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Checking the CT and VT circuits
Chapter 6
Checking the external circuitry
2
Checking the CT and VT circuits
Check that the wiring is in strict accordance with the supplied wiring diagram.
Note
Do not continue further until any errors are corrected.
Test the circuitry. The following tests are recommended:
• Polarity check.
• CT circuit current measurement (primary injection test).
• Grounding check.
The polarity check verifies the integrity of the circuits and the phase relationship. The
check should be performed as close as possible to the terminal.
The primary injection test verifies the CT ratio and the wiring all the way through from
the primary system to the terminal. Injection must be performed for each phase-to-neu-
tral circuit and each phase-to-phase pair. In each case currents in all phases and the neu-
tral line are measured.
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