On 04/01/2018 15:36, Andy Burns wrote:
The Natural Philosopher wrote:

cost of repairing overhead 11KV fault. £2000.
Cost of undergrounding it - £30,000 per kilometer.

£250m for 8 miles in Stratford

https://www.arup.com/projects/london-2012-powerlines-undergrounding

Not 11 kV though: 132 and 400 kV.

A bit more detail here

http://www.icevirtuallibrary.com/doi....2011.164.6.11

Tunnels were 4.15 and 2.8 metres diameter.

I guess trenched undersea cables are much more lossy. It would be
interesting to know at what point it becomes worth going to DC.