The double-circuit transmission line on the same tower has been widely used in Chinese UHV transmission lines because of its advantages of less ground, lower investment and transmission efficiency. However, the fault condition is more complicated than on the single transmission line. This makes the setting, fault phase and line selection of the relay protection complicated. Based on the analysis of the coupling relationship between six phases, a fault phase selection method based on transient component is proposed. The algorithm uses wavelet transform to extract the transient energy of the current fault component and a morphological filter with flat structure element to remove high frequency noise and eliminate the sharp part of the waveform. The transient energy magnitudes are compared to identify fault type and select fault line. The effectiveness of the method has been verified by simulating different fault types, fault location, fault time and transition resistance with ATP-EMTP.

double-circuit transmission line; fault phase and faulty line selection; transient component; morphological filter