a v a i l a b l e o p t i o n s of c u r r e n t t o be used i n a p a r t i c u l a r s e r i e s c i r c u i t . Most aerodrome l i g h t i n g s e r i e s c i r c u i t s a r e e i t h e r 6.6 o r 20 amperes a t r a t e d f u l l i n t e n s i t y , a l t h o u g h o t h e r c u r r e n t s a r e sometimes used. The l i n e power l o s s f o r a f i x e d c a b l e c o n d u c t o r and l e n g t h f o r 6.6 ampere c i r c u i t s i s a b o u t o n e n i n t h t h a t f o r 2 0 ampere c i r c u i t s . E i t h e r v a l u e of c u r r e n t can be c a r r i e d i n 5 000 v o l t i n s u l a t i o n c a b l e by c o n d u c t o r s of 4 mm d i a m e t e r w i t h o u t e x c e s s i v e t e m p e r a t u r e r i s e . The l o a d on t h e r e g u l a t o r of s e r i e s c i r c u i t s , s h o u l d be a t 6.6 ampere c i r c u i t s a r e commonly u s e d f o r l o n g l e a s t one-half of i t s r a t e d c a p a c i t y . c i r c u i t s w i t h s m a l l e r e l e c t r i c a l l o a d s , and 20 a a p e r e c i r c u i t s a r e u s e d f o r l a r g e r l o a d s for regulator capacities.) Runway edge and s h o r t e r c a b l e l e n g t h s ( s e e p a r a g r a p h 3.2.1.4 l i g h t s and taxiway edge l i g h t s a r e u s u a l l y 6,6 aolpere c i r c u i t s , and a p p r o a c h l i g h t s and rouchdown zone l i g h t s a r e o f t e n 20 ampere c i r c u i t s , Kunway c e n t r e l i n e a n d t a x i w a y c e n t r e l i n e l i g h t s may be e x t h e r 6.6 a n p e r e o r 20 ampere c i r c u i ~ s , Koce t h a t &he c l r -

c u i t c u r r e n t i s n o t n e c e s s a r i l y d e t e r m i n e d by t h e c u r r e n t of t h e lamps i n t h e f i x t u r e s . F o r example by s e l e c t i n g t h e i s o l a t i n g t r a n s f o r m e r s p r o p e r l y , 6.6 ampere lamps can be u s e d on 20 ampere c i r c u i t s and 20 ampere lamps on 6.6 ampere c i r c u i t s o r c o m b i n a t i o n s of lamp c u r r e n t s can be used on e i t h e r c i r c u i t . The p r e f e r r e d a r r a n g e m e n t f o r a e r o d r o m e l i g h t 3.2.1.3 i n g c i r c u i t s i s a number of h i g h v o l t a g e s e r i e s c i r c u i t l o o p s w i t h a s e r i e s i s o l a t i n g t r a n s f o r m e r f o r e a c h f i t t i n g , and e a c h c i r c u i t f e d f r o m a n e l e c t r i c a l s u p p l y s u b s t a t i o n a d j a c e n t t o t h e runway end. One s u b s t a t i o n p e r runway end i s p r e f e r r e d f o r a l l a e r o dromes. a)

8.2 of Annex 1 4 s p e c i f i e s t h a t f o r a p r e c i s i o n a p p r o a c h runway t h e e l e c t r i c a l c i r c u i t s be d e s i g n e d s o t h a t t h e f a i l u r e of one c i r c u i t w i l l n o t l e a v e t h e p i l o t w i t h o u t v i s u a l g u i d a n c e and w i l l n o t r e s u l t i n a misleading pattern.

Every a p p r o a c h a n d runway l i g h t i n g s y s t e m s h o u l d be i n t e r l e a v e d o v e r a t l e a s t two c i r c u i t s . Examples of c i r c u i t i n t e r l e a v i n g t o improve i n t e g r i t y a r e shown i n F i g u r e s 3-1 t o 3-7. Each c i r c u i t i n a n i n t e r l e a v e d s e r v i c e s h o u l d e x t e n d t h r o u g h o u t t h e whole of t h a t s e r v i c e and be s o a r r a n g e d t h a t a b a l a n c e d s y m m e t r i c a l l i g h t i n g p a t t e r n r e m a j n s i n t h e e v e n t of f a i l u r e of o n e o r more of t h e c i r c u i t s . T h r e s h o l d l i g h t s a r e u s u a l l y on s e p a r a t e c i r c u i t s . Runway c e n t r e l i n e l i g h t s must be i n t e r l e a v e d i n a way t h a t w i l l n o t d e s t r o y t h e c o l o u r c o d i n g of t h e s e l i g h t s . S e c t i o n s of t h e c e n t r e l i n e s y s t e m c o n s i s t i n g of w h i t e l i g h t s o n l y and of r e d l i g h t s o n l y may be i n t e r Annex 1 4 r e q u i r e s t h e c e n t r e l i n e l e a v e d a s shown on F i g u r e 3-5a. l i g h t s i n t h e s e c t i o n of t h e runway from t h e p o i n t 900 m f r o m t h e runway end ( o r f r o m t h e m i d p o i n t of t h e runway f o r runways l e s s t h a n 1 800 m i n l e n g t h ) t o t h e p o i n t 300 m from t h e runway end b e a l t e r n a t e l y v a r i a b l e w h i t e and r e d l i g h t s e x c e p t t h a t f o r runway c e n t r e l i n e l i g h t s s p a c e d a t 7.5 n a l t e r n a t e p a i r of v a r i a b l e w h i t e and r e d l i g h t s a r e r e q u i r e d . Examples of c i r c u i t i n t e r l e a v i n g which w i l l m a i n t a i n t h e r e q u i r e d c o l o u r c o d i n g a r e shown i n F i g u r e s 3-5b and 3-5c. When one c i r c u i t f a i l s where t h e p a t t e r n of l i g h t s and i n t e r l e a v i n g a r e a s shown i n F i g u r e 3-5c, a p a t t e r n of a l t e r n a t i n g r e d and w h i t e l i g h t s u n i f o r m l y s p a c e d a t t w i c e t h e normal i n t e r v a l w i l l show. T h i s s p a c i n g i s t h e same a s t h a t of t h e a l l w h i t e and a l l r e d s e c t i o n s when one c i r c u i t f a i l s . With t h e p a t t e r n of l i g h t s and i n t e r l e a v i n g shown i n F i g u r e 3-5b, t h e s p a c i n g would be a l t e r n a t e l y t h r e e t i m e s t h e normal i n t e r v a l and t h e n t h e n o r m a l interval.

Visual approach s l o p e i n d i c a t o r systems. Visual approach s l o p e i n d i c a t o r s y s t e m s s h o u l d have two c i r c u i t s p e r runway end. When a v i s u a l approach s l o p e i n d i c a t o r s y s t e m i s a VASIS, 3-BAR VASIS, o r T-VASIS, power t o a l l l i g h t u n i t s on one s i d e of t h e runway s h o u l d be s u p p l i e d by t h e same c i r c u i t . This arrangement e n s u r e s t h a t should one c i r c u i t f a i l a complete p a t t e r n w i l l be r e t a i n e d on t h e o t h e r s i d e of t h e runway. When a p p r o a c h s l o p e i n d i c a t o r s a r e i n s t a l l e d on o n l y one s i d e of t h e runway a s w i t h t h e PAPI, t h e AVASIS, t h e 3-BAR AVASIS, and t h e AT-VASIS, p a r t of t h e lamps i n e a c h L i g h t u n i t s h o u l d be c o n n e c t e d t o o n e c i r c u i t and t h e r e m a i n d e r t o t h e o t h e r c i r c u i t i n o r d e r t o m a i n t a i n t h e Visual approach i n t e g r i t y of t h e p a t t e r n , b u t w i t h r e d u c e d i n t e n s i t y . s l o p e i n d i c a t o i s y s t e m s s h o u l d be d e e n e r g i z e d when a m i s l e a d i n g s i g n a l r e s u l t s from r h e f a i l u r e of a L i g h t u n i t .

Taxiway l i g h t i n g s h o u l d be d e s i g n e d f o r s e r i e s circuits. Taxiway c e n t r e l i n e l i g h t i n g c i r c u i t s s h o u l d b e i n t e r l e a v e d a s shown i n F i g u r e 3-5a on t h o s e p a r t s of t h e t a x i w a y s y s t e m t h a t a r e u s e d i n C a t e g o r y 111 c o n d i t i o n s , b u t f o r economic r e a s o n s a s i n g l e Taxiway l i g h t i n g s h o u l d be c i r c u i t may b e u s e d f o r o t h e r t a x i w a y s . c i r c u i t e d t o p e r m i t s e l e c t i v e l i g h t i n g of segments of t h e s y s t e m t o This c a p a b i l i t y may be o b t a i n e d by provide r o u t e guidance t o p i l o t s . u s i n g a n i n d i v i d u a l c o n s t a n t - c u r r e n t r e g u l a t o r f o r e a c h segment o r by c o n n e c t i n g s e v e r a l segments t o a s i n g l e r e g u l a t o r and u s i n g s e l e c t o r relays, e i t h e r i n the f i e l d o r a t the regulator, t o short-circuit those segments which a r e n o t p a r t of t h e r o u t e . Note t h a t t h e v o l t a g e r a t i n g of t h e s e l e c t o r r e l a y s must be h i g h e r t h a n t h e o p e n - c i r c u i t v o l t a g e of S e l e c t i v e s w i t c h i n g may be o b t a i n e d i n s e v e r a l ways. the regulator. Among t h e s e a r e :

t h e u s e of a c o n t r o l s w i t c h f o r e a c h segment. The p r e f e r r e d l o c a t i o n of s u c h s w i t c h e s i s on a f a c s i m i l e d i a g r a m on t h e c o n t r o l p a n e l i n t h e c o n t r o l tower w i t h e a c h s w i t c h l o c a t e d on t h e segment which i t c o n t r o l s ;

i n t e r c o n n e c t i n g t h e c o n t r o l s which e n e r g i z e t h e r e g u l a t o r s o r s e l e c t o r r e l a y so t h a t actuating a single switch w i l l cause a l l segments on a d e s i g n a t e d r o u t e t o be l i g h t e d ; and

u s i n g a minicomputer programmed t o l i g h t t h e optimum r o u t e a f t e r t h e o p e r a t o r d e s i g n a t e s t h e runway e x i t t o be used and t h e d e s t i n a t i o n of t h e a i r c r a f t .

Stop b a r s . Stop b a r s must be c o n t r o l l e d i n d e p e n d e n t l y of e a c h o t h e r a n d of t h e t a x i w a y l i g h t s . The e l e c t r i c a l c i r c u i t s s h o u l d be d e s i g n e d s o t h a t a l l of t h e l i g h t s of a s t o p b a r w i l l n o t f a i l a t t h e same t i m e . The l i g h t s of a s t o p b a r s h o u l d be i n t e r l e a v e d . They may be s u p p l i e d by two s e p a r a t e c i r c u i t s o r f r o m two common c i r c u i t s w i t h c o n t r o l r e l a y s l o c a t e d a d j a c e n t t o t h e s t o p bar. S t o p b a r s may be c o n n e c t e d i n t o i n t e r l e a v e d runway o r t a x i w a y l i g h t i n g s y s t e m s w i t h e a c h s t o p b a r c o n t r o l l e d by r e l a y s which s h o r t - c i r c u i t t h e l i g h t s of t h e s t o p b a r when i t i s desired t o deenergize t h e bar. In o r d e r t o reduce t h e v o l t a g e r e q u i r e m e n t s of t h e s e r e l a y s , l i g h t s of t h e s t o p b a r s h o u l d be c o n n e c t e d i n t o a runway o r t a x i w a y l i g h t i n g c i r c u i t t h r o u g h a n i s o l a t i n g t r a n s f o r m e r of s u i t a b l e c a p a c i t y w i t h t h e s h o r t - c i r c u i t i n g r e l a y c o n n e c t e d a c r o s s t h e s e c o n d a r y of t h e i s o l a t i n g t r a n s f o r m e r . The a p p l i c a b l e runway o r t a x i w a y l i g h t i n g c i r c u i t must be e n e r g i z e d whenever t h e u s e of a s t o p b a r i s r e q u i r e d . The r e l a y s c o n t r o l l i n g a s t o p b a r must be s o c o n n e c t e d t h a t t h e a p p l i c a t i o n o f c o n t r o l power i s r e q u i r e d t o t u r n t h e s t o p b a r o f f . Thus t h e s t o p b a r w i l l be l i g h t e d i f t h e c o n t r o l c i r c u i t should f a i l .

Grounding, A l l t h e equipment i n t h e c o n t r o l / d i s t r i b u t i o n c e n t r e s h o u l d be bonded t o e a r t h . A ground w i r e ( c o u n t e r p o i s e ) s h o u l d a l s o be r u n The from t h e d i s t r i b u t i o n c e n t r e s w i t h t h e s e r i e s c i r c u i t c a b l e s . s e c o n d a r y s i d e of a l l i s o l a t i n g t r a n s f o r m e r s and t h e s u p p o r t s of a l l e l e v a t e d l i g h t s should be connected t o t h i s w i r e . The g r o u n d w i r e s h o u l d be p o s i t i o n e d above t h e c i r c u i t c a b l e s i n a c o n d u i t nearer t h e s u r f a c e o r i n t h e same r r e n c l ~n o r l e s s t h a n 10 c m above t h e cop, cable.. U s u a l l y u n i n s u l a t e d c o n d u c t o r s a r e used a s ground w i r e s .

0 CIRCUIT 1 Q) CIRCUIT 2

0 CIRCUIT 3 @ CIRCUIT 4

F i g u r e 3-2, Supplementary l i g h t i n g t o expand a p r e c i s i o n a p p r o a c h b i g h t i n g s y s t e m t y p e A ( s y s t e m wPth d i s t a n c e coded c e n t r e l i n e ) t o a p r e c i s i o n approach c a t e g o r y I1 and 111 l i g h t i n g s y s t e m

5-3 0

Aerodrome Design Manual

RUNWAY THRESHOLD

CIliChiiT i

0 CIRCUIT 2

OPTION A.

r ' l g u r e 3-3.

I N T E R L E A V I N G BY ALTERNATING BARRETTES

P r e c i s i o n approach lighting s y s t e m t y p e B (system with b a r r e t t e c e n t r e l i n e )

0 CIRCUIT 1 6 CIRCUIT 2

OPTION B.

F i g u r e 3-3,

INTERLEAVING BY ALTERNATING LIGHTS IN EACH BARRETTE TO FROVIDE S I M I M R APPEARANCE IN EITH SINGLE-CIRCUIT OPERATION Precision approach l i g h t i n g system type B (system w i t h b a r r e t t e c e n t r e l i n e )

RUNWAY THRESHOLD

0 CIRCUIT 1. $ CIRCUIT 2

OPTION C .

F i g u r e 3-3.

INTERLEAVING BY ALTERNATING LIGHTS I N EACH BARRETTE WITH ALL STATION ALIKE I N ANY OPERATING C I R C U I T MODE

P r e c i s i o n a p p r o a c h iighting s y s t e m t y p e B ( s y s t e m w i i h b a r r e t c e c e n t r e iinej

RUNWAY THRESHOLD

e..

Q CIRCUIT 1

PART OF CENTRE LlNE LIGHTS OF PRECISION APPROACI-I LIGHTING SYSTEM TYPE B

0 CIRCUIT l

PART OF CENTRE LlNE LIGHTS OF PRECISION APPROACH LIGHTING SYSTEM TYPE B

@ CIRCUIT 2

CIRCUIT 2 OPTION A. INTERLEAVING BY ALTERNATlNG BARRETTES

OPTION B. INTERLEAVING BY ALTERNATING LIGHTS IN EACH BARRETTE TO PROVIDE SIMILAR APPEARANCE FOR EITHER SINGLE-CIRCUIT OPERATION

Figure 3-4. Supplementary lighting to expand a precision approach lighting system type B (system with barrette centre line) to a precision approach category 11 and I11 lighting system (Supplementary lighting for a system with distance coded centre line is shown in Figure 3-2.)

WHITE L I G H T CIRCUIT 1 CIRCUIT 2 CIRCUIT l

INTERLEAVING I N S E C T I O N S C O N S I S T I N G O F ALTERNATING RED AND WHITE L I G H T S FOR L I G H T S P A C I N G S O F 15 AND 30 METERS

0 WHITE L I G H T C I R C U I T I. @

'WfiITE EIZHT CIRCUIT 2 CIRCUIT l

INTERLEAVING I N S E C T I O N S I N WHICH ALL L I G H T S ARE O F T H E SAME COLOUR

Figure 3-5.

INTERLEAVING I N S E C T I O N S C O N S I S T I N G O F ALTERNATE TWO RED AND TWO WHITE L I G H T S FOR L I G H T S P A C I N G S O F 7.5 METERS

Runway or taxiway centre L ~ n eirghting on two interleaved circuits

Part 5, - Electrical Svstems

5-35

0 CIRCUIT 1 @ CIRCUIT 2

F i g u r e 3-6.

Runway edge Lights on two ~ n t e r l e a v e dseries circuits

RUNWAY

NOTE: When used i n c o n j u n c t i o n w i t h Type A p r e c i s i o n approach l i g h t i n g sys terns each barrette shaul d have four lights . F kb~ u r e3-7,

Touchdown zone L i g h t s o i l t w ~ interleavecj series c i r c u i t s

The e l e c t r i c a l power f o r most aerodrome ground 3.2.1.4 These l i g h t i n g c i r c u i t s i s s u p p l i e d by c o n s t a n t - c u r r e n t ( s e r i e s c i r c u i t ) r e g u l a t o r s . r e g u l a t o r s a r e designed t o produce a constant-current o u t p u t independent of v a r i a t i o n s i n t h e c i r c u i t l o a d and i n t h e v o l t a g e of t h e power s o u r c e . They a r e a l s o d e s i g n e d t o Some t y p e s p r o v i d e two o r more o u t p u t c u r r e n t s when dimming of t h e l i g h t s i s r e q u i r e d . of c o n s t a n t - c u r r e n t r e g u l a t o r s u s e d f o r aerodrome l i g h t i n g a r e a s f o l l o w s . a)

Moving c o i l r e g u l a t o r s h a v e been u s e d f o r many Moving c o i l r e g u l a t o r s . y e a r s t o s u p p l y power t o s e r i e s l i g h t i n g c i r c u i t s . T h i s t y p e r e g u l a t o r h a s s e p a r a t e p r i m a r y and s e c o n d a r y c o i l s which a r e f r e e t o move w i t h r e s p e c t t o e a c h o t h e r , t h u s v a r y i n g t h e m a g n e t i c l e a k a g e r e a c t a n c e of t h e i n p u t and o u t p u t c i r c u i t s . This r e a c t a n c e a u t o m a t i c a l l y a d j u s t s i t s e l f t o a v a l u e which, when added t o t h e l o a d impedance, p e r m i t s a c o n s t a n t c u r r e n t t o f l o w . The d e s i r e d o u t p u t c u r r e n t s e t s up a f o r c e o f r e p u l s i o n which f l o a t s t h e moving c o i l i n t h e p o s i t i o n which p r o d u c e s t h i s c u r r e n t . A s t a t e of m e c h a n i c a l e q u i l i b r i u m i s a t t a i n e d s u c h t h a t t h e f o r c e of r e p u l s i o n e x a c t l y b a l a n c e s t h e w e i g h t of t h e moving c o i l . Any change i n l o a d o r i n p u t v o l t a g e i s i m m e d i a t e l y c o u n t e r a c t e d by a movement of t h e f l o a t i n g c o i l t o r e s t o r e t h e m e c h a n i c a l e l e c t r i c a l balance. I n t e n s i t y c o n t r o l i s o b t a i n e d t h r o u g h t h e u s e of a t a p p e d t r a n s f o r m e r a c r o s s t h e o u t p u t of t h e r e g u l a t o r . The main d i s a d v a n t a g e s of moving c o i l r e g u l a t o r s a r e t h e m e c h a n i c a l movement of t h e c o i l s a n d t h e low power f a c t o r s f o r l o a d s l e s s t h a n r a t e d l o a d . F o r a l o a d of 50 p e r c e n t of t h e r a t e d l o a d , t h e power f a c t o r may be 75 p e r c e n t o r l e s s . I n a d d i t i o n some moving c o i l r e g u l a t o r s must be p r e c i s e l y l e v e l l e d and i s o l a t e d from v i b r a t i o n .

Monocyclic s q u a r e r e g u l a t o r s . One s t a t i c t y p e (no moving p a r t s ) c o n s t a n t - c u r r e n t r e g u l a t o r f o r s e r i e s c i r c u i t s i s t h e monocyclic square regulator. The c u r r e n t r e g u l a t i n g n e t w o r k u s u a l l y c o n s i s t s of two i n d u c t i v e and two c o n d e n s i v e r e a c t o r s , e a c h of e q u a l r e a c t a n c e ( r e s o n a n c e ) a t t h e power f r e q u e n c y , a r r a n g e d i n a b r i d g e t y p e c i r c u i t . With s u c h a network, t h e s e c o n d a r y c u r r e n t i s i n d e p e n d e n t of t h e impeda n c e of t h e l o a d . I n t e n s i t y c o n t r o l c a n b e p r o v i d e d by a t a p p e d i n p u t o r o u t p u t t r a n s f o r m e r o r by c o n t i n u o u s l y v a r i a b l e i n p u t t r a n s f o r m e r . The a d v a n t a g e s o f t h i s t y p e of r e g u l a t o r a r e no moving p a r t s and h i g h power f a c t o r . The d i s a d v a n t a g e s a r e l a c k of compensation f o r v a r i a t i o n s i n i n p u t v o l t a g e and a d v e r s e e f f e c t s on t h e r e g u l a t i o n c a u s e d by l o a d s which c a u s e h i g h harmonic f r e q u e n c i e s i n t h e r e s o n a n t c i r c u i t , s u c h a s o p e n - c i r c u i t e d s e c o n d a r i e s of s e r i e s i s o l a t i n g t r a n s f o r m e r s and g a s e o u s v a p o u r lamps.

By s e n s i n g t h e s e c o n d a r y c u r r e n t Compensation s t a t i c - t y p e r e g u l a t o r s . f r o m t h e r e g u l a t o r , a d j u s t m e n t may be made i n t h e m o n o c y c l i c s q u a r e o r i n t h e c u r r e n t - r e g u l a t i n g network t o compensate f o r p r i m a r y v o l t a g e v a r i a t i o n s and f o r harmonic f r e q u e n c i e s c a u s e d by o p e n - c i r c u i t e d seconda r i e s of i s o l a t i n g t r a n s f o r m e r s . T h i s compensation p r o v i d e s improved current r e g u l a t i o n and p r e v e n t s s h o r t e n i n g of lamp l i f e f r o m above r a t e d secondary current.

Solid s t a t e c o n t r c l constant-current regulators. These r e g u l a t o r s u s e a c s o l i d s t a t e c i r c u i t s f o r c o n t r o l l i n g t h e transformer leakage reactance. T h i s t e c h n i q u e p e r m i t s t h e u s e of low c o n t r o l l e v e l s t o o b t a i n c o n s t a n t c u r r e n t f r o m r e g u l a t o r s w i t h t h e e l e c t r i c a l c h a r a c t e r i s t i c s of

c o n s t a n t v o l t a g e , s e r i e s - r e s o n a n t c i r c u i t s . These s o l i d s t a t e c o n t r o l s p r o v i d e f a s t r e s p o n s e , h i g h power f a c t o r , compact r e g u l a t o r s w i t h e a s y m a i n t e n a n c e of t h e r e g u l a t o r c o n t r o l s . 3.2.1.5 Constant-current r e g u l a t o r s s u p p l y i n g power t o aerodrome l i g h t i n g c i r c u i t s s h o u l d h a v e t h e f o l l o w i n g capabilities: a)

maintain a constant-current o u t p u t w i t h i n k 2 p e r c e n t f o r any load from one-half t o f u l l l o a d w i t h up t o 30 p e r c e n t of i s o l a t i n g t r a n s f o r m e r s having open-circui t s e c o n d a r i eS;

i n d i c a t e a g r o u n d i n g f a u l t on t h e c i r c u t t w h i l e p e r m i t t i n g t h e c i r c u i t t o o p e r a t e n o r m a l l y when a s i n g l e ground f a u l t p r e v a i l s ;

h a v e a h i g h d e g r e e of r e l i a b i l i t y and t h e r e f o r e h a v e n o moving p a r t s ;

i n c o r p o r a t e a n o p e n - c i r c u i t d e v i c e which l o c k s o u t t h e p r i m a r y v o l t a g e w i t h i n two s e c o n d s a n d r e q u i r e s r e s e t t i n g of t h e r e g u l a t o r ;

respond t o c i r c u i t changes w i t h i n 15 c y c l e s ;

i n c o r p o r a t e a s e c u r i t y device t h a t s e t s t h e r e g u l a t o r o u t of s e r v i c e o r a s s u r e s a r e d u c t i o n of t h e c u r r e n t i n e a s e of a n o v e r c u r r e n t ;

p r o v i d e t h e r e q u i r e d number of i n t e n s i t y s e t t i n g s o r a c o n t i n u o u s l y v a r i a b l e c o n t r o l a s required. The r e g u l a t o r s h o u l d be d e s i g n e d s o t h a t t h e i n t e n s i t y s e t t i n g c a n be changed w i t h o u t d e e n e r g i z i n g t h e r e g u l a t o r ;

e l e c t r i c a l l y i s o l a t e t h e p r i m a r y power c i r c u i t f r o m t h e s e c o n d a r y l i g h t i n g c i r c u i t ; and

o p e r a t e c o n t i n u o u s l y a t f u l l l o a d i n ambient t e m p e r a t u r e s between -40째C and +55"C and r e l a t i v e h u m i d i t y between 1 0 and 100 p e r c e n t and a t a l t i t u d e s up t o 2 000 m.

3.2.1.6 R a t i n g c h a r a c t e r i s t i c s of c o n s t a n t - c u r r e n t examples of r a t i n g c h a r a c t e r i s t i c s of c o n s t a n t - c u r r e n t

regulators. The f o l l o w i n g a r e r e g u l a t o r s which a r e a v a i l a b l e :

Power. Output ( s e c o n d a r y ) l o a d s between 4 and 70 k i l o w a t t s . i n t h i s range a r e a v a i l a b l e .

6.6 and 20 amperes a r e most common. U n i t s s u p p l y i n g 6.6 amperes f o r l o a d s up t o 30 k i l o w a t t s and 20 amperes f o r l o a d s of 10 k i l o w a t t s and more a r e o f t e n u s e d .

Frequency. A s r e q u i r e d by t h e f r e q u e n c y of t h e p r i m a r y power, u s u a l l y 5 0 o r 60 h e r t z .

Rated p r i m a r y v o l t a g e s between 120 a n d 1 2 000 v o l t s have been used. P r i m a r y v o l t a g e s of 240 v o l t s f o r s i z e s up t o 30 k i l o w a t t s a n 4 2 400 v o l t s f o r s i z e s of i O t o 7 0 k i l o w a t t s a r e used by one S t a t e , O t h e r p r i m a r y v o l t a g e s may a l s o be used.

Many s i z e s

P a r t 5,- E l e c t r i c a l Svstems

5-39

3.2.1.7 Most aerodrome l i g h t i n g c i r c u i t s u s e i s o l a t i n g t r a n s f o r m e r s t o p r o v i d e c o n t i n u i t y of t h e s e r i e s c i r c u i t s o t h a t f a i l u r e o f a lamp d o e s n o t make a n o p e n - c i r c u i t f a u l t . The second f u n c t i o n of i s o l a t i n g t r a n s f o r m e r s i s t o p r o v i d e e l e c t r i c a l i s o l a t i o n o f t h e lamp from t h e h i g h v o l t a g e c i r c u i t f o r s a f e t y C i r c u i t c o n t i n u i t y c a n a l s o b e a t t a i n e d by u s i n g b y - p a s s d e v i c e s , s u c h a s purposes. f i l m c u t o u t s , which s h o r t a c r o s s t h e lamp when t h e lamp f a i l s , b u t i n t h i s a r r a n g e m e n t Isolating transt h e lamp may be a t a h i g h p o t e n t i a l when t h e c i r c u i t i s e n e r g i z e d . f o r m e r s a r e used t o p r o v i d e t h e p r o p e r c u r r e n t t o t h e lamp i f t h e lamp c u r r e n t d i f f e r s f r o m t h a t of t h e s e r i e s c i r c u i t . a

An i s o l a t i n g t r a n s f o r m e r c o n s i s t s of a p r i m a r y a n d a s e c o n d a r y c o i l wound on a m a g n e t i c c o r e i n a w a t e r p r o o f c a s e w i t h p r i m a r y and s e c o n d a r y l e a d s f o r c o n n e c t i n g t h e s e r i e s c i r c u i t t o t h e lamp. The p r i m a r y and s e c o n d a r y c o i l s a r e i s o l a t e d e l e c t r i c a l l y b u t l i n k e d by t h e m a g n e t i c c i r c u i t . The s e c o n d a r y c i r c u i t i s s u b j e c t e d t o a l e s s e r e l e c t r i c a l p o t e n t i a l and one s i d e of t h e s e c o n d a r y s h o u l d be The c o r e of a n i s o l a t i n g t r a n s brought o u t t o a grounding connection. f o r m r i s m a g n e t i c a l l y u n s a t u r a t e d i n o p e r a t i o n b u t becomes s a t u r a t e d i f t h e lamp f a i l s o r t h e s e c o n d a r y c i r c u i t i s o p e n - c i r c u i t e d , t h u s maint a i n i n g t h e i n t e g r i t y o f t h e primary c i r c u i t . I f t h e lamp c i r c u i t s h o u l d be s h o r t - c i r c u i t e d , t h e i s o l a t i n g t r a n s f o r m e r would b e i n a nol o a d c o n d i t i o n and h a v e minimum e f f e c t on t h e s e r i e s c i r c u i t . These t r a n s f o r m e r s s h o u l d b e c a p a b l e of c o n t i n u o u s o p e r a t i o n a t r a t e d l o a d , o p e n - c i r c u i t , o r s h o r t - c i r c u i t w i t h o u t damage. The t u r n s r a t i o of t h e p r i m a r y c o i l t o t h e s e c o n d a r y c o i l of a s e r i e s l s e r i e s t r a n s f o r m e r i s 1 : 1 i f t h e lamp c u r r e n t i s t h e same a s t h e s e r i e s c i r c u i t c u r r e n t b u t i s i n v e r s e l y proportional t o t h e c u r r e n t r a t i o otherwise.

Enclosure. The w a t e r p r o o f c a s e f o r e n c l o s i n g t h e c o r e , w i n d i n g s , and l e a d s may be of m e t a l , r u b b e r , o r p l a s t i c and s h o u l d be s u i t a b l e f o r i n s t a l l i n g by d i r e c t b u r i a l , u n d e r w a t e r , i n b a s e s , o r e x p o s u r e d t o t h e weather. The c a s e s h o u l d p r o t e c t t h e u n i t f r o m damage i f t h e t r a n s f o r m e r i s dropped o r i s c a r r i e d by a s i n g l e l e a d . The c a s e s h o u l d p r e v e n t w a t e r from e n t e r i n g t h r o u g h t h e c a s e o r where j o i n e d t o t h e l e a d s , m a i n t a i n r e s i l i e n c e t o a v o i d s h a t t e r i n g o r damage a t v e r y low temperat u r e s , and p r o t e c t t h e u n i t d u r i n g h a n d l i n g , s t o r a g e , i n s t a l l i n g , and The p r i m a r y l e a d s s h o u l d be n o t l e s s t h a n 8.4 mm2 i n s i z e and service. These l e a d s s h o u l d s h o u l d b e i n s u l a t e d f o r n o t l e s s t h a n 5 000 v o l t s . be n o t l e s s t h a n 50 cm l o n g . U s u a l l y t h e s e l e a d s w i l l be p r o v i d e d w i t h a p l u g t y p e c o n n e c t o r on one l e a d and a r e c e p t a c l e on t h e o t h e r s u i t a b l e f o r connecting t o t h e s e r i e s - c i r c u i t cable. The s e c o n d a r ~l e a d s s h o u l d be two-conductor w i t h c o n d u c t o r s i z e n o t l e s s t h a n 3.3 mm and i n s u l a t e d f o r n o t l e s s t h a n 600 v o l t s and have a l e n g t h of n o t less t h a n 100 cm. U s u a l l y t h e s e l e a d s a r e p r o v i d e d w i t h a s u i t a b l e two-conductor c o n n e c t o r f o r connecting t o t h e l i g h t .

Ambient t e m p e r a t u r e . These t r a n s f o r m e r s s h o u l d be c a p a b l e of o p e r a t i n g i n t e m p e r a t u r e s between -55째C and +65 "C.

S e r i e s l s e r i e s i s o l a t i n g transformer r a t i n g s . R a t i n g s of i s o l a t i n g t r a n s f o r m e r s a r e by o u t p u t power, p r i m a r y and s e c o n d a r y c u r r e n t , t h e f r e q u e n c y , and t h e i n s u l a t i o n v o l t a g e of p r i m a r y and s e c o n d a r y c i r c u i t s . These t r a n s f o r m e r s may be e a s i l y manufactured f o r a l m o s t a n y d e s i r e d rating. Seme ccmr",cnly a v a i l a b l e r a t i n g s a r e a s f o l l o w s :

Power. R a t i n g s o f 3 0 / 4 5 , 6 5 , 1 0 0 , 2 0 0 , 3 0 0 and 5 0 0 w a t t s a r e f r e q u e n t l y used and sometimes 1 0 0 0 and 1 500 w a t t u n i t s a r e used.

Current. C u r r e n t r a t i n g s a r e u s u a l l y g i v e n a s a r a t i o of p r i m a r y t o 2 0 1 2 0 , 6.6,'s e c o n d a r y c u r r e n t . Common c u r r e n t r a t i n g s a r e 6 . 6 / 6 . 6 , 2 0 and 2 0 / 6 . 6 amperes.

Frequency. The common f r e q u e n c i e s a r e 5 0 and 6 0 h e r t z . Preferably t h e t r a n s f o r m e r s h o u l d be used on t h e f r e q u e n c y f o r which i t was designed.

I n s u l a t i o n . Most i s o l a t i n g t r a n s f o r m e r s a r e i n s u l a t e d f o r 5 0 0 0 v o l t s on t h e p i i m a r y c i r c u i t and 6 0 0 v o l t s on t h e s e c o n d a r y . L a r g e r power s i z e s of t r a n s f o r m e r s may r e q u i r e a h i g h e r s e c o n d a r y i n s u l a t i o n b e c a u s e of t h e i r h i g h e r o p e n - c i r c u i t v o l t a g e .

S e v e r a l lamps from a s i n g l e t r a n s f o r m e r . P r e f e r a b l y e a c h l i g h t is s u p p l i e d by i t s own i s o l a t i n g t r a n s f o r m e r . Sometimes t o r e d u c e t h e i n s t a l l a t i o n c o s t s , s u c h a s f o r i n s t a l l i n g c e n t r e l i n e l i g h t s on e x i s t i n g ninways, o r t o r e d u c e t h e mass and s t r e n g t h of c a b l e s , as f o r t a l l f r a n g i b l e a p p r o a c h l i g h t s u p p o r t s , s e v e r a l lamps may be connected i n a s e r i e s across a s i n g l e i s o l a t i n g transformer. Of c o u r s e t h e t r a n s f o r m e r must have t h e c a p a c i t y t o s u p p l y t h e t o t a l lamp l o a d p l u s l i n e l o s s e s . Two problems of t h i s arrangement a r e : f i r s t , i f one lamp f a i l s c a u s i n g a n o p e n - c i r c u i t , t h e o t h e r lamps a r e i n o p e r a t i v e u n l e s s s u i t a b l e by-pass d e v i c e s a r e u s e d ; and s e c o n d l y , at t h e i n s t a n t of t h e o p e n - c i r c u i t f a i l u r e t h e i n s t a n t a n e o u s s e c o n d a r y v o l t a g e may become v e r y g r e a t e s p e c i a l l y f o r t h e l a r g e r s i z e s of i s o l a t i n g t r a n s f o r m e r s . These problems a r e d i s c u s s e d below.

E f f e c t s of o p e n - c i r c u i t e d s e c o n d a r i e s of i s o l a t i n g t r a n s f o r m e r s . The d e s i g n of most i s o l a t i n g t r a n s f o r m e r s l i m i t s t h e r o o t m e a n - s q u a r e (rms) However, v o l t a g e of o p e n - c i r c u i t e d s e c o n d a r i e r s t o 3 0 0 v o l t s o r l e s s . t h e i n s t a n t a n e o u s v o l t a g e of some i s o l a t i n g t r a n s f o r m e r s a t t h e t i m e t h e o p e n - c i r c u i t o c c u r s may e x c e e d 1 0 0 0 v o l t s . I s o l a t i n g transformers with magnetic cores designed t o s a t u r a t e a t a v o l t a g e only s l i g h t l y g r e a t e r t h a n t h e i r o p e r a t i n g v o l t a g e u s u a l l y have l o w e r r m s and i n s t a n t a n e o u s peak o p e n - c i r c u i t s e c o n d a r y v o l t a g e s t h a n do l e s s s a t u r a t e d t r a n s f o r m e r s . High r m s o p e n - c i r c u i t v o l t a g e s r e q u i r e h i g h e r s e c o n d a r y i n s u l a t i o n and p r e s e n t a g r e a t e r e l e c t r i c a l shock h a z a r d , b u t t h e y a l s o make f i l m c u t o u t o p e r a t i o n s more r e l i a b l e . The r e a c t a n c e of s e r i e s / s e r i e s i s o l a t i n g transformers with open-circuit secondaries d i s t o r t s the primary c u r r e n t waveform, and t h e r e s u l t i n g harmonic f r e q u e n c i e s may a f f e c t t h e r e g u l a t i o n of some t y p e s of c o n s t a n t - c u r r e n t r e g u l a t o r s .

Lamp by-pass d e v i c e s . Whether lamps a r e c o n n e c t e d d i r e c t l y i n t o t h e s e r i e s c i r c u i t o r a s a group i n s e r i e s a c r o s s a s i n g l e i s o l a t i n g t r a n s f o r m e r , when t h e f i l a m e n t of one lamp b u r n s o u t , a l l t h e lamps of t h e group a r e o u t u n l e s s a s u i t a b l e by-pass d e v i c e i s connected a c r o s s t h e t e r m i n a l s of t h e f a i l e d lamp. From t h e e a r l y days of s e r i e s l i g h t i n g c i r c i n i t s witb--,* i s o l a t t n g t r a n s f ~ r m e r s , f u s e d f i l m c u t o u t s have been used t o by-pass f a i l e d lamps. For t h i s d e v i c e , s p r i n g - l o a d e d c o n t a c t s are c o n n e c t e d a c r o s s t h e t e r m i n a l s of each lamp. The s p r i n g - l o a d e d consarrs zrcl s e p a r a t e d by 3 f i l n l c i l t o u ~w h i c h i s a s m a P i eisk of a tklm

non-conducting f i l m between c o n d u c t i n g o u t e r s u r f a c e s . When t h e lamp i s o p e r a t i n g , t h e f i l m d i s k k e e p s t h e lamp t e r d n a l s i n s u l a t e d f r o m e a c h o t h e r and t h e lamp f i l a m e n t c o m p l e t e s t h e s e r i e s c i r c u i t . I f a lamp f i l a m e n t f a i l s , t h e v o l t a g e a c r o s s t h e lamp t e r m i n a l s r a p i d l y r i s e s t o a v a l u e ( p e r h a p s 1 000 v o l t s ) which p e r f o r a t e s t h e f i l m and s h o r t s o u t t h e lamp t e r m i n a l s and r e s t o r e s t h e s e r i e s c i r c u i t b e f o r e t h e c o n s t a n t When t h e lamp i s current r e g u l a t o r ' s open-circuit p r o t e c t i o n operates. r e p l a c e d a new f u s e d f i l m c u t o u t must be i n s t a l l e d . The o u t a g e of t h e o t h e r lamps of a s m a l l c i r c u i t c o n n e c t e d i n s e r i e s w i t h t h e s e c o n d a r y o f a n i s o l a t i n g t r a n s f o r m e r when one lamp f a i l s may n o t be a c c e p t a b l e , and b y - p a s s d e v i c e s f o r t h e s e lamps a r e needed. The o p e n - c i r c u i t s e c o n d a r y v o l t a g e peak of some i s o l a t i n g t r a n s f o r m e r s may be 100 t o 200 v o l t s o r l e s s . Fused f i l m c u t o u t s which o p e r a t e a t t h e s e v o l t a g e s a r e a v a i l a b l e b u t may be u n r e l i a b l e a s t h e o p e n - c i r c u i t v o l t a g e may f a i l t o p e r f o r a t e t h e f i l m c u t o u t and s h o r t o u t t h e f a i l e d lamp. A r e c e n t development o f a by-pass d e v i c e f o r lamps i n t h e s e c i r c u i t s i s a s h o r t i n g r e l a y . These r e l a y s a r e more e x p e n s i v e t h a n f u s e d f i l m c u t o u t s b u t p r o v i d e more r e l i a b l e operation. 3.2.1.8 Connections f o r s e r i e s c i r c u i t s . The c o n n e c t i o n s i n s e r i e s c i r c u i t s s h o u l d be c a r e f u l l y made t o a s s u r e c i r c u i t c o n t i n u i t y and t o p r e v e n t development o f ground f a u l t s . An o p e n - c i r c u i t f a u l t i n t h e p r i m a r y w i l l c a u s e a n o u t a g e of a l l l i g h t s i n t h a t c i r c u i t . Unless t h e constant-current r e g u l a t o r i s equipped w i t h o p e n - c i r c u i t p r o t e c t i o n , t h e r e g u l a t o r may be damaged. Most ground-type f a u l t s on s e r i e s c i r c u i t s o c c u r a t c o n n e c t i o n s . A s i n g l e ground f a u l t d o e s n o t c a u s e a n o u t a g e of t h e l i g h t s , b u t two o r more ground f a u l t s w i l l s h o r t - c i r c u i t a l l l i g h t s between t h e f a u l t s .

3.3

PARALLEL (MULTIPLE) CIRCUITRY

3.3.1.1 The u s e of p a r a l l e l ( m u l t i p l e ) c i r c u i t s f o r a v i a t i o n ground l i g h t i n g i s n o t recommended f o r l a r g e aerodromes a n d / o r c o m p l i c a t e d l i g h t i n g s y s t e m s f o r t h e f o l l o w i n g reasons : a)

p a r a l l e l c i r c u i t s u s u a l l y e n t a i l a much more e x p e n s i v e c a b l i n g i n s t a l l a t i o n t h a n does a high-voltage s e r i e s c i r c u i t ;

a c c u r a t e b r i l l i a n c y b a l a n c e of a l l l i g h t s i n t h e p a t t e r n c a n n o t b e o b t a i n e d e a s i l y ; and

t h e mass b u r n o u t of lamps i n a c i r c u i t i s much more l i k e l y due t o t h e i n a b i l i t y of a v e r a g e v o l t a g e r e g u l a t o r s t o c o n t r o l v e r y r a p i d f l u c t u a t i o n s i n incoming s u p p l y v o l t s .

3.3.1.2 I n view of t h e s e c o n s i d e r a t i o n s , p a r a l l e l c i r c u i t s s h o u l d o n l y b e used when t h e r e a r e o n l y a few f i t t i n g s e x i s t i n g i n t h e c i r c u i t and a c c u r a t e i n t e n s i t y b a l a n c e i s n o t c r i t i c a l ; f o r example, a s h o r t t a x i w a y . S m a l l e r aerodromes w i t h s h o r t runways a n d t a x i w a y s c a n employ p a r a l l e l v o l t a g e f o r t h e l i g h t i n g . 2 2 1 2

J O J - I e J

E f f e c t s ~f f a u l t s .

c i r c u i t ,a L UUL,lc~-O laiiiip iit o r

If t h e l i g h t f i x t u r e s are connected across t h e l i g h t i n g a n opt.n-cireuit f a u l t in a f i x t u r ed o e s :lot s e r i o i ; s l y

a f f e c t t h e l i g h t i n g c i r c u i t , but a s h o r t - c i r c u i t f a u l t w i l l be a n overload c o n d i t i o n a n d , d e p e n d i n g on which p r o t e c t i v e d e v i c e ( f u s e o r c i r c u i t b r e a k e r ) o p e r a t e s , may make t h e c i r c u i t of l i g h t s i n o p e r a t i v e . To p r o t e c t t h e l i g h t i n g c i r c u i t , o f t e n e a c h lamp i s c o n n e c t e d t o t h e l i n e v o l t a g e s i d e of t h e c i r c u i t by a f u s e . Most p a r a l l e l - t y p e l i g h t f i x t u r e s a r e d e s i g n e d f o r 3.3.1.4 low a p p l i e d v o l t a g e s ( l e s s t h a n 300 v o l t s ) , and t h e c i r c u i t v o l t a g e i s t h a t r e q u i r e d by t h e lamps o r step-down t r a n s f o r m e r s a r e u s e d . The l i g h t s may be s u p p l i e d f r o m a s i n g l e c i r c u i t c o n n e c t e d between t h e l i n e and n e u t r a l o r by a l t e r n a t i n g between n e u t r a l and l i n e v o l t a g e on e a c h s i d e of t h e n e u t r a l . Examples of t h e s e c i r c u i t s a r e 120 v o l t s l i n e - t o - n e u t r a l and 2401120 v o l t (240 v o l t s l i n e - t o - l i n e and 120 v o l t s l i n e - t o - - n e u t r a l ) Usually t h e c a b l e i n s u l a t i o n of p a r a l l e l circuits. Other v o l t a g e s a r e o f t e n u s e d . l i g h t i n g c i r c u i t s i s r a t e d a t 600 v o i t s , which limits t h e v o l t a g e f o r p a r a l l e l l i g h t i n g c i r c u i t s t o n o t more t h a n 500 v o l t s . 3.3.1.5 Step-down t r a n s f o r m e r s . The u s e of h i g h e r v o l t a g e s f o r t r a n s m i s s i o n o f power r e d u c e s t h e l i n e v o l t a g e d r o p and t h e n step-down d i s t r i b u t i o n t r a n s f o r m e r s r e d u c e t h e v o l t a g e t o t h a t more s u i t a b l e f o r l o c a l d i s t r i b u t i o n . S i m i l a r l y , t h e power t o a e r o drome l i g h t i n g c i r c u i t s may be a t a h i g h e r v o l t a g e on t h e f e e d e r c i r c u i t s a n d r e d u c e d by a step-down t r a n s f o r m e r a t t h e b e g i n n i n g of t h e l i g h t i n g c i r c u i t t o match t h e d e s i r e d c i r c u i t voltage. Of c o u r s e , t h e s e f e e d e r c a b l e s must be a d e q u a t e l y i n s u l a t e d f o r t h e feeder voltage. Sometimes i t i s d e s i r a b l e t o u s e l o n g l o w - v o l t a g e c a b l e s f o r f e e d e r s , s u c h a s when t h e s e c a b l e s a r e a l r e a d y i n s t a l l e d and a v a i l a b l e . Assuming t h e s e f e e d e r s h a v e 6 0 0 - v o l t i n s u l a t i o n , t h e l i n e d r o p c a n be r e d u c e d by u s i n g a h i g h e r v o l t a g e w i t h i n t h e i n s u l a t i o n l i m i t of t h e c a b l e on t h e f e e d e r s and r e d u c i n g t h e v o l t a g e w i t h step-down transformers a t the input t o the c i r c u i t o r t o the individual l i g h t fixtures. An example i s t o u s e 480 v o l t s on t h e f e e d e r s and step-down t o 120 v o l t s a t t h e l i g h t i n g c i r c u i t . Use of lamps i n t h e v o l t a g e r a n g e of 6 t o 30 v o l t s i n aerodrome l i g h t f i x t u r e s i s u s u a l l y more e f f e c t i v e t h a n t h e u s e of 120 o r of 240 v o l t lamps. Thus, when s t e p down t r a n s f o r m e r s a r e t o be used f o r i n d i v i d u a l l i g h t s , o r f o r a s m a l l g r o u p of l i g h t s i n a b a r r e t t e , c o n s i d e r a t i o n s h o u l d b e g i v e n t o c h o o s i n g l i g h t s which u s e low-voltage Unless i n d i v i d u a l l y f u s e d , step-down t r a n s f o r i n e r s u s e d a s i n d i c a t e d abave s h o u l d lamps. b e of t h e h i g h - r e a c t a n c e t y p e s o t h a t a s h o r t - c i r c u i t i n t h a t p a r t of t h e l i g h t i n g s y s t e m f e d by one t r a n s f o r m e r w i l l n o t c a u s e f a i l u r e of t h e e n t i r e s y s t e m . 3.3.1.6 the location d r o p changes feeder cable v o l t a g e drop

The u s e of a c o n s t a n t v o l t a g e t r a n s f o r m e r a t of a l i g h t s u p p l i e d by a l o n g f e e d e r c a b l e t o compensate f o r l i n e - v o l t a g e may be a d v a n t a g e o u s . For example, a n aerodrome beacon s u p p l i e d by a l o n g which a l s o s u p p l i e s a number of i n t e r m i t t e n t l o a d s which c a u s e s t h e l i n e t o f l u c t u a t e widely.

3.4

CONTROL OF AERODROME LIGHTING SYSTEMS

3.4.1,l The c o n t r o l c i r c u i t r y f o r aerodrome l i g h t i n g p r o v i d e s t h e means o f s w i t c h i n g o n o r o f f and of c h a n g i n g t h e i n t e n s i t y of t h e v a r i o u s l i g h t i n g s y s t e m s . T h e s e c o n t r o l s may be manual o r a u t o m a t i c . 3.4.1.2 Local manual c o n t r o l . Tne s i m p l e s t c o n t r o l s y s t e m i s a s w i t c h a t t h e power s u p p l y u n i t of t h e c i r c u i t . which i s o p e r a t e d by a p e r s o n t o e n e r g i z e o r d e e n e s g i z e the

c i r c u i t . T h i s c o n t r o l method i s u s e d a t some s m a l l aerodromes o r some m i s c e l l a n e o u s associated l i g h t i g circuits. Some aerodromes may u s e l o c a l manual c o n t r o l s as a n a l t e r n a t e c o n t r o l p o i n t f o r emergency o p e r a t i o n s . The l i g h t i n g s y s t e m s f o r l a r g e r aerodromes a r e complex a n d Remote c o n t r o l . 3.4.1.3 p r o p e r c o n t r o l i s r e l a t e d t o a t m o s p h e r i c c o n d i t i o n s , t i m e of d a y , p e r h a p s t h e p i l o t ' s p r e f e r e n c e , t h e p o s i t i o n s and manoeuvring of s e v e r a l a i r c r a f t , and o t h e r a c t i v i t i e s on the field. The p e r s o n o r p e r s o n s most knowledgeable of t h e s e c o n d i t i o n s a r e t h e a i r t r a f f i c c o n t r o l l e r s ; t h e r e f o r e , most of t h e aerodrome l i g h t i n g c o n t r o l s a r e on a remote l i g h t i n g c o n t r o l p a n e l i n t h e aerodrome c o n t r o l tower and o p e r a t e d by t h e t r a f f i c controllers. Some aerodromes may h a v e s p e c i a l c o n t r o l s t a t i o n s o t h e r t h a n i n t h e c o n t r o l tower w i t h t h e o p e r a t o r i n d i r e c t communication w i t h t h e a i r t r a f f i c c o n t r o l l e r s . The remote l i g h t i n g c o n t r o l p a n e l i s c o n n e c t e d t o t h e a p p r o p r i a t e l i g h t i n g v a u l t by a s y s t e m of c o n t r o l c a b l e s t o p r o v i d e c a p a b i l i t y of c o n t r o l l i n g t h e v a r i o u s l i g h t i n g circuits.

3.4.1.4 Types of remote c o n t r o l s y s t e m s . S e v e r a l t y p e s of c o n t r o l s y s t e m s a r e u s e d f o r aerodrome l i g h t i n g . A l t e r n a t i n g c u r r e n t ( a c ) power i s o f t e n used t o e n e r g i z e t h e T h i s a c power may be a t t h e low d i s t r i b u t i o n v o l t a g e o r a t a s p e c i a l v o l t a g e controls. more s u i t a b l e f o r t h e l e n g t h of t h e c o n t r o l c a b l e r u n s and t h e s i z e of t h e c o n d u c t o r . These c o n t r o l s may be c o n n e c t e d d i r e t l y t o t h e power c o n t r o l d e v i c e f r o m t h e remote c o n t r o l p a n e l o r by a u x i l i a r y r e l a y s t o o p e r a t e t h e c o n t r o l d e v i c e s . Some c o n t r o l c i r c u i t s u s e d i r e c t c u r r e n t f o r t h e c o n t r o l voltage, e s p e c i a l l y t o reduce i n d u c t i v e c o u p l i n g between c i r c u i t s . Some major aerodromes w i t h v e r y complex c o n t r o l c i r c u i t s u s e multiplex c o n t r o l systems t o provide g r e a t e r f l e x i b i l i t y f o r extensions and v a r i a t i o n s t o l i g h t i n g p a t t e r n s and t o f a c i l i t a t e changes i n t h e c o n t r o l r e q u i r e m e n t s . Some a e r o dromes u s e r a d i o s i g n a l s f o r c o n t r o l , e i t h e r a i r - t o - g r o u n d f o r p i l o t s o r g r o u n d - t o ground f o r equipment l o c a t e d i n a r e a s n o t e a s i l y a c c e s s i b l e t o c o n t r o l c i r c u i t s . These c o n t r o l s y s t e m s s h o u l d be c a p a b l e of a h i g h d e g r e e of o p e r a t i o n a l r e l i a b i l i t y and s h o u l d b e d e s i g n e d t o p r o v i d e , a s f a r a s p o s s i b l e , t h e i n t e g r i t y of t h e l i g h t i n g p a t t e r n s s e l e c t e d r e g a r d l e s s of c o n t r o l c a b l e f a u l t s o r equipment f a i l u r e s . Solid s t a t e equipment may be used where p r a c t i c a b l e , a l t h o u g h r e l a y s may be more s a t i s f a c t o r y a t t h e i n t e r f a c e between t h e c o n t r o l c i r c u i t s and t h e l i g h t i n g c i r c u i t power e q u i p m e n t . Control panels

3.4.2.1 Primary c o n t r o l p a n e l . The p r i m a r y c o n t r o l p a n e l i s u s u a l l y l o c a t e d i n t h e c o n t r o l tower a t a l i g h t i n g c o n t r o l d e s k o r p a n e l . T h i s p a n e l s h o u l d be d e s i g n e d t o p r o v i d e t h e o p e r a t o r w i t h c o n t r o l s w i t c h e s , o p e r a t i n g c i r c u i t i n d i c a t o r l i g h t s and i n t e n s i t y c o n t r o l s , and t h e i r a s s o c i a t e d i n d i c a t i n g f e a t u r e s which a r e e a s i l y i n d e n t i f i a b l e under a l l c o n d i t i o n s o f i l l u m i n a t i o n i n t h e c o n t r o l room. For t h i s p u r p o s e i t may b e n e c e s s a r y t o p r o v i d e s e l f - i l l u m i n a t e d l e g e n d s f o r c o n t r o l s e l e c t o r s and a d e s k There a r e a d v a n t a g e s t o b e d e r i v e d b r i l l i a n c y l e v e l s e l e c t o r f o r t h e i n d i c a t o r lamps. f r o m a s t a n d a r d i z e d f o r m of l a y o u t f o r c o n t r o l and i n d i c a t i n g f a c i l i t i e s a n d t h e c u r r e n t t r e n d i s towards s t a n d a r d modular p a n e l l a y o u t s . Each s e r v i c e s h o u l d be p r o v i d e d w i t h i t s own c o n t r o l s e l e c t o r and g r o u p of i n d i c a t o r lamps. Where a s e p a r a t e c o n t r o l d e s k i s p r o v i d e d f o r e a c h runway, a d i a g r a m c a n b e combined w i t h t h e c o n t r o l d e s k b u t where one c o n t r o l d e s k s e r v e s t h e whole a i r p o r t a s e p a r a t e f a c s i m i l e d i a g r a m may need t o be Complex t a x i i n g g u i d a n c e s y s t e m s u s i n g s e l e c t i v e s w i t c h i n g o f c e n t r e l i n e provided. l i g h t s and s t o p b a r s can b e s t be c o n t r o l l e d from a n o p e r a t i o n a l d i a g r a m f i t t e d w i t h combined i n d i c a t i o n lamplpush b u t t o n s f o r s t o p b a r s and i n d i c a t o r lamps f o r t a x i w a y routes.

3.4.2.2 Facsimile diagrams a r e r e q u i r e d f o r aerodromes having complex p a t t e r n s . They a r e s p e c i a l l y made t o s u i t i n d i v i d u a l l a y o u t s and s o i n v o l v e considerable cost. P a n e l s w i t h runways and t a x i w a y s d e l i n e a t e d i n a c o n t r a s t i n g c o l o u r a r e accommodated t o p r o v i d e a d i a g r a m m a t i c d i s p l a y of l i g h t i n g s e r v i c e s . Fibre optics may a l s o be u s e d f o r t h i s p u r p o s e . 3.4.2.3 C o n t r o l s . The s w i t c h e s and c o n t r o l s s h o u l d b e t y p e s which a r e e a s y t o i d e n t i f y , p r o v i d e p o s i t i v e i n d i c a t i o n of t h e o p e r a t i n g s t a t u s , and be g r o u p e d t o a s s o c i a t e r e l a t e d f u n c t i o n s and c i r c u i t s . These c o n t r o l s s h o u l d be a t y p e w h i c h a r e n o t e a s i l y switched i n a d v e r t e n t l y .

3.4.2.4 Alternate c o n t r o l panel. P r o v i s i o n s h o u l d be made f o r l o c a l c o n t r o l of aerodrome l i g h t i n g i n t h e l i g h t i n g v a u l t s o r c o n t r o l c e n t r e s t o e n a b l e o p e r a t i o n of t h e l i g h t i n g s y s t e m s a t t i m e s when t h e remote c o n t r o l s y s t e m i s i n o p e r a t i v e . A l l l i g h t i n g s y s t e m s e s s e n t i a l t o t h e aerodrome o p e r a t i o n s h o u l d have a n a l t e r n a t e c o n t r o l p a n e l . The a l t e r n a t e c o n t r o l p a n e l s h o u l d be l o c a t e d s o t h a t i t i s a c c e s s i b l e t o a n o p e r a t o r w i t h o u t h i s h a v i n g t o e n t e r a n a r e a h o u s i n g h i g h v o l t a g e equipment o r s w i t c h g e a r . Often t h e a l t e r n a t e c o n t r o l p a n e l i s l o c a t e d i n a s e c t i o n of t h e l i g h t i n g v a u l t n e a r t h e Usually only e n t r a n c e , which i s s e p a r a t e d f r o m t h e a r e a c o n t a i n i n g t h e power equipment. one a l t e r n a t e c o n t r o l p a n e l i s p r o v i d e d , and i t i s l o c a t e d i n t h e v a u l t c o n t a i n i n g t h e equipment f o r s u p p l y i n g power t o t h e p a r t i c u l a r l i g h t i n g c i r c u i t s i n v o l v e d . Thus t h e r e may be s e v e r a l a l t e r n a t e c o n t r o l p a n e l s , e a c h of which c o n t r o l s d i f f e r e n t c i r c u i t s . Some aerodromes may u s e a c e n t r a l a l t e r n a t e c o n t r o l p a n e l , s i m i l a r t o t h e p r i m a r y remote c o n t r o l p a n e l l o c a t e d i n a c o n t r o l c e n t r e , f o r emergency o p e r a t i o n s . Constant-current r e g u l a t o r s u s u a l l y p r o v i d e c o n t r o l s on e a c h r e g u l a t o r f o r o p e r a t i o n of t h a t r e g u l a t o r f o r m a i n t e n a n c e o r d u r i n g a n emergency. A u t h o r i z e d p e r s o n s a r e u s u a l l y t h e o n l y ones permitted t o operate t h e s e controls. 3.4.2.5 Transfer r e l a y panel. For s a f e t y of m a i n t e n a n c e p e r s o n n e l a n d t o a v o i d c o n f l i c t i n g o p e r a t i o n of t h e c o n t r o l s , o n l y one c o n t r o l s t a t i o n s h o u l d b e a b l e t o opera t e a g i v e n c i r c u i t a t any t i m e . Transfer r e l a y panels a r e used t o s w i t c h t h e o p e r a t i n g c a p a b i l i t y f r o m t h e p r i m a r y c o n t r o l . panel. t o t h e a l t e r n a t e c o n t r o l p a n e l , To accommod a t e a l l t h e c o n t r o l c i r c u i t s involved i n t h e t r a n s f e r , s e v e r a l t r a n s f e r c o n t r o l panels may be used b u t u s u a l l y a s i n g l e t r a n s f e r s w i t c h a c t u a t e s a l l of t h e c o n t r o l p a n e l s . The t r a n s f e r c o n t r o l p a n e l s and t h e t r a n s f e r s w i t c h a r e u s u a l l y l o c a t e d a t t h e s i t e o f t h e a l t e r n a t e c o n t r o l panel. 3.4.3

Use of r e l a y s

3.4.3.1 Relay p a n e l s f o r l o n g c o n t r o l c i r c u i t s . Where c o n t r o l c i r c u i t s a r e l o n g , t h e v o l t a g e d r o p i n t h e l i n e s may be s u c h t h a t power c o n t r o l d e v i c e s c a n n o t b e o p e r a t e d d i r e c t l y f r o m t h e p r i m a r y remote c o n t r o l p a n e l . Even c i r c u i t s which e a r l i e r o p e r a t e d s a t i s f a c t o r i l y may become i n o p e r a t i v e a f t e r a d d i t i o n a l c o n t r o l c i r c u i t s a r e added. To p e r m i t c o n t r o l a t t h e l o n g e r d i s t a n c e , r e l a y s w i t h l o w - c u r r e n t c o i l s may be u s e d t o e n e r g i z e t h e c o n t r o l s of t h e power equipment. These r e l a y s a r e o f t e n a s s e m b l e d i n p a n e l s c o n t a i n i n g s e v e r a l (16 o r more) r e l a y s . (These r e l a y p a n e l s a r e sometimes c a l l e d p i l o t r e l a y panels.) A r e l a y may be p r o v i d e d f o r e a c h c o n t r o l l i n e f r o m t h e p r i m a r y remote c o n t r o l p a n e l . The c o n t a c t s of t h e s e r e l a y s c o n t r o l t h e power t o t h e s w i t c h e s o r c o n t r o l s of t h e power equipment f u n c t i o n s . 3.4.3,2 Some i n d i v i d u a l v i s u a l a i d s o r s h o r t l i g h t i n g c i r c u i t s (aerodrome beacons, wind d i r e c t i o n i n d i c a t o r s , s e c t i o n s of o b s t a c l e l i g h t s , s i m p l e a p p r o a c h l i g h t i n g s y s t e m s , e t c . ) may o b t a i n power from a l i g h t i n g v a u l t o r f r o m a l o c a l If t h e power is; froin a l o c a l scjurce, t h e r e l a y f o r c o n t r o l l i n g t h e s e s o u r c e o f power. l i g h t s is u s u a l l y l o c a t e d a t o r t h e l i g h t o r s o i i r c e o f r u w c r , If t h e

c a b l e s a r e l o n g , t h e c o n d u c t o r s of t h e c o n t r o l c a b l e may need t o be l a r g e t o r e d u c e t h e v o l t a g e d r o p . The r e l a y s h o u l d be s e l e c t e d t o o p e r a t e f r o m t h e c o n t r o l v o l t a g e a v a i l a b l e when t h e r e l a y i s a c t u a t e d . Also i f t h e r e l a y i s t o be l o c a t e d o u t d o o r s , i t w i l l need t o be p r o v i d e d w i t h p r o t e c t i o n from t h e most s e v e r e w e a t h e r t o which i t w i l l be It s h o u l d have a p r o v i s i o n t o l o c k i t f o r s e c u r i t y . subjected. 3.4.4

I n t e r c o n n e c t i o n of c o n t r o l s

Often t h e o p e r a t i o n s a t t h e aerodrome a r e s u c h t h a t c e r t a i n c o m b i n a t i o n s o f 3.4.4.1 l i g h t s a r e always used t o g e t h e r o r o t h e r c o m b i n a t i o n s a r e p r o h i b i t e d . Examples a r e :

3.4.5

runway edge l i g h t s , t h r e s h o l d l i g h t s , and runway end l i g h t s may be o p e r a t e d a t t h e same t i m e a l t h o u g h t h e power may be p r o v i d e d from different circuits;

runway e d g e l i g h t s may be o p e r a t e d w i t h o u t t h e runway c e n t r e l i n e l i g h t s b u t i f t h e runway c e n t r e l i n e l i g h t s a r e u s e d t h e runway e d g e l i g h t s a r e always e n e r g i z e d ;

t h e s e q u e n c e d - f l a s h i n g l i g h t s of t h e a p p r o a c h l i g h t i n g s y s t e m c a n b e u s e d o n l y when t h e i n c a n d e s c e n t l i g h t s of t h e s y s t e m a r e a t t h e h i g h e r intensity steps;

s e t t i n g of t h e i n t e n s i t y c o n t r o l f o r a g i v e n a t m o s p h e r i c c o n d i t i o n may o p e r a t e t h e a p p r o a c h l i g h t i n g s y s t e m a t one i n t e n s i t y s t e p , t h e runway l i g h t s a t a n o t h e r i n t e n s i t y s t e p , and t h e t a x i w a y l i g h t s a t y e t a n o t h e r i n t e n s i t y s t e p ; and

i n t e r s e c t i n g runways s h o u l d n o t be l i g h t e d s i m u l t a n e o u s l y . Only by p r o p e r l y i n t e r c o n n e c t i n g t h e c o n t r o l s and c o n t r o l c i r c u i t s , c a n t h e d e s i r e d c o m b i n a t i o n s be o b t a i n e d o r u n d e s i r e d c o m b i n a t i o n s p r o h i b i t e d w i t h s i m p l e r o p e r a t i o n s by t h e c o n t r o l l e r and l e s s e r c h a n c e of e r r o r ; Each aerodrome s h o u l d c o n s i d e r p o s s i b l e c o n t r o l i n t e r c o n n e c t i o n c o m b i n a t i o n s i n r e l a t i o n t o t h e i r i n s t a l l a t i o n s and o p e r a t i n g procedures.

Automatic c o n t r o l s

3.4.5.1 Some t y p e s of aerodrome l i g h t i n g a i d s may be c o n t r o l l e d s a t i s f a c t o r i l y by automatic controls. More o f t e n t h e s e a u t o m a t i c c o n t r o l s a r e u s e d a t s m a l l e r a i r p o r t s , b u t t h e y may be used f o r l e s s c r i t i c a l v i s u a l a i d s a t l a r g e aerodromes e s p e c i a l l y a t l o c a t i o n s n o t e a s i l y connected t o t h e c o n t r o l c i r c u i t s . P h o t o e l e c t r i c c o n t r o l s may b e used t o e n e r g i z e and d e e n e r g i z e aerodrome b e a c o n s , wind d i r e c t i o n i n d i c a t o r s , and o b s t a c l e l i g h t s i n l e s s c r i t i c a l a r e a s . The c o n t r o l s a r e u s u a l l y a c t u a t e d by s k y i l l u m i n a n c e l e v e l s . Most of t h e s e c o n t r o l s e n e r g i z e t h e c i r c u i t when t h e i l l u m i n a n c e from t h e n o r t h s k y d e c r e a s e s t o a b o u t 400 l u x and d e e n e r g i z e s t h e c i r c u i t when t h e illumi-nance i n c r e a s e s t o a b o u t 600 l u x . Time-clock c o n t r o l s may b e u s e d t o a u t o m a t i c a l l y c o n t r o l t h e aerodrome l i g h t i n g a t aerodromes w i t h n o n - i n s t r u m e n t c a p a b i l i t y o n l y . Time-clock c o n t r o l s a r e o f t e n used a t aerodromes where t h e v i s u a l a i d s a r e t u r n e d o f f a f t e r a c e r t a i n hour a t n i g h t t o c o n s e r v e e n e r g y . Thermal c o n t r o l s may b e u s e d t o a c t u a t e h e a t e r s of some v i s u a l a i d s t o p r e v e n t t h e f o r m a t i o n o r a c c u m u l a t i o n of i c e , snow o r c o n d e n s a t i o n . These t h e r m a l c o n t r o l s may be o b t a i n e d w i t h f i x e d o r a d j u s t a b l e c o n t r o l f o r many d i f f e r e n t t e m p e r a t u r e s . Some i n s t a t l a t i o n may need manual c o n t r o l t o o v e r r i d e t h e a u t o m a t i c c u i i t r u i o f c e r t a i n lighting circulLts.

3.4.6

Radio remote c o n t r o l s

3.4.6.1 Radio s i g n a l s from a i r c r a f t t o c o n t r o l aerodrome l i g h t i n g s y s t e m s have been u s e d , t o a l i m i t e d d e g r e e , a t s m a l l e r aerodromes f o r s e v e r a l y e a r s . T h i s c o n t r o l method h a s s e v e r a l a d v a n t a g e s i n t h a t i t p e r m i t s t h e p i l o t t o s e l e c t t h e l i g h t i n t e n s i t y of h i s c h o i c e , e l i m i n a t e s t h e need f o r c o s t l y c o n t r o l c a b l e s , and c o n s e r v e s power by h a v i n g t h e Radio c o n t r o l s f o r a i r - t o - g r o u n d , groundl i g h t i n g s y s t e m d e e n e r g i z e d when n o t needed. to-ground, and a c o m b i n a t i o n of air-to-ground and ground-to-ground s y s t e m s a r e available. Radio c o n t r o l c a n p r o v i d e i n t e n s i t y c o n t r o l a s w e l l a s e n e r g i z i n g t h e l i g h t i n g c i r c u i t s . Most r a d i o c o n t r o l s a u t o m a t i c a l l y d e e n e r g i z e t h e l i g h t i n g c i r c u i t s 15 t o 60 m i n u t e s a f t e r t h e l a s t c o n t a c t . Radio c o n t r o l s h a v e been u s e d t o c o n t r o l runway e d g e l i g h t s , t a x i w a y e d g e l i g h t s , s i m p l e a p p r o a c h l i g h t i n g s y s t e m s , v i s u a l approach s l o p e i n d i c a t o r systems, a s i n d v i d u a l systems o r i n p r e d e t e r d n e d combinations. Radio c o n t r o l of aerodrome l i g h t i n g systems from a i r c r a f t s h o u l d b e u s e d o n l y a t u n c o n t r o l l e d aerodromes o r a t o t h e r aerodromes d u r i n g p e r i o d s when t r a f f i c c o n t r o l i s not i n operation. L i g h t i n g s y s t e m s which s h o u l d n o t be r a d i o c o n t r o l l e d i n c l u d e o b s t a c l e l i g h t s , aerodrome b e a c o n s , p r e c i s i o n a p p r o a c h l i g h t i n g s y s t e m s , runway c e n t r e l i n e l i g h t s , and touchdown zone l i g h t s . 3.4.6.2 For a i r - t o - g r o u n d o p e r a t i o n o n l y a r e c e i v e r and d e c o d e r a r e i n s t a l l e d on t h e airport. The a c t u a t i n g s i g n a l may be p r o v i d e d by a s p e c i f i e d s h o r t s e r i e s of c l i c k s accomplished by k e y i n g t h e microphone of a n a i r c r a f t communications t r a n s m i t t e r . Ground-to-ground c o n t r o l i s u s e d m o s t l y when c a b l e c o n t r o l c i r c u i t s a r e n o t a v a i l a b l e and a r e n o t p r a c t i c a l t o i n s t a l l . Ground-to-ground c o n t r o l may be u s e d o n l y t e m p o r a r i l y u n t i l c a b l e s can be i n s t a l l e d o r p e r m a n e n t l y e s p e c i a l l y t o remote l o c a t i o n s .

3.5

?,5il

LAMPS

C h a r a c t e r i s t i c s ~f incaxdescent lamps

3.5.1.1 I n c a n d e s c e n t lamps a r e u s e d i n most f i t t i n g s i n s t a l l e d i n a e r o d r o m e l i g h t i n g s y s t e m s . The f o l l o w i n g c h a r a c t e r i s t i c s of i n c a n d e s c e n t lamps a r e p e r t i n e n t t o t h e d e s i g n of t h e aerodrome l i g h t i n g c i r c u i t s . 3.5.1.2 The l i g h t o u t p u t , l i f e , power consumed, and e f f i c a c y ( e f f i c i e n c y ) of i n c a n d e s c e n t lamps i s a complex f u n c t i o n of t h e a p p l i e d v o l t a g e o r c u r r e n t , a s i n d i c a t e d by F i g u r e 3-8 and Table 3-1. For example, i f t h e v o l t a g e a p p l i e d t o a lamp i s f i v e p e r c e n t g r e a t e r t h a n r a t e d v o l t a g e , t h e l i g h t o u t p u t w i l l be a b o u t 120 p e r c e n t o f r a t e d l i g h t o u t p u t , and t h e lamp l i f e w i l l be a b o u t one-half t h e d e s i g n l i f e . The e f f e c t s of changes i n lamp c u r r e n t a r e g r e a t e r , If t h e c u r r e n t t h r o u g h a lamp i s f i v e p e r c e n t above r a t e d c u r r e n t , t h e l i g h t o u t p u t w i l l be a b o u t 1 3 5 p e r c e n t of t h e r a t e d l i g h t o u t p u t , and t h e lamp l i f e w i l l be a b o u t t h r e e - t e n t h s t h e d e s i g n l i f e . These v a l u e s i l l u s t r a t e t h e need f o r c l o s e c o n t r o l of t h e a p p l i e d v o l t a g e o r c u r r e n t .

Table 3-1. output

Table of tamp Exponents

OUTPUT life

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LIFE

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amperes 2.85 [mpEm,i

amperes

AMPERES Note:

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The d e s i g n e r of a n aerodrome l i g h t i n g s y s t e m may h a v e some l a t i t u d e i n h i s 3.5.1.3 c h o i c e of lamps f o r c e r t a i n aerodrome l i g h t f i x t u r e s , s e l e c t i n g a s e r i e s lamp, a lowv o l t a g e m u l t i p l e lamp, o r a h i g h e r - v o l t a g e m u l t i p l e lamp. The f o l l o w i n g f a c t o r s are p e r t i n e n t i n t h e choice: a)

t h e v o l t a g e d r o p a c r o s s s e r i e s lamps u s u a l l y f a l l s i n t h e " l o w - v o l t a g e " c a t e g o r y ; t h e v o l t a g e d r o p a c r o s s a 6.6 ampere, 200 w a t t runway edge l i g h t i s 30 v o l t s , and t h e v o l t a g e d r o p a c o r s s a 20 ampere, 500 w a t t a p p r o a c h l i g h t lamp i s 2 5 v o l t s ;

b e c a u s e of t h e i r d i f f e r e n c e s i n d e s i g n t o l e r a n c e s , s e r i e s lamps s h o u l d n o t be u s e d i n p a r a l l e l c i r c u i t s , and m u l t i p l e lamps s h o u l d no'% be u s e d I n series c i r c u i t s ; and

t h e l i f e of a " l o w - v o l t a g e " lamp w i l l b e g r e a t e r t h a n t h a t of a " h i g h v o l t a g e w * lamp, f o r a g i v e n r a t e d power consumption and l i g h t o u t p u t .

" H i g h v o l t a g e " i s used i n t h i s s e c t r i o n a s b e i n g t h e v o l t a g e n o r m a l l y u s e d f o r household l i g h t s .

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5 PER CENT NORMAL AMPERES

(a) SERIES TYPE LAMPS

PER CENT NORMAL VOLTS

(b)

PARALLEL (MULTIPLE) TYPE LAMPS

F i g u r e 3-8. E f f e c t s of c u r r e n t and v o l t a g e v a r i a t i o n s o n o p e r a t i n g c h a r a c t e r i s t i c s of i n c a n d e s c e n t lamps

3.5.1.4 Many lamps now b e i n g u s e d f o r aerodrome l i g h t i n g a r e t u n g s t e n - h a l o g e n lamps. The f i l a m e n t s o f t h e s e lamps a r e e n c l o s e d i n s m a l l q u a r t z t u b e s which c o n t a i n s m a l l amounts of a h a l o g e n , s u c h a s i o d i n e , i n a d d i t i o n t o t h e u s u a l i n e r t f i l l g a s . When t h e f i l a m e n t i s h e a t e d , t u n g s t e n e v a p o r a t e s from t h e f i l a m e n t and c o n d e n s e s on t h e i n s i d e w a l l s of t h e lamp e n v e l o p e . The v a p o u r i z e d h a l o g e n combines w i t h t h i s condensed t u n g s t e n f o r m i n g a vapour. T h i s vapour t r a v e l s t o t h e h o t f i l a m e n t where i t d i s a s s o c i a t e s and r e d e p o s i t s t h e t u n g s t e n on t h e f i l a m e n t . T h i s p r o c e s s r e d u c e s b l a c k e n i n g of t h e lamp b u l b , i n c r e a s e s t h e l i f e o f t h e lamp, m a i n t a i n s b e t t e r l i g h t i n t e n s i t y , and improves t h e e f f i c i e n c y of t h e lamp. The c o s t of t h e lamps i s however i n c r e a s e d .

3.5.2.1 The lamps u s e d i n t h e sequenc ge l i g h t s and n o t i n c a n d e s c e n t lamps. The lamp i s a t u b e which may be formed i n t o v a r i o u s s h a p e s c o n t a i n i n g a n i n e r t g a s s u c h a s a r g o n o r k r y p t o n which e m i t s l i g h t when a n a r c i s c r e a t e d i n the gas. The power s u p p l y c h a r g e s e l e c t r i c a l c a p a c i t o r s t o p r o v i d e power f o r t h e a r c and p r o v i d e s a t r i g g e r i n g v o l t a g e t o i n i t i a t e t h e a r c upon a p p l i c a t i o n of t h e t r i g g e r i n g signal. The a r c i n t h e g a s e m i t s a h i g h - i n t e n s k t y f l a s h of i i g h t of s h o r t d u r a t i o n ( ~ c r o s e c o n d s )which r a p i d l y expends t h e c h a r g e of t h e c a p a c i t o r s and e x t i n g u i s h e s t h e arc. Very h i g h voitages a r e P n v ~ i u e df o r t h e power s u p p l y and lamp. T h i s h a z a r d s h o u l d b e c o n s l a e r e d i n ~ Z l ed e s i g n of tlae i i g i ~ t i r ~sysirem. g The peak i i i t e i l s i C y uf ; k s e l',gtits

may be v e r y g r e a t b u t of s h o r t d u r a t i o n , The f l a s h must b e i n t e g r a t e d t o d e t e r m i n e t h e e f f e c t i v e i n t e n s i t y of t h e e m i t t e d l i g h t and i t s e f f e c t i v e n e s s a s a v i s u a l a i d . The f r e q u e n c y of f l a s h i n g of t h e s e l i g h t s i s l i m i t e d by t h e t i m e r e q u i r e d t o r e c h a r g e t h e The o u t p u t of t h e l i g h t i s proc a p a c i t o r s and u s u a l l y i s o n l y a few t i m e s p e r second. p o r t i o n a l t o t h e s q u a r e of t h e v o l t a g e a p p l i e d t o t h e l i g h t f i t t i n g , u n l e s s i t h a s a r e g u l a t e d power s u p p l y . 3.5.2.2 lamps e n c o u r a g e s t h e i r m e t a l - h a l i d e , and lowthese types is usually t h e u s e of f l u o r e s c e n t When c o n s i d e r i n g u s i n g investigated.

3.6

3.6.1

The h i g h e r e f f i c i e n c y of g a s e o u s d i s c h a r g e use. Types of t h e s e lamps i n c l u d e f l u o r e s c e n t , mercury-vapour, o r h i g h - p r e s s u r e s o d i u m - v a p o u r l i g h t s . The u s e of l i g h t s of l i m i t e d t o i l l u m i n a t i o n of a r e a s s u c h a s a p r o n a r e a s , e x c e p t f o r lamps i n some t a x i w a y e d g e l i g h t s and f o r i l l u m i n a t i n g s i g n s . l i g h t s of t h e s e t y p e s t h e f o l l o w i n g a r e f a c t o r s t h a t s h o u l d be

R e s t a r t i n e Some of t h e s e lamps c a n n o t b e r e s t a r t e d f o r s e v e r a l s e c o n d s t o minutes a f t e r t h e a r c i s extinguished. Power i n t e r r u p t i o n s o r s w i t c h i n g c a n c a u s e l o s s of l i g h t s a t c r i t i c a l t i m e s . Emergency l i g h t i n g by o t h e r t y p e s of lamps may be d e s i r a b l e .

Cold s t a r t i n g . Some of t h e s e lamps c a n n o t be s t a r t e d o r are d i f f i c u l t t o s t a r t i n low a m b i e n t t e m p e r a t u r e s .

Intensity control. These lamps o f t e n a r e n o t c a p a b l e of i n t e n s i t y cont r o l o r h a v e a l i m i t e d r a n g e of c o n t r o l as compared t o i n c a n d e s c e n t lamps.

Stroboscopic e f f e c t s . The s t r o b o s c o p i c e f f e c t s of t h e lamps may b e d i s t u r b i n g . Where s u c h l i g h t s a r e u s e d , i n c l u d i n g f o r i l l u m i n a t i o n of a r e a s , t h e u s e of t h r e e - p h a s e e l e c t r i c a l s u p p l y s y s t e m s w i t h a b a l a n c e i n c o n n e c t i n g t h e l i g h t s may be d e s i r a b l e .

T y p i c a l l y t h e l i g h t e m i t t e d f r o m t h e s e lamps c o v e r s a l i m i t e d p a r t of t h e v i s u a l spectrum. T h i s makes r e c o g n i t i o n of c o l o u r c o d i n g d i f f i c u l t a s c o l o u r s may n o t h a v e t h e i r o r d i n a r y a p p e a r a n c e when i l l u m i n a t e d by g a s e o u s - d i s c h a r g e lamps. The c o l o u r " r e d " i s particularly affected.

METHODS OF OBTAINING INTEGRITY AND RELIABILITY FOR AERODROME LIGHTING

D e f i n i t i o n s of t e r m s

3.6.1.1 The terms i n t e g r i t y and r e l i a b i l i t y a s a p p l i e d t o aerodrome l i g h t i n g a r e n o t p r e c i s e , e a s i l y d e f i n e d o r measured t e r m s . P r e v i o u s e f f o r t s t o d e f i n e t h e s e terms have c o n c l u d e d t h a t r e l i a b i l i t y i s a q u e s t i o n of mean t i m e between f a i l u r e of components w h i l e i n t e g r i t y i s a q u e s t i o n c o m p r i s i n g s u c h m a t t e r s as f a i l u r e s u r v i v a l o f t h e o v e r a l l It i s c o n s i d e r e d t h a t v i s u a l a i d s s h o u l d h a v e a comparable i n t e g r i t y and r e l i a system. b i l i t y t o t h a t a f f o r d e d by n o n - v i s u a l a i d s . Thus r e l i a b i l i t y i s a f f e c t e d by t h e s e l e c t i o n of components and o p e r a t i o n a l u s e , aiid i n t e g r l t j i i s a f f e c t e d by t h e d e s i g n and i n s t a l l a t i o n of t h e s y s t e m s and m a i n t e n a n c e o f t h e equipment. It i s d i f f i c u l t t o s t a t e what t h e r e l i a b i l i t y of p r e s e n t v i s u a l a i d s i s , I n g e n e r a l i t i s c o n s i d e r e d chat w e l l

d e s i g n e d and m a i n t a i n e d v i s u a l a i d s have a v e r y h i g h i n t e g r i t y and t h a t t h e p r o b a b i l i t y o f a f a i l u r e o c c u r r i n g a t a c r i t i c a l moment i s e x t r e m e l y low. N e v e r t h e l e s s a l l r e a s o n Electrical faca b l e e f f o r t s s h o u l d be made t o improve upon i n t e g r i t y and r e l i a b i l i t y . t o r s which a f f e c t i n t e g r i t y and r e l i a b i l i t y may be c l a s s i f i e d as f o l l o w s : a)

f a i l u r e of t h e c i r c u i t ;

f a i l u r e of t h e power s u p p l y ; a n d

f a i l u r e of t h e c o n t r o l c i r c u i t .

Reducing f a i l u r e of t h e c i r c u i t . A s t a n d a r d p r a c t i c e i s t o u s e s e v e r a l 3.6.2.1 c i r c u i t s t o p r e v e n t a f a i l u r e of one c i r c u i t b l a c k i n g o u t a n e n t i r e l i g h t i n g system. One Four c i r c u i t s a r e sometimes employed f o r l i g h t i n g t h e a p p r o a c h and t h r e s h o l d . c i r c u i t i s u s e d f o r t h e t h r e s h o l d l i g h t s and t h r e e f o r t h e a p p r o a c h l i g h t i n g system. The l a t t e r t h r e e c i r c u i t s a r e s o d e s i g n e d t h a t i f one s h o u l d f a i l o n l y e v e r y t h i r d b a r r e t t e would be o u t of o p e r a t i o n . Where a l i g h t i n g p a t t e r n i s f e d by s e v e r a l c i r c u i t s , t h e p r a c t i c e of e a c h c i r c u i t f e e d i n g o n e p a r t i c u l a r g e o g r a p h i c a l s e c t i o n o f t h e p a t t e r n i s n o t recommended b e c a u s e l o s s of one c i r c u i t c a n t h e n change t h e p a t t e r n i n t o something e n t i r e l y d i f f e r e n t . For example, a n a p p r o a c h l i g h t i n g p a t t e r n c o m p r i s i n g a c e n t r e l i n e and f i v e c r o s s b a r s i f f e d i n two d i s t i n c t h a l v e s by two c i r c u i t s c o u l d change f r o m a c e n t r e l i n e and f i v e b a r s y s t e m t o a c e n t r e l i n e and t h r e e b a r s y s t e m w i t h t h e l o s s of one c i r c u i t . 3.6.2.2 Reducing f a i l u r e of t h e power s u p p l y . S t e p s c a n b e t a k e n t o e n s u r e a cont i n u o u s s u p p l y of power t o t h e l i g h t i n g system. h e o f t h e most s i m p l e and most r e l i a b l e i s t o h a v e a l t e r n a t i v e s o u r c e s of power f r o m two d i f f e r e n t g e n e r a t o r s w h i c h a r e c a p a b l e of a u t o m a t i c a l l y s t a r t i n g i n c a s e of a power f a i l u r e . Equipment h a s b e e n d e v e l oped w h i c h w i l l r e d u c e t o a v e r y s h o r t i n t e r v a l t h e t i m e between power f a i l u r e and d e l i * - --" V C L ~ ~ f c u r r e n t from t h e a l t e r n a t i v e system. S w i t c h i n g r a t e s a s l o w a s 0 = 3 t o 0.5 s e c o n d s a r e b e i n g o b t a i n e d f o r equipment i n s t a l l e d i n c o n j u n c t i o n w i t h p r e c i s i o n a p p r o a c h runways. S w i t c h i n g r a t e s f o r o t h e r s y s t e m s v a r y between 1 0 t o 20 s e c o n d s . Another p r o c e d u r e which i s u s e d i s t o o p e r a t e from t h e s e c o n d a r y g e n e r a t o r s c o n t i n u o u s l y d u r i n g c r i t i c a l t i m e s s u c h a s d u r i n g low v i s i b i l i t y c o n d i t i o n s o r when a s t o r m i s forecast. I n c a s e of a f a i l u r e of t h e g e n e r a t o r , t h e s w i t c h - o v e r i s t h e n made t o t h e p r i m a r y power s u p p l y . These systems and a r r a n g e m e n t s a r e d i s c u s s e d i n C h a p t e r 2. 3.6.2.3 Sometimes a l t e r n a t e c u i t s a r e neglected. Careful a t t e n t i o n i s given t o t h e l i g h t i n g c i r c u i t s power s u p p l i e s a r e p r o v i d e d f o r them, b u t p r o v i s i o n of a l t e r n a t e c i r c u i t s The p r o b a b i l i t y of a o f t h e l i g h t s f r o m t h e c o n t r o l tower i s o v e r l o o k e d . c u i t f a i l i n g may be e q u a l t o t h a t of a l i g h t i n g c i r c u i t f a i l i n g , and d u a l c i r c u i t s s h o u l d be p r o v i d e d .

control cirand secondary f o r controls control circontrol

D e s i g n i n g f o r i n t e g r i t y and r e l i a b i l i t y . 3.6.2.4 The d e s i g n and i n s t a l l a t i o n o f aerodrome l i g h t i n g s y s t e m s c a n a f f e c t i n t e g r i t y and r e l i a b i l i t y i n ways o t h e r t h a n s e l e c t i o n of components and i n t e r l e a v i n g of c i r c u i t s . These f e a t u r e s a r e o f t e n t h e same a s t h o s e u s e d t o r e d u c e and s i m p l i f y maintenance. Some of t h e f e a t u r e s d e t e r m i n e d i n t h e d e s i g n d e c i s i o n s a r e i n s t a l l i n g c a b l e s i n c o n d u i t ( d u c t s ) i n s t e a d of d i r e c t b u r i a l , u s i n g i n s e t l i g h t s i n s t e a d oE e l e v a t e d l i g h t s i n a r e a s where s u r f a c e t r a f f i c o f t e n c o l l i d e s w i t h t h e l i g h t f i x t u r e s , providing ground-wire c i r c u i t s throughout t h e system ts r e d u c e t h e e f f e c t s of i i g h ~ n i n gand h i g h v o l t a g e s u r g e s , e q u i p p i n g l i g h t f i x t u r e s wkth

h e a t i n g e l e m e n t s t o e l i m i n a t e m o i s t u r e c o n d e n s a t i o n and i c i n g p r o b l e m s , e t c . Reliab i l i t y and i n t e g r i t y a r e f a c t o r s which s h o u l d be c o n s i d e r e d i n t h e d e s i g n and installation.

3.7

3.7.1

MONITORING OF AERODROME LIGHTING CIRCUITS

Methods o f m o n i t o r i n g

8.3 of Annex 1 4 s t a t e s t h a t a s y s t e m of m o n i t o r i n g v i s u a l a i d s s h o u l d be 3.7.1.1 employed t o e n s u r e l i g h t i n g s y s t e m r e l i a b i l i t y . M o n i t o r i n g may be accomplished by v i s u a l o b s e r v a t i o n s o r by a n a u t o m a t i c s e n s o r . V i s u a l m o n i t o r i n g , e x c e p t f o r what A i r T r a f f i c C o n t r o l s e e s and p i l o t s r e p o r t , i s seldom used. Some of t h e m o n i t o r i n g of l i g h t i n g s y s t e m s i n u s e c o n s i s t of i n d i c a t o r l i g h t s which i n d i c a t e o n l y t h a t t h e s w i t c h e s which c o n t r o l t h e c i r c u i t s a r e t u r n e d t o ON o r t h a t one o r more l i g h t s i n a c i r c u i t have f a i l e d . R e l i a b l e monitoring is very d e s i r a b l e , but p a r t i a l o r incomplete m o n i t o r i n g can c r e a t e a s e c u r e f e e l i n g which h i n d e r s i n s t e a d of a i d s i n r e l i a b i l i t y . Examples a r e : i n d i c a t o r l i g h t s which respond o n l y t o s w i t c h p o s i t i o n o r c o n t r o l r e l a y o p e r a t i o n may n o t d e t e c t a m a l f u n c t i o n i n g c o n s t a n t - c u r r e n t r e g u l a t o r o r a grounded o u t l i g h t i n g c i r c u i t ; o r m o n i t o r s of power waveform d i s t o r t i o n t o d e t e c t lamp f a i l u r e s may n o t respond t o f a u l t s of t h e l i g h t i n g c i r c u i t s o r f a i l u r e of power o r c o n t r o l equipment. 3.7.2

Desien o f m o n i t o r i n g d e v i c e s

3.7.2.1 The i d e a l m o n i t o r i n g d e v i c e f o r aerodrome l i g h t s measures t h e i n t e n s i t y o f e a c h l i g h t i n t h e d i r e c t i o n s from which i t w i l l be o b s e r v e d and i n d i c a t e s a n y d e f i c i e n c i e s by l o c a t i o n and amount. Such m o n i t o r i n g may n o t be p r a c t i c a l o r p o s s i b l e . The d e s i g n of m o n i t o r i n g d e v i c e s s h o u l d c o n s i d e r r e l a t e d i n f o r m a t i o n t h a t would be h e l p f u l Some d e v i c e s may s e n s e i m p o r t a n t a s w e l l a s t h e f a i l u r e s which t h e y can d e t e c t . I n s t r u c t i o n s f o r u s e of t h e i n f o r m a t i o n which i s not p r e s e n t e d by t h e i n d i c a t o r . m o n i t o r i n g s y s t e m s h o u l d e x p l a i n t h e l i m i t a t i o n s as w e l l a s t h e c a p a b i l i t i e s of t h e system. The q u a n t i t i e s u s u a l l y measured a r e c u r r e n t , v o l t a g e , power, waveform, t i m e , and p h o t o e l e c t r i c e m i s s i o n . R e c o r d e r s of t h e s e v a l u e s a r e a form of m o n i t o r , b u t t h i s t y p e i n f o r m a t i o n i s seldom used f o r immediate r e s p o n s e o r t o produce a c t i o n s automatically. 3.7.3

C l a s s e s of m o n i t o r s

3.7.3.1 M o n i t o r s may be c l a s s e d a s a c t i v e o r p a s s i v e . Active monitors take a p r e d e t e r m i n e d a c t i o n when a s p e c i f i c c o n d i t i o n is s e n s e d o r a t a s e l e c t e d t i m e a f t e r t h e c o n d i t i o n o c c u r s . Examples of m o n i t o r s i n t h i s c l a s s a r e t h e p r i m a r y s o u r c e v o l t a g e s e n s o r s which a u t o m a t i c a l l y s t a r t t h e s e c o n d a r y e n g i n e - g e n e r a t o r s e t and t r a n s f e r t h e l o a d when t h e p r i m a r y power s o u r c e f a i l s , o r t h e h i g h i n t e n s i t y t i m e l i m i t c o n t r o l which a u t o m a t i c a l l y r e s e t s t o a lower i n t e n s i t y s t e p and sounds a b u z z e r a n d / o r e n e r g i z e s an i n d i c a t o r lamp a f t e r t h e l i g h t s have been a t f u l l i n t e n s i t y f o r 15 m i n u t e s . * Passive m o n i t o r s p r o v i d e a s i g n a l s u c h a s an i n d i c a t o r lamp o r b u z z e r when a p r e d e t e r m i n e d

A u t o m t $ c r e s e t t i n g of t h e i n t e n s i t y Is n o t d e s i r a b l e s i r l c e t h e change e ~ u l c "be ; made -L .," a pi:ot is i:-I a c-'"' L L L i Ca i- 'p a-. .Ll ?'L W .-.C I l --F; L aypLua%-I-Il. l

LILO

c o n d i t i o n o c c u r s and does n o t change any of t h e systems o p e r a t i o n s . A human o p e r a t o r must e v a l u a t e t h e meaning of t h e s i g n a l and t a k e t h e a p p r o p r i a t e a c t i o n . Examples of p a s s i v e m o n i t o r i n g a r e t h e s e q u e n c e - f l a s h i n g l i g h t s m o n i t o r which a l e r t s when a p r e s e l e c t e d number of l i g h t s i s i n o p e r a t i v e , o r t h e i n d i c a t o r lamp which shows t h a t s p e c i f i c c i r c u i t s a r e e n e r g i z e d and o p e r a t i n g . 3.7.4

Monitor o v e r r i d e c o n t r o l s

Often c o n t r o l s o r p r o c e d u r e s which can be u s e d t o o v e r r i d e o r c i r c u m v e n t t h e 3.7.4.1 a c t i o n of t h e monitor a r e p r o v i d e d . By a c t i v a t i n g a s p e c i a l c i r c u i t o r r e s e t t i n g a c o n t r o l , t h e o p e r a t o r can m a i n t a i n t h e s y s t e m s o p e r a t i o n w i t h o u t change f o r new o r The s i g n a l i n d i c a t i n g t h e m o n i t o r ' s r e s p o n s e may b e p r o v i d e d i n d e f i n i t e t i m e period. d u r i n g t h e o v e r r i d e o p e r a t i o n t o k e e p t h e o p e r a t o r informed t h a t t h e s y s t e m i s i n a n u n d e s i r a b l e o p e r a t i n g s t a t u s . An example i s t o r e s e t t h e t i m e r t o f u l l i n t e n s i t y o p e r a t i o n s a t t h e b e g i n n i n g of e a c h a p p r o a c h i n low v i s i b i l i t y c o n d i t i o n s t o e n s u r e t h a t t h e l i g h t s w i l l n o t a u t o m a t i c a l l y be changed t o a lower i n t e n s i t y d u r i n g t h e approach.

3.8

3.8.1

ELECTRICAL CIRCUITS FOR RADIO NAVIGATION AIDS

Types of r a d i o n a v i g a t i o n a i d s

The t y p e s of r a d i o n a v i g a t i o n a i d s which may be l o c a t e d on o r n e a r t h e 3.8.1.1 aerodrome and r e q u i r e e l e c t r i c a l power e i t h e r f r o m t h e aerodrome power s y s t e m o r a s a s e p a r a t e s y s t e m v a r i e s w i t h t h e aerodrome. These r a d i o n a v i g a t i o n a l a i d s o f t e n i n c l u d e i n s t r u m e n t l a n d i n g s y s t e m ( I L S ) , v e r y h i g h f r e q u e n c y o m n i d i r e c t i o n a l r a d i o r a n g e (VOR), n o n - d i r e c t i o n a l beacon ( N D B ) , d i r e c t i o n f i n d i n g (DF) f a c i l i t i e s , p r e c i s i o n a p p r o a c h r a d a r s y s t e m s , d i s t a n c e m e a s u r i n g equipment (DME), a i r s u r v e i l l a r ~ c er a d a r (ASR), and s i m i l a r equipment, Most aerodromes a r e equipped w i t h some of t h e s e d e v i c e s a n d t h e Note t h a t t h e ILS f o r e l e c t r i c a l power r e q u i r e m e n t s may r e q u i r e s p e c i a l c o n s i d e r a t i o n . c a t e g o r y I1 and 111 o p e r a t i o n s i s more p r e c i s i o n equipment t h a n t h a t r e q u i r e d f o r category I operations. 3.8.2

Electrical characteristics

E l e c t r i c a l power f o r r a d i o n a v i g a t i o n a i d s i s u s u a l l y a l t e r n a t i n g c u r r e n t 3.8.2.1 B a t t e r i e s may be used t o p r o v i d e power f o r s t a r t i n g s e c o n d a r y power s o u r c e s and (ac). T h i s a c power i s u s u a l l y t o s u p p l y energy f o r some u n i n t e r r u p t i b l e power s y s t e m s . e i t h e r 50 o r 60 h e r t z . 3.8.2.2 Primary power. For r a d i o n a v i g a t i o n a i d s l o c a t e d on o r a d j a c e n t t o t h e aerodrome, t h e primary power s o u r c e i s u s u a l l y t h e same a s t h e aerodrome p r i m a r y s o u r c e . 'I'hese s o u r c e s a r e d i s c u s s e d i n p a r a g r a p h 2.1.2, S i n c e t h e t o t a l k i l o w a t t s r e q u i r e d by r a d i o n a v i g a t i o n a i d s u s u a l l y i s n o t l a r g e , t h e i n p u t power t o t h e s e i n s t a l l a t i o n s i s o f t e n t r a n s m i t t e d a t t h e i n t e r m e d i a t e v o l t a g e l e v e l and f e d t o Local d i s t r i b u t i o n t r a n s f o r m e r s f o r step-down t o t h e v o l t a g e s u i t a b l e f o r t h e equipment, Secondary power* S i n c e t h e s e r a d i o n a v i g a t i o n a i d s p r o v i d e s i g n a l s f o r 3.8.2.3 i n s t r u m e n t g u i d a n c e of t h e a i r c r a f t and a r e e s s e n t i a l f o r o p e r a t i o n s i n a t l e a s t some c o n d i t i o n s , Annex 10, Voiurne I, P a r t i , C'napter 2 r e q u i r e s s e c o n d a r y power aoinrces f o r most of t h e s e r a d i o a i d s . The s w i t c h - o v e r time f o r some of t h e s e r a d i o n a v i g a t i o n a i d s a r e shown i n Table 2-1 and d i s c u s s e d i n paragraphs 2 , 2 and 2 , 3 o f t h i s manual. The r a d i o navis--: , a L L-u u a i d s a r e o f t e n l o c a t e d In - isolated . a r e a s o r a r e a s w e l l s e p a r a t e d from

Secondary power i s u s u a l l y p r o v i d e d by o t h e r b u i l d i n g s r e q u i r i n g e l e c t r i c a l power. e n g i n e - g e n e r a t o r power u n i t s b e c a u s e , f o r t h e amount of power needed, s e c o n d a r y power I f a n independent may be more e c o n o m i c a l t o i n s t a l l t h a n a s e c o n d f e e d e r t o t h e s i t e . power s o u r c e i s u s e d , t h e f e e d e r f r o m t h i s s o u r c e s h o u l d b e i n a s e p a r a t e d u c t o r e v e n a Some of t h e r a d i o n a v i g a t i o n a i d s a r e s e p a r a t e r o u t e f r o m t h e p r i m a r y power f e e d e r . more l i k e l y t o r e q u i r e u n i n t e r r u p t i b l e power s u p p l i e s t h a n a r e aerodrome l i g h t i n g s y s t e m s . The r e d u n d a n t c o n f i g u r a t i o n of F i g u r e 2-3 i s o f t e n a d v i s a b l e f o r some r a d i o n a v i g a t i o n a i d s and r e l a t e d computers.

3.8.2.4

Groundin@ Radio n a v i g a t i o n a i d s may r e q u i r e lower r e s i s t a n c e and more g r o u n d i n g t h a n d o aerodrome l i g h t i n g s y s t e m s . The g r o u n d i n g , as d i s c u s s e d i n The g r o u n d i n g p a r a g r a p h 2.5.14, a p p l i e s b u t g r o u n d i n g n e t w o r k s a r e more o f t e n r e q u i r e d . r e q u i r e m e n t s of b o t h t h e e l e c t r i c a l s y s t e m a t t h e r a d i o a i d s b u i l d i n g and a t t h e a n t e n n a Some of t h e a n t e n n a s may r e q u i r e s p e c i a l g r o u n d i n g s h o u l d be c o n s i d e r e d c a r e f u l l y . p l a n e s i n some l o c a t i o n s . P r o t e c t i o n of t h e g r o u n d i n g s y s t e m s f r o m c o r r o s i o n may be n e c e s s a r y f o r some r a d i o n a v i g a t i o n a i d s . St a b l e

3.8.2.5 Lightning a r r e s t e r s . L i g h t n i n g and s u r g e p r o t e c t i o n f o r r a d i o n a v i g a t i o n a i d s i s more i m p o r t a n t t h a n f o r most e l e c t r i c a l s y s t e m s b e c a u s e t h e r a d i o s i g n a l s a r e more e a s i l y a f f e c t e d , and a n t e n n a s a r e o f t e n t h e t a r g e t of l i g h t n i n g s t r i k e s . P a r a g r a p h 2.5.12 d i s c u s s e s l i g h t n i n g p r o t e c t i o n . Also t h e s e r a d i o a i d s o f t e n u s e s o l i d - s t a t e d e v i c e s which a r e v u l n e r a b l e t o v o l t a g e and power s u r g e s . O f t e n b a t t e r i e s o r c o n v e r t e r s a r e u s e d t o p r o v i d e d c power f o r t h e s o l i d - s t a t e d e v i c e s t o e l i m i n a t e o r r e d u c e t h e l i g h t n i n g and power s u r g e problems. 3.8.2.6 Feeds t o a n t e n n a a r r a y s . The c a b l i n g between t h e r a d i o e q u i p m e n t and t h e antenna o f t e n r e q u i r e s s p e c i a l handling. U s u a l l y c o a x i a l c a b l e s a r e u s e d t o conduct t h e s e s i g n a l s . The c a b l e may be r e q u i r e d t o p r o v i d e a p r o p e r impedance m a t c h between t h e o u t p u t of t h e s i g n a l g e n e r a t o r and t h e i n p u t t o t h e a n t e n n a b u t may a l s o need t o be The r a d i o equipment o f t e n e x p l i c i t l y of a n a c c u r a t e l e n g t h f o r f r e q u e n c y p h a s i n g . s t a t e s t h e s e c a b l i n g r e q u i r e m e n t s b u t some r a d i o a i d s may n o t f u r n i s h t h e s e d e t a i l s . The f e e d s t o t h e a n t e n n a a r r a y s s h o u l d be c a r e f u l l y c o o r d i n a t e d w i t h t h e s u p p l i e r of t h e equipment and t h e i n s t a l l e r s of t h e a n t e n n a and r a d i o equipment.

3.8.3,1 Uses of c o n t r o l c i r c u i t s . The c o n t r o l c i r c u i t s f o r r a d i o n a v i g a t i o n a i d s a r e p r i m a r i l y u s e d t o e n e r g i z e and d e e n e r g i z e t h e s y s t e m s , t o t r a n s f e r f r o m p r i m a r y t o stand-by o r a l t e r n a t e t r a n s m i t t e r , and t o t r a n s f e r from p r i m a r y t o s e c o n d a r y power source

3.8.3.2 The r a d i o n a v i g a t i o n a i d s may b e l o c a t e d on t h e aerodrome o r s e v e r a l m i l e s away. Most r a d i o n a v i g a t i o n a i d s p r o v i d e l o c a l c o n t r o l a t t h e t r a n s m i t t e r s i t e and r e m o t e c o n t r o l a t one o r more a i r t r a f f i c o r equipment c o n t r o l s i t e s . I f t h e r a d i o a i d s a r e l o c a t e d on o r n e a r t h e aerodrome and t h e c o n t r o l s a r e r e l a t i v e l y s i m p l e , a c o r d c power c o n t r o l c i r c u i t s s i m i l a r t o t h o s e u s e d f o r aerodrome l i g h t i n g may be used. These c o n t r o l c i r c u i t s a r e d i s c u s s e d i n p a r a g r a p h s 3.4.1.4, 3.4.2.3, 3.4.3.1, and 3.4.3.2 a s guides. If t h e d i s t a n c e s a r e g r e a t o r t h e c o n t r o l c i r c u i t s a r e complex, t e l e p h o n e c i r c u i t s a r e o f t e n used f o r remote c o n t r o l . By d i a l i n g a p a r t i c u l a r code of o n e , two, o r t h r e e numbers, t h e d e s i r e d s w i t c h i n g c a n be o b t a i n e d . The t e l e p h o n e d i a l i n g c o n t r c l s y s t e m i s a form o f m u l t i p l e x c o n t r o l which c a n be expanded f o r c o n t r o i l i n g v e r y complex s y s t e m s .

3.8.4

R e l i a b i l i t y and i n t e g r i t y of r a d i o n a v i g a t i o n a i d s

A s d i s c u s s e d i n p a r a g r a p h 3.6.1, t h e r e l i a b i l i t y and i n t e g r i t y of n o n - v i s u a l 8.4.1 d s ( r a d i o n a v i g a t i o n a i d s ) s h o u l d be comparable t o t h a t of v i s u a l a i d s . I n a d d i t i o n t h e e l e c t r i c a l f a c t o r s a f f e c t i n g aerodrome l i g h t i n g of f a i l u r e of t h e c i r c u i t , f a i l u r e of t h e power s u p p l y , and f a i l u r e of t h e c o n t r o l c i r c u i t , t h e r a d i o n a v i g a t i o n a i d s must t r a n s m i t a s i g n a l h a v i n g s e v e r a l q u a l i t i e s w i t h i n a c c e p t a b l e t o l e r a n c e s . These s i g n a l q u a l i t i e s and t o l e r a n c e s f o r t h e s e a i d s a r e d i s c u s s e d i n Annex 1 0 , Volume I , P a r t 1 , C h a p t e r 3. Not o n l y must t h e equipment be o p e r a t i n g and t r a n s m i t t i n g a s i g n a l , b u t i t s h o u l d be monitored t o a s s u r e a n a c c e p t a b l e s i g n a l . U s u a l l y no s i g n a l i s p r e f e r a b l e t o a bad s i g n a l . To improve r e l i a b i l i t y many r a d i o n a v i g a t i o n a i d s h a v e a l t e r n a t e t r a n s m i t t e r s e n e r g i z e d and r e a d y f o r s w i t c h i n g t o t r a n s m i s s i o n upon f a i l u r e of t h e p r i m a r y t r a n s m i t t e r o r of a d e f i c i e n t s i g x a l . The r a d i o n a v i g a t i o n a i d s o f t e n h a v e i n d i v i d u a l s e c o n d a r y power s o u r c e s t o a u t o m a t i c a l l y assume power i f t h e p r i m a r y power source f a i l s . The c o n t r o l s y s t e m s h o u l d be d e s i g n e d s o t h a t i f t h e c o n t r o l s h o u l d f a i l when t h e a i d is b e i n g o p e r a t e d by remote manual c o n t r o l , t h e r a d i o a i d w i l l remain o p e r a t i n g and s w i t c h t o a u t o m a t i c c o n t r o l . Attachment F t o P a r t I of Annex 10 c o n t a i n s a d d i t i o n a l g u i d a n c e m a t e r i a l r e g a r d i n g r e l i a b i l i t y and a v a i l a b i l i t y of r a d i o n a v i g a t i o n aids.

M o n i t o r i n g of r a d i o n a v i g a t i o n a i d s 3.8.5.1 Signal monitoring. The m o n i t o r i n g of r a d i o n a v i g a t i o n a i d s , e x c e p t f o r l i g h t s t o i n d i c a t e t h a t t h e equipment i s e n e r g i z e d , r e q u i r e s a u t o m a t i c s e n s o r s of t h e S e v e r a l q u a l i t i e s of t h e s i g n a l and f u n c t i o n s i g n a l t o determine i f i t i s acceptable. i n g of s e c t i o n s of t h e equipment may r e q u i r e m o n i t o r i n g . The m o n i t o r i n g of t h e s i g n a l q u a l i t y f o r t h e s e r a d i o a i d s a r e d i s c u s s e d i n Annex 1 0 , Volume I , P a r t 1, C h a p t e r 3 . The m o n i t o r may be r e q u i r e d t o a u t o m a t i c a l l y s w i t c h t o t h e a l t e r n a t e t r a n s m i t t e r o r d e a c t i v a t e t h e equipment and a l s o s i g n a l t h e d e s i g n a t e d c o n t r o l p o i n t s of t r a n s m i t t e d s i g n a l d e f i c i e n c i e s . O t h e r l e s s e s s e n t i a l r a d i o n a v i g a t i o n a i d s may have m o n i t o r s which I f i t is not s a t i s f a c t o r y , i n d i c a t e a t t h e c o n t r o l p o i n t s i f operation is s a t i s f a c t o r y , +-L.e l l = o p e r a t o r can make the r e q u i r e d t r a n s f e r s , For t h e r a d i o a i d s w i t h c r i t i c a l s i g n a l r e q u i r e m e n t s , t h e m o n i t o r may a u t o m a t i c a l l y d e a c t i v a t e t h e equipment t o p r e v e n t t r a n s m i s s i o n of a d e f i c i e n t s i g n a l i f a s a t i s f a c t o r y s i g n a l from an a l t e r n a t e t r a n s m i t t e r is not obtained. 3.8.5.2 Monitoring a u x i l i a r y f u n c t i o n s . S e v e r a l o t h e r f u n c t i o n s may be monitored t o a s s u r e s a t i s f a c t o r y o p e r a t i o n of r a d i o n a v i g a t i o n a i d s . These may i n c l u d e b a t t e r y v o l t a g e s f o r t h e s t a r t i n g of t h e s e c o n d a r y power s e t o r f o r o p e r a t i n g u n i n t e r r u p t i b l e power s u p p l i e s , ambient o r room t e m p e r a t u r e t o m a i n t a i n s u i t a b l e e n v i r o n m e n t s f o r t h e e q u i p m e n t , and f u e l s u p p l y f o r t h e s e c o n d a r y power s o u r c e . These m o n i t o r s may p r o v i d e a l a r m s o r i n d i c a t i o n s t h a t t h e f u n c t i o n s exceed e s t a b l i s h e d c r i t e r i a .

3.9

ACCEPTANCE TESTING OF AERODROME ELECTRICAL CIRCUITS

3.3.1.2 The t e s t p r o c e d u r e s d e s c r i b e d i n t h i s s e c t i o n a p p l y t o t h e a c c e p t a n c e t e s t s of new i n s t a l l a t i o n s and s h o u l d be performed b e f o r e making t h e s y s t e m o p e r a t i o n a l .

3.9.2.1 Each i n s t a l l a t i o n c o n t r a c t s h o u l d i n c l u d e a g u a r a n t e e c l a u s e s p e c i f y i n g a p e r i o d of a t l e a s t one y e a r d u r i n g which t h e i n s t a l l i n g c o n t r a c t o r c a n be h e l d r e s p o n s i b l e f o r r e p a i r i n g and r e p l a c i n g a l l c a b l e and equipment f a i l u r e s r e s u l t i n g f r o m poor work o r d e f e c t i v e m a t e r i a l s and equipment. (Damp o r d i r t y c a b l e c o n n e c t o r s and c a b l e damage due t o f a u l t y i n s t a l l a t i o n p r a c t i c e s o f t e n f a i l s e v e r a l months a f t e r installation. )

3.9.3.1 Visual examination. The most i m p o r t a n t o f a l l i n s p e c t i o n and t e s t procedures a r e thorough v i s u a l i n s p e c t i o n s . V i s u a l i n s p e c t i o n s s h o u l d be made f r e q u e n t l y d u r i n g i n s t a l l a t i o n , a t c o m p l e t i o n of i n s t a l l a t i o n , and b e f o r e e n e r g i z i n g t h e circuits. A c a r e f u l v i s u a l i n s p e c t i o n w i l l r e v e a l d e f e c t s t h a t c a n be c o r r e c t e d p r i o r S e r i o u s damage may o c c u r i f d e f e c t s a r e s u b j e c t e d t o a c c e p t a n c e t e s t s and e n e r g i z a t i o n . t o e l e c t r i c a l t e s t s o r energization. Visual i n s p e c t i o n s should i n c l u d e i n s p e c t i o n appraisal of: a)

c o r r e c t n e s s of e x t e r n a l c o n n e c t i o n s ;

good work p e r f o r m a n c e ;

c l e a n l i n e s S;

s a f e t y hazards; and

s p e c i f i c requirements f o r i n d i v i d u a l items.

A l l equipment manufactured u n d e r s p e c i f i c a t i o n s s h o u l d p a s s s t r i c t f a c t o r y t e s t s p r i o r t o s h i p m e n t , b u t i t s h o u l d be v i s u a l l y i n s p e c t e d f o r s h i p p i n g damage i m m e d i a t e l y upon receipt.

The p r i m a r y and 3.9.3.2 s e c o n d a r y c a b l e l e a d s of t h e t r a n s f o r m e r s s h o u l d be s u p p l i e d w i t h f a c t o r y i n s t a l l e d molded c o n n e c t o r s . V i s u a l i n s p e c t i o n of t h e s e i t e m s d u r i n g i n s t a l l a t i o n i s e s p e c i a l l y i m p o r t a n t , a s minor c u t s , b r u i s e s , o r m i s h a n d l i n g may r e s u l t i n a p r o g r e s s i v e d e t e r i o r a t i o n which w i l l e v e n t u a l l y c a u s e c o m p l e t e f a i l u r e , b u t n o t u n t i l some t i m e a f t e r a c c e p t a n c e t e s t s . During i n s t a l l a t i o n , t h e s e i t e m s s h o u l d b e i n s p e c t e d t o determine t h e following: a)

t h a t t h e m a t i n g s u r f a c e s of molded c o n n e c t o r s a r e c l e a n and d r y when plugged t o g e t h e r . I f c l e a n and d r y i n s i d e , t h e s e h i g h v o l t a g e c o n n e c t o r s w i t h t a p i n g form a c o n n e c t i o n e q u a l t o , o r s u p e r i o r t o , a c o n v e n t i o n a l h i g h v o l t a g e s p l i c e . C o n v e r s e l y , i f t h e y a r e wet o r d i r t y i n s i d e , no amount of t a p i n g c a n p r o d u c e a s a t i s f a c t o r y c o n n e c t i o n . Two o r t h r e e t u r n s of t a p e a r e recommended t o h o l d t h e c o n n e c t o r t o g e t h e r and k e e p t h e p a r t i n g l i n e s c l e a n . C l e a n l i n e s s of m a t i n g s u r f a c e s c a n b e s t be i n s u r e d by k e e p i n g t h e f a c t o r y i n s t a l l e d c a p s i n p l a c e u n t i l t h e The m a t i n g s u r f a c e s of uncapped c o n n e c t o r s f i n a l c o n n e c t i o n i s made. s h o u l d n o t be l a i d down, touched, o r b r e a t h e d upon. If i t i s necessary t o b r e a k a c o n n e c t i o n , t h e c o n n e c t o r s s h o u l d be i m m e d i a t e l y capped;

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t h a t t h e c o n n e c t o r s a r e c o m p l e t e l y plugged t o g e t h e r . A f t e r i n i t i a l p l u g g i n g , t r a p p e d a i r p r e s s u r e may p a r t i a l l y d i s e n g a g e t h e p l u g and I f t h i s h a p p e n s , w a i t a few s e c o n d s and push them t o g e t h e r receptacle. a g a i n . Apply two o r t h r e e t u r n s of t a p e t o h o l d them i n p l a c e ;

t h a t t h e c a b l e s h a v e n o t been c u t by s h o v e l s , k i n k e d , c r u s h e d by v e h i c l e w h e e l s , b r u i s e d by r o c k s , o r damaged i n any way d u r i n g h a n d l i n g and i n s t a l l a t i o n ;

t h a t t h e c a b l e s a r e b u r i e d t o t h e s p e c i f i e d d e p t h below f i n i s h e d g r a d e and a l l o t h e r d e t a i l e d r e q u i r e m e n t s of t h e i n s t a l l a t i o n s p e c i f i c a t i o n a r e accomplished;

t h a t t h e c a b l e s do n o t d i r e c t l y c r o s s e a c h o t h e r and a r e s e p a r a t e d by t h e required distances;

t h a t s c r e e n e d m a t e r i a l h a s been p l a c e d u n d e r and o v e r t h e c a b l e s , and t h a t r o c k s o r p e b b l e s do n o t c o n t a c t t h e c a b l e s ; and

t h a t t h e c a b l e s h a v e n o t been b e n t s h a r p l y where t h e y e n t e r ( o r l e a v e ) a c o n d u i t and a r e s u p p o r t e d p r o p e r l y by tamped ground, s o f u t u r e s e t t l i n g c a n n o t c a u s e s h a r p bends.

3.9.3.3 Constant-current r e g u l a t o r inspection. Each c o n s t a n t - c u r r e n t r e g u l a t o r s h o u l d be i n s p e c t e d t o e n s u r e t h a t p o r c e l a i n b u s h i n g s have n o t been c r a c k e d , n o s h i p p i n g damage h a s o c c u r r e d , c o n n e c t i o n s a r e c o r r e c t , s w i t c h e s and r e l a y s o p e r a t e f r e e l y and a r e n o t t i e d o r b l o c k e d , f u s e s ( i f r e q u i r e d ) a r e c o r r e c t , and t h a t t h e o i l l e v e l o f o i l f i l l e d regulators is correct. Only r e l a y p a n e l c o v e r s s h o u l d be removed f o r t h i s It i s n o t n e c e s s a r y t o open t h e main t a n k of o i l - f i l l e d r e g u l a t o r s . inspection. I n f o m r a t i o n on t h e r e g u l a t o r i n s p e c t i o n p l a t e must be f o l l o w e d . All c o v e r s s h o u l d be c l e a n e d and t i g h t l y r e p l a c e d a f t e r i n s p e c t i o n and t e s t s a r e completed. 3.9.3.4 An i n s p e c t i o n s h o u l d be made t o d e t e r m i n e t h a t t h e c o l o u r , q u a n t i t y , and l o c a t i o n s of l i g h t s a r e i n a c c o r d a n c e w i t h t h e i n s t a l l a t i o n d r a w i n g s . Each l i g h t s h o u l d be i n s p e c t e d t o d e t e r m i n e t h a t i t i s o p e r a b l e , t h a t g l a s s i s n o t broken o r c r a c k e d , t h a t c o r r e c t iamps a r e i n s t a l l e d , and t h a t -it h a s been p r o p e r l y l e v e l e d and aimed. 3.9.3.5 I n s p e c t i o n of m i s c e l l a n e o u s components. Components s u c h a s c o n t r o l p a n e l s , r e l a y c a b i n e t s , p a n e l b o a r d s , e t c . , s h o u l d be v i s u a l l y i n s p e c t e d f o r damage, c o r r e c t c o n n e c t i o n s , p r o p e r f u s e and c i r c u i t - b r e a k d e r r a t i n g s , and compliance w i t h t h e i n s t a l l a t i o n drawings. 3.9.3.6 System o p e r a t i o n t e s t . A f t e r components and c i r c u i t s h a v e been i n s p e c t e d , a s i n d i c a t e d i n t h e p r e c e e d i n g p a r a g r a p h s , t h e e n t i r e s y s t e m s h o u l d be r e s t e d a s follows : a)

e a c h s w i t c h of t h e l i g h t i n g p a n e l s i n t h e c o n t r o l tower s h o u l d b e o p e r a t e d s o t h a t e a c h s w i t c h p o s i t i o n i s r e a c h e d a t l e a s t t w i c e , During t h i s p r o c e s s , a l l L i g h t s and v a u l t equipment s h o u l d be o b s e r v e d t o determine t h a t each switch properly c o n t r o l s t h e corresponding c i r c u i t ;

P a r t 5.

3.9.4

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E l e c t r i c a l Svstems

t h e above t e s t should be r e p e a t e d u s i n g t h e p a n e l s i n t h e a l t e r n a t e c o n t r o l s t a t i o n ( v a u l t ) and t h e n r e p e a t e d a g a i n u s i n g t h e l o c a l c o n t r o l s w i t c h e s on t h e r e g u l a t o r s ; and

e a c h l i g h t i n g c i r c u i t s h o u l d b e t e s t e d by o p e r a t i n g i t c o n t i n u o u s l y a t maximurn i n t e n s i t y f o r a t l e a s t 6 h o u r s . Visual i n s p e c t i o n should be made a t t h e b e g i n n i n g a n d a t t h e e n d o f t h i s t e s t t o d e t e r m i n e t h a t t h e c o r r e c t number of l i g h t s are o p e r a t i n g a t f u l l i n t e n s i t y . Dimming of some o r a l l o f t h e l i g h t s i n a c i r c u i t i s a n i n d i c a t i o n o f g r o u n d faults. I n a d d i t i o n , t h e l a m p - t e r m i n a l v o l t a g e s h o u l d be measured o n a t l e a s t one l i g h t t n e a c h m u l t i p l e c i r c u i t , t o d e t e r m i n e t h a t i t i s w i t h i n t 5 p e r c e n t o f t h e r a t e d lamp v o l t a g e a s marked o n t h e l a m p .

E l e c t r i c a l tests o f s e r i e s - c i r c u i t e q u i p m e n t

3.9.4.1 E l e c t r i c a l tests a r e h e l p f u l i n determining t h a t t h e q u a l i t y of t h e i n s t a l l a t i o n i s a c c e p t a b l e a n d t h a t t h e p e r f o r m a n c e w i l l meet t h e o p e r a t i o n a l r e q u i r e m e n t s . These Some o f t h e t e s t s i n v o l v e t h e u s e a n d measurements o f h i g h v o l t a g e c i r c u i t s . t e s t s s h o u l d b e p e r f o r m e d o n l y by q u a l i f i e d p e r s o n s who a r e f a m i l i a r w i t h h i g h - v o l t a g e e l e c t r i c a l e q u i p m e n t a n d t h e s a f e t y p r e c a u t i o n s w h i c h must b e o b s e r v e d . 3.9.4.2 E l e c t r i c a l t e s t s on c a b l e . Cables b u r i e d i n e a r t h ( t h a t i s , n o t i n d u c t ) s h o u l d be t e s t e d b e f o r e and a f t e r b a c k f i l l i n g t h e c a b l e t r e n c h . 3.9.4.3 Each s e r i e s c i r c u i t s h o u l d b e t e s t e d f o r c o n t i n u i t y by ohmmeter o r e q u i v a l e n t method. The r e s i s t a n c e o f t h e c i r c u i t t o g r o u n d s h o u l d t h e n b e c h e c k e d w i t h a s u i t a b l e t e s t s e t t o make s u r e i t i s f r e e o f g r o u n d s . Any f a u l t s i n d i c a t e d by t h e s e t e s t s s h o u l d be l o c a t e d and r e p a i r e d b e f o r e proceeding w i t h high-voltage t e s t s . 3.9.4.4 Each s e r i e s c i r c u i t s h o u l d b e s u b j e c t e d t o h i g h v o l t a g e i n s u l a t i o n r e s i s t a n c e t e s t s t o d e t e r m i n e c o m p l e t f r e e d o m f r o m g r o u n d s . Whenever p o s s i b l e , t h e s e t e s t s s h o u l d b e p e r f o r m e d when t h e g r o u n d i s t h o r o u g h l y w e t . E x p e r i e n c e h a s shown t h a t c i r c u i t s which p a s s i n s u l a t i o n r e s i s t a n c e t e s t s d u r i n g d r y w e a t h e r may f a i l a f t e r a heavy rain. Each c i r c u i t , i n c l u d i n g t r a n s f o r m e r s , s h o u l d be t e s t e d a s f o l l o w s : a)

Msconilect b o t h l e a d s from t h e r e g u l a t o r o u t p u t t e r m i n a l s . Support b o t h l e a d s s o t h a t a i r gaps of s e v e r a l i n c h e s e x i s t between b a r e c o n d u c t o r s a n d g r o u n d . Make s u r e t h a t t h e c a b l e s h e a t h i s c l e a n a n d d r y f o r a d i s t a n c e o f a t l e a s t 30 cm f r o m t h e e n d o f t h e c a b l e . A l s o make s u r e t h a t exposed i n s u l a t i o n a t each end of t h e c a b l e i s c l e a n and d r y .

Each c i r c u i t s h o u l d b e t e s t e d i m m e d i a t e l y a E t e r i n s t a l l a t i o n , i n a c c o r d a n c e w i t h " F i r s t T e s t F o r New C i r c u i t s " d e s c r i b e d i n s u b - p a r a g r a p h e ) . Any c i r c u i t which h a s b e e n i n s t a l l e d f o r 60 d a y s o r more, e v e n i f i t h a s n o t been o p e r a t e d , s h o u l d b e t e s t e d i n a c c o r d a n c e w i t h " S u c c e e d i n g T e s t (See s u b - p a r a g r a p h e ) . ) a n d Old C i r c u i t s

The maximum a c c e p t a b l e l e a k a g e c u r r e n t , i n m i c r o a m p e r e s , s h o u l d n o t e x c e e d t h e v a l u e s i n d i c a t e d i n p a r a g r a p h 3.9.4.7.

When a d d i t i o n s a r e made t o o l d c i r c u i t s , o n l y t h e new s e c t i o n s s h o u l d b e t e s t e d i n a c c o r d a n c e w i t h " F i r s t T e s t On New C i r c u i t s " . The c o m p l e t e c i r c u i t s h o u l d be c h e c k e d a t t h e r e d u c e d v o l t a g e s t o e n s u r e r e l i a b l e o p e r a t ton.

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Connect b o t h c o n d u c t o r s , a n d a p p l y t h e t e s t v o l t a g e i n d i c a t e d b e l o w f o r a p e r i o d o f 5 m i n u t e s between c o n d u c t o r s and g r o u n d .

F i r s t : T e s t on New C i r c u i t s

Succeeding T e s t s a n d Old C i r c u i t s

Complete a p p r o a c h l i g h t i n g system (transformers with 5 OOO-volt p r i m a r y l e a d s ) Touchdown z o n e a n d c e n t r e line light circuits ( t r a n s f o r m e r s w i t h 5 000v o l t primary l e a d s ) High i n t e n s i t y runway e d g e l i g h t c i r c u i t s (transformers w i t h 5 OOOvolt primary leads)

9 000 V, d c

Medium i n t e n s i t y runway a n d taxiway l i g h t s c i r c u i t s ( t r a n s f o r m e r s w i t h 5 000v o l t primary l e a d s )

6 000 V, d c

600-volts c i r c u i t s

l 800 V, d c

600 V, d c

p -

3.9.4.5 The t e s t s o u t l i n e d a b o v e s h o u l d b e p e r f o r m e d w i t h a s u i t a b l e h i g h - v o l t a g e t e s t e r which h a s a s t e a d y , f i l t e r e d d c o u t p u t v o l t a g e . The h i g h - v o l t a g e t e s t e r s h o u l d c o n t a i n a n a c c u r a t e v o l t m e t e r a n d microammeter f o r r e a d i n g t h e v o l t a g e a p p l i e d t o t h e c i r c u i t and t h e i n s u l a t i o n l e a k a g e c u r r e n t . These t e s t s shors2.d b e s u p e r v i s e d c a r e f u l l y by q u a l i f i e d p e r s o n n e l t o a s c e r 3.9.4.5 t a i n t h a t excessive voltages a r e not applied.

3.9.4.7 D u r i n g t h e l a s t m i n u t e of t h e t e s t s t h e i n s u l a t i o n l e a k a g e c u r r e n t i n m i c r o a m p e r e s f o r e a c h c o m p l e t e c i r c u i t s h o u l d be measured a n d s h o u l d n o t e x c e e d t h e v a l u e c a l c u l a t e d f o r e a c h c i r c u i t as f o l l o w s : a)

a l l o w 2 micorampere f o r e a c h s e r i e s t r a n s f o r m e r ;

a l l o w 1 microampere f o r e a c h 1 0 0 m e t e r s o f c a b l e ( T h i s v a l u e i n c l u d e s a l l o w a n c e s f o r t h e n o r m a l number o f c o n n e c t o r s a n d s p l i c e s . ) ; a n d

add t h e v a l u e s o b t a i n e d t o d e t e r m i n e t h e t o t a l a l l o w a b l e microampere leakage f o r each complete c i r c u i t .

3.9.4.8 Lf t h e l e a k a g e c u r r e n t e x c e e d s t h e v a l u e c a l c u l a t e d a s o u t l i n e d a b o v e , t h e c i r c u i t s h o u l d b e s e c t i o n a l i z e d arid t h e t e s t s r e p e a t e d f o r e a c h s e c t i o n . I k f e c t i v e components must b e l o c a t e d a n d r e p a i r e d , o r r e p l a c e d u n t i l t h e e n t i r e c i r c u i t p a s s e s t h e test.

Make s u r e t h a t t h e t e s t v o l t a g e s p e c i f i e d i n p a r a g r a p h 3.9.4.4 e ) i s 3.9.4.9 a c t u a l l y a p p l i e d t o t h e c i r c u i t a t t h e t i m e t h e l e a k a g e c u r r e n t i s measured. The v o l t age should be adjusted s o t h e voltmeter reads t h e desired value before t h e leakage I f any d i f f i c u l t y i s encountered i n o b t a i n i n g t h e d e s i r e d v o l t a g e , c u r r e n t i s read. e i t h e r t h e c i r c u i t b e i n g t e s t e d o r t h e test s e t i s d e f e c t i v e , and s h o u l d be c o r r e c t e d before t h e t e s t i s continued. 3.9.4.10 On new c i r c u i t s , a r e s i s t a n c e measurement s h o u l d b e made i m m e d i a t e l y a f t e r t h e c i r c u i t h a s p a s s e d t h e h i g h v o l t a g e t e s t s w i t h t h e t e s t s e t u s e d by a e r o d r o m e maintenance. T h i s measurement r e a d i n g t h e n c a n b e u s e d d u r i n g m a i n t e n a n c e as a c o m p a r i s o n w i t h f u t u r e r e a d i n g s t o d e t e r m i n e c i r c u i t c o n d i t i o n s . Ambient t e m p e r a t u r e and weather c o n d i t i o n s s h o u l d be r e c o r d e d a t t h e t i m e of t e s t . 3.9.5

E l e c t r i c a l t e s t s of o t h e r cables

3.9.5.1 Power c a b l e s r a t e d 5 000 v o l t s and more. Power c a b l e s s h o u l d b e t e s t e d a s o u t l i n e d u s i n g t h e methods i n p a r a g r a p h 3.9.4.4 e x c e p t t h a t , c a b l e s r a t e d a t 5 000 v o l t s s h o u l d b e t e s t e d a t 1 0 000 v o l t s a n d power c a b l e s r a t e d a b o v e 5 000 v o l t s s h o u l d b e t e s t e d a t t w i c e t h e c a b l e v o l t a g e r a t i n g p l u s 1 000 v o l t s . The t e s t s h o u l d b e made between conductors and from conductors t o ground w i t h t h e c a b l e ' s s h i e l d and armor g r o u n d e d a n d f o r a p e r i o d o f n o t l e s s t h a n o n e m i n u t e a f t e r i n s t r u m e n t r e a d i n g s have stabilized. The minimum a c c e p t a b l e r e s i s t a n c e v a l u e i s 50 megohms. Original insulation v a l u e s o f t h e c a b l e h a v e b e e n s u b s t a n t i a l l y r e d u c e d t o t h e s p e c i f i e d 5 0 megohms i n o r d e r t o compensate f o r c a b l e l e n g t h , a g i n g of cotlductor i n s u l a t i o n , and o t h e r f a c t o r s which may a f f e c t t e s t r e s u l t s b o t h b e f o r e a n d d u r i n g i n s t a l l a t i o n . Unless c a b l e l e n g t h should a p p r e c i a b l y e x c e e d 3 000 m e t r e s , n o r e d u c t i o n i n t h e s p e c i f i e d i n s u l a t i o n r e s i s t a n c e s h o u l d be c o n s i d e r e d . (Note. I n s u l a t i o n r e a d i n g s w i l l be e r r o n e o u s u n t i l t h e c a b l e h a s been c o m p l e t e l y c h a r g e d by t h e m e a s u r i n g i n s t r u m e n t . ) A t e s t s h o u l d b e made f o r c o n t i n u i t y o f t h e c a b l e ' s s h i e l d o r armor. An ohmmeter t y p e i n s t r u m e n t may b e u s e d . 3.9.5.2 Power c a b l e r a t e d 600 v o l t s a n d below. S e c o n d a r y power c a b l e s r a t e d a t 6 0 0 v o l t s and below and u s e d f o r l i g h t i n g a n d power w i r i n g s h o u l d h a v e a r e s i s t a n c e of n o t l e s s t h a n 5 0 megohms between c o n d u c t o r s a n d between c o n d u c t o r s a n d g r o u n d when measurem e n t s a r e made a t n o t l e s s t h a n 500 v o l t s dc. 3.9.5.3 w i t h t h e following requirements: Size cable 12 p a i r o r less Over 1 2 p a i r t o 25 p a i r , inclusive Over 25 p a i r

~f~~~

i---+..l LID ~ a 1~ . ~ a tt h i e~s ei l c a b l e s s h o u l d comply

Minimum no. of a c c e p t a b l e c o n d u c t o r s All A l l , e x c e p t one p a i r

A l l , except 2 p a i r

Acceptable conductors i n c l u d e s a t i s f a c t o r y t e s t a s t o c o n t i n u i t y , freedom from s h o r t c i r c u i t s , and a m i n i m m o f 5 0 megohms r e s i s t a n c e betwen c o n d u c t o r s a n d f r o m e a c h cond u c t o r t o grounded s h i e l d when t e s t e d a t n o t l e s s t h a n 500 v o l t s d c .

Radio f r e q u e n c y c a b l e s s h o u l d be t e s t e d f o r i n s u l a t i o n and Coaxial cables. 3.9.5.4 The i n s u l a t i o n t e s t l o o p r e s i s t a n c e p r i o r t o i n s t a l l a t i o n and t h e r e s u l t s r e c o r d e d . s h o u l d be made between t h e c e n t r e c o n d u c t o r a n d s h i e l d w i t h a 5 0 0 v o l t d c i n s t r u m e n t . The l o o p r e s i s t a n c e t e s t s h o u l d be a l s o made a s above, b u t w i t h t h e c e n t r e c o n d u c t o r s s h o r t e d t o t h e s h i e l d a t t h e f a r end of t h e c a b l e . This t e s t may be made w i t h a b r i d g e , ohmmeter, o r o t h e r s u i t a b l e i n s t r u m e n t . A f t e r i n s t a l l a t i o n , t h e c o n d u c t o r - t o - s h i e l d and conductor-to-grond r e s i s t a n c e s h o u l d exceed 5 0 megohms when measured a t 5 0 0 v o l t s d c . Loop r e s i s t a n c e s h o u l d be w i t h i n p l u s o r minus 1 0 p e r c e n t of t h e measured v a l u e s p r i o r t o i n s t a l l a t i o n , e.g. measured r e s i s t a n c e p e r 1 0 0 0 m e t r e s of c a b l e on r e e l , m u l t i p l i e d S h i e l d - t o ground r e s i s t by e a c h 1 0 0 0 m e t r e s and f r a c t i o n t h e r e o f of i n s t a l l e d c a b l e . a n c e s h o u l d a l s o be measured and t h e r e s u l t s r e c o r d e d . 3.9.5.5 Coaxial cable, pressurized. f o l l o w i n g t e s t s h o u l d be made:

Upon c o m p l e t i o n of t h e c a b l e i n s t a l l a t i o n , t h e

E l e c t r i c a l t e s t . A h i g h - v o l t a g e i n s u l a t i o n t e s t e r w i t h microammeter c u r r e n t - l e a k a g e m e t e r s h o u l d be u s e d and 3 0 0 0 v o l t s d c a p p l i e d between t h e i n n e r and o u t e r c o n d u c t o r s f o r a minimum p e r i o d of t h r e e m i n u t e s . While t h i s v o l t a g e i s a p p l i e d no n o t i c a b l e c u r r e n t s h o u l d f l o w between t h e conductors a f t e r charging c u r r e n t has s t a b i l i z e d .

Nitrogen gas t e s t . Nitrogen gas a t t h e s p e c i f i e d p r e s s u r e s h o u l d b e a p p l i e d t o t h e c a b l e , t h e g a s v a l v e c l o s e d , and a m b i e n t t e m p e r a t u r e recorded. S i x s u c c e s s i v e , h o u r l y measurement of p r e s s u r e s h o u l d be t a k e n and r e c o r d e d . A f t e r t h e s i x t h measurement i s t a k e n and a f t e r a t i m e i n t e r v a l of a b o u t 24 h o u r s , a s e v e n t h measurement s h o u l d be made. I f v a r i a t i o n s i n g a s p r e s s u r e a r e due o n l y t o changes i n a m b i e n t tempera t u r e , t h e l e n g t h of c a b l e i s a c c e p t a b l e . A t e m p e r a t u r e c o r r e c t i o n f a c t o r of 0.017 p e r d e g r e e C s h o u l d be used.

3,9,6.X ' f i e s u p p l y v o l t a g e and t h e i n p u t t a p of t h e r e g u l a t o r s h o u l d he checked t o s e e t h a t they correspond.

-..

3.9.6.2 w r t h l o a d d i s c o n n e c t e d , e n e r g i z e t h e r e g u l a t o r o n c e , and watch t h e openc i r c u i t p r o t e c t o r t o s e e t h a t i t deenergizes t h e r e g u l a t o r w i t h i n 2 o r 3 seconds.

Connect t h e l o a d c i r c u i t a f t e r i t h a s been checked f o r opens and ground and 3.9.4.4 and i n s p e c t e d t o s e e t h a t a s r e q u i r e d i n p a r a g r a p h s 3.9.4.3 a l l transformers a r e properly lanped.

Obtain a v o l t m e t e r and a n ammeter w i t h a n e r r o r of n o t more t h a n L 1 p e r c e n t of f u l l s c a l e , and s i m u l t a n e o u s l y measure i n p u t v o l t a g e and o u t p u t c u r r e n t ( c o n n e c t t h e ammeter t o t h e t e r m i n a l s of a n i s o l a t i n g t r a n s f o r m e r i n s e r t e d i n t o t h e o u t p u t c i r c u i t of t h e r e g u l a t o r ) f o r e a c h i n t e n s i t y s e t t i n g tap.

Use a r e c o r d i n g v o l t m e t e r o r t a k e r e a d i n g s d u r i n g b o t h d a y and n i g h t a t s u f f i c i e n t i n t e r v a l s t o o b t a i n an average supply voltage.

I f r e g u l a t o r h s s i n p u t v o l t a g e t a p s , s e l e c t t h e t a p w h i c h most n e a r l y corresponds t o average supply voltage. The o u t p u t c u r r e n t f o r e a c h i n t e n s i t y s e t t i n g t a p s h o u l d be wfchfn IL 2 p e r c e n t of t h e n a m e p l a t e v a l u e s a f t e r a n y necessary s u p p l y v o l t a g e c o r r e c t i o n i s made.

I n a l l c u r r e n t r e g u l a t o r s which have i n p u t v o l t a g e t a p s , t h e o u t p u t c u r r e n t 3.9.6,3 I f a s u p p l y v o l t a g e of 2 350 i s w i l l v a r y i n p r o p o r t i o n t o i n p u t v o l t a g e changes. a p p l i e d t o t h e 2 4 0 0 v o l t t a p , t h e o u t p u t c u r r e n t v a l u e s s h o u l d b e 2 p e r c e n t below t h e nameplate values. R e g u l a t o r s which h a v e a u t o m a t i c s u p p l y v o l t a g e c o r r e c t i o n i n l i e u of i n p u t 3.9.6.4 t a p s do n o t change t h e o u t p u t c u r r e n t a s t h e s u p p l y v o l t a g e v a r i e s . a)

I f t h e o u t p u t c u r r e n t on f u l l i n t e n s i t y d e v i a t e s f r o m t h e n a m e p l a t e v a l u e by more t h a n 2 p e r c e n t (and i f t h e r e g u l a t o r i s n o t o v e r l o a d e d ) , t h e i n t e r n a l a d j u s t m e n t s h o u l d be checked, a s d e s c r i b e d o n t h e r e g u l a t o r instruction plate. S i n c e t h e a d j u s t m e n t may be d e l i c a t e , i t i s recommended t h a t a d e v i a t i o n of +- 5 p e r c e n t h e a l l o w e d o n l o w e r s e t tings before a t t e m t i n g t o readjust the regulator.

F u r t h e r m o r e , a check s h o u l d be made t o s e e w h e t h e r t h e a d j u s t m e n t h a d been changed p u r p o s e l y f o r a n u n u s u a l l o c a l f l i g h t o p e r a t i o n a l requirement.

The f o l l o w i n g t e s t s h o u l d h e l p l o c a t e t h e f a u l t i n t h e e v e n t t h a t t h e t e s t s 3.9.7.1 i n d i c a t e improper operation.

3.9.7.2 Disconnect t h e l o a d , s h o r t - c i r c u i t r e g u l a t o r o u t p u t t e r m i n a l s t h r o u g h a n ammeter, and measure o u t p u t c u r r e n t . I f measured v a l u e s a r e e q u a l t o o r s l i g h t l y h i g h e r t h a n n a m e p l a t e v a l u e s , t h e r e g u l a t o r i s o p e r a t i n g s a t i s f a c t o r i l y and t h e l o a d c i r c u i t s h o u l d be checked f o r f a u l t s . 3.9.7.3 Connect t h e l o a d c a b l e s ( a f t e r l o a d c i r c u i t h a s been checked f o r o p e n s a n d and 3.9.4.4 and i n s p e c t e d t o s e e t h a t a l l g r o u n d s , a s s p e c i f i e d i n p a r a g r a p h s 3.9.4.3 t r a n s f o r m e r s a r e p r o p e r l y lamped), and measure o u t p u t c u r r e n t and o u t p u t v o l t a g e s i m u l t a n e s u s l y w i t h t h e regulator o p e r a c i i i g on i h e h i g h e s t i n t e n s i t y s e t t i n g . The s i g n i f i c a n c e of t h e r e a d i n g s i s a s f o l l o w s : a)

S a c i s f a c t o r y o p e r a t i o n i s i n d i c a t e d by c o r r e c t o u t p u t c u r r e n t and a n o u t p u t v o l t a g e which i s s l i g h t l y h i g h e r t h a n t h a t e s t i m a t e d f o r t h e The v o l t a g e l o a d , b u t which d o e s n o t exceed t h e r a t e d o u t p u t v o l t a g e . r e q u i r e d f o r t h e l o a d may be e s t i m a t e d by m u l t i p l y i n g t h e i s o l a t i n g transformer primary v o l t a g e a t r a t e d load ( w a t t s d i v i d e d by primary c u r r e n t ) by t h e number of t r a n s f o r m e r s c o n n e c t e d i n s e r i e s i n t h e l o a d circuit

A c o r r e c t output c u r r e n t with an output v o l t a g e a p p r e c i a b l y l e s s t h a n t h e e s t i m a t e d l o a d v o l t a g e i n d i c a t e s c o m p l e t e o r p a r t i a l s h o r t i n g of t h e load.

A c o r r e c t output c u r r e n t with an output v o l t a g e exceeding t h e r a t e d l o a d o u t p u t v o l t a g e i n d i c a t e s a n overload.

A reduced o u t p u t c u r r e n t w i t h an o u t p u t v o l t a g e i n d i c a t i n g a n o v e r l o a d i s p o s s i b l y caused by a poor c o n n e c t i o n i n t h e l o a d c i r u i t . The r e g u l a t o r s h o u l d be d e e n e r g i z e d immediately t o p r e v e n t damage.

3.9.8

A reduced o u t p u t c u r r e n t w i t h a n o u t p u t v o l t a g e n o t exceeding t h e r a t e d o u t p u t v o l t a g e i n d i c a t e s a f a u l t y r e g u l a t o r o r reduced s u p p l y v o l t a g e .

A z e r o o u t p u t c u r r e n t w i t h e x c e s s i v e o u t p u t v o l t a g e i n d i c a t e s a n open i n t h e l o a d c i r c u i t and f a i l u r e o f t h e o p e n - c i r c u i t p r o t e c t o r i n t h e regulator. I n t h i s c a s e , t h e r e g u l a t o r must be d e e n e r g i z e d i m m e d i a t e l y t o p r e v e n t s e r i o u s damage.

CAUTION: The o p e n - c i r c u i t p r o t e c t o r of t h e r e g u l a t o r must n o t b e d e a c t i v a t e d o r by-passed d u r i n g t h e s e t e s t s .

E l e c t r i c a l tests of o t h e r equipment

3.9.8.1 Measure t h e i n p u t and o u t p u t v o l t a g e s and c u r r e n t s and d e t e r m i n e t h e l o a d s of t h e connected c i r c u i t s . Check t o d e t e r m i n e i f t h e s e v o l t a g e s and l o a d s a r e w i t h i n t h e m a n u f a c t u r e r ' s r a t i n g of t h e equipment. Record t h e s e measurements f o r f u t u r e r e f e r e n c e d u r i n g maintenance o r f o r m o d i f i c a t i o n of t h e c i r c u i t . T e s t s of m o n i t o r s 3.9.9.1 A f t e r t h e t e s t s l i s t e d above have been completed and t h e s y s t e m i s f u n c t i o n i n g a s d e s i g n e d , m o n i t o r s s h o u l d be t e s t e d by s i m u l a t i n g s u c h f a i l u r e s a s o p e n - c i r c u i t s , s h o r t - c i r c u i t s , g r o u n d s , f a i l u r e of l i g h t s , l o s s o f power i n b o t h t h e l i g h t i n g c i r c u i t s and t h e c o n t r o l c i r c u i t s , and o b s e r v i n g t h e performance of t h e monitor. M o n i t o r s which f a i l t o p e r f o r m a s i n t e n d e d s h o u l d be r e p a i r e d b e f o r e t h e s y s t e m i s a c c e p t e d .

4.1

4.1.1

GENERAL KEQUIKEMENTS

I n i t i a l considerations

4.1.1.1 I n s t a l l a t i o n of e l e c t r i c a l c a b l e s underground i s e x p e n s i v e a n d t e c h n i q u e s t o a s s u r e l o n g and e f f e c t i v e s e r v i c e w i t h a minimum of m a i n t e n a n c e s h o u l d b e used. All work s h o u l d be done by e x p e r i e n c e d p e r s o n n e l r e g u l a r l y engaged i n t h e i r t y p e of work. Most underground c a b l e s w i l l be l o c a t e d o n , o r v e r y c l o s e t o , t h e manoeuvring a r e a of t h e aerodrome. Hence, a t a c t i v e aerodromes g r e a t c a r e must be e x e r c i s e d t o e n s u r e t h a t t h e i n s t a l l a t i o n does n o t p r e s e n t a hazard t o a i r c r a f t o r t o t h e i n s t a l l e r s . 4.1.2

P r e c o n s t r u c t i o n arrangements

Obtain p r i o r a p p r o v a l of t h e e n g i n e e r i n c h a r g e f o r t h e m a t e r i a l s , workmen, 4.1.2.1 t i m e of d a y o r n i g h t f o r t h e work, method and p r o c e d u r e s f o r t h e i n s t a l l a t i o n , and p r o c e d u r e f o r any t e m p o r a r y o r permanent r e p a i r s t o be made. Arrange f o r c o - o r d i n a t i n g t h e e f f o r t w i t h A i r T r a f f i c C o n t r c l i f i t may be i n v o l v e d . C a r e f u l l y d e t e r m i n e and mark the route f o r the cables. Take a l l r e a s o n a b l e p r e c a u t i o n s t o p r o t e c t e x i s t i n g underground u t i l i t i e s s u c h a s f u e l t a n k s , w a t e r l i n e s , b u r i e d c o n t r o l and power c a b l e s , A l l known u t i l i t i e s and power and c o n t r o l c a b l e s l e a d i n g t o and f r o m a n y o p e r a t i n g etc. f a c i l i t y s h o u l d be marked i n t h e f i e l d b e f o r e any work i n t h e g e n e r a l v i c i n i t y i s s t a r t e d . T h e r e a f t e r and t h r o u g h o u t t h e e n t i r e t i m e of c o n s t r u c t i o n t h e y s h o u l d b e p r o t e c t e d f r o m any p o s s i b l e damage. Any underground c a b l e s which a r e damaged d u r i n g i n s t a l l a t i o n s h o u l d be i m m e d i a t e l y r e p a i r e d w i t h e q u a l q u a l i t y m a t e r i a l . 4.1.3

Methods of i n s t a l l a t i o n

4,1,3.1 There a r e two methods of i n s t a l l i n g underground e l e c t r i c a l c a b l e s , by d i r e c t b u r i a l o r i n d u c t ( c o n d u i t ) . These methods a r e d i s c u s s e d below.

4.2

UIUCT UUKXAL OF CABLE

4.2.1.1 The major s t e p s of i n s t a l l i n g e l e c t r i c a l c a b l e s by d i r e c t b u r i a l a r e t r e n c h i n g , placement of t h e c a b l e , and b a c k f i l l i n g . 4.2.2

Trenching

4.2.2.1 Basic requirements. Unless r e q u i r e d o t h e r w i s e , a l l c a b l e s i n t h e s a n e l o c a t i o n and r u n n i n g i n t h e same g e n e r a l d i r e c t i o n s h o u l d be i n s t a l l e d i n t h e same trench. Walls of t r e n c h e s s h o u l d be e s s e n t i a l l y v e r t i c a l s o t h a t a minimum of s h o u l d e r The bottom s u r f a c e of t r e n c h e s s h o u l d be e s s e n t i a l l y smooth and s u r f a c e i s disturbed. f r e e from c o a r s e a g g r e g a t e . I f p o s s i b l e , t r e n c h e s s h o u l d be opened o n l y t o t h e e x t e n t t h a t c a b l e s c a n be i n s t a l l e d and t h e t r e n c h c l o s e d i n t h e same working d a y . Where t u r f i s w e l l e s t a b l i s h e d and t h e s o d c a n be reanved, i t s h o u l d h e c a r e f u l l y s t r i p p e d and properly stored.

4.2.2.2 The t r e n c h d e p t h s h o u l d be n o t l e s s t h a n 5 cm below t h e l e v e l of t h e lowes l e s s h o u l d be a minimum of 5 0 cm below t h e f i n i s h e d g r a d e when on t h e aerodrome p r o p e r t y and 7 5 cm below t h e f i n i s h e d g r a d e when o f f t h e a e r o d r o m e property. I f c a b l e s a r e t o be p l a c e d a t more t h a n one l e v e l , t h e v e r t i c a l s e p a r a t i o n except s h o u l d be t h e same a s t h e h o r i z o n t a l s e p a r a t i o n i n d i c a t e d i n p a r a g r a p h 4.2.3, v e r t i c a l s e p a r a t i o n of c o n t r o l and t e l e p h o n e c a b l e s and of low v o l t a g e s power c a b l e s s h o u l d be n o t l e s s t h a n 6 cm. The ground w i r e o r c o u n t e r p o i s e s h o u l d be a minimum o f 1 5 cm above t h e uppermost l a y e r of c a b l e s . Trench d e p t h s s h o u l d a l l o w f o r t h e s e vertical separations. 4.2.2.3 Cables s h o u l d n o t be d i r e c t b u r i e d u n d e r paved a r e a s , Heavy t r a f f i c a r e a s . roadways, r a i l r o a d t r a c k s , o r d i t c h e s . In t h e s e a r e a s t h e c a b l e should be i n s t a l l e d i n concrete-encased ducts o r i n r i g i d s t e e l conduit. 4.2.2.4 Areas of r o c k s . Where r o c k e x c a v a t i o n i s e n c o u n t e r e d t h e r o c k s h o u l d b e removed t o a d e p t h of a t l e a s t 8 cm below t h e r e q u i r e d c a b l e d e p t h and i t s h o u l d be r e p l a c e d w i t h bedding m a t e r i a l of e a r t h o r s a n d c o n t a i n i n g no m i n e r a l a g g r e g a t e p a r t i c l e s l a r g e r t h a n S mm i n d i a m e t e r . When s o l i d r o c k i s e n c o u n t e r e d , a l t e r n a t i v e s such a s r e r o u t i n g t h e t r e n c h o r i n s t a l l a t i o n i n r i g i d s t e e l conduit should b e considered. 4.2.2.5 Trench w i d t h . Trench w i d t h f o r a s i n g l e c a b l e s h o u l d be n o t l e s s t h a n 1 5 cm. Where more t h a n one c a b l e i s l o c a t e d i n a t r e n c h , t h e t r e n c h w i d t h s h o u l d be a d j u s t e d s o t h a t t h e s e p a r a t i o n s g i v e n below can be m a i n t a i n e d . 4.2.3

S e p a r a t i o n between c a b l e s a)

Power c a b l e s , of t h e same c i r c u i t , may be l a i d s i d e by s i d e i n t h e t r e n c h w i t h o u t s e p a r a t i o n , e x c e p t a s n o t e d below. Series lighting c a b l e s may be c o n s i d e r e d a s of t h e same c i r c u i t .

Power c a b l e s of t h e same o r d i f f e r e n t c i r c u i t s of l e s s t h a n 600 v o l t s , may be l a i d t o g e t h e r i n t h e same t r e n c h w i t h o u t h o r i z o n l s a i s e p a r a t i o n .

Power c a b l e s of d i f f e r e n t c i r c u i t s w i t h v o l t a g e s between 600 a n d 5 000 v o l t s s h o u l d be s e p a r a t e d a miniimlim of 10 cm.

A l l power c a b l e s , 5 000 v o l t s and below, s h o u l d be s e p a r a t e d f r o m a l l c o n t r o l , t e l e p h o n e , and c o a x i a l t y p e c a b l e s by a minimum of 1 5 cm.

Power c a b l e s , of more t h a n 5 000 v o l t s , s h o u l d be s e p a r a t e d f r o m a l l o t h e r c a b l e s by a minimum of 3 0 cm.

C o n t r o l , t e l e p h o n e , and c o a x i a l c a b l e s may be l a i d i n t h e t r e n c h w i t h o u t h o r i z o n t a l s e p a r a t i o n from each o t h e r .

V e r t i c a l s e p a r a t i o n s s h o u l d be s i m i l a r t o t h o s e g i v e n i n a ) t h r o u g h f ) e x c e p t t h a t c a b l e s which do n o t r e q u i r e h o r i z o n t a l s e p a r a t i o n s h o u l d be s e p a r a t e d a minimum of 6 cm v e r t i c a l l y . No c a b l e s h o u l d d i r e c t l y o v e r l a p a n o t h e r c a b l e b e c a u s e compacting may damage t h e c a b l e .

Ground w i r e s and c o u n t e r p o i s e s s h o u l d be a p p r o x i m a t e l y 15 cm a b o v e t h e uppermost l e v e l of t h e c a b l e s .

4.2.4

I n s t a l l a t i o n of d i r e c t - b u r i a l

cables

4.2.4.1 B e f o r e p l a c i n g any c a b l e s , b a c k f i l l and compact a 5 cm l a y e r of e i t h e r e a r t h o r s a n d c o n t a i n i n g n o m a t e r i a l a g g r e g a t e p a r t i c l e s l a r g e r t h a n 6 mm i n d i a m e t e r . 4.2.4.2 Wherever p o s s i b l e , c a b l e s h o u l d be r u n i n o n e p i e c e , without s p l i c e s , from connection t o connection. Use t h e l o n g e s t p r a c t i c a b l e l e n g t h s of c a b l e i n o r d e r t o minimize s p l i c i n g r e q u i r e m e n t s . When c a b l e c u t t i n g i s r e q u i r e d , c a b l e e n d s s h o u l d be e f f e c t i v e l y s e a l e d a g a i n s t m o i s t u r e i m m e d i a t e l y a f t e r c u t t i n g . Bends of a r a d i u s l e s s t h a n e i g h t t i m e s t h e d i a m e t e r f o r r u b b e r - o r p l a s t i c - c o v e r e d c a b l e and t w e l v e t i m e s t h e d i a m e t e r f o r m e t a l l i c - a r m o r e d c a b l e s h o u l d n o t be made. Cable t h a t has been k i n k e d s h o u l d n o t be i n s t a l l e d . A man s h o u l d be s t a t i o n e d a t t h e r e e l t o o b s e r v e and r e p o r t any i r r e g u l a r i t i e s i n t h e c a b l e when t h e c a b l e i s b e i n g u n r e e l e d . Cable f o r d i r e c t e a r t h b u r i a l s h o u l d be u n r e e l e d i n p l a c e i n t h e open t r e n c h o r u n r e e l e d n e a r t h e t r e n c h and c a r e f u l l y p l a c e d i n t h e t r e n c h bottom. P u l l i n g t h e c a b l e i n t o t h e t r e n c h by d r a g g i n g o v e r t h e ground s h o u l d n o t be p e r m i t t e d . A c a b l e s l a c k l o o p of a p p r o x i m a t e l y one m e t r e s h o u l d be 4.2.4.3 Cable s l a c k l o o p s . l e f t on e a c h end of c a b l e r u n s , and a t a l l p o i n t s where c a b l e c o n n e c t i o n s a r e b r o u g h t above ground. The s l a c k l o o p s h o u l d b e i n s t a l l e d a t t h e same minimum d e p t h a s t h e c a b l e run. Loops s h o u l d have bends w i t h a n i n n e r r a d i u s n o t l e s s t h a n t w e l v e t i m e s t h e o u t s i d e d i a m e t e r of t h e c a b l e . Where c a b l e i s b r o u g h t a b o v e ground, a d d i t i o n a l s l a c k A t a l l c a b l e s p l i c e s , p r o v i d e s l a c k l o o p s f r e e of bends a t s h o u l d be l e f t above ground. t h e s p l i c e o r w i t h i n 3 0 cm of t h e e n d s of t h e s p l i c e .

4.2.4.4 Final backfilling. b a c k f i l l e d a s follows:

A f t e r t h e c a b l e h a s been i n s t a l l e d , t h e t r e n c h s h o u l d b e

The c a b l e B a c k f i l l s e p a r a t i n g c a b l e s s h o u l d be f i r m l y tamped i n p l a c e . s e p a r a t i o n s g i v e n i n 4.2.3 .should be m a i n t a i n e d . These s e p a r a t i o n s may be e i t h e r h o r i z o n t a l , v e r t i c a l , o r a c o m b i n a t i o n of t h e two.

The f i r s t l a y e r of b a c k f i l l i n g s h o u l d be n o t l e s s t h a n 7.5 cm d e e p , l o o s e measurement, and s h o u l d be e i t h e r e a r t h o r s a n d c o n t a i n i n g no This l a y e r m a t e r i a l a g g r e g a t e p a r t i c l e s l a r g e r t h a n 6 mm d i a m e t e r . s h o u l d n o t be compacted, e x c e p t f o r tamping t o m a i n t a i n s e p a r a t i o n of cables.

The s e c o n d l a y e r s h o u l d be n o t l e s s t h a n 12 cm d e e p , l o o s e measurement, and s h o u l d c o n t a i n n o p a r t i c l e s l a r g e r t h a n 25 mm d i a m e t e r .

The r e m a i n d e r of t h e b a c k f i l l i n g may be e x c a v a t e d o r i m p o r t e d m a t e r i a l and s h o u l d n o t c o n t a i n s t o n e s o r a g g r e g a t e l a r g e r t h a n 1 0 0 mm i n diameter. The t h i r d and s u b s e q u e n t l a y e r s of t h e b a c k f i l l i n g s h o u l d n o t e x c e e d 2 0 cm i n maximum d e p t h , l o o s e measurement. The s e c o n d and s u b s e q u e n t l a y e r s s h o u l d be t h o r o u g h l y tamped and compacted t o a t l e a s t t h e d e n s i t y of t h e a d j a c e n t u n d i s t u r b e d s o i l . If necessary t o o b t a i n t h e d e s i r e d compaction, t h e b a c k f i l l m a t e r i a l may be m o i s t e n e d o r a e r a t e d a s required. T r e n c h e s s h o u l d n o t be e x c e s s i v e l y w e t and s h o u l d n o t c o n t a i n p o o l s of w a t e r d u r i n g t h e b a c k f i l l i n g o p e r a t i o n s . The t r e n c h s h o u l d be c o m p l e t e l y b a c k f i l l e d and tamped l e v e l w i t h t h e adjacent surface.

When s o d i s t o be p l a c e d o v e r t h e t r e n c h , t h e b a c k f i l l i n g s h o u l d be s t o p p e d a t a d e p t h e q u a l t o t h e t h i c k n e s s of t h e s o d t o b e u s e d . Any e x c e s s e x c a v a t e d m a t e r i a l s h o u l d be removed. Where sod h a s been removed i t s h o u l d be r e p l a c e d a s soon a s p o s s i b l e a f t e r t h e b a c k f i l l i n g i s completed. A l l a r e a s d i s t u r b e d by t h e t r e n c h i n g , s t o r i n g of d i r t , c a b l e l a y i n g , pad c o n s t r u c t i o n , and o t h e r work s h o u l d be r e s t o r e d t o i t s o r i g i n a l c o n d i t i o n . The r e s t o r a t i o n s h o u l d i n c l u d e any n e c e s s a r y t o p s o i l i n g , f e r t i l i z i n g , l i m i n g , s e e d i n g , s o d d i n g , s p r i g g i n g , o r nrulching. I f t r e n c h i n g c u t s a r e made t h r o u g h paved a r e a s , t h e c u t s , a f t e r p r o p e r b a c k f i l l i n g , s h o u l d b e r e s u r f a c e d w i t h p a v i n g s i m i l a r t o t h e o r i g i n a l paving. R e s u r f a c e d c u t s s h o u l d be l e v e l w i t h t h e o r i g i n a l p a v i n g , f r e e f r o m c r a c k s , and c a p a b l e of w i t h s t a n d i n g t r a f f i c l o a d s imposed w i t h o u t s e t t l i n g o r c r a c k i n g .

4.3

INSTALLATION OF DUCTS (CONDUIT)

I n s t a l l a t i o n t e c h n i q u e s and p r o c e d u r e s 4.3.1,l S e l e c t i o n of r o u t e s . D u c t - l i n e r o u t e s s h o u l d be s e l e c t e d t o b a l a n c e maxirnum f l e x i b i l i t y w i t h minimum c o s t and t o a v o i d f o u n d a t i o n s f o r f u t u r e b u i l d i n g s a n d o t h e r s t r u c t u r e s . Where i t may be n e c e s s a r y t o r u n communication l i n e s a l o n g w i t h e l e c t r i c power d i s t r i b u t i o n l i n e s , two i s o l a t e d s y s t e m s i n s e p a r a t e rnanhole compartments s h o u l d be provided. Where p o s s i b l e , d u c t s s h o u l d be i n s t a l l e d i n t h e same c o n c r e t e e n v e l o p e . E l e c t r i c and communication d u c t s s h o u l d be k e p t c l e a r of a l l o t h e r u n d e r g r o u n d u t i l i t i e s , e s p e c i a l l y high-temperature water o r steam pipes.

4.3.1,2 Duct m a t e r i a l s . A c c e p t a b l e s t a n d a r d m a t e r i a l s f o r d u c t s i n c l u d e f i b e r , a s b e s t o s - c e m e n t , t i l e , and p l a s t i c . K g i d s t e e l c o n d u i t may a l s o be i n s t a l l e d below g r a d e and s h o u l d be p r o v i d e d w i t h f i e l d o r f a c t o r y a p p l i e d c o a t i n g s where r e q u i r e d . 4.3.1.3 S i z e of d u c t s . S i z e of c o n d u i t s i n a d u c t bank s h o u l d be n o t less t h a n 10 cm i n s i d e d i a m e t e r e x c e p t t h a t d u c t s f o r c o m m n i c a t i o n l i n e s w i t h a minimum d i a m e t e r of 7.5 cm a r e a c c e p t a b l e .

4.3.1.4 I n s t a l l a t i o n of d u c t s w i t h o u t c o n c r e t e encasement. Trenches f o r s i n g l e - d u c t l i n e s s h o u l d be n o t l e s s t h a n 1 5 cm n o r more t h a n 30 cm w i d e , and t h e t r e n c h f o r two o r more d u c t s i n s t a l l e d a t t h e same l e v e l s h o u l d be p r o p o r t i o n a t e l y w i d e r . Trench bottoms f o r d u c t s w i t h o u t c o n c r e t e encasement s h o l d be made t o confo.rm a c c u r a t e l y t o g r a d e s o a s t o p r o v i d e u n i f o r m s u p p o r t f o r t h e d u c t a l o n g i t s e n t i r e l e n g t h . A l a y e r of f i n e e a r t h m a t e r i a l a t l e a s t 10 cm t h i c k ( l o o s e measurement) s h o u l d be p l a c e d i n t h e b o t t o m of t h e t r e n c h a s bedding f o r t h e d u c t . The bedding m a t e r i a l s h o u l d c o n s i s t of s o f t d i r t , s a n d , o r o t h e r f i n e f i l l , and i t s h o u l d c o n t a i n no p a r t i c l e s l a r g e r t h a n 6 mn d i a m e t e r . The bedding m a t e r i a l s h o u l d be tamped u n t i l f i r m . When two or rnore d u c t s a r e i n s t a l l e d i n t h e same t r e n c h w t t h o u t c o n c r e t e encasement, t h e y s h o u l d be s p a c e d n o t less t h a n 5 cm a p a r t (measured from o u t s i d e w a l l t o o u t s i d e w a l l ) i n a h o r i z o n t a l d i r e c t i o n o r o o t l e s s R i g i d s t e e l ancl h e a v y - w a l l c o n d u i t may be t h a n 1 5 cm a p a r t i n a v e r t i c a l d i r e c t i o n . d i r e c t e a r t h buried. A l l o t h e r c o n d u i t s s h o u l d be e n c a s e d . 4.3.1.5 L n s t a l l a t i o n of d u c t s e n c a s e d i n c o n c r e t e . Al.]. d u c t s i n s t a l l e d i n c o n c r e t e encasement s h u u l d be p l a c e d on a L a y e r of c o n c r e t e n o t l e s s t h a n 9 - 5 c m thick. Where

(measured f r o m o u t s i d e w a l l t o o u t s i d e w a l l ) . A s t h e d u c t l a y i n g p r o g r e s s e s , c o n c r e t e n o t l e s s t h a n 7.5 cm t h i c k s h o u l d be p l a c e d around t h e s i d e s and t o p of t h e d u c t bank. F l a r e d e n d s of d u c t s o r c o u p l i n g s s h o u l d b e i n s t a l l e d f l u s h w i t h t h e c o n c r e t e encasement o r i n s i d e w a l l s of manholes o r h a n d h o l e s . I n t e r l o c k s p a c e r s s h o u l d be u s e d a t n o t more Joints i n adjacent t h a n 1.5 m e t r e s p a c i n g t o i n s u r e u n i f o r m s p a c i n g between d u c t s . d u c t s s h o u l d be s t a g g e r e d a minimum of 6 0 cm a p a r t and s h o u l d b e made w a t e r p r o o f p r i o r Concrete-encased t o c o n c r e t i n g . No d u c t h a v i n g a d e f e c t i v e j o i n t s h o u l d be i n s t a l l e d . d u c t o r r i g i d s t e e l c o n d u i t s h o u l d b e i n s t a l l e d s o t h a t t h e t o p of t h e c o n c r e t e e n v e l o p e o r c o n d u i t i s n o t l e s s t h a n 4 0 cm below t h e bottom of t h e p a v i n g where i t i s i n s t a l l e d under roadways, r a i l r o a d s , runways, t a x i w a y s , o t h e r paved a r e a s , and d i t c h e s and n o t l e s s t h a n 4 0 cm below t h e f i n i s h e d g r a d e e l s e w h e r e .

4.3.1.6 Grounding b u s h i n g s . Mhere r i g i d s t e e l c o n d u i t e n t e r s o r l e a v e s a manhole o r h a n d h o l e a g r o u n d i n g b u s h i n g s h o u l d be p r o v i d e d f o r a l l c o n d u i t s . 4.3.1.7 Arrangement of d u c t banks. An a r r a n g e m e n t of two d u c t s wide o r h i g h s h o u l d be used f o r b e s t h e a t d i s s i p a t i o n . C o r r e s p o n d i n g l y , t h e d u c t banks may b e s e v e r a l d u c t s The ( T h i s may be i m p o s s i b l e where a l a r g e number of d u c t s a r e i n v o l v e d . ) h i g h o r wide. v e r t i c a l two conduit-wide a r r a n g e m e n t e n a b l e s t h e c a b l e s t o be more e a s i l y r a c k e d on manhole w a l l s b u t may n o t b e a s economical a s t h e h o r i z o n t a l two c o n d u i t - h i g h a r r a n g e m e n t . For dimensions and arrangement of d u c t banks, s e e F i g u r e 4-1. 4.3.1.8 Drainage. A l l d u c t l i n e s s h o u l d be l a i d s o a s t o s l o p e toward h a n d h o l e s , manholes and d u c t ends f o r d r a i n a g e . Grades s h o u l d be a t l e a s t 2.5 m i l l i m e t r e s p e r m e t r e . Where i t i s n o t p r a c t i c a b l e t o m a i n t a i n t h e s l o p e a l l one way, t h e d u c t l i n e s may be s l o p e d from t h e c e n t e r i n b o t h d i r e c t i o n s toward manholes, h a n d h o l e s , o r d u c t P o c k e t s o r t r a p s where m o i s t u r e may a c c u m ~ i l a t es h o u l d be a v o i d e d . ends. 4.3.1.9 Each s p a r e d u c t i n s t a l l e d s h o u l d be p r o v i d e d w i t h a c o p p e r - c l a d P u l l wire. s t e e l p u l l w i r e of n o t l e s s t h a n 5 mm2 i n a r e a * The open ends of t h e s p a r e d u c t s s h o u l d The p l u g s h o u l d s e c u r e t h e p u l l w i r e f i r m l y . be plugged w i t h removable t a p e r e d p l u g s . 4.3.1.10 S u f f i c i e n t d u c t s f o r planned i n s t a l l a t i o n s , f u t u r e e x p a n s i o n , p l u s a minimum of 2 5 p e r c e n t of s p a r e d u c t s , s h o u l d be i n c l u d e d f o r a l l new underground s y s t e m s .

4.4 4.4.1

MANHOLES AND HANDHOLES

Selection

4.4.1.1 F a c t o r s b e a r i n g on t h e c h o i c e of manholes and h a n d h o l e s a r e number, d i r e c t i o n , and l o c a t i o n of d u c t r u n s ; c a b l e r a c k a r r a n g e m e n t s ; method o f d r a i n a g e ; adequacy of work s p a c e ( e s p e c i a l l y i f equipment i s t o be i n s t a l l e d i n t h e manhole); a n d t h e s i z e of t h e o p e n i n g r e q u i r e d t o i n s t a l l and remove equipment.

SINGLE DUCT

ELECTRIC OR COMMUNICATION

COMBINED ELECTRIC (E) A N D COMMUNlCATlON (C)

1.5 cm TYPICAL 1.25 cm BARS AT 15 cm TO 20 cm ON CENTRES$ 7.5 cm TYPICAL

(2.5 cm WIRE HOOP) APPROXIMATELY 20 cm ON C E N T R E S ~

REINFORCED DUCT BANKS 1. WHERE REINFORCEMENT IS PROVIDED UNDER RAILROAD TRACKS I T SHOULD EXTEND A T LEAST 3.5 m BEYOND THE OUTER RAILS.

4.4.2

Location

4.4.2,1 Manholes o r h a n d h o l e s s h o u l d b e p l a c e d where r e q u i r e d f o r c o n n e c t i o n s o r s p l i c e s a n d where c o n f l i c t w i t h o t h e r u t i l i t i e s w i l l b e a v o i d e d * Manhole s e p a r a t i o n s h o u l d n o t e x c e e d 200 m e t r e s on s t r a i g h t r u n s and 100 metres on c u r v e d d u c t r u n s . S p a c i n g s h o u l d b e d e c r e a s e d where n e c e s s a r y t o p r e v e n t i n s t a l l a t i o n damage d u r i n g S t r a i n s h o u l d b e limi.ted d u r i n g i n s t a l l a t i o n t o a p o i n t t h a t w i l l p u l l i n g of c a b l e s . n o t damage c a b l e i n s u l a t i o n o r deform t h e c a b l e ( s e e T a b l e 4-1). 4.4.3

Stubs

4.4.3.1 It i s good p r a c t i c e t o p r o v i d e a s e t of two o r more s p a r e s t u b s ( s h o r t l e n g t h s o f d u c t s l e a d i n g o u t f r o m t h e manhole) s o t h a t t h e manhole w a l l n e e d n o t b e The s t u b s s h o u l d b e p l u g g e d o n b o t h e n d s . d i s t u r b e d when a f u t u r e e x t e n s i o n i s made. 4.4.4

Hardware

4.4.4.1 Hardware a p p l i c a b l e t o t h e i n s t a l l a t i o n s h o u l d be c h o s e n . Where f l a r e d e n d s of d u c t s a r e p r o v i d e d , c a b l e - d u c t s h i e l d s a r e n e c e s s a r y o n l y f o r p r o t e c t i o n o f m e t a l l i c sheathed cables. Two-section manholes 4.4.5.1 T w o s e c t i o n manholes s h o u l d be u s e d t o m a i n t a i n s e p a r a t i o n of t h e c i r c u i t s w h e r e e l e c t r i c power a n d communication l i n e s a r e i n s t a l l e d i n t h e same d u c t bank o r u s e t h e same manhole.

4.5

4.5.1

INSTALLATION OF UNDERGROUND CABLES

P r e ~ a r a t i o nof d u c t s

4.5.1.1 A f t e r t h e d u c t i n s t a l l a t i o n i s c o m p l e t e d , t h e c a b l e s a r e i n s t a l l e d by d r a w i n g o r p u l l i n g i n t o t h e d u c ~ s . The d u c t s h o u l d be open, c o n t i n u o u s , a n d c l e a r of debris before the cable is installed. The c a b l e s h o u l d be i n s t a l l e d i n a manner t o p r e v e n t h a r m f u l s t r e t c h i n g o f t h e c o n d u c t o r , i n j u r y t o t h e i n s u l a t i o n , o r damage t o t h e o u t e r p r o t e c t i v e c o v e r i n g . The e n d s of a l l c a b l e s s h o u l d b e s e a l e d w i t h m o i s t u r e s e a l t a p e b e f o r e i n s t a l l i n g , and t h e y s h o u l d b e k e p t s e a l e d u n t i l c o n n e c t i o n s are made. Where more t h a n one c a b l e i s t o b e i n s t a l l e d i n a d u c t o r c o n d u i t , a l l c a b l e s h o u l d be i n s t a l l e d a t t h e same t i m e . In no c a s e s h o u l d a s p l i c e o r c o n n e c t i o n be p l a c e d i n a duct o r conduit. 4.5.2

Cable p u l l i n g i n d u c t s

4.5.2.1 The c a b l e t o be i n s t a l l e d i n t h e d u c t may b e p u l l e d by a power winch o r by hand. An a d e q u a t e amount of c a b l e p u l l i n g compound s h o u l d b e used on The s u r f a c e of any c a b l e s h e a t h o r Petroleum g r e a s e should n o t be used. a l l pulls. j a c k e t s h o u l d n o t be damaged t o a d e p t h g r e a t e r t h a n 1 1 1 0 t h i t s o r i g i n a l t h i c k n e s s . The c a b l e s h o u l d n o t b e f l a t t e n e d o u t of round more t h a n 1110th i t s o u t s i d e d i a m e t e r . Maximm p u l l i n g t e n s i a n s f o r commonly i n s t a l l - e d c a b l e s a r e l i s t e d i n T a b l e 4-1. The l i m i t a t i o n s i n Table 4-1 a r e n o t i n t e n d e d t o p r e c l u d e t h e u s e of s t e e l o r w i r e r o p e a s a m e a n s of p u l l i n g . However, u r i l e s s a dynamometer i s u s e d t o i n d i c a t e t h e g r o p e r t e n s i o n f ~ the s c a b l e b e i n ga p u l l e d , a h a r n e s s of Che p r o p e r sLze r o p e t h a t will l i m i t t h e

T a b l e 4-1 MAXIMUM ALLOWABLE NON-ARMOKED CABLE PULL USING DYNAMOMETER OR ROPE

CABLE

ROPE DIAMETER

TENSION

2 - l c 8.4 mm2 S o l 3 - l c 8.4 mm2 S o l 4 - l c 8.4 mm2 S o l

125 kg 165 kg 250 kg

4.8 mm C 6.4 mm C

2 - 1 c 1 3 , 3 mm2 S t s 3 - l c 13.3 mm2 S t r 4 - l c 1 3 . 3 mm2 S t r

190 kg 285 kg 380 kg

6.4 mm C 8.0 mm C 9.6 mm c

1 - 2c 8.4 mm2 S t r 1 - 3c 8.4 mm2 S t r 1 - 4c 8.4 mm2 S t r

140 kg 180 kg 265 kg

6.4 mm C 6.4 mm C

4.8 mm M 6.4 mm M 4.8 mm M 6.4 mm M 4.8 mm D

6.4 mm M

p -

l - 2c 13.3 mm2 S t r 1 - 3c 13.3 mm2 S t r 1 - 4c 13.3 mm2 S t r

220 kg 310 kg 400 kg

6.4 mm C 8.0 mm C 9.6 mm C

1 - 6c 3.3 mm2 S t r 1 - 12c 3.3 mm2 ~ t r

140 kg 285 kg

6.4 mm C 8.0 mm C

5 5 kg

4.8 m C 4.8 mm C:

KG KG

213/U 214/U

65 kg

4.8 mm M 8.0 mm M

- 216/U

RG RG

217/U 218/U

- Conductor

Sol

-Cotton

60 kg 1 1 5 kg 360 kg

Solid -Manila

6.4 mm M

( f o r m e r l y KG-8/U) ( f o r m e r l y KG--9/U)

p -

4.8 mm D

4.8 mm C 6.4 mm M 1 1 . 5 mm C S t r - Stranded - Dacron

( f o r m e r l y RG-13/U) ( f o r m e r l y RG-14/U) ( f o r m e r l y RG-17/U) PK N

- Pair - Nylon

Maximum p u l l i n g t e n s i o n s f o r c a b l e s n o t l i s t e d s h o u l d be o b t a i n e d from t h e m a n u f a c t u r e r of the cable.

Any c o m b i n a t i o n of t e n s i o n of t h e p u l l t o f o r c e s i n d i c a t e d i n T a b l e 4-1 s h o u l d be u s e d . a group of c a b l e s t o be p u l l e d i n t o a d u c t s h o u l d n o t e x c e e d t h e sum o f i n d i v i d u a l a l l o w a b l e t e n s i o n of e a c h c a b l e p l u s 1 5 p e r c e n t .

4.5.2.2 Length of p u l l . To minimize s p l i c i n g , t h e l o n g e s t p r a c t i c a b l e l e n g t h s o f c a b l e s h o u l d be p u l l e d i n t o t h e d u c t s a t one time. Unless o t h e r w i s e r e q u i r e d , manholes and h a n d h o l e s s h o u l d be a s f a r a p a r t a s p r a c t i c a b l e f o r t h e t y p e of c a b l e b e i n g i n s t a l l e d , b u t u n d e r no c o n d i t i o n s h o u l d t h e d i s t a n c e between h a n d h o l e s o r manholes e x c e e d 200 m e t r e s . 4.5.2.3 S e v e r a l c a b l e s i n s t a l l e d i n one d u c t . The f o l l o w i n g a r e a p p l i c a b l e t o t h e i n s t a l l a t i o n of two o r more c a b l e s i n t h e same d u c t . a)

Power c a b l e s of t h e same v o l t a g e may be i n s t a l l e d i n t h e same d u c t .

Power c a b l e s of l e s s t h a n 600 v o l t s may be i n s t a l l e d i n t h e same d u c t .

Power c a b l e s of l e s s t h a n 600 v o l t s s h o u l d n o t be i n s t a l l e d i n t h e same d u c t w i t h c o n t r o l , telephone, o r c o a x i a l type cables.

Power c a b l e s of more t h a n 600 v o l t s s h o u l d n o t be i n s t a l l e d i n t h e same d u c t w i t h c o n t r o l . t e l e p h o n e , c o a x i a l o r power c a b l e s o f less t h a n 600 volts.

C o n t r o l , t e l e p h o n e , and c o a x i a l c a b l e s may be i n s t a l l e d i n t h e same duct.

Power, c o n t r o l , and t e l e p h o n e c a b l e s may be i n s t a l l e d i n t h e same d u c t system, s u b j e c t t o p r o v i s i o n s of sub-paragraphs g ) and h ) .

Cable i n s t a l l a t i o n i n manholes o r h a n d h o l e s . Power and c o n t r o l c a b l e s s h o u l d be i n s t a l l e d i n s e p a r a t e manholes and h a n d h o l e s u n l e s s r e q u i r e d otherwise. If s p a c e i s a v a i l a b l e , c a b l e s l a c k s u f f i c i e n t f o r one s p l i c e f o r e a c h c a b l e s h o u l d be l e f t i n e a c h manhole.

S e p a r a t i o n of c a b l e s i n manholes and h a n d h o i e s . When i t i s n o t p o s s i b i e t o i n s t a l l power and o t h e r t y p e c a b l e s i n s e p a r a t e manholes o r handh o l e s , t h e y s h o u l d be i n s t a l l e d i n s e p a r a t e compartments o r on o p p o s i t e s i d e s of t h e manhole o r handhole.

I n s t a l l a t i o n of c a b l e s i n manholes and h a n d h o l e s

4.5.3.1 Cable r a c k s . Cables s h a l l be c a r e f u l l y formed a r o u n d t h e i n t e r i o r of manh o l e s o r h a n d h o l e s a v o i d i n g s h a r p bends o r k i n k s . A l l s p l i c e s and c a b l e s s h o u l d be t i e d t o c a b l e r a c k s u s i n g 3.2 mm d i a m e t e r n y l o n l i n e . Handhole and manhole r a c k s s h o u l d be t h e p l a s t i c type o r provided w i t h p o r c e l a i n i n s u l a t o r s . S p l i c e s o r c o n n e c t o r s s h o u l d be a minimum of 0.6 m e t r e from t h e mouth of t h e d u c t o p e n i n g i n t o t h e manhole o r h a n d h o l e . Where f e a s i b l e , s p l i c e s i n d i f f e r e n t c a b l e s s h o u l d be s t a g g e r e d . 4S.3.2 Cable t e r m i n a t i o n s . T e r m i n a t i o n of a l l c o n t r o l , t e l e p h o n e , a n d c o a x i a l c a b l e s s h o u l d be a s r e q u i r e d . T e r m i n a t i o n of a l l power c a b l e s r a t e d above 5 000 v o l t s s h o u l d be made w i t h a s t r e s s r e l i e f d e v i c e . Where p o t h e a d s a r e u s e d , s t r i c t conformance t o m a n u f a c t u r e r ' s recommendations s h o u l d be f o l l o w e d . Where t e r m i n a t i o n s a r e made a t t r a n s f o r m e r b u s h i n g s , exposed c o a d u c t i n g s u r f a c e s on b o t h h i g h - and l o w - v o l r a g e s i d e s s h o u l d be t a p e d f o r f u l l v o l t a g e and p a i n t e d w i t h a h i g h i n s u l a t i o n w a t e r - r e s i s t a n t coa t i n g e

The f o l l o w i n g c o n d i t i o n s a p p l y t o t h e g r o u n d i n g o f

4.5.3.3 cables.

4.5.4

A l l s h i e l d e d power c a b l e s s h o u l d h a v e t h e s h i e l d grounded a t e a c h e n d . The g r o u n d i n g c o n d u c t o r s h o u l d be c o n n e c t e d t o a ground r o d by means o f The a grounding connector s p e c i f i c a l l y designed f o r t h i s purpose. s h i e l d s o r armor on d i r e c t e a r t h - b u r i e d power c a b l e s s h o u l d be grounded on e a c h e n d , b u t n o t a t t h e s p l i c e s .

A l l s h i e l d e d c o n t r o l c a b l e s s h o u l d h a v e t h e s h i e l d grounded a t e a c h e n d . The s h i e l d a t e a c h s p l i c e s h o u l d have i n s u l a t i o n r e s i s t a n c e f r o m ground e q u a l t o t h a t of t h e o r i g i n a l c a b l e .

Telephone c a b l e s s h o u l d have t h e s h i e l d s grounded a t one end o n l y . The s h i e l d a t e a c h s p l i c e s h o u l d have i n s u l a t i o n r e s i s t a n c e f r o m ground e q u a l t o t h a t of t h e o r i g i n a l c a b l e .

C o a x i a l c a b l e s h i e l d s s h o u l d be i n s u l a t e d f r o m ground t h r o u g h o u t t h e l e n g t h of t h e c a b l e r u n . The s h i e l d s s h o u l d be grounded o n l y a t t h e c o a x i a l c o n n e c t o r t e r m i n a t i n g i n t o t h e equipment on e a c h end o f t h e c a b l e run,

Pressurized type coaxial cables

4.5.4.1 Precautions. S p e c i a l p r e c a u t i o n s s h o u l d be o b s e r v e d d u r i n g t h e i n s t a l l a t i o n of g a s - f i l l e d c o a x i a l c a b l e s . These c a b l e s s h o u l d be f u r n i s h e d and i n s t a l l e d i n one p i e c e u n d e r n i t r o g e n g a s p r e s s u r e w i t h c a b l e and s e a l s k e p t s e c u r e l y i n p l a c e a t a l l t i m e s d u r i n g c a b l e h a n d l i n g , s h i p p i n g , and i n s t a l l a t i o n . Do n o t c u t o r s p l i c e t h i s c a b l e a t a n y t i m e . A s t h e c a b l e i s unwound from t h e r e e l , a s u p p l e m e n t a r y d e v i c e f o r s t r a i g h t e n i n g t h i s c a b l e i s d e s i r a b l e , Utmost c a r e s h o u l d be e x e r c i s e d a t a l l t i m e s t o p r e v e n t k j n k i n g a n y p a r t of t h e c a b l e d u r i n g i n s t a l l a t i o n . 4.5.4.2 P r e - i n s t a l l a t i o n c h e c k , I n o r d e r t o d e t e r m i n e whether t h e c a b l e h a s b e e n damaged o r p u n c t u r e d , d e t e r m i n e i f t h e n i t r o g e n g a s s h i p p i n g p r e s s u r e i s s t i l l r e t a i n e d i n the cable. I f t h i s g a s p r e s s u r e r e a d i n g h a s d e c r e a s e d and t h e l o s s i s n o t due t o t e m p e r a t u r e change, a n i t r o g e n g a s t e s t s h o u i d be conducted.

4.5.4.3 S t y r o f l e x c o a x i a l c a b l e of 4 5 mm d i a m e t e r s h o u l d n o t be s u b j e c t e d t o a bending r a d i u s of l e s s t h a n one m e t r e d u r i n g i n s t a l l a t i o n The maximum a l l o w a b l e p u l l i n g o r l e s s t h a n 0.6 m e t r e r a d i u s when s e c u r e d i n p l a c e . t e n s i o n f o r t h i s s i z e of c a b l e i s 800 kg. H e l i a x c o a x i a l c a b l e s h o u l d n o t b e s u b j e c t e d t o a b e n d i n g r a d i u s of l e s s t h a n 0.75 m e t r e d u r i n g i n s t a l l a t i o n n o r l e s s t h a n a 0.5 m e t r e r a d i u s when s e c u r e d i n p l a c e . The maximum a l l o w a b l e p u l l i n g t e n s i o n f o r t h i s s i z e of c a b l e i s 380 kg. 4.5.4.4 S l a c k c o i l c a b l e l o o p s s h o u l d n o t be used f o r p r e s s u r i z e d c o a x i a l c a b l e s . The c a b l e end s h o u l d be f e d t h r o u g h t h e o p e n i n g p r o v i d e d a t t h e b u i l d i n g f r o m t h e r e e l located outside the building. The c a b l e between t h e s t r u c t u r e e n t r a n c e and t h e r e s p e c t i v e c a b l e end s h o u l d c o n t i n u e i n t o t h e b u i l d i n g on r e l a t i v e l y t h e same h o r i z o n t a l plane. Bends s h o u l d n o t be l e s s t h a n t h e minimum p r e s c r i b e d above. T e m p o r a r i l y s u p p o r t t h e c a b l e end s o t h a t t h e c a b l e w i l l n o t "droop" o r "hang", p e n d i n g f i n a l c o n n e c t i o n t o the e l e c t r o n i c apparatus.

Cable i n s t a l l a t i o n i n saw c u t s 4.5.5.1 Use of saw c u t s . When new l i g h t s a r e i n s t a l l e d i n e x i s t i n g p a v e m e n t s , f o r example, runway c e n t r e l i n e and touchdown zone l i g h t s and t a x i w a y c e n t r e l i n e l i g h t s , Only s e c o n d a r y c i r c u i t s of c a b l e i n s t a l l a t i o n i n saw c u t s o r k e r f s may be r e q u i r e d . This technique should = b e i s o l a t i n g t r a n s f o r m e r s s h o u l d be i n s t a l l e d i n saw c u t s . used i n new pavement a s i t weakens t h e pavement. 4.5.5.2 C u t t i n g t h e pavement. Saw c u t s a r e made w i t h diamond b l a d e s a w s . The saw c u t o r k e r f s h o u l d be n o t l e s s t h a n 1 cm wide and n o t l e s s t h a n 2 cm d e e p . The w i d t h and d e p t h s h o u l d be i n c r e a s e d i f s e v e r a l c a b l e s a r e t o be i n s t a l l e d i n t h e same saw c u t and a t e n t r a n c e s t o l i g h t f i x t u r e s , t r a n s f o r m e r e n c l o s u r e s , and s p l i c e chambers. The d e p t h of t h e k e r f s h o u l d be i n c r e a s e d s u f f i c i e n t l y t o a l l o w s l a c k w i r e u n d e r t h e paveA l l saw c u t s ment j o i n t where a saw c u t c r o s s e s a c o n s t r u c t i o n j o i n t i n t h e pavement. s h o u l d be i n s t r a i g h t l i n e s w i t h v e r t i c a l s i d e s . The i n t e r s e c t i n g e d g e s s h o u l d be chamfered where saw c u t s i n t e r s e c t t o r e d u c e damage t o t h e c a b l e i n s u l a t i o n . It may be d e s i r a b l e t o c o l l e c t t h e d e b r i s from saw c u t t i n g and p r o c e s s i t t o r e c o v e r t h e diamond grit. 4.5.5.3 C l e a n i n g t h e saw c u t . The saw c u t s h o u l d be s a n d b l a s t e d t o remove a l l f o r e i g n and l o o s e m a t e r i a l . Sand f o r b l a s t i n g s h o u l d be of t h e p r o p e r s i z e and q u a l i t y f o r t h i s work and a p p l i e d w i t h p r o p e r s i z e n o z z l e s and a i r p r e s s u r e . Immediately p r i o r t o i n s t a l l i n g t h e c a b l e s o r w i r e s , t h e saw c u t s h o u l d be f l u s h e d w i t h a high-speed j e t of w a t e r o r s t e a m and d r i e d w i t h a h i g h s p e e d j e t of a i r . Keep t h i s a r e a c l e a n u n t i l c o m p l e t i o n of t h e work. I n s t a L l a t i o n of c a b l e s i n saw c u t s . Since t h e s e c a b l e s a r e f o r t h e 4.5.5.4 s e c o n d a r y c u r r e n t of i s o l a t i n g t r a n s f o r m e r s , 6 0 0 - v o l t i n s u l a t i o n s u i t a b l e f o r wet o r damp l o c a t i o n s s h o u l d be u s e d . P o l y v i n y l - c h l o r i d e , p o l y e t h y l e n e , r u b b e r , and e t h y l e n e probylene-rubber a r e s u i t a b l e t y p e s of i n s u l a t i o n . A j a c k e t o v e r t h e i n s u l a t i o n i s n o t The c o n d u c t o r s h o u l d be s t r a n d e d c o p p e r n o t l e s s t h a n 3.3 mm2 i n c r o s s required. sectional area. I f t h e t o t a l l e n g t h of t h e c o n d u c t o r w i l l e x c e e d 350 m e t r e s , t h e cotlductor s i z e s h o u l d be n o t l e s s t h a n 5.2 mm2. Usuaily single-conductor w i r e i s used, Do n o t s p l i c e t h e c a b l e i n t h e s a w c u t s ; u s e b u t two-conductor c a b l e i s a c c e p t a b l e . o n l y f u l l l e n g t h r u n s of c a b l e . Tile c a b l e s s h o u l d be p l a c e d a t t h e b o t t o m o f t h e saw c a t s and a n c h o r e d w i t h r u b b e r o r p l a s t i c wedges o r w i t h n o n - c o r r o s i v e m e t a l c l i p s . There i s n o need f o r s e p a r a t i o n of c a b l e s when more t h a n o n e c a b l e i s p l a c e d i n t h e same cut. The wedges o r c l i p s s h o u l d be s p a c e d a p p r o x i m a t e l y one m e t r e a p a r t e x c e p t t h a t c l o s e r s p a c i n g may be d e s i r e d a t pavement j o i n t s , saw c u t i n t e r s e c t i o n s , a n d e n t r a n c e s t o s p l i c e chambers o r l i g h t s . C a b l e s s h o u l d be e n c a s e d i n f l e x i b l e t u b i n g o f p o l y e t h l e n e o r o t h e r s u i t a b l e m a t e r i a l of n o t l e s s t h a n 0.3 m e t r e i n l e n g t h a t j o i n t s i n t h e pavements. The s i z e of t h e t u b i n g s h o u l d be s u f f i c i e n t t o a l l o w movement of t h e cables. The t u b i n g s h o u l d be c e n t e r e d on t h e j o i n t and t h e e n d s o f t h e t u b i n g wrapped w i t h t a p e t o p r e v e n t t h e e n t r a n c e of s e a l i n g m a t e r i a l s . 4.5.5.5 S e a l i n g t h e saw c u t . The saw c u t s h o u l d be s e a l e d w i t h s u i t a b l e a d h e s i v e compounds a l o n g t h e e n t i r e l e n g The compounds a r e - th a f t e r the cables a r e installed. u s t i a l l y two-component l i q u i d t y p e s s u i t a b l e f o r t h e c a b l e i n s u l a t i o n and t h e t y p e o f concrete. T e s t samples of t h e s e a l a n t s h o u l d have a minimum e l o n g a t i o n o f 4 5 p e r c e n t . The a d h e s i v e components s h o u l d n o t be o l d e r t h a n recommended by t h e m a n u f a c t u r e r and s h o u l d n o t be s t o r e d where t h e t e m p e r a t u r e e x c e e d s 30째C o r t h e m a n u f a c t u r e r ' s The m a n u f a c t u r e r ' s i r ~ s t r u c t i o n ss h o u l d be f o l l o w e d i n m i x i n g and recommendations.

U s u a l l y i f t h e a d h e s i v e components a r e p r e v a r m e d t o 25OC b e f o r e a n d d u r i n g installing. m i x i n g , t h e compound may b e s a t i s f a c t o r i l y i n s t a l l e d a n d c u r e d w i t h o u t t h e a p p l i c a t i o n The j o i n t s o f pavement o f e x t e r n a l h e a t i f t h e a m b i e n t t e m p e r a t u r e i s 7OC o r g r e a t e r . i n t h e a r e a s o f saw c u t s s h o u l d b e packed w i t h r o v i n g m a t e r i a l s u c h a s hemp, j u t e , All c o t t o n , o r f l a x t o p r e v e n t t h e s e a l i n g m a t e r i a l from f l o w i n g i n t o t h e open j o i n t . s u r p l u s a n d s p i l l e d m a t e r i a l s h o u l d b e removed.

4.5.5.6 Cable t e r m i n a t i o n s . Cables s h o u l d b e p r o p e r l y t e r m i n a t e d i n f i x t u r e s , t r a n s f o r m e r e n c l o s u r e s , a n d s p l i c e chambers. The e n t r a n c e s t o t h e s e t e r m i n a t i o n u n i t s s h o u l d be s e a l e d . The t e r m i n a t i o n e n d s of t h e c a b l e s s h o u l d b e s u i t a b l y c o n n e c t e d a n d t h e c a b l e p r o t e c t e d f r o m m o i s t u r e e n t e r i n g t h e c a b l e between t h e c o n d u c t o r a n d t h e e n d of t h e i n s u l a t i o n . 4.5.6

Cable marking

4.5.6.1

A l l c a b l e s a n d c a b l e r o u t e s s h o u l d b e marked f o r e a s y i d e n t i f i c a t i o n i n t h e

future.

4.5.6.2 C a b l e t a g g i n g . A l l c a b l e s s h o u l d b e t a g g e d i n e a c h manhole o r h a n d h o l e w i t h n o t less t h a n two t a g s p e r c a b l e , o n e n e a r e a c h d u c t e n t r a n c e h o l e . Tags s h o u l d be a t t a c h e d t o t h e c a b l e immediately a f t e r i n s t a l l a t i o n . Cable t e r m i n a t i o n s and p o t h e a d s s h o u l d be tagged a s t o f u n c t i o n , f a c i l i t y which i t s e r v e s , and o t h e r p e r t i n e n t d a t a . Tags s h o u l d be o f s u i t a b l e s i z e a n d t h i c k n e s s , p r e f e r a b l y o f c o p p e r . They s h o u l d b e s e c u r e l y a t t a c h e d t o t h e c a b l e u s i n g n y l o n c o r d . Marking o f t a g s s h o u l d c o n s i s t o f a n a b b r e v i a t i o n o f t h e name of f a c i l i t y o r f a c i l i t i e s s e r v e d by t h e c a b l e , t h e l e t t e r i n d i c a t i n g t h e t y p e of s e r v i c e (power, t e l e p h o n e , c o n t r o l and r a d i o f r e q u e n c y ( c o a x ) ) p r o v i d e d by t h e c a b l e . Where t e l e p h o n e t y p e c a b l e i s u s e d f o r c o n t r o l f u n c t i o n s , i t s h o u l d b e marked a s a c o n t r o l c a b l e , n o t a t e l e p h o n e c a b l e . Where two o r more i d e n t i c a l c a b l e s are u s e d t o s e r v e t h e same f a c i l i t y , t h e y may b e b u n d l e d u n d e r o n e t a g . 4.5.6.3 Cable r o u t e markers. D i r e c t e a r t h - b u r i a l c a b l e r o u t e s s h o u l d b e marked e v e r y 6 0 m e t r e s a l o n g t h e c a b l e r u n , a t e a c h c h a n g e o f d i r e c t i o n o f t h e c a b l e , and a t e a c h c a b l e s p l i c e w i t h a c o n c r e t e s l a b m a r k e r of s u i t a b l e s i z e a n d t h i c k n e s s i % e s e m a r k e r s s h o u l d b e i n s t a l l e d s h o r t l y a f t e r t h e f i n a l b a c k f i l l of t h e c a b l e t r e n c h . The m a r k e r s s h o u l d b e i n s t a l l e d f l a t i n t h e g r o u n d w i t h t h e t o p a p p r o x i m a t e l y 2.5 c m a b o v e t h e f i n i s h e d g r a d e , A f t e r t h e c o n c r e t e m a r k e r h a s s e t a minimum o f 2 4 h o u r s , t h e t o p s u r f a c e shoilld be p a i n t e d b r i g h t orange w i t h pairit s u i t a b l e f o r uncured e x t e r i o r concrete. Each c a b l e marker s h o u l d h a v e t h e f o l l o w i n g i n f o r m a t i o n i m p r e s s e d upon i t s top surface: a)

The l e t t e r d e s i g n a t i n g t h e t y p e o f c a b l e t h e word "CABLE" o r "SPLICL". s p l i c e d s h o u l d p r e c e d e t h e word "SPLICE";

t h e name of t h e f a c i l i t y s e r v e d ;

t h e t y p e o f c a b l e i n s t a l l e d s h o u l d b e marked w i t h "POWEK", "CONTROL", "Tk3LEPHONE", o r "COAXIAL", o r w i t h s u i t a b l e a b b r e v i a t i o n s f o r t h e s e terms. The d e s i g n a t i o n o f a l l t y p e c a b l e s i n s t a l l e d s h o u l d b e shown o n t h e marker;

arrows t o i n d i c a t e t h e d i r e c t i o n o r change of d i r e c t i o n o f t h e c a b l e run;

4.5.7

t h e l e t t e r s s h o u l d n o t be less t h a n 10 cm h i g h , 7 c m w i d e a n d 1 c m d e e p ;

c a b l e s i n s t a l l e d i n d u c t o r conduit should have c a b l e markers i n s t a l l e d e v e r y 60 m e t r e s a n d a t e v e r y c h a n g e i n d i r e c t i o n of c a b l e , e x c e p t markers should n o t be i n s t a l l e d i n c o n c r e t e o r a s p h a l t s u r f a c e s ; and

manholes a n d h a n d h o l e s s h a l l b e i d e n t i f i e d by p u r p o s e .

Enclosures f o r connections

4.5.7.1 I n s t a l l a t i o n of e n c l o s u r e s . Most c a b l e c o n n e c t i o n s t o t h e i s o l a t i n g t r a n s f o r m e r s a r e i n t r a n s f o r m e r e n c l o s u r e s , i n b a s e s f o r l i g h t i n g f i x t u r e s which a r e below t h e s u r f a c e a t t h e e d g e o f paved runways o r t a x i w a y s , o r i n t h e pavement. P r e f e r a b l y , t h e s e e n c l o s u r e s a r e i n s t a l l e d a t t h e d e s i g n a t e d l o c a t i o n s i n a poured c o n c r e t e f o u n d a t i o n w h i c h e n c a s e s t h e e n c l o s u r e c o n t a i n e r by n o t l e s s t h a n 1 0 t o 1 5 cm of c o n c r e t e around t h e bottom and s i d e s . Metal c o n d u i t s connected t o e n t r a n c e s of t h e c o n t a i n e r f o r a d m i t t i n g t h e c a b l e s of t h e c i r c u i t s h o u l d e x t e n d t h r o u g h t h e c o n c r e t e walls. T h e s e c o n d u i t s s h o u l d b e p r o v i d e d w i t h clamps f o r c o n n e c t i n g t h e g r o u n d w i r e s o r c o u n t e r p o i s e s . The t o p o f t h e c o n t a i n e r must be l e v e l a n d a t t h e p r o p e r d e p t h below t h e A holding t o p s u r f a c e of t h e c o n c r e t e f o r m o u n t i n g t h e l i g h t f i x t u r e o r c o v e r p l a t e . d e v i c e o r j i g s h o u l d be used t o m a i n t a i n l e v e l , a l i g n m e n t , and p r o p e r d e p t h of t h e t o p o f t h e e n c l o s u r e c o n t a i n e r d u r i n g i n s t a l l a t i o n a n d c u r i n g of t h e c o n c r e t e . The e n d s of c a b l e s a r e p u l l e d i n t o t h e e n c l o s u r e c o n t a i n e r a n d t h e e n d of t h e c o n d u i t o u t s i d e t h e c o n c r e t e f o u n d a t i o n i s s e a l e d a r o u n d t h e c a b l e w i t h a s u i t a b l e compound t o k e e p t h e e n c l o s u r e f r e e of w a t e r . The e l e v a t e d l i g h t s , s e m i - f l u s h l i g h t s , o r b l a n k c o v e r s mounted on t h e s e c o n t a i n e r s s h o u l d i n c l u d e a g a s k e t o r o t h e r means o f s e a l i n g t o p r e v e n t water from e n t e r i n g t h e c o n t a i n e r . 4.5.7.2 I n s t a l l a t i o n i n e x i s t i n g pavement. I f l i g h t s a r e t o be i n s t a l l e d i n e x i s t i n g p a v e m e n t s , i n s t a l l i n g t h e t r a n s f o r m e r e n c l o s u r e s i n c o n c r e t e f o u n d a t i o n s may n o t be p r a c t i c a l . Usually t h e t r a n s f o r m e r e n c l o s u r e i s l o c a t e d a t t h e e d g e of t h e pavement a n d t h e s e c o n d a r y c a b l e s t o t h e l i g h t a r e i n s t a l l e d i n saw c u t s . A transformer e n c l o s u r e , j u n c t i o n box, o r t h e l i g h t f i x t u r e may b e i n s t a l l e d a t t h e l o c a t i o n f o r t h e l i g h t f o r making t h e c o n n e c t i o n s t o t h e l i g h t by b o r i n g a h o l e of t h e p r o p e r s i z e a n d d e p t h i n t h e pavement. The l i g h t f i x u t r e may b e mounted o n a n e n c l o s u r e o r b e of a t y p e s u i t a b l e f o r i n s t a l l i n g d i r e c t l y i n t h e h o l e . H o l e s of p r o p e r d i a m e t e r f o r r h e f i x t u r e s o r e n c l o s u r e s s h o u l d b e b o r e d i n t h e pavement w i t h diamond-edged b i t s . The b o t t o m o f t h e h o l e f o r j u n c t i o n b o x e s and l i g h t E i x t u r e s s h o u l d b e f l a t o r s l i g h t l y c o n c a v e e x c e p t t h a t a n a r e a 2.5 cm wide a r o u n d t h e p e r i m e t e r s h o u l d b e f l a t , If t h e holes a r e d r i l l e d t o o d e e p , t h e y s h o u l d b e f i l l e d w i t h s e a l a n t compound t o t h e d e s i r e d d e p t h a n d t h e compound p e r m i t t e d t o c u r e b e f o r e p r o c e e d i n g w i t h t h e i n s t a l l a t i o n . 4.5.7.3 Installing t h e enclosure. The s i d e s a n d b o t t o m of t h e t r a n s f o r m e r e n c l o s u r e , j u n c t i o n box, o r f i x t u r e s h o u l d be s a n d b l a s t e d i m m e d i a t e l y p r i o r t o installation. Also s a n d b l a s t t h e i n s i d e f a c e s of t h e bored h o l e . The b o t t o m and s i d e s o f t h e e n c l o s u r e o r f i x t u r e a n d t h e f a c e s and bottom o f t h e b o r e d h o l e s h o u l d be c o v e r e d w i t h a c o a t i n g of a s u i t a b l e s e a l a n t w i t h a minimum amount t h a t w i l l c o m p l e t e l y f i l l t h e s p a c e b e t w e e n t h e c o n c r e t e a n d t h e f i x t u r e o r e n c l o s u r e . 'L'he s e a l a n t compound i s u s u a l l y a t w o - p a r t p a s t e compound which i s mixed a n d i n s t a l l e d i n a c c o r d a n c e w i t h t h e m a n u f a c t u r e r ' s i n s t r u c t i - o n s . A h o l d i n g d e v i c e o r j i g s h o u l d be u s e d f o r i n s t a l l i n g e a c h l i g h t o r e n c l o s u r e t o a s s u r e i t s p r o p e r e l e v a t i o n a n d a l i g n m e n t . The h o l d i n g d e v i c e s h o u l d b e l e f t i n p l n c e u n t i l t h e s e a l a n t h a s s e t - The c a b l e s s h o u l d b e p u l l e d i n a n d brought i n t o p o s i t i o n f o r c o n n e c t i n g o r s p l i c i n g a s r e q u i r e d and t h e e n t r a n c e should be qeaied. A l l s u r p l u s s e a l a n t o r embedding compound s h o u l d b e re:noved.

4.5.7.4

Direct-burial i s o l a t i n g transformers depth a s the cables connected t o the transformers. Transformers and c a b l e s s h o u l d be a r r a n g e d s o t h a t t h e r e w i l l be n o bends o r s t r e s s e s on t h e c o n n e c t o r s , and t h e c a b l e s and l e a d s s h o u l d be p r o v i d e d w i t h Use p r o p e r c o n n e c t o r s and t a p e s l a c k t o accommodate e a r t h s e t t l i n g and f r o s t heaves. t h e o u t s i d e j o i n t w i t h 2 o r 3 t u r n s of e l e c t r i c a l tape. Do n o t make s p l i c e s f o r connecting t h e cables t o t h e transformers.

4.5.7.5 I n s t a l l i n g i s o l a t i n g transformers i n transformer enclosures. When i s o l a t i n g transformers a r e i n s t a l l e d i n transformer enclosures, t h e transformers should be p o s i t i o n e d w i t h a f l a t s i d e on t h e bottoms of t h e e n c l o s u r e s , i f p o s s i b l e . Connect t h e c a b l e s t o t h e l e a d s of t h e t r a n s f o r m e r s u s i n g s u i t a b l e c o n n e c t o r s , n o t s p l i c e s , and t a p e the joints. Connectors s h o u l d l i e f l a t on t h e bottoms of t h e e n c l o s u r e s w i t h o u t bending o r tension i f possible. Ground c o n n e c t i o n s on i s o l a t i n g t r a n s f o r m e r s s h o u l d b e c o n n e c t e d t o t h e ground w i r e i f s u c h c o n n e c t i o n s a r e p r o v i d e d . If t h e i n t e r n a l temperat u r e s i n t h e e n c l o s u r e s w i l l be more t h a n 120째C, a s e c t i o n of alurninum f o i l between t h e l i g h t f i x t u r e s and t h e t r a n s f o r m e r s w i l l r e d u c e t h e e f f e c t s of t h e h e a t on t h e transformer.

W m S FOR UPJD 5.1

UND SERVICE AT AEELODROaS

FEATURES OF THE CABLES

5.1.1.1 Insulation. The f o l l o w i n g i n s u l a t i o n m a t e r i a l s a r e commonly s p e c i f i e d b e c a u s e t h e y p r o v i d e t h e maximum r a t e d c o n d u c t o r t e m p e r a t u r e s f o r o p e r a t i n g , o v e r l o a d , a n d s h o r t - c i r c u i t c o n d i . t i o n s f o r c a b l e s r a t e d up t o a maximum o f 35 k i l o v o l t s : a)

C r o s s - l i n k e d p o l y e t h y l e n e (XLP). T h i s t h e r m o - s e t t i n g compound h a s e x c e l l e n t e l e c t r i c a l p r o p e r t i e s , good c h e m i c a l r e s i s t a n c e , good p h y s i c a l s t r e n g t h c h a r a c t e r i s t i c s , a n d r e m a i n s f l e x i b l e a t low t e m p e r a t u r e s .

E t h y l e n e - p r o p y l e n e r u b b e r (EPR). T h i s compound h a s e l e c t r i c a l p r o p e r ties which a r e c o n s i d e r e d e q u a l t o c r o s s - l i n k e d p o l y e t h y l e n e ; theref o r e , t h e c o n t r a c t o r should be given t h e option t o provide e i t h e r type.

5.1.1.2 The f o l l o w i n g i n s u l a t i o n m a t e r i a l s may b e u s e d where s p e c i a l c i r c u m s t a n c e s w a r r a n t t h e i r l o w e r r a t e d c o n d u c t o r t e m p e r a t u r e s o r t h e i r l o w e r r a t e d maximum v o l t a g e class. a)

Rubber. Rubber i n s u l a t e d c o n d u c t o r s p r o v i d e e a s e o f s p l i c i n g , good m o i s t u r e r e s i s t a n c e , a n d low d i e l e c t r i c l o s s e s .

Varnished cambric. Varnished cambric i n s u l a t i o n i s used f o r r e s i s t a n c e t o o z o n e a n d o i l and f o r e a s e of s p l i c i n g . Use v a r n i s h e d c a m b r i c p r i n c i p a l l y i n conjlanction w i t h p a p e r i n s u l a t e d c a b l e where o i l m i g r a t i o n i s a problem, Where i n s t a l l e d i n wet o r h i g h l y humid l o c a t i o n s o r u n d e r g r o u n d , v a r n i s h e d - c a m b r i c i n s l i l a t i o n must be p r o v i d e d w i t h a s u i t a b l e sheath. P a p e r i n s u l a t e d . Use p a p e r i r l s u l a t e d c a b l e f o r low i o n i z a t i o n , l o n g l i f e , h i g h d i e l e c t r i c s t r e n g t h , low d i e l e c t r i c l o s s e s , a n d good s t a b l e c h a r a c t e r i s t i c s under temperature v a r i a t i o n s . As w i t h varnished-cambric i n s u l a t i o n , paper i n s u l a t i o n requires a s u i t a b l e p r o t e c t i v e m e t a l l i c sheath. It may b e s p e c i f i e d a s a n o p t i o n when e x i s t i n g c a b l e s a r e p a p e r i n s u l a t e d , o r as a r e q u i r e m e n t when t h e e x t r a c o s t i s j u s t i f i e d b e c a u s e n e i t h e r cross-linked polyethylene o r ethylene-propylene rubber provide the required qualities.

Butyl rubber. This t h e r m o s e t t i n g i n s u l a t i o n h a s h i g h d i e l e c t r i c T t can s t r e n g t h and i s h i g h l y r e s i s t a n t t o m o i s t u r e , h e a t , and ozone. b e u s e d up t o 3 5 k i l o v o l t s , b u t h a s l o w e r r a t e d c o n d u c t o r t e m p e r a t u r e s than e i t h e r cross-linked polyethylene o r ethylene-propylene rubber.

5.1.1.3

This t h e r m o s e t t i n g i n s u l a t i o n i s h i g h l y r e s i s t a n t t o It c a n b e u s e d i n w e t o r d r y l o c a t i o n s , corona. It h a s t h e h i g h e s t r a t e d c o n d u c t o r t e m p e r a t u r e s exposed, o r i n conduit. b u t c a n be u s e d o n l y f o r a p p l i c a t i o n s u p t o f i v e k i l o v o l t s . Silicone rubber.

Cable s h e a t h s a)

Nonmetallic. Nonmetallic s h e a t h s s h o u l d be f l e x i b l e , m o i s t u r e r e p e l l a n t , and l o n g l a s t i n g . Neoprene, w h i c h i s o f t e n u s e d as n o n m e t a l l i c c a b l e s h e a t h s , i s u n s u i t a b l e i n many l o c a t i o n s . T h i s material f r e q u e n t l y a b s o r b s e x c e s s i v e amounts o f w a t e r w h i c h may p e n e t r a t e t h r o u g h t o the insulation. Some n o n m e t a l l i c s h e a t h m a t e r i a l s , e s p e c i a l l y i n some t r o p i c a l a r e a s , are r e p o r t e d t o b e damaged by m i c r o - o r g a n i s m s , i n s e c t s , and p l a n t l i f e . Some s h e a t h materials, w h i c h p e r f o r m w e l l where i n s t a l l e d u n d e r g r o u n d o r i n c o n d u i t s , d e t e r i o r a t e r a p i d l y i f i n s t a l l e d where i t i s e x p o s e d t o s u n l i g h t . M a t e r i a l s w h i c h become b r i t I n some t l e a t low t e m p e r a t u r e s s h o u l d n o t b e u s e d i n c o l d r e g i o n s . l o c a t i o n s , r o d e n t s f r e q u e n t l y damage n o n m e t a l l i c - s h e a t h e d c a b l e . In t h e s e a r e a s t h e c a b l e s h o u l d be i n s t a l l e d i n d u c t s o r m e t a l l i c - s h e a t h e d c a b l e s h o u l d be u s e d *

Metallic. C a b l e s e x p o s e d t o m e c h a n i c a l damage o r h i g h i n t e r n a l p r e s s u r e Certain r e q u i r e a m e t a l l i c s h e a t h , s u c h a s l e a d , aluminurn, o r s t e e l . i n s u l a t i o n s , s u c h as p a p e r a n d v a r n i s h e d c a m b r i c , r e q u i r e s u c h protection i n a l l cases.

5.1.1.4 Cable coverings. A s u i t a b l e c o v e r i n g o r j a c k e t may b e r e q u i r e d f o r c o r r o s i o n p r o t e c t i o n of m e t a l l i c s h e a t h s . 5.1.1.5 Shielded cables. S h i e l d i n g of a m e d i u m v o l t a g e d i s t r i b u t i o n c a b l e i s r e q u i r e d t o c o n f i n e t h e e l e c t r i c f i e l d t o t h e i n s u l a t i o n i t s e l f and t o p r e v e n t l e a k a g e Insulation shielding i s c u r r e n t s from r e a c h i n g t h e o u t s i d e s u r f a c e of t h e c a b l e . r e q u i r e d on a l l n o n m e t a l l i c - s h i e l d e d c a b l e r a t e d two k i l o v o l t s a n d a b o v e , e x c e p t f o r aerodrome-lighting s e r i e s - c i r c u i t c a b l e s , and a l l m e t a l l i c - s h e a t h e d c a b l e r a t e d f i v e k i l o v o l t s a n d above. S h i e l d s should be grounded t o reduce t h e h a z a r d s of shock. tirouttding i s r e q u i r e d a t e a c h t e r m i n a t i o n , o t h e r w i s e d a n g e r o u s i n d u c e d s h i e l d v o i t a g e s may o c c u r . 5.1.1.6 Cable f i r e p r o o f i n g . C a b l e s i n m a n h o l e s , h a n d h o l e s , and t r a n s f o r m e r v a u l t s o p e r a t i n g a t 2 400 v o l t s o r o v e r , o r e x p o s e d t o t h e f a i l u r e o f o t h e r c a b l e s o p e r a t i n g a t t h e s e v o l t a g e s , s h o u l d be f i r e p r o o f e d w i t h a s u i t a b l e s p r a y c o a t i n g . E x c e p t i o n s may b e made w h e r e p h y s i c a l ~ e p a r a t i o n , i s o l a t i o n by b a r r i e r s , o r o t h e r c o n s i d e r a t i o n s p e r m i t . 5.1.1.7 P r o t e c t i o n a g a i n s t c o r o n a damage. I n s u l a t i o n o f h i g h v o l t a g e c a b l e s which may b e damaged by ozone s h o u l d b e p r o t e c t e d a g a i n s t t h i s damage by c o n t r o l l i n g c o r o n a , which p r o d u c e s o z o n e , by p l a c i n g a t h i n s e m i - c o n d u c t i n g f i l m b e t w e e n t h e c o n d u c t o r and i t s i n s u l a t i o n . T h i s f i l m f i l l s t h e v o i d s between t h e c o n d u c t o r a n d t h e i n s u l a t i o n t h u s p r e v e n t i n g t h e g e n e r a t i o n of corona and hence ozone. ( S e e 5.1.3.6.) 5.1.1.8 C a b l e c o n d u c t o r s . Annealed c o p p e r i s u s e d i n most f o r m s o f i n s u l a t e d cond u c t o r s because of i t s h i g h c o n d ~ t c t i v i t y ,f l e x i b i l i t y , and e a s e of h a n d l i n g . Mediumh a r d d r a w n c o p p e r has g r e a t e r t e n s i l e s t r e n g t h t h a n s n n e a l e d c o p p F r , Aluminure cond u c t o r s may be p e r m i t t e d a s a c o n d u c t o r P s o p t i o n e x c e p t where c o r r o s i v e c o n d i t i o n s l i m i t t h e i r tLsage;

Classes of s e r v i c e

L o w v o l t a g e c a b l e s -- i n s u l a t i o n r a t e d a t 600 v o l t s o r 5.1.2.1 less a r e u s e d t o c o n n e c t t h e s e c o n d a r i e s of s e r i e s / s e r i e s i s o l a t i n g transformers t o t h e lamps i n t h e f i x t u r e s , f o r l o w v o l t a g e d i s t r i b u t i o n c i r c u i t s , a n d as l o w v o l t a g e f e e d e r c i r c u i t s t o s i n g l e u n i t s a n d t h e s h o r t e r c i r c u i t s . The c o n d u c t o r s are u s u a l l y Both c o p p e r b u t may b e aluminum, a n d e i t h e r s i n g l e - o r m u l t i - c o n d u c t o r c a b l e s are u s e d . s o l i d and s t r a n d e d c o n d u c t o r s a r e u s e d b u t s t r a n d e d i s p r e f e r r e d i f f r e q u e n t f l e x i n g o f The c r o s s s e c t i o n a l a r e a o f t h e c o n d u c t o r may v a r y f r o m 2 mm2 t o t h e c a b l e i s expected. 8 mm 2 o r l a r g e r i f n e c e s s a r y t o d e c r e a s e t h e v o l t a g e d r o p .

5.1.2.2 High-voltage c a b l e s . For aerodrome l i g h t i n g , h i g h v o l t a g e c a b l e s a r e u s e d m o s t l y f o r s o u r c e power d i s t r i b u t i o n a n d f e e d e r c a b l e s . The c r i t e r i a a n d materials are t h e same as f o r power d i s t r i b u t i o n c a b l e s d i s c u s s e d i n p a r a g r a p h s 2.5.5 t o 2.5.7. The v o l t a g e s u s e d u s u a l l y r a n g e f r o m 1 000 t o 5 000 v o l t s . Conductor s i z e s u s u a l l y a r e i n t h e r a n g e o f 3.3 mm2 t o 21 mm2 i n c r o s s s e c t i o n b u t l a r g e r s i z e s a r e o c c a s i o n a l l y u s e d . T h e s e c a b l e s may be e i t h e r s i n g l e - c o n d u c t o r o r two- o r t h r e e - c o n d u c t o r c a b l e s . Consider t h e s o i l , e n v i r o n m e n t , method o f i n s t a l l a t i o n , s u b j e c t i o n t o c h e m i c a l s , a n d a n y s p e c i a l problems i n s e l e c t i n g t h e i n s u l a t i o n , j a c k e t s , s h e a t h i n g , and s h i e l d i n g f o r t h e s e cables. 5.1.2.3 S e r i e s a e r o d r o m e l i g h t i n g c a b l e s . The r e q u i r e m e n t s o f t h e c a b l e s f o r t h i s p u r p o s e h a v e b e e n s t a n d a r d i z e d more t h a n h a v e t h e c a b l e r e q u i r e m e n t s f o r m o s t power The c i r c u i t s . The s e r i e s c u r r e n t u s e d i n t h e s e c i r c u i t s i s b e t w e e n 6 a n d 20 a m p e r e s . c o n d u c t o r s i z e commonly u s e d i s 8.4 mm2 i n c r o s s - s e c t i o n b u t some 3.3 mm2 c a b l e i s a l s o These c a b l e s a r e s i n g l e - c o n d u c t o r . The c o n d u c t o r i s u s u a l l y s t r a n d e d b u t s o l i d used. A non-metallic c o n d u c t o r c a n a l s o be used. The i n s u l a t i o n i s u s u a l l y 5 O O O v o l t r a t e d . j a c k e t o v e r t h e i n s u l a t i o n i s commonly u s e d . M e t a l l i c - t a p e s h i e l d i n g b e t w e e n t h e i n s u l a t i o n a n d j a c k e t o r between t h e j a c k e t a n d n o n - m e t a l l i c c o v e r i n g i s o f t e n u s e d b u t may n o t b e r e q u i r e d f o r some i n s t a l l a t i o n . The p r e f e r r e d s e r i e s - l i g h t i n g c a b l e s a r e s t r a n d e d , c o p p e r , 8.3 mm2 c o n d u c t o r ; c r o s s - l i n k e d p o l y e t h y l e n e , e t h y l e n e - p r o p y l e n e - r u b ber, o r bunarubber insulation; chlorosulfonated polyethylene, polyvinyl chloride, p o l y e t h y l e n e , o r heavy d u t y n e o p r e n e j a c k e t e d ; m e t a l - t a p e s h i e l d e d t y p e s . 5.1.2.4 Control cables. Control cables a r e l o w v o l t a g e cables u s u a l l y i n p a i r s o r multi-condiictor. A g r o u p of s i n g l e - c o n d u c t o r c a b l e s may be u s e d f o r some s i m p l e c o n t r o l circuits. Some c o n t r o l c a b l e s h a v e one o r two l a r g e r c o n d u c t o r s f o r t h e l i n e v o l t a g e a n d / o r n e u t r a l and s e v e r a l s m a l l e r conductors f o r t h e i n d i v i d u a l c o n t r o l s , Other i n s t a l l a t i o n s may u s e a p a i r o f l a r g e r w i r e s f o r t h e l i n e a n d n e u t r a l and o t h e r c a b l e s w i t h many s m a l l e r c o n d u c t o r w i r e s f o r t h e i n d i v i d u a l c o n t r o l s . M u l t i - c o n d u c t o r c o n t r o l c a b l e s h a v e 7, 1 2 , 1 6 , o r many more c o n d u c t o r s a r e u s e d . Most c o n t r o l c a b l e s h a v e s t r a n d e d c o p p e r c o n d u c t o r s . The s i z e o f t h e c o n d u c t o r i s s e l e c t e d tc:, k e e p t h e l i n e The c r o s s s e c t i o n a l s i z e o f t h e c o n d u c t o r s i s voltage drop within an acceptable range. u s u a l l y b e t w e e n 3.3 mm2 a n d 0.5 mm2. The i n s u l a t i o n r e s i s t a n c e r a t i n g must b e s u i t a b l e Rubber, p o l y e t h y l e n e , p o l y f o r t h e c o n t r o l v o l t a g e which i s u s u a l l y 250 v o l t s o r l e s s . v i n y l c h l o r i d e , v a r n i s h e d c a m b r i c , a n d p a p e r a r e some of t h e t y p e s o f i n s u l a t i o n f o r c o n t r o l c a b l e s . Thin i n s u l a t i o n i s d e s i r a b l e t o r e d u c e t h e d i a m e t e r o f t h e c a b l e . T w i s t e d p a i r s o r s p i r a 1 . i n g o f t h e c o n d u c t o r s i s d e s i r a b l e f o r a l t e r n a t i n g - c u r r e n t cont r o l c i r c u i t s t o r e d u c e t h e i n d u c e d v o l t a g e between c i r c u i t s . Multi-conductor c a b l e s must h a v e a n o u t s i d e j a c k e t a n d may b e s h i e l d e d w i t h metal t a p e .

5,1,2,5 Cormnunications c a b l e . S p e c i a l interco~nmnunications o r t e l e p h o n e c i r c u i t s s h o u l d b e i n s t a l l e d t o p r o v i d e communications b e t w e e n c o n t r o l t o w e r , l i g h t i n g v a u l t s , and o f f i c e s o r s t a t i o n s , The c i r c u i t s a r e u s u a l l y o n e o r inore t w i s t e d - p a i r t e l e p h o r s e

Although These c a b l e s s h o u l d be s u i t a b l e f o r underground i n s t a l l a t i o n . type cables. t h e c o n t r o l c a b l e s may be u s e d f o r c o m m n i c a t i o n s a t some i n s t a l l a t i o n s , s e p a r a t e c a b l e s i n s e p a r a t e conduits o r w e l l separated i n t h e trench, i f d i r e c t b u r i a l , a r e p r e f e r r e d . 5.1.2,6 Ground w i r e s . A ground w i r e o r c o u n t e r p o i s e w i r e s h o u l d be i n s t a l l e d t o p r o t e c t underground power and c o n t r o l c a b l e s f r o m h i g h ground c u r r e n t s u r g e s i n a r e a s The ground w i r e s h o u l d b e i n s t a l where damage from l i g h t n i n g s t r i k e s may b e e x p e c t e d . l e d between t h e e a r t h ' s s u r f a c e and t h e underground c a b l e s . It i s u s u a l l y a n u n i n s u l The s i z e of t h i s ground w i r e s h o u l d be n o t l e s s t h a n a t e d , s t r a n d e d copper c o n d u c t o r . t h e l a r g e s t s i z e conductors which i t p r o t e c t s . C r o s s - s e c t i o n a r e a of t h e c o n d u c t o r may It s h o u l d be a c o n t i n u o u s c o n d u c t o r a n d r a n g e f r o m 8.4 mm2 t o 21 mm2 o r l a r g e r . c o n n e c t e d t o e a c h f i x t u r e , l i g h t b a s e , and ground r o d o r c o n n e c t i o n a l o n g i t s r o u t e . 5.1.3

Causes of c a b l e damage

5.1.3.1 Cable f a u l t s a r e f r e q u e n t r e a s o n s f o r aerodrome l i g h t i n g c i r c u i t f a i l u r e s and o f t e n r e q u i r e c n s i d e r a b l e t i m e and e f f o r t t o l o c a t e and r e p a i r . E f f e c t i v e methods of r e d u c i n g c a b l e f a u l t s improve r e l i a b i l i t y of t h e s y s t e m . B e t t e r knowledge of t h e c a u s e s of damage t o c a b l e s h o u l d a i d i n c h o o s i n g t y p e s of c a b l e and i n s t a l l a t i o n procedures. Some of t h e s e c a u s e s a r e d i s c u s s e d below. 5.1.3.2 Mechanical damage. P r o b a b l y most c a b l e f a u l t s a r e c a u s e d by m e c h a n i c a l damage. Poor i n s t a l l a t i o n t e c h n i q u e s and p r o c e d u r e s a r e p r o b a b l y t h e most common c a u s e of m e c h a n i c a l damage, b u t f r o s t h e a v e s , v i b r a t i o n f r o m a i r c r a f t o r v e h i c l e t r a f f i c , r o d e n t s , ground s h i f t i n g o r s e t t l i n g , and many o t h e r r e a s o n s may p h y s i c a l l y damage t h e cable. Some t y p e s of mechanical damage a r e : a)

Nicks and s c r a p e s of t h e i n s u l a t i o n .

Over s t r e s s i n g of t h e c a b l e when p u l l i n g i n t o d u c t s o r u n r o l l i n g t h e cable for d i r e c t burial.

Stones o r f o r e i g n o b j e c t s i n t h e beds o r b a c k f i l l s of t r e n c h e s .

I n a d e q u a t e s l a c k a t e n t r a n c e s t o o r i n s i d e of h a n d h o l e s , m a n h o l e s , l i g h t bases, c o n d u i t s , f i x t u r e s , connections t o equipment, c o n n e c t o r s , s p l i c e s , a l o n g t r e n c h e s o r c o n d u i t , o r o t h e r l o c a t i o n s where s e t t l i n g , m a i n t e n a n c e , i n s t a l l a t i o n s , o r w e a t h e r may i n c r e a s e s t r e s s e s .

Nicking of t h e c o n d u c t o r a t s p l i c e s o r c o n n e c t o r j o i n t s may l a t e r b r e a k t h e conductor.

I n a d e q u a t e s e p a r a t i o n of c a b l e s i n t r e n c h e s , e i t h e r v e r t i c a l l y o r h o r i z o n t a l l y , a t s l a c k l o o p s of c a b l e , o r p l a c e s where e a r t h c o m p a c t i o n o r f r e e z i n g a c t i o n may f o r c e two s e c t i o n s of c a b l e i n t o d i r e c t c o n t a c t .

Freezing o r f r o s t heaves f o r c i n g t h e c a b l e a g a i n s t i c e , f r o z e n e a r t h , o r any o t h e r s o l i d o b j e c t o r m a t e r i a l . P r o p e r c u s h i o n i n g and s l a c k t o reduce s t r e s s a t t h e s e p o i n t s i s necessary.

Improperly s u p p o r t e d c a b l e s i n manholes o r o t h e r a r e a s where s a g g i n g o r e x p o s u r e may r e s u l t i n o b j e c t s o r p e r s o n s p u t t L n g p r e s s u r e o n t h e c a b l e .

V i b r a t i o n f r o m t r a f f i c p a s s i n g o v e r t h e c a b l e o r f r o m equipment o p e r a t i o n a t t a c h e d t o o r n e a r t h e c a b l e may c a u s e f a t i g u e o f t h e c o n d u c t o r o r of t h e j a c k e t and i n s u a l t i o n . Where s u c h c o n d i t i o n s may e x i s t o r b e d e v e l o p e d , i n s t a l l t h e c a b l e s i n d u c t s which e x t e n d w e l l beyond t h e a r e a of v i b r a t i o n .

Breaking o r s e p a r a t i o n of c o n d u i t s o r d u c t s may b r e a k t h e c a b l e . The i n s t a l l a t i o n of t h e d u c t s and c o n d u i t must be p r o p e r l y j o i n e d and s u i t a b l y b a c k f i l l e d and tamped.

A ground f a u l t i s formed when w a t e r i s a b l e t o p e n e t r a t e 5.1.3.3 Water p e n e t r a t i o n . t h r o u g h t h e c a b l e s h e a t h and i n s u l a t i o n t o t h e c o n d u c t o r . Water p e n e t r a t i o n o r l e a k a g e may o c c u r a t s p l i c e s , c o n n e c t i o n s , c a b l e t e r r d i i a t i o n s , p h y s i c a l damage a r e a s , s n s a t i s f a c t o r y i n s u l a t i o n , pinholes from l i g h t n i n g o r over v o l t a g e , o r o t h e r d e f e c t s .

Improperly made s p l i c e s and i m p r o p e r l y i n s t a l l e d c o n n e c t o r k i t s a r e a f r e q u e n t s o u r c e of w a t e r p e n e t r a t i o n . See S e c t i o n 5.2 f o r i n s t r u c t i o n s f o r making s p l i c e s and i n s t a l l i n g c o n n e c t o r s .

I n o r d e r t o a v o i d w a t e r p e n e t r a t i o n a t t h e e n d s of c a b l e , t h e s e e n d s s h o u l d be k e p t c l e a n and f r e e from m o i s t u r e b e f o r e a s w e l l a s a f t e r The e n d s of s p a r e c a b l e s s h o u l d be c o n n e c t i n g t o t h e equipment. similarly protected. Some t y p e s of i n s u l a t i o n , e s p e c i a l l y p a p e r and m i n e r a l f i l l e d , may a t t r a c t m o i s t u r e f r o m t h e a t m o s p h e r e d u r i n g p e r i o d s of h i g h h u m i d i t y . The ends of t h e c a b l e s of t h e s e t y p e s s h o u l d be k e p t s e a l e d a t a 1 1 t i m e s even a f t e r c o n n e c t i n g t o t h e e q u i p m e n t .

Some i n s u l a t i o n s , e i t h e r f r o m d e f e c t s o r composition, may p e r m i t e x c e s s i v e water penetration. Q u a l i t y t e s t s of i n s u l a t i o n r e s i s t a n c e s h o u l d d e t e c t such d e f e c t s . There a r e r e p o r t s t h a t some n e o p r e n e - j a c k e t e d c a b l e i s not adequately water r e s i s t a n t , although o t h e r r e p o r t s s t a t e Before c a b l e i s purchased, t h e t h a t c a b l e of t h i s t y p e performs w e l l . performance of t h e t y p e of c a b l e a t o t h e r i n s t a l l a t i o n s , p r e f e r a b l y f r o m t h e same m a n u f a c t u r e r , s h o u l d be i n v e s t i g a t e d .

L i g h t n i n g s t r i k e s may s e v e r i y damage c a b l e s o r t h e i n d u c e d v o l t a g e s may These p i n h o l e s be enough t o damage t h e i n s u l a t i o n by c r e a t i n g p i n h o l e s . a r e more l i k e l y t o o c c u r a t p o i n t s of c r o s s i n g c a b l e s o r where t h e c a b l e i s n e a r o r i n c o n t a c t w i t h m e t a l c o n d u c t o r s . P r o p e r l y i n s t a l l e d ground w i r e o r c o u n t e r p o i s e s s h o u l d r e d u c e t h e damage f r o m l i g h t n i n g s t r i k e s .

E x c e s s i v e v o l t a g e may be a p p l i e d t o a c a b l e , e i t h e r a c c i d e n t a l l y o r f r o m f a u l t y operation. Damage t o t h e c a b l e may n o t be n o t i c e a b l e immediately.

5.1.3.4 Often aerodrome l i g h t i n g c a b l e s a r e l o c a t e d i n a r e a s where Chemical damage. f u e l , o i l , a c i d s , o r o t h e r c h e m i c a l s may be p r e s e n t r e g u l a r l y o r o c c a s i o n a l l y . These c h e m i c a l s a f f e c t t h e i n s u l a t i o n r e s i s t a n c e of some t y p e s of c a b l e s . I f i t i s known, o r s u s p e c t e d , t h a t c a b l e s may be exposed t o s u c h c i l e m i c a l s , s e l e c t a t y p e of c a b l e which i s r e s i s t a n t t o t h e s e chemicals.

I n some a r e a s , d i r e c t b u r i a l c a b l e i s damaged b y r o d e n t s , 5.1.3.5 especially g the insulation. T h e r e i s some e v i d e n c e t h a t t h e r o d e n t s may be a t t r a c t e d t o t h e c a b l e e i t h e r by t h e h e a t e m i t t e d f r o m i t o r by i t s t a s t e . Where r o d e n t damage i s a s e r i o u s problem, i t may be d e s i r a b l e t o i n s t a l l t h e c a b l e i n d u c t s o r t o use metalsheathed cable, 5.1.3.6 Micro-organism o r p l a n t damage. M i c r o - o r g a n i s m s a n d p l a n t s a r e r e p o r t e d t o h a v e damaged some t y p e s o f c a b l e s i n t r o p i c a l o r s u b t r o p i c a l a r e a s . O t h e r t y p e s of I f i t i s a n t i c i p a t e d t h a t s u c h p r o b l e m s may o c c u r , cable a r e not seriously affected. s e l e c t a t y p e of c a b l e w h i c h i s known t o b e r e s i s t a n t t o s u c h m i c r o - o r g a n i s m s and plants. Some c a b l e i n s u l a t i o n s a r e damage6 by o z o n e a n d 5.i.3.7 Ozone and c o r o n a damage. t h u s by t h e c o r o n a p r o d u c e d by t h e c i r c u i t o r by n e a r b y c i r c u i t s . C a b l e i n s u l a t i o n s a r e Select cables with t h e s e q u a l i t i e s a v a i l a b l e which s a t i s f a c t o r i l y resist t h e s e e f f e c t s . i f t h e c a b l e i s c a r r y i n g h i g h v o l t a g e s o r may be e x p o s e d t o o t h e r s o u r c e s o f o z o n e o r corona. I n t h e p a s t some S t a t e s h a v e u s e d c a b l e s w h i c h were n o t p r o t e c t e d a g a i n s t c o r o n a damage f o r runway a n d a p p r o a c h l i g h t s e r i e s s y s t e m s r e a s o n i n g t h a t t h e s e s y s t e m s a r e o p e r a t e d a t f u l l i n t e n s i t y f o r o n l y a r e l a t i v e l y s m a l l number of h o u r s p e r y e a r . C o n s e q u e n t l y , t h e s e c a b l e s a r e s u b j e c t e d t o h i g h - v o l t a g e stress d u r i n g o n l y a s m a l l f r a c t i o n oE t h e t i m e i n s e r v i c e . T h i s p r a c t i c e h a s b e e n f o u n d t o b e u n d e s i r a b l e s i n c e t h e r e d u c t i o n i n c o s t i s small a n d b e c a u s e some o f t h i s c a b l e i n v a r i a b l y i s i n s e r t e d i n t o t h e power d i s t r i b u t i o n c i r c u i t s a n d a r e s u b j e c t e d t o c o n t i n u o u s h i g h v o l t a g e stress. 5.1.3.8 U l t r a v i o l e t damage. Some u n d e r g-r o u n d i n s t a l l a t i o n s , may become s u n l i g h t i f u s e d on e l e v a t e d s u p p o r t s r e c e . i v e t h i s s o r t of e x p o s u r e , s e l e c t i n s t a l l t h e cable i n metal conduit.

c a b l e i n s u l a t i o n , which performs s a t i s f a c t o r i l y i n b r i t t l e and d e t e r i o r a t e r a p i d l y where exposed t o If the cable w i l l s u c h as a p p r o a c h l i g h t t o w e r s . c a b l e w i t h i n s u l a t i o n which resists u l t r a v i o l e t o r

5,!.3,9 C a b l e d e t e r i o r a t i o n , Nosh c a b l e I n s u l a t i o n d e t e r i ~ r z t e ss l o w l y s e r v i c e L i f e of u n d e r g r o u n d c a b l e s s h o u l d b e 1 0 t o 20 y e a r s .

5.2

5.2.1

CABLE CONNECT I O N S

Cable s p l i c e s

5.2.1.1 A l l c a b l e s p l i c e s s h o u l d b e p e r f o r m e d by e x p e r i e n c e d a n d q u a l i f i e d c a b l e s p l i c e r s u s i n g h i g h s t a n d a r d s o f workmaSlship. S p l i c i n g methods and m a t e r i a l s s h o u l d b e of t y p e s recommended by t h e m a n u f a c t u r e r o f t h e s p l i c i n g m a t e r i a l f o r t h e p a r t i c u l a r t y p e of c a b l e b e i n g s p l i c e d . A 1 1 c a b l e s p l i c e s s h o u l d meet t h e f o l l o w i n g r e q u i r e m e n t s . 5.2.1.2 Power c a b l e s i n s u l a t e d f o r more t h a n 5 000 v o l t s . Splice k i t s designed f o r t h e t y p e of c a b l e b e i n g s p l i c e d s h o u l d b e u s e d . When s u c h k i t s are n o t a v a i l a b l e , t a p e d s p l i c e s made i n a c c o r d a n c e w i t h p a r a g r a p h 5.2.2 may be u s e d . Epoxy o r r e s i n s p l i c e s should n o t be used.

5.2.1.3 Power c a b l e s w i t h 610- t o 5 000-volt i n s u l a t i o n . Pressure epoxy-resin s p l i c e s envelopes and c a s t s p l i c e k i t s designed f o r t h e c a b l e s h o u l d be u s e d i n s t r i c t c o n f o r m a n c e w i t h t h e m a n u f a c t u r e r " i n s t r u c t i o n s . Taped s p l i c e s s h o u l d b e u s e d o n l y i f necessary. 5.2.1.4 Power c a b l e s i n s u l a t e d f o r 600 v o l t s o r less. Cast s p l i c e k i t s o r p r e s s u r e e p- o x-y - r e s i n s p l i c e e n v e l o p e s s u i t a b l e f o r a l l d i r e c t e a r t h - b u r i a l c a b l e may b e u s e d . Taped s p l i c e s u s i n g p r e s t r e t c h e d o r h e a t - s h r i n k a b l e t u b i n g as a c o v e r i n g may a l s o b e used. A t y p e of r e - e n t e r a b l e f i l l e d s p l i c e e n v e l o p e u l a t e d non-pressurized cables. Splices t o i la c c o r d a n c e e x i s t i n g p r e s s u r i z e d , lead-covered, o r paper-insulated c a b l e s should b e l w i t h t h e r e q u i r e m e n t s of t h e a u t h o r i t y i n v o l v e d .

5.2.1.5

C o n t r o l and t e l e p h o n e c a b l e s .

is availabl

5.2.2

Taped s p l i c e s

Taped s p l i c e s a r e u s u a l l y u s e d o n l y when s a t i s f a c t o r y c o n n e c t o r s a n d s p l i c e 5.2.2.1 k i t s c a n n o t be o b t a i n e d . I f t a p e d s p l i c e s a r e t o b e made, t h e c o r r e c t t e c h n i q u e must b e u s e d i n o r d e r t o o b t a i n s a t i s f a c t o r y s e r v i c e . The t e c h n i q u e d e s c r i b e d b e l o w i s i n t e n d e d f o r single-conductor cable but a p p l i e s with s u i t a b l e adaption t o multi-conductor cable splice. 5.2.2.2 Keep t h e e n d s o f t h e c a b l e s t o b e j o i n e d c l e a n a n d p r o t e c t e d f r o m m o i s t u r e a t a l l times. 5.2.2.3 C a r e f u l l y t a p e r a n d remove t h e c o v e r i n g , j a c k e t , m e t a l l i c s h i e l d , s h e a t h , a n d i n s u l a t i o n f r o m t h e e n d s o f t h e c a b l e s t o be j o i n e d . Remove a l l t r a c e s o f i n s u l a t i o n f r o m t h e c o n d u c t o r s f o r a l e n g t h of a p p r o x i m a t e l y 2 cm b e i n g v e r y c a r e f u l n o t t o nick t h e conductor, Smoothly t a p e r t h e i n s u l a t i o n b a c k f r o m t h e c o n d u c t o r f o r 2 cm o r Remove t h e s h e a t h , m e t a l t a p e , j a c k e t , e t c . b a c k a l o n g t h e o u t e r s u r f a c e of t h e more. This o f f s e t of t h e t a p e r i n g i n s u l a t i o n layer f o r an a d d i t i o n a l 2 c m ( s e e Figdze S-la), s h o u l d b l o c k p a t h s of w a t e r p e n e t r a t i n g a l o n g t h e t a p e r i n g . Keep i n t a c t t h e metal t a p e f o r shielding, i f involved, over the e n t i r e length of t h e s p l i c e . Similarly, taper the Remove a n y s t e e l o r m e t a l a r m o r o r o u t e r metal n o n m e t a l l i c s h e a t h f o r 2 cm o r more. covering but leave s t u b s o r ends f o r reconnecting across t h e s p l i c e . Use a crimp-type c o n n e c t o r t o j o i n t h e e n d s o f t h e c o n d u c t o r . Crimp t h e 5.2.2.4 c o n n e c t o r o n t o t h e e n d s of t h e c o n d u c t o r s u s i n g a t o o l d e s i g n e d t o make a c o m p l e t e crimp The c o n d u c t o r c o n n e c t o r may a l s o be b e f o r e t h e t o o l c a n be removed ( s e e F i g u r e 5 - l b ) . soldered i f desired. 5.2.2.5 Using r u b b e r o r s y n t h e t i c r u b b e r t a p e o f good q u a l i t y , c a r e f u l l y wrap t h e j o i n t o n e l a y e r a t a t i m e m a i n t a i n i n g enough t e n s i o n on t h e t a p e f o r a p p r o x i m a t e l y 25 p e r c e n t e l o n g a t i o n and o v e r l a p p i n g t h e t a p e approximately 50 p e r c e n t of i t s width. Each l a y e r w i l l e x t e n d f u r t h e r up t h e t a p e r a l o n g t h e i n s u l a t i o n . Continue t h i s buildup o f l a y e r s o f r u b b e r t a p e t o t h e f u l l s i z e of t h e i n s u l a t i o n l a y e r . See F i g u r e 5 - l c 5.2.2.6 I f s h i e l d i n g t a p e i s u s e d o v e r t h e i n s u l a t i o n , c o n n e c t t h e metal t a p e , w h i c h s h o u l d h a v e b e e n k e p t i n t a c t , a c r o s s t h e s p l i c e by s o l d e r i n g o r u s i n g s u i t a b l e c o n n e c t o r s . Wrap w i t h e x t r a m e t a l t a p e of s i m i l a r t y p e i f n e e d e d .

(a) TAPERING INSULATION.

CONNECTOR*

Attach w i t h a t o o l designed t o make a complete crimp b e f o r e t h e t o o l can be removed.

(b)

CONDUCTOR CONNECTION.

WEATHER-RESISTANT

P L A S T I C TAPE

RUBBER INSULATION TAPE

I n d i c a t e t a p e l a y e r s are wound i n b o t h d i r e c t i o n s

(c)

CROSS SECTION OF SPLICE.

r r g u r e 5-i.

s p l i c e of s ~ . n g i e - c o n d u c t o r c a b l e

5.2.2.7 Continue t o wrap t h e r u b b e r t a p e a s i n 5.2.2,5 t o n o t l e s s t h a n 1.5 t i m e s t h e d i a m e t e r of t h e c a b l e . C a r e f u l l y a p p l y t e n s i o n on t h e t a p e t o p r e v e n t a n y v o i d s and o b t a i n good a d h e s i o n t o t h e c a b l e s u r f a c e s and e a c h i n s i d e l a y e r of t a p e . 5.2.2.8 Over t h e r u b b e r t a p e , add s e v e r a l l a y e r s o f h i g h - i n s u l a t i o n - r e s i s t a n c e , f l a m e - r e t a r d a n t , weather- and c o l d - r e s i s t a n t t a p e . Apply t h e p l a s t i c t a p e w i t h a p p r e c i a b l e t e n s i o n and o v e r l a p p i n g e a c h t u r n by a p p r o x i m a t e l y 5 0 p e r c e n t of i t s w i d t h . The p l a s t i c t a p e s h o u l d e x t e n d f o r 3 cm o r more a l o n g t h e s u r f a c e of t h e i n s u l a t i o n of s h e a t h on e a c h s i d e of t h e s p l i c e . 5.2.2.9 If t h e c a b l e h a s a s t e e l - a r m o r o r o t h e r m e t a l l i c c o v e r , c o n n e c t a l e n g t h o f g r o u n d i n g b r a i d a c r o s s t h e s p l i c e and f a s t e n t o t h e armor on t h e c a b l e w i t h s u i t a b l e If t h e clamp c o n n e c t o r s a n d / o r s o l d e r on e a c h s i d e of t h e s p i i c e s ( s e e F i g u r e 5-2a). c a b l e i s l e a d e n c a s e d , make a s u i t a b l e wiped-lead j o i n t o v e r t h e s p l i c e t o p r o v i d e a w a t e r p r o o f s e a l t o t h e l e a d c o v e r i n g on t h e c a b l e . If t h e metal covering i s p r o t e c t e d f r o m c o r r o s i o n by a c o a t i n g , a p p l y a c o a t i n g of s i m i l a r m a t e r i a l o v e r t h e e n t i r e s u r f a c e of t h e c a b l e and s p l i c e i n t h e a r e a of t h i s work.

5.2.3.1 Use of c o n n e c t o r k i t s . I n r e c e n t y e a r s most s e r i e s - c i r c u i t c o n n e c t i o n s h a v e been made u s i n g c o n n e c t o r k i t s . Although t h e c o s t of c o n n e c t o r k i t s i s s i g n i f i c a n t , t h e t i m e s a v e d i n i n s t a l l a t i o n and t h e e a s e w i t h wich c i r c u i t s c a n b e opened a n d r e c l o s e d when l o c a t i n g f a u l t s h a v e made t h e i r u s e d e s i r a b l e . S i n c e t h e l e a d s of m o s t i s o l a t i n g t r a n s f o r m e r s a r e now manufactured w i t h c o n n e c t o r s , c a b l e c o n n e c t o r s a r e r e q u i r e d and p r o v i d e a n e a s y means of c o n n e c t i n g o r d i s c o n n e c t i n g t h e t r a n s f o r m e r i n t o t h e s e r i e s c i r c u i t and t o t h e l i g h t . S i n g l e - c o n d u c t o r c o n n e c t o r s a r e shown i n F i g u r e 5-3. 5.2.3.2 I n s t a l l a t i o n of c o n n e c t o r s . The c a b l e e n d s s h o u l d be p r e p a r e d c a r e f u l l y i n a c c o r d a n c e w i t h t h e i n s t r u c t i o n s , k e e p i n g b o t h t h e c a b l e e n d s and t h e c o n n e c t o r s u r f a c e s f r e e of d i r t and m o i s t u r e , Make c e r t a i n t h a t a n y c a v i t i e s b e t w e e n . t h e c a b l e and i n i e t i o r o i t h e c o n n e c t o r a r e f i l l e d w i t h t h e g e l p r o v i d e d CO p r e v e n t v o i d s . A f t e r j o i n i n g t h e c o n n e c t o r s e n s u r e t h a t a i r i s n o t t r a p p e d which may t e n d t o f o r c e t h e connection apart. Taping o v e r t h e j o i n t w i t h v i n y l e l e c t r i c t a p e t o keep t h e a r e a c l e a n and f r o m s e p a r a t i n g i s s u g g e s t e d . 5.2.4

Coaxial cables

5.2.4.1 Non-pressurized c o a x i a l c a b l e s . C o a x i a l c a b l e s h o u l d be j o i n e d u s i n g a p p r o p r i a t e c o a x i a l connectors. Each c o n n e c t o r s h o u l d be c o v e r e d w i t h a 1 5 cm m i n i m m l e n g t h of h e a t s h r i n k a b l e t u b i n g h a v i n g a 3 : 1 o r h i g h e r s h r i n k r a t i o . A s u i t a b l e s p r a y c a b l e a d h e s i v e may be s p r a y e d on t h e c a b l e b u t n o t t h e c o n n e c t o r p r i o r t o s h r i n k i n g . A flamel e s s h e a t gun s h o u l d be used f o r s h r i n k i n g t h e h e a t s h r i n k a b l e t u b i n g . An a l t e r n a t e c o v e r i n g may be p r e s t r e t c h e d , m e c h a n i c a l l y s h r i n k a b l e t u b i n g a p p l i e d as recommended by the manufacturer. 5.2.4.2 Splices i n pressurized coaxial cables. No f i e l d - i n s t a l l e d s p l i c e i n p r e s s u r i z e d c o a x i a l c a b l e s h o u l d be a l l o w e d u n l e s s s p e c i f i c a l l y a u t h o r i z e d .

I---

VINYL P L A S T I C TAPE ANCHOR FOR BRAID METAL ARMOR

SOLDER FILL

ELECTRICAL GROUND BRAID RUBBER INSULATION TAPE

(a)

CONNECTING ARMOR ACROSS THE S P L I C E

WEATHER-RESISTANT P L A S T I C TAPE ( 4 LAYERS-1/2 LAPPED, WITH L I Q U I D ELECTRICAL COATING A P P L I E D )

(b) OUTER COVERING OF THE S P L I C E

(a)

FACTORY MOLDED PLUG

-_METAL SOCKET

(b)

FACTOR MOLDED RECEPTACLE

MIN 2 SAW SLOTS

PIN -

OPTION&

INTERN L O m I NG BESIGH

(c)

F I E L D ATTACHED CONNECTORS

SOCKET

OPTIONAL INTER LbCRlNG DESIGN

5.2.5

Connection of c o n d u c t o r s

5.2.5.1 Power c o n d u c t o r s . Connections of c a b l e c o n d u c t o r s s h o u l d b e made u s i n g crimp c o n n e c t o r s u t i l i z i n g a crimping t o o l d e s i g n e d t o make a complete crimp b e f o r e t h e S p l i t - b o l t c o n n e c t o r s may be used f o r l o w v o l t a g e c i r c u i t s of 600 t o o l can be removed. volts o r less. 5.2.5.2 C o n t r o l and t e l e p h o n e c a b l e s . J o i n i n g of t e l e p h o n e o r c o n t r o l c o n d u c t o r s s h o u l d be done w i t h a t w i s t e d and s o l d e r e d s p l i c e o r a n a p p r o p r i a t e s e l f - s t r i p p i n g , p r e i n s u l a t e d c o n n e c t o r i n s t a l l e d w i t h t h e s p e c i f i c t o o l d e s i g n e d t o crimp t h e c o n n e c t o r . Color coding of t h e c o n d u c t o r s s h o u l d be f o l l o w e d t h r o u g h o u t t h e i n s t a l l a t i o n . 5.2.5.3 Cable armor and s h i e l d s . Armor s h i e l d s s h o u l d be e l e c t r i c a l l y bonded a c r o s s t h e s p l i c e by c l e a n i n g and s o l d e r i n g . Use s e c t i o n s of m e t a l b r a i d and c o n d u c t i n g t a p e , i f needed. Armor and s h i e l d i n g s h o u l d be c o m p l e t e l y i n s u l a t e d from e a c h and from ground, e x c e p t a s n o t e d i n p a r a g r a p h 4.5.3.3.