Northwest Lineman College
LINEMAN APPRENTICESHIP PROGRAM
CURRICULUM SAMPLE EXCERPTS
ELECTRICAL TEST EQUIPMENT
Testing Voltage
When reading voltage, all possible voltage combinations are checked.
Lineworkers most commonly use multimeters to read AC voltage. This should occur after every transformer installation to prove that the required voltage is supplied to the customer. It also confirms that the transformer is connected correctly to the system primaries and the customer’s service. When reading voltage, all possible voltage combinations are checked. On a 120/240-volt, single-phase service, three readings would be checked at the meter panel or at the transformer: hot leg 1 to neutral, hot leg 1 to hot leg 2, and hot leg 2 to neutral.
HL 1 N
HL 2
HL 1 N
HL 2
HL 1 N
HL 2
Always confirm that the meter is set to the proper voltage range.
120 OFF
240
V
OFF
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Hot Leg 1 to Neutral
Notice that this meter is rated for a maximum voltage of 1,000 volts DC and 750 volts AC.
120
V
OFF
Hot Leg 1 to Hot Leg 2
V
Hot Leg 2 to Neutral
Multimeters have a voltage limit that should never be exceeded. Severe injury and equipment damage can occur if a multimeter is used for a higher voltage than it is rated for. Always confirm that the meter is set to the proper voltage range for the given circuit.
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Testing Continuity Multimeters are usually equipped with a continuity test function. Continuity ensures that a conductor is not broken, or that the conductor is continuous.
Transformer Continuity lcvid.com/transcont
An audible sound should not be heard between the primary and secondary windings of a transformer.
The multi-tester will give off an audible sound when the two probes contact one another, either directly or through a conductive object. This feature is especially useful when proving the integrity of transformer coils. Knowing that the primary coil should be connected between the H1 and the H2, an audible sound will be heard when the probes touch the bushings. The multimeter is now set to continuity. An audible sound will also be heard between all combinations of the secondary bushings. An audible sound should not be heard between the primary and secondary windings of a transformer. If continuity is proven between the primary and secondary coils, the transformer is defective and should not be used.
CHAPTER ONE | LOW-VOLTAGE TEST EQUIPMENT
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When set to continuity test, the multimeter will give off an audible tone when the probes contact one another.
Some utility companies require a continuity test before transformers, new or rebuilt, are placed in service. Continuity testing transformer coils can also be part of the troubleshooting process when a customer loses power due to a blown fuse. NO TONE
H2
x3
x2
x1
Primary coil continuity
H1
H2
x3
x2
x1
Secondary coil continuity
H1
H2
x3
x2
x1
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H1
Primary to secondary NO continuity
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NORTHWEST LINEMAN COLLEGE 7600 S MERIDIAN RD, MERIDIAN, ID 83642 PHONE: 888-LINEWORK FAX: 208-888-4275
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© 2016 Northwest Lineman College Published February 2016