DWT based symmetrical fault detection method during power swing

Distance relays are mal-operated during power swings, they have to block. However if a fault occurs during power swing, the relay should be unblocked to clear the fault quickly. This paper presents fault detection algorithm based on DWT during power swings. DWT is used to capture the travel time of the fault transients along the monitored lines between the fault points and relays. Travelling wave theory is utilized for analyzing power system fault transients. The voltage data at one end is sufficient to detect the fault, which reduces the errors caused due to current transformers. High sampling frequency is not required which reduces the burden of data acquisition. High resistance faults are also detected. Performance test is carried out in MatLab environment by considering different fault situations. Simulation results show the efficacy of the algorithm.