Modern methods for synchronous switching of circuit-breakers in 400 kV substations of the Romanian Power System

The papers show an interesting case of two 400 kV substations, two of the most important substations of the Romanian Power System called Tantareni and Urechesti. In each of these two substations there are two and one shunt reactors respectively. In the paper the modern methods are summarised for synchronous switching of circuit-breakers, especially the ones of the shunt reactors, in order to limit the transients that occur. Breaker switching causes transient over- or undervoltages and/or overcurrents in the system that cannot always be tolerated. The magnitude of the transients depends on the phase position at which the switching takes place. At conventional switching the phase position is determined at random on each switching occasion, which means that switching in a very unfavourable phase position will occur sooner or later. Conventional transient limiting methods, e.g., preinsertion resistors, are dimensioned taking this into consideration. The synchronous switching enables synchronisation of the switching moment so that switching always takes place in a phase position that eliminates the switching transients or limits them as far as possible. This technique is an alternative to conventional methods and gives, where it is suitable to use, a smoother switching operation. The switching is performed by the Switchsync F236 synchronisation unit.