A Novel Voltage Transients Base Protection Criterion for T-Type High Voltage Transmission Lines

Based on the wavelet transform results of the voltage transients from the three ends of the line, a novel protection criterion for T-type high voltage power transmission line is presented. The attenuation effects of high voltage transmission line and busbar capacitance to high-frequency current signals is analyzed. The Transient Voltage Content Ratio (TVCR) and Transient Voltage Singularity Ratio (TVSR) are deduced according to the analysis of the differences 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 wavelet modulus maxima of voltage transients are used to calculate TVCR and TVSR. EMTP simulations of different faults are carried out for testing and analyzing the protection criterion. A 100kHz sample rate is used in the simulations. According to the simulation results, the protection criterion is proved simple, reliable and whole-line protective.