what is zero phase current transformer?

A zero phase current transformer (ZCT), also known as a zero-sequence current transformer, is a device used to measure the sum of currents in three-phase systems. It detects unbalanced currents, typically caused by faults or leakage currents, by capturing the vector sum of the phase currents. The ZCT is essential for protective relaying and monitoring systems, ensuring safety and reliability in electrical installations by identifying ground faults and other anomalies.