Distributed on-line HV transmission condition monitoring information system

China Light & Power Company Ltd. (CLP) is responsible for supplying electricity to the whole of Hong Kong except Hong Kong Island and Lamma Island. In CLP's Castle Peak power plant, 18 kV and 23 kV electric supplies are generated. The voltage is then stepped up to 400 kV for transmission. The intermediate control between those transformers and the major 400 kV overhead transmission system lies with a standard `One and a half Breaker Configuration' switch substation. The substation houses single phase encapsulated SF6 circuit breakers. In the urban centres, 400 kV substations are installed to step down 400 kV to 132 kV or further to 11 kV for distribution. This paper describes the development of a on-line distributed information system for monitoring the conditions of the whole HV transmission system. The system continuously monitors status of each circuit breaker (CB) together with important operational parameters, such as duration during making and breaking, operations of hydraulic pumps and SF6 gas pressure etc. Each group of CBs is monitored by a standalone microcontroller which is interconnected with all other microcontrollers using a local area network with a baud rate of 9,600. The information can be recorded on the harddisk of an on-site microcomputer and further transmitted back to a remote computer for alarm generation and multi-station supervision. The CLP 400 kV substation and the Tsz Wan Shah 400 kV substation are amongst the first targets for development.