The Type IBC directional overcurrent relays are employed primarily for the protection of feeders and transmission lines in applications where single-phase relays are desired or required.

The Types IBC and IBCG relays consist of two units, an instanta-neous power-directional unit (bottom) of the induction-cup type, and a time overcurrent unit (top) of the induction-disk type. The direc-tional- unit contacts control the operation of the overcurrent unit (directional control).