A New Current Differential Protection Criterion for Active Distribution Network

The current differential protection based on KCL can effectively solve the feeder protection problem in active distribution networks (ADN) caused by distributed generation (DG) in theory. Due to different fault characteristics, the differential protection criteria applied to transmission lines cannot be directly transplanted to distribution network. For this reason, the paper first briefly analyzes the amplitude and phase characteristics of fault currents in ADN. Then, the restraint current of differential protection is improved by decoupling the amplitude and phase angle of fault currents. Here, the amplitude characteristic is used to deal with the inverter-based distributed generation (IBDG), and the phase angle characteristic is introduced to deal with the synchronous- based distributed generation (SBDG). By setting compensate coefficient, high sensitivity and reliability are guaranteed. Finally, the simulation based on PSCAD/EMTDC software is carried out, and the validity of the proposed criterion is verified.