Earth fault protection using transient signals in non-solid earthed network

Existing earth protections are not satisfactory in practical application due to the nature of weak fault current and unstable fault arc. Three earth fault protection methods using the transient zero sequence signals in special frequency band are presented and evaluated in this paper. The faulty feeder is selected by comparing amplitude and polarity of selected component of transient zero sequence currents of all feeders, an measuring the direction of selected component of transient zero sequence currents. They have higher sensitivity and reliability. Recorded real fault data proved the proposed techniques.