Hierarchical collaborative internal protection for DER based on fault distance identification

With the widespread application of distributed energy in distribution networks, the system has developed into an active distribution network with multi-source coordination. Internal protection of DER faces challenges in coordination in terms of selectivity, speed, and reliability. This paper proposes a partitioned coordination protection scheme to address issues such as misoperation of line protection caused by internal DER faults and unnecessary trips of non-fault DERs. By analyzing the impact of internal DER faults on both islanding protection and line protection, a multi-criteria protection system was established, mainly based on impedance criteria, complemented by undervoltage blocking and directional overcurrent. Simulations indicate that this approach can rapidly isolate faults within 0.1 seconds, effectively prevent the tripping of non-faulted lines, and significantly enhance selective operation and power supply reliability.