PURPOSE AND SCOPE

New OHL tower routes and existing legacy OHL tower routes that are to undergo structural analysis as part of a refurbishment or uprating scheme should be the trigger for the implementation of this technical guidance document.

The objective of this TGN is to comply as far as is reasonably practical with BS EN 50341[1] and that the associated cost of mitigation chosen to comply with the above standard be capitalised as part of necessary safety works against that scheme.

This document details the process which should be used to determine the need for and choice of mitigation when managing risks to third parties from rise of earth potential (ROEP) seen during local circuit fault conditions on or adjacent to NGC owned ‘Often Frequented’ towers (see Figure 1).

Legacy OHL routes that are not subjected to tower structural analysis as part of a refurbishment or uprating scheme should not be considered as falling within the scope of this document. In cases such as this, identification, verification and implementation will be by other means.

For in-depth detail associated with touch, step and transferred potentials see EA TS 41-24 [2]