Switching Analysis of a Transmission Substation and Its Effect on the Downstream Sub-transmission Substation: A Case Study

The switching overvoltage is one of the main causes of faults and failures in power systems. In this regard, in order to avoid unpredictable outage and increase the network reliability, the investigation and identification of such overvoltages is of vital importance. Toward this goal, through extensive simulations in EMPT software, this paper investigates the voltage disturbances in a sub-transmission substation, which is caused by the switching of its respective upstream transmission substation. Various scenarios, including both the daily scenarios and faulty scenarios, in a 400kV air-insulated substation are considered and their effects on downstream substation are analyzed in order to investigate whether or not successive cable failures in downstream substation is due to these switching activities. Simulation results show that the damping of transient overvoltages are remarkably influenced by not only the length of underground cables and overhead lines, but also the operation of the surge arrester.