A fast recursive wavelet based boundary protection scheme

By virtue of a fast recursive wavelet based dual-band-pass filter, a novel boundary protection scheme for HV transmission lines is presented. Among which, the filter of relatively lower central frequency aims at evaluating the spectrum energy of the transient current with a relatively longer time-window guarantee the stability of the criterion. The filter of relatively higher central frequency can effectively detect faint high-frequency signal with relative longer frequency-window to assure the sensitivity of the protection criterion. It has been proved with extensive EMTP simulation tests that the internal faults even including high resistance earth fault and in low fault inception-angle can be identified from the external faults. This scheme provides an option to implement the novel concept of transient based protection, boundary protection.