Positive sequence differential impedance protection for distribution network with IBDGs

The fault characteristics of inverter-based distributed generator (IBDG) differ from those of traditional resources, which makes the conventional protection schemes ineffective in active distribution networks. This paper first analyses the features of measured positive sequence impedance at both ends of protected line section in internal and external fault cases. Based on the amplitude difference of defined differential impedance in various fault cases, a novel pilot protection scheme applicable to distribution networks with IBDGs is proposed. To diminish the negative influence of load branches, an operation criterion with restraining characteristic is constructed, and a current amplitude difference coefficient is introduced for the further improvement of the protection performance. The proposed strategy has no need for data synchronization measurement and owns stronger ability to resist transition resistance. Simulation results verify the validity and feasibility of the protection scheme.