Study On The Transient Protection Principles For EHV Transmission Line

Transient based protection can do well in settling the conflict between speediness andreliability in traditional protection for EHV transmission line. Mathematical Morphology(MM) provides an efficient tool for signal processing in transient based protection. Startedfrom theory of MM and transient protection,several aspects of transient protection aredisplayed in this thesis, this paper discusses MM principle and its applications in detectingsignals' singularity. :The transient current generated by the internal and external faults inEHV transmission lines contains different high frequencies because of the line traps andbus-bar capacitance. So there exit differences in singularity degree of transient current waveforms at sudden change point between internal and external fault. The difference is extractedand amplified by Multi-resolution Morphological Gradient (MMG) to construct a novel ultrahigh-speed protection scheme. On the base of MM, a transient current based fault phaseselection algorithm is also presented. A simplified 500kV transmission line is simulated usingATP and its simulation data are treated with MATLAB to validate the algorithms. Thesimulation results prove the algorithms are correct and creditable.