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Testing of Current Transfomers
The type tests of current transformers as per IS 2705 (Part 1): 1992, are as follows:
- Short-Time Current Tests (Clause 9.6)
- Short-time thermal current test.
- Dynamic current test.
- Temperature-Rise Test (Clause 9.7)
- Lightning Impulse Voltage Test (Clause 9.8)
- For current transformers for service in electrically exposed installations.
- Switching Impulse Voltage Tests (Clause 9.11)
- For current transformers of 420 kV and above.
- High Voltage Power-Frequency Wet Withstand Voltage Test (Clause 9.9)
- For outdoor current transformers up to and including 245 kV.
- 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:
- Verification of terminal marking and polarity: Ensures compliance with specified standards.
- Power frequency dry withstand tests on primary windings: Tests the primary windings’ insulation against high voltage.
- Power frequency dry withstand tests on secondary windings: Checks the secondary windings’ insulation.
- Over-voltage inter-turn test: Evaluates the turn-to-turn insulation of the transformer windings.
- Partial discharge tests: Assesses insulation performance under partial discharge conditions (applicable for specific insulation types).
- 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):
- Visual checking and dimension checking
- Terminal marking and polarity
- High voltage test on primary
- 3 KV test on secondary winding
- Class of Accuracy
- Instrument Security Factor (I.S.F)
- Knee Point Voltage (for PS class core)
- Rct (Resistance) Measurement (for PS class core)
- Over Voltage Inter-turn Test
- Insulation Resistance Test.
