Optimizing the re-closing time to improve the transmission capacity of power system

The re-closing time of a transmission line has a distinct influence on power system transient stability. There is an optimal re-closing time (ORT) for all transmission line faults, no matter the instantaneous fault or permanent one. Based on the transient energy function (TEF) theory with classical models considered, the ORT can be calculated accurately. This paper mainly focuses attention on the validity and practicability of ORT obtained from this method. After analyzing the characteristic and influencing factors of the ORT, the setting strategy of re-closing time for transmission line is presented. And it will conduct simulations with a complex real system of China North Grid. Simulation studies show that this technique can significantly increase the security margin and damp the oscillation of the power system. It is indicated that the variation of ORT of a certain transmission line is insensitive to the influencing factors: the fault location, fault clearing time and pre-fault power flow. Finally, the setting scheme is drawn to optimize the re-closing time of the key transmission lines in the network under current technological conditions.