On the Dynamic Response of Static Var Compensators in Faulted Transmission Systems

This paper assesses the performance of static var compensators (SVC) connected to power systems during short-circuits and reclosing procedures. The long transmission line used for simulations interconnects two substations in Brazil, which are close to the wind and photovoltaic parks. The real parameters-based 500 kV power system is modeled in the EMTP-RV software, as well as the distance function-based relay. The SVC is connected at a terminal of the transmission line, and it is composed of a thyristor-controlled reactor (TCR) and thyristor-switched capacitors (TSC). The power system is then submitted to short-circuits mainly with different types and fault resistances, as well as to single-pole and three-pole reclosing scenarios. This work then allows to visualize in detail the sequence of the control scheme by analyzing the susceptance, the firing angle of the TCR, and the logic states of TSCs. From the results, it is demonstrated that the type of fault and reclosing, depending on the number of faulted phases, as well as the transmission line loading and fault resistance, are relevant factors to modify the SVC response. In addition, the simulations demonstrate that the SVC may be submitted to severe efforts in the case of three-pole reclosing of transmission lines once the reactive power to be delivered is higher if compared with the single-pole reclosing procedure, reaching even its operation limits. Finally, this kind of study could help to define the best alternative to switching the transmission lines during faults watching out for the lifetime of the compensation equipment. This evaluation may be relevant, especially in renewable resources-penetrated power systems where these power electronic devices could be allocated.