Page 30 - Practical Power System and Protective Relays Commissioning

26 Practical Power System and Protective Relays Commissioning

3. Polarity test.
4. Ratio test by primary injection.
5. Magnetizing current test.
6. Loop resistance burden test.
7. Continuity of secondary circuits.
Terminations, shorting links by primary and secondary injection test.
8. High voltage test, which is done during the air insulated substation or gas
insulated substation (GIS) high voltage test at the final stages of commis-
sioning tests, but with disconnecting the current transformer (CT) con-
nections to the relays and shorting the CT secondaries during the high
voltage test.
9. Demagnetizing the CT cores by connecting the secondaries of the CTs to
the ground at the end of all tests. Refer to Chapter 10, Current
Transformers, for further details.

3.5 VOLTAGE TRANSFORMER COMMISSIONING TESTS
3.5.1 Visual Checks
Check visually for any damage or craking or oil leakage in the VT.

3.5.2 Electrical Commissioning Tests
An electrical test can include any of the following:
1. Winding resistance test.
2. Insulation resistance test.
3. Ratio test.
4. Polarity test.
5. Miniature circuit breakers (MCBs) trips check by secondary injection in
voltage transfer secondary circuits.
6. Phasing test.
7. Loop resistance burden test.
8. Tan δ test.

3.6 GAS INSULATED SWITCHGEAR COMMISSIONING TEST

3.6.1 Visual Check and Mechanical Tests
Checks should include the nameplate information for all components [e.g.,
circuit breaker (CB), earthing switch (ES), disconnect switch (DS), voltage
transformer (VT), current transformer (CT)], enclosure earthing, gas handling
unit, mechanical interlocks, and a dew point test for each gas compartment
at rated gas pressure of each compartment.