A current differential protection criterion based on amplitude and phase difference of fault current

A current differential protection criterion based on amplitude and phase difference of fault current is proposed. When fault happens, the amplitude of the fault current component on both sides has nothing to do with the load current, the phase difference won´t be influenced basically by transition resistance, distributed capacitance, load current, and the effect of TA saturation is also small, so by using amplitude and phase difference of the fault current to constitute a current differential protection criterion, we can get better operating characteristics. With the method of numerical analysis, in various value conditions, this paper compares and analyzes the performances of the new proposed criterion and the fault current phasor differential criterion, then by simulating some examples through PSCAD/EMTDC, analyzes the performances of these two criteria under different transition resistances, distributed capacitances, TA saturation and other conditions. The analysis results show that compared with the traditional fault current phasor differential protection, the new criterion has higher sensitivity in internal faults and higher levels of security in external faults, and less influenced by transition resistance, distributed capacitance, TA saturation, which has bettter performances.