CT Failure Detection For Differential Protection Applications

Current transformers are used widely in the power system for metering and protective relaying purposes., where they replicate the high magnitude currents into low currents. The capability of replicating hundreds and thousands of amps current into low currents and provide input for metering and protective relaying, makes them some of the most important devices to be regularly maintained. Aging of the CT and its wiring insulation, and the environment are also some of causes for failures. Variety of CT failure detection schemes can be employed in the transformer protective relays depending on the availability of power system measurements, computation of signals using the measurements, and the flexibility of creating logic. The minimum measurements for the transformer differential relay would include phase currents from each winding, and ground current from winding grounded neutral.