A New 115-Kv Stored-Energy-Type Capacitor Switch [includes discussion]

Shunt capacitors for supplying leading reactive for power factor correction have been used on power systems for a great many years, but it is only recently that large shunt capacitor banks have been extensively applied to power systems at primary transmission voltages. Such applications have given rise to a requirement for satisfactory high-voltage switching equipment at minimum cost. Up until the present the power system engineer has had but little choice of equipment other than the standard commercially available power circuit breakers for his capacitor switching applications. Such circuit breakers were fundamentally designed for the relatively infrequent interruption of system fault currents, they were very often without special design considerations for interruption of capacitive currents, and were so costly as definitely to restrict the economic feasibility of many potential applications. Conversely, a capacitor switch should be designed to function satisfactorily when subjected to a very large number of routine switching operations, possibly several per day, without frequent maintenance periods; it may be designed with relatively low fault-interrupting capacity, as fault protection is usually obtained by individual capacitor fuses and station bus differential; and it should be designed for minimum cost to extend the range of economic feasibility of shunt capacitor installations at transmission voltages. Field tests on a prototype of such a switch have now been successfully performed and are outlined in this article.