Current Based Transmission Line Protection Algorithm Using Signal Processing Techniques

Abstract

The research work included in the paper is focussed on design of a current based protection scheme using signal processing methods which is effective to provide the main as well as back up protection using the same algorithm. Current signals associated with all the three-phases are decomposed using the discrete ortonormal Stockwell transform (DOST) and absolute magnitude of output of DOST are evaluated and designated as DOS-index. Current signals of all the three phases are also decomposed with the aid of Fast Fourier transform (FFT) and absolute magnitudes of the output are evaluated and designated as FFT-index. Further, the current are also decomposed with the aid of Hilbert transform (HT) and evaluated using the absolute magnitudes of output which is assumed as H-index. Element by element multiplication of the DOS-index, FFT-index and H-index are evaluated to calculate the proposed current based Fault index (FI). Threshold magnitude of 10000 is finalized for proposed current based fault index. By comparing values of FI with threshold, the different natures of faults are detected. Classification of the faults is achieved with the help of decision rules using the peak values of the FI. It is established that current based fault indexes will be the key factors for detection of various types of faults on transmission line. It will also be established that proposed current based algorithms will be fast compared to the algorithms such as Wavelet transform, HT, Stcokwell transform and fast Fourier transform used individually.