A novel fuzzy-logic-based phase selection technique for power system relaying

Abstract

Fast tripping and consequent single-pole auto-reclosure of the faulted phase for single-phase earth faults is extensively used in long line applications. Traditional phase selection techniques can suffer some drawbacks due to their dependency on varying system and fault conditions. However, with the advent of fuzzy-logic techniques, and their ability to map complex and non-linear power system configurations provide a very attractive solution to accurate and fast phase selection procedure. This paper presents a new approach to real-time phase selection in power transmission systems using fuzzy-logic-based multi-criteria approach. Only the three line currents are utilised to detect the faulted phase. An online wavelet-based pre-processor stage [IEEE Trans. Power Delivery, 18 (4) (2003) 1158; IEEE Trans. Power delivery 17(4) (2002) 908; IEEE Trans. Power Delivery, 18 (1) (2003) 170; Paper # 01TD069, IEEE T&D Conference, 28 October–2 November 2001, Atlanta, GA] is used with 10 samples data window (based on 4.5 kHz sampling rate and 50 Hz power frequency). The paper demonstrates the multi-criteria algorithm that is based on fuzzy sets for the decision making part of the scheme. Computer simulation have been conducted using EMTP programs. Results proved that the correct detection is achieved in less than half a cycle and that computational burden is simpler than the recently postulated phase selection techniques, and this approach can be used as an effective tool for high speed digital relaying.