Systematic protective scheme for mega‐city power systems against stray currents caused by metro systems

Abstract

Abstract In modern megacities, stray currents from metro systems intrude into multiple transformers' neutral points becoming a potential threat to the high‐capacity transformers. Neutral current anomalies are exacerbated in unprotected substations when we instal guards at single stations. This paper presents a system protection strategy for multiple substations affected by stray currents in modern megacities. The model, taking Shanghai as an example, includes the spatial distribution information of the urban electrical energy transmission structure, the power system, and the metro system. A Particle swarm algorithm is used to calculate the resistance values of the devices for each station. Further stability tests are performed to select the optimal protection solution. The results show that when protection is considered as a system, the protection runs well and the neutral current level remains below the unprotected level when the protection fails at a single station or multiple stations.