Analysis of surge current due to closiing loop in distribution network

Loop closing operation in distribution network will brings about steady-state loop current and the transient surge current??Recent papers mainly analyze the theory and calculation method of the steady-state loop current, but seldom discuss the transient surge current, only a rough evaluation presented. This paper fully studys the mechanism of occurrence of the transient surge current and establishs mathmatical model for the calculation of it. This paper also gives the calculation fomulas of the maximum of the transient surge current and the maximum of effective value of the transient surge current. What´s more, the occurring time of the maximum of the transient surge is presented . An equivalent model of local distribution network is developed to simulate the closing loop operation using PSCAD/EMTDC program A pre and post closing current curve is recorded simultaneously. Both the maximum of the transient surge current and the maximum of effective value of the transient surge current are read out from the simulation curve. Mealwhile, the maximum of the transient surge current and the maximum of effective value can be calculated from the .the calculation fomulas. By comparing the simulation and theoretical results, it is proved that the method for the calculation of transient surge current is suitable. The surge current in practice must´t exceed the theoretical result in order to avoiding accident. It will be safe as long as acting within the theortical limits. The theory this paper puts forward will be an effective instructs for people engaging in Power System Operation and Control.