NG PS(T) 081 PDF

PURPOSE AND SCOPE

This policy briefly describes the background to the current situation that exists with L3 towers with respect to non-compliance with National Grid's latest internal electrical clearance requirements and defines the policy for their continued use.

It is applicable to existing L3 lines operating at 275kV on the National Grid transmission system. It is equally applicable to planned 275kV new build or line diversions within an existing 275kV L3 route.

This policy is not applicable to schemes which are already in development and/or delivery at the time of issue of this document.

This policy does not consider strength or deal with climbing clearances. In common with other towers (including those designed internationally) the L3 tower was not specifically designed to allow for additional ‘climbing' clearance under live conditions. OHL Safety Bulletin 03-2006 provides guidance in respect of climbing on L3 towers.

A review of the relative reliability of the originally specified clearances compared with the new requirements along with the impact on performance of reduced length insulator sets is in progress. Following the outcome of this piece of work the Policy will be reviewed and re-issued.