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2
Checking the CT and VT circuits
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).
•
Earthing 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 pri-
mary system to the terminal. Injection must be performed for each phase-to-neutral circuit and
each phase-to-phase pair. In each case currents in all phases and the neutral line are measured.
Chapter 6
Checking the external circuitry
47
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