A wavelet-fuzzy combined approach for classification and location of transmission line faults

Abstract

This paper presents a real-time wavelet-Fuzzy combined approach for digital relaying. The algorithm for fault classification employs wavelet multi resolution analysis (MRA) to overcome the difficulties associated with conventional voltage and current based measurements due to effect of factors such as fault inception angle, fault impedance and fault distance. The proposed algorithm for fault location, different from conventional algorithms that are based on deterministic computations on a well-defined model to be protected, employs wavelet transform together with fuzzy logic. The wavelet transform captures the dynamic characteristics of the non-stationary transient fault signals using wavelet MRA coefficients. The fuzzy logic is employed to incorporate expert evaluation through fuzzy inference system (FIS) so as to extract important features from wavelet MRA coefficients for obtaining coherent conclusions regarding fault location. Computer simulations using MATLAB have been conducted for a 300 Km 400 KV line. Simulation results indicate that both the classification and localization algorithms are immune from effects of faults inception angle, impedance and distance. The most significant contribution of this paper is that the proposed location algorithm has a maximum error of 6.5% with a computational time of about one cycle. Thus both classification and location algorithms can be used as effective tools for real-time digital relaying purpose.