Phase selection and differential protection based on Wavelet Transform for half-wavelength AC transmission line

The traditional distance protection is no longer applicable to the half-wavelength AC transmission line for the completely different characteristics from the conventional transmission line. In order to solve this problem, phase selection and differential protection based on wavelet transform is proposed. The mode components of the reverse current traveling wave and the zero sequence current of the half-wavelength line are transformed by wavelet transform, and the phase selection is carried out according to the results of the wavelet transform. The wave heads of both sides of the mode current after the fault phase wavelet transform are respectively integrated. The differential protection is constructed with the absolute value of the sum of integral current on both sides as the differential current and the absolute value of the integral difference as the braking current. PSCAD simulation shows that the protection scheme is suitable for half-wavelength line, which can protect the full length of the transmission line, effectively distinguish internal from external faults, and has a certain ability to resist transition resistance.