Communication-Free Travelling Wave-Based Method for Ground Fault Location in Radial Distribution Network with DG

Faulty zone in distribution grid might be inferred by operation of protective devices. However, fault point is wanted for accelerating fault repair. This paper proposes a travelling wave (TW)-based method for locating ground faults in a radial distribution system integrating DGs. The proposed method is based on voltage signal sensed at local end only, then arrival times of first two waves are determined and analyzed. To avoid fault type identification or faulty phase selection, three-phase signals are firstly transformed into aerial and ground mode signals. Next, first-level discrete wavelet transform (DWT) is applied to the denoised mode signals in order to specify the times of arrival of the first two backward propagating waves. For every possible fault zone, mathematical analysis of TW propagation diagrams is achieved to diagnose the second TW arrival at measuring end. Therefore, general equations are formed to give accurately the position of fault. The method is independent of DG existence, fault type and resistance.