A novel protection scheme for multi-terminal transmission lines based on wavelet transform

Abstract

Identification of the fault section and fault phase selection are considered the main tasks of a multi-terminal transmission line protection scheme. The current study classifies the methods applied to multi-terminal transmission lines. Moreover, investigated solutions for the drawbacks that appeared with the previous methods are suggested. Based on wavelet packet transform, a scheme for a multi-terminal transmission line is presented in this article. The suggested technique uses the wavelet packet transform (WPT) to get the approximate and detail coefficients of the differential current and model voltage for all buses in a system, detects and classifies the faults (FDC) within a half-cycle window, and identifies the faulted section (FSI). A fast mother wavelet is used with a three-coefficient high pass filter to analyze signals of the model voltage and differential. In this regard, two frequency levels were chosen, in which the first level of the differential current signal was chosen to detect and classify a fault, while the first level of the model voltage signal was chosen to identify the faulted section. Several fault cases are simulated and analyzed in the ATP/EMTP environment for an N-terminal system followed by successful testing on three- and five-terminal systems to evaluate the performance of the proposed scheme. The simulation results obtained show that the proposed scheme is efficient and shows high speed and accuracy of fault detection compared to other methods in the literature.