The type IRQ is a directional overcurrent ground relay in which the directional unit operates on negative sequence current and voltage, and the overcurrent units operates on residual (or ground) current. The negative sequence current and voltage are obtained by means of self-contained negative sequence filters connected between the directional unit and the current and voltage transformers.
The relay is intended for use at locations where the present equipment or system conditions do not permit the use of the conventional types of directional ground relays operating entirely on residual current and voltage.