Enhanced transmission line protection based on discrete wavelet transform (DWT)

Abstract

In order to reduce damage of transmission line due to fault, reliable, high-speed, sensitive and dependable protection system is a primary requirement of today’s interconnected power system. It is pertinent to not only detect faults at exactly their time of occurrence, but also to classify them for appropriate restorative decision to be made. In this paper, approach for the protection of transmission line which uniquely manipulates the coefficient energy of Wavelet Transforms to generate ratios that are used for both detection and classification of transmission line faults. The fault current signals generated by MATLAB/SIMULINK simulation have been analyzed using Daubechie-4 (d4) mother wavelet at 7th level decomposition with the help of Wavelet Toolbox embedded in MATLAB. The value of the coefficient energy of the current signals gives the indication of fault and no-fault conditions. Also, the coefficient energy ratios were calculated to help classify the faults. This approach was applied to 132Kv case study and ten classes of fault could be correctly identified and classified within fault duration of 0.01 seconds.