A new technique to detect the fault direction of a single-phase-to-earth fault for a Petersen's coil compensated earthed power system is presented. The proposed technique can make a precise decision on detecting the single-phase-to-earth fault, not requiring higher frequency sampling rates or higher-accuracy measurements. It can be implemented in a traditional feeder relay with a low sampling rate. It has been implemented in MiCOM P14x feeder relays by Alstom Grid.
