scope:

PURPOSE AND SCOPE

The Technical Specifications for all new plant, equipment, apparatus and services, for use on the National Grid UK Electricity Transmission system are contained in a three level hierarchy of documents. Level 1 covers ratings and general requirements, Level 2 covers major plant categories and Level 3 covers specific related plant functions.

This document is a Level 3 specification, which describes the functional and performance requirements for a system to lock-out delayed automatic reclosure (DAR) sequences following the occurrence of a cable, gas insulated busbar (GIB) or gas insulated line (GIL) fault on a composite overhead line (OHL) and cable/GIB/GIL circuit.

PS(T) 010 , Application and Protection Setting Policy for the National Grid UK Transmission System defines when cable/GIB/GIL lockout should be applied. It must be emphasised that the default position for any particular installation is not to apply a DAR lockout system, it should only be applied where a suitable risk assessment has determined there is an unacceptable level of danger to National Grid staff or the General Public from a potential reclosure onto a faulted cable or GIL/GIB section.

This specification refers to Cable DAR Lockout in the sections below; it is equally applicable to GIB or GIL DAR Lockout.