Transient based protection using current transients

A transient based protection criterion using the wavelet transform results of current transients from the two ends or three ends (T-type line) of high voltage power transmission line is presented. According to the attenuation effects of high voltage transmission line and busbar capacitance to high-frequency current transients, differences of current transients at each end of the transmission line when in-zone faulted and out-zone faulted are analyzed and used to deduce the transient current content ratio (TCCR). Protection criterion using TCCR is proposed, and the principles of protection settings are given. Wavelet modulus maxima of current transients are used to calculate TCCR. EMTP simulations of different faults using a 100 kHz sample rate are carried out for testing and analyzing the protection criterion. The protection criterion, which is proved simple, reliable and whole-line protective, is suitable for both two-end line and T-type line.