A new principle for high resistance earth fault detection during fast power swings for distance protection

The combined effects of a high impedance ground fault condition and a fast power swing condition cause the apparent impedance 'seen' by power system distance protection schemes to vary over a wide range. Previous research work has shown that the detection and location of high impedance faults during power swings is very difficult. A new principle for high impedance fault detection during fast power swings is presented which overcomes these deficiencies. This method forms a part of a complete power swing relaying scheme and can be implemented on standard relaying hardware. Results are presented based on extensive simulation studies carried out on a typical 400 kV transmission system, using the Electromagnetic Transient program (EMTP).