scope:

PURPOSE AND SCOPE

This Technical Guidance Note (TGN) addresses the application of metal oxide surge arresters to provide over-voltage protection and control of substation primary plant on the National Grid Transmission (Electricity) system. Surge arresters are deployed for the surge protection of transformers, reactors, gas insulated switchgear (GIS) substations and for some reactive compensation. This document expands on the policy statement PS(T) 021 'Surge arresters for substations', implements the recommendations made in TR(E) 409 'Over-voltage protection in substations using surge arresters' and provides further information on the requirements detailed in the policy.

This document does not cover the over-voltage protection of overhead line circuits, cable sheath voltage limiters (SVL) for cable bonding systems, HVDC converters and power electronic systems.