Evaluation method for impact on protection of distribution network with distributed electric resources

Recent gradual improvement of the distributed electric resources (DER) penetration results in the change of original topology and power flow direction of distributed network. The short circuit current, which is provided by distributed electric resources, has changed the distributed network fault current both in size and distribution, will reduce the protection sensitivity, and bring negative impacts such as blinding and tripping. However, the actual structures of active distribution network are complex, it is difficult to measure the impact levels in traditional methods. These situations must be avoided. In this paper, the worst situations on protection are analyzed, an evaluation method based on maximum value of short circuit current provided by DER is proposed. The simulation with Matlab/Simulink software is introduced, the error sources of the method are analyzed, and the results indicate the feasibility and validity of the proposed method.