Feasibility Analysis of Adaptive Coordination for Inverse-Time Protection in Active Distribution Networks
Chang Nana1, Song Guobing2,3, Jiang Jiaheng2,3, Chang Zhongxue2,3
1. School of Electrical Engineering Xi’an University of Technology Xi’an 710048 China; 2. School of Electrical Engineering Xi’an Jiaotong University Xi’an 710049 China; 3. State Key Laboratory of Electrical Insulation and Power Equipment Xi’an 710049 China
Abstract：Inverse-time overcurrent (ITOC) backup protection is difficult to coordinate in active distribution networks with distributed generations (DGs) and converter-interfaced sources. Changes in DG access location, operating state, and network topology alter fault-current paths and relay operating conditions. Preset coordination relationships established for one operating mode may therefore become invalid in another mode. This study analyzes the mechanism of coordination degradation and examines an adaptive coordination formulation for active distribution networks. The analysis is based on the coupling among fault current, relay settings, and inverse-time characteristic parameters, which determines the coordination capability of conventional ITOC protection. Fault-network relationships and inverse-time operating-time expressions are used to examine the effects of source-characteristic changes and topology changes on adjacent-relay coordination. The IEC inverse-time characteristic equation is used to quantify the variation of the coordination time interval under different DG access locations. The results show that DG integration and topology reconfiguration can compress or enlarge the operating-time difference between adjacent protections, and may violate preset coordination requirements in some scenarios. Time-current characteristic curves and simulation results under different operating conditions show that fixed offline settings are difficult to maintain coordination performance across multiple modes. To reduce dependence on fixed-scenario preset grading, relay coordination is reformulated as an operating-time generation problem. Relay operating times are generated by combining an inverse-time characteristic equation with the same type of electrical quantity (or its constructed quantity) measured by upstream and downstream protections along the same fault path. The formulation is used to examine feasibility and to explain the method construction principle, rather than as a complete engineering setting procedure. Its purpose is to build a physically interpretable mapping between spatially distributed fault-related electrical quantities and relay operating times, so that relay operating order can follow the spatial relationship between measuring points and the fault point under varying DG and topology conditions. The feasibility of this formulation is examined by analyzing the spatial distribution characteristics of candidate electrical quantities in different fault stages, including the transient/free-response stage and the fault steady stage. Under the analyzed conditions, the magnitude of the electrical quantity, or a constructed scalar quantity derived from it, mainly varies with the electrical distance between the measuring point and the fault point. This provides the basis for adaptive operating-time generation. A generalized inverse-time expression is then discussed to describe the mapping from the selected electrical quantity to relay operating time. The physical meanings of the parameters are clarified, and parameter constraints such as positivity and monotonicity are considered to ensure meaningful operating-time distribution and adjacent-relay coordination. Analytical and simulation results show that the dynamic failure of preset ITOC coordination in active distribution networks originates from changes in the coupling among fault current, relay settings, and inverse-time parameters under DG and topology variations, and that electrical quantities with spatial distribution characteristics can be used to form relay operating times, providing a feasible basis for adaptive ITOC backup-protection coordination in active distribution networks under high DG penetration conditions.
常娜娜, 宋国兵, 蒋嘉桁, 常仲学. 有源配电网反时限保护自适应配合可行性分析[J]. 电工技术学报, 2026, 41(13): 4635-4647.
Chang Nana, Song Guobing, Jiang Jiaheng, Chang Zhongxue. Feasibility Analysis of Adaptive Coordination for Inverse-Time Protection in Active Distribution Networks. Transactions of China Electrotechnical Society, 2026, 41(13): 4635-4647.
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2026, Vol. 41 
