Hioki 3283-20 - Locating an insulation failure

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Measuring Leakage Current
Locating an insulation failure
For a transformer, rst measure the ground wire to determine
the overall circuit leak current (see 1 in the gure), then use the
variation in the leak current to diagnose the presence or absence
of leakage.
If you diagnose leakage to be present, use bundled measurement
of all the wires to locate it. Start from the power source and work
toward the load.
• Suppose an insulation fault in the wiring has occurred at (1)
in the gure. It will be possible to detect the leak current with
bundled measurement at position 2, but not at 2'.
• Suppose an insulation fault in the load equipment has occurred at
(2) in the gure. It will be possible to detect the leak current with
bundled measurement at position 3, but not at 3'.
• To detect intermittent leak current (occurring only when a certain
piece of equipment is operating), the use of a memory recorder
will be helpful.
2
lg
Load
equipment
Ground wire
Single-phase
3-wire circuit
1
2'
3 3'
Load
equipment
(2)
(1)