Protection Scheme for the HK Electric's New 132kV and 22kV Busbar Configurations

New 132kV and 22kV GIS / Insulated busbar configurations will be adopted for HK Electric's MRS Substation. Unit busbar protection is used to ensure prompt and discriminative isolation of the faulty busbar and to minimize the supply interruption to customers. Traditional high impedance differential protection is applied as main protection for the busbars of the new 132kV and 22kV busbar configurations because it is simple, reliable and well-proven in HK Electric This paper describes a non-conventional design of the busbar protection system for the new 132kV busbar configuration with an aim to enhancing the protection availability while maintaining adequate selectivity and discrimination. For the new 22kV busbar configuration, special features like feeder common overcurrent and earth fault (OCEF) protection, rough balanced back-up OCEF protection and cross-tripping of bus-interconnector circuits are introduced to minimize the impact of abnormal conditions such as protection / circuit breaker failure during fault in the 22kV system.