In England & Wales, the only major new electricity transmission lines built in the last 10 years by National Grid are all in the London Power Tunnels Project. This involved 32km of tunnels and 64 circuit kms installed from 2011 to February 2016. Otherwise, major projects have been asset replacement projects. These have generally been like-for-like, in that overhead line components have replaced older overhead line components, and underground cables have replaced underground cables.
In the north of Scotland, of SHE Transmission’s total new circuits in the last 10 years (1,007km), 171km of these were underground cable (approx. 17%).
In the south of Scotland, of Scottish Power Transmission’s total new circuits in the last 10 years (184km), 107.5km of these were underground cable (approx. 58%).