A new current differential protection method for active distribution networks based on fault-phase interline currents
DOI:10.19783/j.cnki.pspc.243001
Key Words:distributed generator  current differential protection  active distribution network
Author NameAffiliation
WANG Yang1 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
ZHAO Ruoyang1 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
LI Dayong1 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
HUANG Jiakai2 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
JIN Yao2 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
ZHENG Zhiyan3 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
CHEN Xiaolong3 1. State Grid Tianjin Electric Power Company, Tianjin 300010, China
2. Electric Power Research Institute, State Grid Tianjin Electric Power Company, Tianjin 300392, China
3. State Key Laboratory of Smart Power Distribution Equipment and System, Tianjin University, Tianjin 300072, China 
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Abstract:To address the challenge that traditional protection schemes become unsuitable after distributed generators (DGs) are integrated into distribution networks, a novel current differential protection method is proposed for active distribution networks based on fault-phase interline current. First, considering the control strategies of various DGs during low-voltage ride-through, the fault characteristics of both T-connected and bus-connected DGs are analyzed. The variation patterns of phase currents and fault-phase interline currents measured by protection devices on both ends of the line are revealed with respect to fault location. Second, a new current differential protection criterion is constructed using the interline current information from both line terminals, leveraging the distinction between internal and external faults. On this basis, the calculation methods of the operating and restraining quantities are improved to reduce dependency on communication synchronization. Finally, a 10  kV active distribution network model built in PSCAD validates the reliability and effectiveness of the proposed method. Simulation results demonstrate that the method is simple and practical, and compared with traditional positive-sequence current-based differential protection methods, it is less affected by DG outputs under different DG capacities, fault locations, and fault types.
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