National Grid’s Dorset underground cable installation project nears completion | New Civil Engineer

2022-05-28 07:44:07 By : Mr. Bobo Feng

With all the underground cables needed to replace overhead wires and pylons across the Dorset Area of Outstanding Natural Beature (AONB) laid and testing being carried out, the National Grid Going Underground project is close to completion.

The project involves the removal of 22 pylons and 8.8km of overhead cables and the laying of 108km of underground cables, with the purpose of diminishing the visual impact of electricity infrastructure on the landscape near the villages of Martinstown and Winterbourne Abbas.

The area’s steep slopes have posed challenges to the teams from Morgan Sindall and civil subcontractor MJ Church who are delivering the scheme. One particular incline was so steep that required the deployment of a specialist machine usually seen on the Swiss Alps.

“The notoriously sharp gradient of Corton Hill meant we had to anchor a spider digger to the hill during operation to ensure the safety of all involved,” said National Grid senior project manager Paul Hamnett.

Apart from the spider digger, an ex-military vehicle and specialist rope access training for cable layers were also needed for the preparation of the site and the successful installation of the power cables underground.

The cables have been laid in sections of 1km at a time and connecting these together required precise technical engineering. Once that process ended, testing began.

The site team has now successfully completed high voltage testing of one of the two underground cable circuits. Full circuit testing is due to be complete by June 7.

Aside from testing, work on site currently involves the restoration of the land to the way it was before the pylon removal and underground cable laying activities. Prior to the commencement of works in autumn 2019, National Grid took an exact scan of the undulations and tracks present on the hillside and has now been able to return this hill precisely to its original state.

This is not the only project National Grid is replacing overhead lines with underground cables to reduce the visual impact on the landscape. As part of the Hinkley Connection Project, it is installing 8.5km of underground cables in the Mendip Hills Area of Outstanding Natural Beauty ( NCE, June 2022).

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