Hybrid Adaptive Algorithm to Fast Distance Relaying

This paper presents the design of a hybrid scheme of wavelet transforms and an adaptive Fourier filtering technique for on line fault detection and phasor estimation to fast distance protection of transmission lines. The wavelet transform is used as a signal processing tool. The sampled voltage and current signals at the relay location are decomposed using wavelet transform-Multi Resolution Analysis (MRA). The decomposed signals are used for the fault detection and the phasor estimation. The phasor estimation algorithm possesses the advantage of recursive computing and a decaying dc offset component is removed from fault signals by using an adaptive compensation method. Fault detection index and a variable data window scheme are embedded in the algorithm. The proposed scheme provides capability for fast tripping decision, taking accuracy into account.