scope:

PURPOSE AND SCOPE

This Technical Guidance Note (TGN), in conjunction with related functional specifications, details the requirements for Selective Protection Asset Replacement (SPAR) within TPS 5/33 and hard-wired feeder bay protection panels/cubicles on feeder bays at double busbar and mesh substations on National Grid's 400 and 275 kV transmission system.

Selective Protection Asset Replacement (SPAR) projects in TPS 5/33 and hard-wired protection panels/cubicles comprise the replacement of existing obsolete feeder main protection relays with modern numeric protection relays, whilst retaining the existing bay infrastructure as far as possible and necessary.

In terms of primary protection functionality, in all but exceptional cases, the new feeder main protection relays shall be a like-for like replacement of the existing feeder main protection relays, whilst at the same time enabling in the relay as many of the requirements of relevant current National Grid Technical Specifications as practicable.

This TGN defines what the functional requirements for SPAR projects are and in particular those areas where deviations from current technical specifications and policy are required and permitted.