Detection of transmission line faults in the presence of thyristor controlled reactor using discrete wavelet transform

The transmission line relaying is an extremely important device used to provide the protection of transmission and distribution of the power system. The relays must operate as fast as and as accurate as possible to switch off the faulted line in order to protect the system against the harmful faulty effects. The wide spread use of power electronics based devices in the power system has made the protection issue critical. The power system faults do occur in power system network and are more frequent in transmission and distribution systems. The behaviour of the faults changes in the presence of FACTS devices. This paper presents the detection of power system faults in the presence of thyristor controlled reactor (TCR). The power system faults such as line to ground (LG), double line (LL), double line to ground (LLG) and three phase fault involving ground (LLLG) have been investigated. An algorithm based on discrete wavelet transform has been utilized for detection of faults under investigation. The current drawn by the load in the presence of TCR and voltage at the point of common coupling (PCC) have been found to be key features for detection of power system faults. The study has been performed using a test system and results have been validated in MATLAB/Simulink environment.