Adaptive Restraint Coefficient-Based Differential Protection for Main Transformers in Wind Farms

Abstract

Influenced by factors such as fault current frequency deviation, current transformer (CT) saturation and abnormal data, the traditional transformer current differential protection scheme contains the risks of slow operating speed or false operation in the wind power system. To guarantee the safe operation of the power system, by improving the traditional current differential protection scheme, a differential protection scheme based on the adaptive restrain coefficient was proposed for the main transformers of wind farms. The proposed protection adaptively adjusts the restraint coefficient according to the time-domain distribution characteristics of differential current. When the internal fault occurs, the restraint coefficient will be adaptively reduced; the restraint coefficient will adaptively increase when the non-internal fault occurs. The proposed protection scheme significantly surpasses the traditional current different protection in terms of operating performance, because it can accurately identify the internal faults and strongly resist abnormal data, CT saturation and magnetizing inrush current.