Mitigation of transient recovery voltage issues associated with transmission capacitor banks

The failure of several transmission capacitor banks prompted The United Illuminating Company to perform an engineering study to evaluate the transient recovery voltage capabilities of existing 123-kV, oil-filled capacitor bank circuit breakers at the East Shore 115-kV substation. The study determined if the transient recovery voltage capability of existing bus and capacitor bank circuit breakers is sufficient for the present system configuration. Furthermore, the study determined the required design and application changes related to the circuit breakers and capacitor bank component equipment, required to ensure that the bus and capacitor bank circuit breaker transient recovery voltage capabilities are not exceeded. The study recommended a future capacitor bank configuration to mitigate transient recovery voltage issues. The results of the study also lead to an expansion of the study area to include an adjacent substation, Grand Avenue Substation, due to concerns about the required transient recovery voltage capabilities of new gas-insulated switchgear to be installed.