A novel unit transient based protection criterion for high-voltage power transmission line

A novel unit transient based protection criterion for high voltage power transmission line based on the wavelet transform results of voltage transient signals at each end of the line is presented. The transient voltage content ratio (TVCR) and transient voltage singularity ratio (TVSR) are deduced according to the difference of high frequency voltage transients at each end of the transmission line when in-zone faulted and out-zone faulted. Protection criterion using TVSR is proposed, and the principles of protection settings are given. The criterion is suitable for both two-end line and T-type line. Simulations of different faults and different line types are carried out for testing and analyzing the protection criterion.