Core Balance Current Transformer

Core Balance CT for Earth Fault Protection

Reliable Core Balance Current Transformer (CBCT) for Accurate Earth Fault Detection

A Core Balance CT for Earth Fault Protection, also known as a Core Balance Current Transformer (CBCT) or Zero Sequence Current Transformer (ZSCT), is specially designed to detect earth leakage and earth fault currents in electrical power systems. These current transformers play a vital role in protecting electrical equipment, motors, generators, transformers, switchgear, and industrial installations from insulation failures and ground faults.

The operating principle of a Core Balance Current Transformer is based on measuring the residual (zero sequence) current flowing through a three-phase circuit. Under normal operating conditions, the vector sum of the currents in all three phases is zero. Therefore, no current is induced in the secondary winding of the CBCT.

However, when an earth fault or earth leakage occurs, the balance between the three-phase currents is disturbed. The resulting residual current passes through the secondary winding of the CBCT, generating a signal that activates the connected Earth Fault Relay (EFR) or protection relay. This enables fast fault detection and helps isolate the faulty circuit before significant damage occurs.