Scottish & Southern Electricity Networks has applied a minimum nine-metre clearance from the ground to overhead wires as a default along the route of the Tealing to Kintore upgrade Project (“TKUP”) and suggests that only half of the proposed route will achieve clearances in excess of 11 metres.

TKUP is partly publicly funded and has been given Accelerated Strategic Transmission Investment (ASTI) by the electricity regulator Ofgem. ASTI requires a minimum height for overhead lines which varies according to the voltage carried; for a 400kV line that is nine metres. The designers appear to have omitted to obtain adequate information from landowners with regards to the height of machinery habitually used along the length of the proposed project, to inform them on design risk.

SSEN has selected a route through prime agricultural land from the outset, but appears to be designing to minimum standards rather than considering all the risks. Along the proposed route, large machinery is used often and typical sizes are increasing. For example, a combine with its discharge auger out, when filling a trailer during harvest, is currently about 6.50 metres high, which would suggest a minimum 9.6 metres from the ground to provide safe clearance. Self-propelled forage harvesters used on upland grassland for silage production have similar heights.

Design freeze

Sprayers used across Angus and Aberdeenshire, when folding booms to manoeuvre round an obstacle, can be up to 10.5 metres high. SSEN’s project is now well advanced and will shortly be going to ‘design freeze’, with no further design changes anticipated, before the final consultation takes place prior to planning permission being sought. Decisions taken during the design phase should result in a line being built that keeps everyone safe along the route. As affected landowners are now finding, there appear to be flaws in the process.

Agricultural equipment or even water from irrigators used along the route coming into contact with an overhead power line can conduct electricity through to earth, with potentially lethal consequences. Electricity can sometimes ‘flash over’ or ‘arc’, jumping across gaps.

SSEN appears to suggest it is for those working underneath high-voltage lines to address safety issues. That may be so for existing installations but not for new projects. Under the Construction and Design Management Regulations 2015 (“CDM Regulations”) those responsible for the design of new construction projects must critically assess proposals from the inception of the project and throughout the design process, to eliminate or minimise the risk of death or serious injury.

This involves evaluating and addressing the risks that may arise from design decisions such as pylon heights. This approach aims to achieve safer construction while promoting long-term safety for building users, maintenance teams, and the public. It would seem however SSEN and its principal design contractor Balfour Beattie have focused on reducing visual impact by working to minimum heights rather than addressing the risk to those working on the land.

Prime farmland

SSEN points out that larger towers increase the cost of the project. It is also concerned that the increased footprint of larger towers would lead to a greater loss of prime agricultural land. Mr Thornton-Kemsley said this should have been considered from the outset. He is concerned that, having chosen a route through prime agricultural land, SSEN appears to be focused on cost and visual impact rather than the safety of farmers, their workforce and their businesses.

The surveyor and his team have called on SSEN to ensure TKUP fully complies with the CDM Regulations and ensure the proposed line is safe and future-proofed to protect agriculture productivity.

SSEN has tried to limit pylon heights to 57 metres and consultations to date have been based on this. Significantly higher pylons may require further consultation. SSEN already faces considerable opposition to its proposals. Campaigners highlight environmental risk, impact on agriculture and visual impact on some of Scotland’s best-loved landscapes. The utility says existing 275kV overhead line cannot be upgraded to 400kV as the lines would not achieve the 9-metre minimum clearance due to the size of the towers. The CDM regulations apply as much to upgrade projects as well as the new line.

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