Behaviour of internal fault and external fault in power transformer using discrete wavelet transform

The differential protection is aimed at detecting internal faults in transformer windings. Therefore, it is necessary to understand fault behaviour before doing performing decision algorithm. This paper presents behaviour of internal winding fault and external short circuit in a three-phase two-winding transformer. The advantage of the discrete wavelet transform (DWT) is considered herein. The fault is simulated using ATP/EMTP and the behaviour analysis of signals is performed using DWT. The variation of high frequency components of differential current signals is presented in this paper. The results obtained from the analysis will be useful in the development of a fault detecting scheme for power transformer in the future.