The application of controlled reactive power compensators in electric distribution networks, whether for power factor improvement, losses reduction, voltage control or released capacity has been accepted as a necessary step in the design of distribution systems. The operation of such equipment necessitate the switching on and off of steps of capacitor banks. Such switching procedure are normally accompanied by transient over current and transient over voltages This paper presents the results of studies of transient over voltages in electric distribution networks due to the installation of switched capacitor banks on the secondary side of primary substations. Transient over voltages due to the switching off steps of the capacitor banks are obtained for both the primary and the secondary sides of the primary substations. The results obtained give an explanation for the problem of terminations failure on the high voltage side of the primary substation. The study is very helpful for manufacturers, operators and planners, for the suitable choice of equipment type, size and steps of capacitor banks.
