A WAVELET TECHNIQUE FOR DIRECTIONAL PROTECTION FOR EHV TRANSMISSION LINES WITH SERIES COMPENSATION

摘要

The author provides a novel directional protection scheme for transmission lines with series compensation capacitors based on travelling waves. The ability of wavelet transform techniques to focus on system transients provides an effective and reliable method for fault detection and classification. Therefore, wavelet transforms are applied to the three phase currents at both ends of the transmission line. Directions and magnitudes of spikes in the wavelet coefficients are used for this purpose. The scheme is able to detect all types of internal faults at different locations in front and back of the series capacitor, at different fault inception angles and at different fault resistances. It also determines the type of fault and detects the faulty phase(s). Furthermore, it can detect external faults and blocks tripping if they exist. The relay remains stable for normal conditions, as well as in the presence of nonfaulty normal transients. The protection scheme is tested by simulating faults using the MATLAB power system toolbox. Simulation results show the high accuracy, security, and dependability of the proposed scheme.