Fast fault detection during power swing on a hybrid transmission line using WPT

This paper presents a new technique for very high speed detection of fault during power swing on a hybrid transmission line consisting of an overhead line and an underground cable. The wavelet packet transform with the mother wavelet db1 is utilised to segregate the high-frequency components from three-phase current signals recorded at the relay point and a fault detection index is calculated using these components to detect faults during power swing. The proposed method is tested on a 400 kV double circuit transmission system and a 400 kV 3-machine 9-bus Western System Coordinating Council system simulated in electromagnetic transient program software for both symmetrical and asymmetrical faults, different fault resistances, load angles, and fault inception times at random locations on the transmission line. Its performance is also analysed for close-in faults, high dc offset current, and the faults on the series compensated transmission line. The method is very fast to detect faults during power swing irrespective of the variations of fault conditions, and a comparative assessment with the existing methods justifies its merit.