A rationalised policy for application and setting of back-up protection on the CEGB supergrid system

There has been increasing pressure from system operators for back-up protection settings which allow unrestricted use of primary plant loading capability. Performance objectives and a setting policy for back-up protection have been developed. The setting policy provides an acceptable compromise between the conflicting requirements of protection sensitivity and system loading. It also seeks to minimise the engineering resources required for the determination of the settings