1. Short all Spare CT secondary cores in Primary current injection path. Otherwise heavy voltage will develop in the Spare core and damage CT secondary.
2. Check any open path in the used secondary taps and tightness of all CT circuit. Any sound hearing in the CT then consider open circuit in the secondary.
3. If any CT cores are open then the equipment will not drive the Primary current more than 50 A.
4. Check the Primary current injection Equipment Auxiliary Supply cable. It should withstand more than 20A continuous rating.
5. Use separate generator supply for Primary current injection test. Otherwise the Primary current wouldn't constant value.
