Research on differential protection algorithm about special phase-shifting angle rectifier transformer

Electrolysis metallurgical production adopts rectifier transformer of special shifting-phase angles to generate more pulses instead of bridge rectifier. Although power quality improved, traditional differential protection cannot be applied because of current phase angle difference of two sides of transformer. Firstly, simulation model has been built in PSCAD upon special shifting-phase transformer theory. Secondly, a new method of special angle compensation is proposed upon current phase compensation and sequence component theory. This method has wider applicability than traditional one, which can compensate any phase-shifting angle. Finally, differential protection algorithm for special phase-shifting angle is proposed in consideration of zero-sequence current´s influence. Through simulation of some cases of circuit fault, sensitivity and reliability of this algorithm in this paper is verified.