Wavelet fuzzy logic framework for digital protection of a double-circuit transmission line

Abstract

Fault classification and location identification are prime apprehensions in power system distance relaying. A digital protection scheme for a double-circuit transmission line based on fuzzy logic is presented in this paper. The discrete wavelet transform (DWT) and discrete Fourier transform (DFT) have been used for analyzing the measured voltage and current signals at the relaying point. This paper proposes an algorithm that combines the discrete wavelet transform (DWT) with fuzzy logic to identify various types of faults. Here, the two mother wavelets, i.e. Daubechies and discrete Meyer (Dmey), have been employed in the DWT domain to measure post-fault currents at a single end of the line. The standard deviation of DWT coefficients has been used in this case. The combined DWT-fuzzy scheme has been tested across various fault types and conditions, including fault resistance, location, and inception angle (FIA). The combination of DFT and fuzzy logic is used to identify fault locations in overhead transmission lines for different fault conditions. The DFT estimates the phasors of voltage and current signals to calculate apparent impedance. This apparent impedance is then analyzed using fuzzy logic to locate faults. The proposed combined DWT-Fuzzy scheme accurately classifies faults under various conditions, including fault resistance, fault location, and fault inception angle variations. This method achieves a fault location error rate of less than 0.5% in most test cases.