New Principle of Fault Phase Selection Based on Wavelet Filter and Its Derived Filter

A new principle of fault phase selection is presented. It is proposed to recognize the non-fault phase by comparing the initial direction fault traveling wave amplitudes and their time derivative polarities near their headers. The wavelet filter and its derived porous filter are employed to detect the amplitudes of the initial direction fault traveling wave in different way. The filter results can supply the modulus maximum of wavelet coefficients in different sample frequency, and can used to carry out the time derivative polarity of fault traveling wave near the singularity. At the fault point, the initial fault current in non-fault phase is zero, and it can be used as judging criterion for non-fault phase selector after being modified reasonably and strictly. The selector can carry out the correct result of the fault with large transition resistances and low initial fault voltages at the same time. The simulation and calculation results by ATP and MATLAB confirm sensitivity and reliability of the principle.