Goose interlock overcurrent protection for 11KV double-busbar substation

Abstract

The hard-wired 11kV Interlock Overcurrent Busbar Protection (ILOC BBP) scheme has been widely applied for the protection of 11kV double-busbar switchboard. Its design is based on a general blocking scheme through the use of programmable logic techniques in numerical relay application. For continuous improvement in the performance and reliability, a new ILOC BBP scheme has recently been developed successfully based on the Generic Object Oriented Substation Events (GOOSE) messages under the well proven standard of IEC61850 for the design of electrical substation automation. Intelligent Electronic Devices (IED), i.e. protection relays with network port, are connected to Ethernet Switches, with the GOOSE messages used for the exchange of protection signals in such a way to determine whether the system fault is located on an outgoing feeder or a busbar section. Comparing with the hard-wired ILOC BBP, the implementation of GOOSE technology provides faster fault clearance, eliminates huge amount of multicore cables and minimises engineering work activities. However, it raises the issue of the reliability of GOOSE message transmission. To overcome this problem, an intelligent communication supervision scheme is developed. It adopts software logic of modern protection relays instead of the hard-wired scheme, and provides supervision and recovery function on GOOSE messages. A pilot project was established to evaluate the benefits of GOOSE technology in 11kV Busbar protection for cost saving and performance enhancement. This paper details the development, implementation, problems encountered, operation and service performance of the GOOSE ILOC BBP scheme commissioned by a team of engineers from CLP Power Hong Kong Limited.