A power based integrated protection scheme for active distribution networks against asymmetrical faults

This paper introduces a power-based integrated protection scheme for active distribution networks to provide protection against asymmetrical faults and over unbalanced conditions. The proposed scheme detects the fault by monitoring the degree of system unbalance and discriminates the fault using the direction of the negative sequence reactive power flow originated from the fault point. The unit characteristic of the new protection scheme eliminates the technical difficulties resulted from the concept of non-unit overcurrent protection and provides protection for both buses and lines of the active distribution networks. Extensive computer simulation studies are carried out to analyze the performance of the new protection scheme under different asymmetrical fault conditions. Simulation studies indicate that the new protection scheme provides very fast tripping as the primary protection and backup protection for the case of any communication failure and also un-cleared faults taking place outside the protection zone.