Unit Transient Based Protection for High Voltage Wind Power Transmission Lines

Based on the wavelet transform results of the transient signals from all ends of the line, a unit protection for high voltage power transmission line is presented. The attenuation effects of high voltage transmission line and busbar capacitance to high-frequency current signals are analyzed. The Transient Current Content Ration(TCCR), Transient Voltage Content Ratio (TVCR) and Transient Voltage Singularity Ratio (TVSR) are deduced according to the analysis of the differences during high frequency voltage transients at each end of the transmission line when in-zone faulted and out-zone faulted. Protection criterion using TCCR and protection criterion using TVSR are proposed. and the principles of protection settings are given. The wavelet modulus maxima of transient signals are used to calculate TCCR and TVSR. Simulation experiments of different faults with EMTP are carried out to test and analyze the protection criteria. A 100kHz sampling rate is used in the simulation experiments. According to the simulation results, the protection criteria prove to be simple, reliable and good for whole line protection.