Abstract

Distance relays used for protection of transmission lines have problems of under-reach, over-reach and mal-operation due to high impedance faults. Further the problem is compounded when distance relays are used for protection of double circuit transmission lines due to effects of zero sequence mutual coupling. Different types of faults on protected transmission line should be located correctly. This paper presents wavelet analysis and Wavelet Modulus Maxima techniques for fault distance location for all the ten types of faults (3 LG, 3LLG, 3LL, 1LLL) in both circuits of a double circuit transmission line fed from sources at both the end. This technique uses only end of data and accurate fault distance location is achieved after one cycle from the the inception of fault. The analysis for fast identification of fault is evaluated based on the representation of the travelling waves through wavelet modulus maxima. The present criterion can detect the instant of fault, location of fault and kind of fault. MATLAB/ Simulink software was used to test the proposed approach. Various fault conditions were simulated by varying fault type, fault resistance, fault location and fault inception angle, on a given power system model. The simulation results demonstrate the validity of the proposed approach of faulted phase selection.

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