Transient-based Ultra-high-speed Directional Protection Using Wavelet Transforms for EHV Transmission Lines

This paper proposes a novel ultra-high-speed directional protection scheme for EHV transmission lines using the wavelet transform. The wavelet transform technique extracts high-frequency transient components from two composite relaying signals, forward and backward traveling-waves, which are derived from the fault-induced voltage and current wave propagating along transmission lines and the wavelet transform spectrum energy (WTSE) is introduced to represent the transient energy of high-frequency component. Then the directional protective relay identifies fault direction by comparing the WTSE values of two relaying signals during a post-fault period. Numerous EMTP simulation tests show that this proposed protection is reliable and sensitive. Meanwhile the relay performance can endure the influences of various factors, including different fault inception angles, fault distances, fault types, fault path resistances and fault arcing