Transmission line protection using spectral energy differential scheme

A transmission line differential relaying scheme based on Discrete Wavelet Transform (DWT) is presented in this paper. Comparison of the transient energy in the current signals at both ends of the transmission line is introduced. The transient energy in the current signals is extracted using DWT. A sliding data window with a length equivalent to half cycle of the fundamental power frequency is used to achieve high speed relaying. The proposed scheme has been extensively tested both in computer simulations and in real-time when implemented using DSP board. The scheme presented in this paper is tested against different internal and external faults. The factors that affect the scheme sensitivity and stability are discussed.