Research on an Ultra-High-Speed Protection Based on Multiresolution Morphological Gradient

A new ultra-high-speed protection scheme based on multi-resolution morphological gradient (MMG) transformation is proposed in this paper. The transient current generated by the internal and external faults in extremely high voltage (EHV) transmission line contains different high frequencies because of the line traps and bus-bar stray capacitance. So there are differences in singularity degree of transient current wave forms at sudden change point between internal and external fault. The differences are extracted and amplified by multi-resolution morphological gradient (MMG). By detecting the singularity of fault transient current signals in one terminal using MMG, the proposed ultra-high-speed protection scheme can discriminate between internal and external faults rapidly and securely. A typical 500 kV EHV transmission system has been simulated by ATP/EMTP to evaluate the scheme. A large of simulation results show that the proposed scheme is effective and capable of providing correct responses under conditions of different fault types, positions, path resistances, and inception angles.