The Impact of Shunt Capacitor Installations on Power Circuit Breaker Application

The duties to which power circuit breakers may be exposed when applied electrically close to shunt capacitor installations are studied. It is shown that, even when the application does not require the breakers to switch capacitors in and out of the circuit, they may still be exposed to capacitive switching duties during close-in faults. In some cases this duty can exceed the breakers' preferred ratings given in ANSI C37.0732-1972. Specific examples are given. Calculation methods for determining the duty imposed on breakers are presented and methods of reducing or eliminating this duty are discussed.