Core Balance Transformer

The Core balance current transformers are intended for providing earth leakage protection on 3-phase electrical system.

In insulated or compensated neutral networks, earth leakage currents are small and generally very much less then the nominal load current. Such earth leakage current should not be allowed to exist for long periods of time, since eventually it leads to insulation failure on the healthy phase and subsequent

development into phase to phase or double to earth faults, to protect cable circuits and also overhead transmission line with cable transmissions, core balance current transformers are commonly employed.

Core Balance current transformers are manufactured with one core and one secondary winding. The no. of secondary turns does not need to related to the cable rated current because no secondary current would flow under normal balanced conditions. This allows the no. of secondary turns to be chosen such as to optimize the effective primary pick-up current.

Core Balance Current Transformers are used with suitable relays for the earth leakage protection purposes. C.B.C.T. encircles a 3 Phase, 3 core cable or 3 single core cables. During healthy conditions i.e. when there is no earth leakage current, the secondary of C.B.C.T. does not carry, any current as there is no magnetic flux in the core. In the event of occurrence of earth leakage an unbalance current sets up flux in the core of the C.B.C.T. and current flows through the secondary winding, causing the relay to operate.