Testing of HV Current Transformer

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Testing of Current Transfomers

The type tests of current transformers as per IS 2705 (Part 1): 1992, are as follows:

  1. Short-Time Current Tests (Clause 9.6)
    • Short-time thermal current test.
    • Dynamic current test.
  2. Temperature-Rise Test (Clause 9.7)
  3. Lightning Impulse Voltage Test (Clause 9.8)
  4. Switching Impulse Voltage Tests (Clause 9.11)
  5. High Voltage Power-Frequency Wet Withstand Voltage Test (Clause 9.9)
  6. Determination of Errors or Other Characteristics (Clause 9.1.1.f)
    • According to the requirements of the appropriate designation or accuracy class.

The routine tests of current transformers as per IS 2705 (Part 1): 1992, are as follows:

  1. Verification of terminal marking and polarity: Ensures compliance with specified standards.
  2. Power frequency dry withstand tests on primary windings: Tests the primary windings’ insulation against high voltage.
  3. Power frequency dry withstand tests on secondary windings: Checks the secondary windings’ insulation.
  4. Over-voltage inter-turn test: Evaluates the turn-to-turn insulation of the transformer windings.
  5. Partial discharge tests: Assess insulation performance under partial discharge conditions (applicable for specific insulation types).
  6. Determination of errors or other characteristics: Verifies performance and accuracy as per the specified designation or accuracy class​.

Acceptance Tests for 33KV Outdoor C.T (as per IS 16227:2016):

  1. Visual checking and dimension checking
  2. Terminal marking and polarity
  3. High voltage test on the primary
  4. 3 KV test on secondary winding
  5. Class of Accuracy
  6. Instrument Security Factor (I.S.F) and Accuracy Limit Factor
  7. Knee Point Voltage (for PS class core)
  8. Rct (Resistance) Measurement (for PS class core)
  9. Over Voltage Inter-turn Test
  10. Insulation Resistance Test.