On site testing of protection and automatic switching equipment in 275 and 400 kV substations

Protection performance is dependent on the availability of accurate and reliable protection relays and their connection to high quality measuring transformers and well designed tripping systems. But it is only in the substation that all elements of protection systems are brought together during site installation and hence can be tested for the first time. The author describes the re-examination of on site testing requirements and methods undertaken during CEGB reorganisation. He shows that the introduction of new technology and increasing system utilisation factor has been fully taken into account