Protective Current Transformer

Protective Current Transformer are required to operate accurately above 100 and upto 10 to 15 times of rated current called overloads in order to provide true fault signal to the relay. Capacity to handle large currents the protective CT costlier and bulkier.

Metering and protective CTs cannot be interchanged for use. Use of a metering CT for protection will the relay as it will saturate earlier than the operating range. Similarly use of a protective CT in material put the meter at risk of the fault currents as it will not saturate for damaging currents flowing thought meter.