MINIMAL TRANSIENT SWITCHING OF CAPACITORS

Capacitor banks are used to compensate the reactive power demand of la rge commercial and industrial loads. When used to switch capacitor ban ks mechanical breakers generate large current transients. These transi ents may cause serious system disturbances, premature wear of the brea ker contacts and, possibly, shorten the life of the capacitors. While thyristor switches are not new and industry has successfully used them to obtain transient-free switching of capacitor banks, there are very few papers, describing this application. This paper tries to fill the void and presents a comparative study of various three-phase configur ations of semiconductor switches intended for low voltage (600 V and l ess) distribution systems. Simple theoretical analysis enables the cal culation of the optimal switching times to minimize transients. These calculations take into account the system impedance and the initial ca pacitor voltages.