University of Patras Department of Electrical and Computer Engineering Electric Power Systems High Voltage Laboratory
5th and 6th MARINELIVE Workshop
Simulation of Lightning Effects on Metallic Ships G. D. Peppas 1, A. G. Telonis 1, E. P. Nicolopoulou2, , I. F. Gonos2, E. C. Pyrgio=1, I. A. Stathopulos2 1 Electrical and Computer Engineering, U. Patras, Greece 2 School of Electrical and Computer Engineering ,Nat. Tech. U. Athens, Greece
hEp://www.hvl.ece.upatras.gr/
Introduc;on Data collec;on
• Regula=ons and standards are collected regarding lightning striking ships, and the safety risks for humans and vessels
• Historic data on lightning
The High Voltage Laboratory of University of Patras has been collec=ng such data for a long period. hEp://www.hvl.ece.upatras.gr/
Lightning Strike Current Ιmax k τ1 τ2
peak current correction factor front time constant tail time constant
Lightning current waveshape 10
⎛ t ⎞ ⎜⎜ ⎟⎟ t − I max ⎝ τ 1 ⎠ τ2 I (t ) = ⋅ ⋅ e 10 k ⎛ t ⎞ 1 + ⎜⎜ ⎟⎟ ⎝ τ 2 ⎠
Simula=on model of a lightning hEp://www.hvl.ece.upatras.gr/
Does lightning hit the sea?
Annual strikes per km2 h6p://geology.com/ar:cles/lightning-‐map/
Global lightning maps, strikes/km2/year h6p://science.nasa.gov/science-‐news/science-‐at-‐nasa/2001/
hEp://www.hvl.ece.upatras.gr/
Does lightning hit the sea? Snapshot of live lightning detec=on maps in Southwest Europe
• Lightning strikes hit the sea • Ships are possible lightning strike targets
www.Blitzortung.org/Webpages/index.php
hEp://www.hvl.ece.upatras.gr/
Goals of current Simula=on • Using Opera 3d → Simula:on of lightning effects on metallic ships • 2 ships with different dimension • 4 points of lightning strike in each ship • Results of the current density J (A/m2)
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Opera 3d Cobham Ø OPera=ng environment for Electromagne=c Research and Analysis – Pre-‐Processor – Modeller – Post-‐Processor
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Opera 3d Cobham Ø FEM (Finite Element Method) -‐ is used to obtain solu=ons to integral equa=ons that can not be solved by
analy=c method -‐ division of the structure into small volumes -‐ applicable to any type of non-‐linearity
Ø The Tosca Algorithm • Sta=onary electrosta=c
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Opera 3d Cobham Ø The Tosca Algorithm Faraday
Poisson
Sta=onary electrosta=c fields
Sta=onary magne=c fields
Laplace
Magnetic Fields Tangential Magnetic Normal Magnetic
Boundary Conditions Field Symmetry H·n=0 H×n=0
Scalar Potential ∂φ/∂n=0 φ= constant
Electric Fields or Current Flow
Field Symmetry
Scalar Potential
Tangential Electric
E·n=0
∂V/∂n=0
Normal Electric
H×n=0
V=constant
H: magnetic field intensity(Α/m) Ε: electrical field intensity(V/m)
hEp://www.hvl.ece.upatras.gr/
Ship Models USS Somerset
HMS Albion
Ships
USS Somerset
HMS Albion
Difference
Length (m)
118
175
57
Beam (m)
12.5
29
16.5
Height (m)
15
28
13
hEp://www.hvl.ece.upatras.gr/
Ship material proper=es
Hull
Carbon steel (Stainless Steel, Aluminium) Rela=ve permi]vity → 107 Conduc=vity → 6,99·∙106 S/m
Salt Water
Rela=ve permi]vity → 85 Conduc=vity → 4,8 S/m
Discon:nuity, imperfect joints and material changes were not included in the analysis hEp://www.hvl.ece.upatras.gr/
Generate Surface Mesh
• Different mesh in surfaces with different interest accuracy↑ • Mesh↑ errors↓ =me ↑ • Mesh ↓ =me ↓
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Lightning Approach Peak Current
Impact Surface (0,2m)x(0,2m)
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Lightning Approach
• Points decision based on maximum lightning strike probability • 4 points in each ship (stern, top1, top2, bow) Choose Surface → Set Boundary Condi=ons → → Current Source → 100.000A
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Post-‐Processor Ø Current density J (A/m2)
• Surface colored contours • Vectors
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USS Somerset Stern Ships Length (m)
USS Somerset 118
HMS Albion 175
Beam (m)
12.5
29
Height (m)
15
28
First Point of lightning strike → Stern
Peak Current Density → J=2.5·∙106A/m2 (Jds=I→J·∙0.2m·∙0.2m=100kA) ↓ same result in all cases studied
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike → Ship1 Stern
Current Density 500A/m2 ≤ J ≤ 2500A/m2 Vectors show direc=on of J Size of vectors show volume of J hEp://www.hvl.ece.upatras.gr/
USS Somerset Top 1 • Point of lightning strike → first top • Height = 13m • Vectors show the point of the lightning strike and the direc:on of current density
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Point of lightning strike →Ship1 Top 1
Ship with mesh
Current Density + Vectors
Current Density values: 200A/m2 ≤ J ≤ 5000A/m2
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike → Ship1 Top 1 LN(J)
8103 A/m2
2980 A/m2
1096 A/m2
403 A/m2
148 A/m2
54 A/m2
LN(J)=10 → J=e10=22026.5 A/m2 LN(J)=4 → J=e4=54.598 A/m2 LN(J) gives detailed perspec;ve
Ship with mesh
hEp://www.hvl.ece.upatras.gr/
USS Somerset Top 2
Peak Current Density J=2.5·∙106A/m2
• Point of lightning strike → second top • Height = 15m • Highest point of USS Somerset • Vectors show the point of the lightning strike and the direc:on of current density
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike →Ship1 Top 2
Current Density 500A/m2 ≤ J ≤ 1500A/m2
Ø Similar results to Top 1
Ship with mesh
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike →Ship1 Top 2
8103 A/m2
2980 A/m2
1096 A/m2
403 A/m2
LN(J)=10 → J=e10=22026.5 A/m2 LN(J)=5 → J=e5=148.413 A/m2
LN(J) gives more detailed perspec;ve than specific range of values
hEp://www.hvl.ece.upatras.gr/
USS Somerset Bow
• Point of lightning strike → Bow (front) • Vectors show -‐the point of the lightning strike -‐the direc;on of Current Density -‐the volume of Current Density hEp://www.hvl.ece.upatras.gr/
Point of lightning strike →Ship1 Bow
Current Density values 200A/m2 ≤ J ≤ 3000A/m2
Ship with mesh
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike → Ship 1 Bow
8103 A/m2
2980 A/m2
1096 A/m2
403 A/m2
148 A/m2
Current Density Values LN(J)=10 → J=e10=22026.5 A/m2 LN(J)=4 → J=e4=54.598 A/m2
hEp://www.hvl.ece.upatras.gr/
HMS Albion Ships Length (m)
USS Somerset 118
HMS Albion 175
Beam (m)
12.5
29
Height (m)
15
28
• 4 points chosen for lightning strikes • 100 kA Boundary Condi=on • Surface of strike (0.2m)x(0.2m)
hEp://www.hvl.ece.upatras.gr/
HMS Albion Stern First Point of lightning strike → S tern
Current Density values 50A/m2 ≤ J ≤ 1500A/m2
Ship with mesh
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike →Ship 2 Stern
Current Density Values LN(J)=7 → J=e7=1096.63 A/m2 LN(J)=4 → J=e4=54.598 A/m2 hEp://www.hvl.ece.upatras.gr/
HMS Albion Top 1 • Lightning strike at second highest point • Height=27m • Possible antennas in Top 1
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Point of lightning strike →Ship 2 Top 1
Current Density Values 10000A/m2 ≤ J ≤ 70000A/m2
Peak Current Density → J=2.5·∙106A/m2 hEp://www.hvl.ece.upatras.gr/
Point of lightning strike →Ship 2 Top 1
Current Density Values + Vectors 100A/m2 ≤ J ≤ 5000A/m2
Ship with mesh
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike →Ship 2 Top 1
Ship with mesh
Current Density Values LN(J)=10 → J=e10=22026.5 A/m2 LN(J)=4 → J=e4=54.598 A/m2 hEp://www.hvl.ece.upatras.gr/
HMS Albion Top 2 Current Density Values 100A/m2 ≤ J ≤ 8000A/m2 • Possible antennas at Top 2 • Highest point of the ship • Height=29m
Difficult to show volumes of current density for the whole ship
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike → Ship 2 Top 2
8103 A/m2
2980 A/m2
403 A/m2
148 A/m2
54 A/m2
Current Density Values LN(J)=10 → J=e10=22026.5 A/m2 LN(J)=3 → J=e3=20.086 A/m2
• LN(J) gives detailed perspec;ve for the whole ship hEp://www.hvl.ece.upatras.gr/
HMS Albion Bow
• Final point of possible lightning strike→ Bow (front) • Different geometry of vectors in comparison with stern
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike → Ship 2 Bow Current Density 100A/m2 ≤ J ≤ 1500A/m2
USS Somerset HMS Albion Strike point J at stern
Bow
Bow
<200A/m2
<600A/m2
hEp://www.hvl.ece.upatras.gr/
Point of lightning strike → Ship 2 Bow Current Density Values LN(J)=10 → J=e10=22026.5 A/m2 LN(J)=3 → J=e3=20.086 A/m2 8103 A/m2
2980 A/m2
1096 A/m2
403 A/m2
148 A/m2
54 A/m2
hEp://www.hvl.ece.upatras.gr/
Conclusion • Results of Simula=on -‐Different current density volumes resulted in ships with different dimensions and
geometric shapes -‐Similar route was observed for current density (J) of both ships -‐Metallic ships give lightning a faster conduc=ve way to sea water
• Lightning
Antennas, electronic devices and external equipment are exposed to direct lightnings Possible threat when people are working exposed on the deck
• Protec;on against direct lightning for external equipment with lightning rods and with use of SPD’s
There is need for a comprehensive research and set of guidelines to protect the equipment and structures of naval ship, , against direct and indirect effects of lightning. hEp://www.hvl.ece.upatras.gr/
Further Inves=ga=on Ø It is substan=al to study the modeled ship, stressed with a full wave
lightning strike in order to simulate the electromagne=c fields in =me domain. Ø Addi=onal research is running concerning joints, glass surfaces and discon=nui=es for more detailed and accurate model analysis.
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5th and 6th MARINELIVE Workshop
This research has been co-‐financed by the European Union (European Social Fund – ESF) and Greek na=onal funds through the Opera=onal Program "Educa=on and Lifelong Learning" of the Na=onal Strategic Reference Framework (NSRF) -‐ Research Funding Program: THALES: Reinforcement of the interdisciplinary and/or inter-‐ins=tu=onal research and innova=on
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