Current‐phase‐comparison‐based pilot protection for normally closed‐loop distribution network with underground cable

Summary Closed‐loop operation of distribution network has attracted more attention recently to improve supply reliability and adopt distributed energy resources friendly. But its protection is usually independent of distribution automation system (DAS). This article presents a pilot protection method for closed‐loop distribution network with underground cable by comparing current phase, which can be accomplished by remote terminal units (RTUs) in DAS. Firstly, operation value of RTUs is designed on the current variation after fault and the RTUs are synchronized automatically based on fault signal. Secondly, the current phase characteristic of positive‐sequence fault component is analyzed when various short circuit fault occurs at different locations. Based on the current phase difference, the state of ring network cabinet is classified into four types, and uniform fault location rule by adjacent RTUs is designed. The fault can be located and isolated directly by cooperation of adjacent RTUs. The setting principle and the operation logic for the pilot protection are given, and its performance is analyzed. Finally, simulation model based on PSCAD is constructed. The simulation results prove that this protection can locate and isolate faults timely on the premise of high sensitivity. It has strong ability of enduring fault resistance, and it can fit closed and open operation mode.