Fault section identification method for loop distribution systems in Korea

Radial distributed system (RDS) has the drawback of decreasing line utilization as load variability increases, and this issue has been exacerbated by the recent surge in integration of distribution generation (DG). To address the limitations of the RDS, loop distribution system (LDS) has been introduced. LDS operates with two interconnected distribution lines running simultaneously. Since each line shares the load, they offer the advantage of increasing line utilization and maintaining voltage stability. However, in the event of a fault, the fault current flows in both directions, which creates blind spots for protection coordination when using conventional protection technologies that are designed to handle unidirectional fault currents. This paper presents a case study of LDS introduced in Korea and discusses potential cases of mis-operation in protection coordination, along with solutions to these issues. The study shows how a ground fault occurring in one line of a system with interconnected DGs can cause the circuit breaker (CB) in a non-faulted section to mis-operate. The scenarios and proposed protection methods are verified using the real site examples introduced in Korea.