KRQ is a high speed, directional overcurrent relay, in which the directional unit operates on negative sequence current and voltage, and the overcurrent unit operates on residual or ground current. It is used for the detection of ground faults on transmission lines, feeder transmission lines, and feeder circuits.
It can also be used, without modification, to provide directional ground fault protection in K-Dar carrier relaying schemes.
The phase angle between negative sequence voltage and negative sequence current is used for directional discrimination. Negative sequence polarization is applied as follows:
1) where zero sequence voltage or polarizing current is not available or the current is not a reliable source, or
2) where incorrect zero sequence polarization of directional units results from mutual indication between transmission lines.