On Mon, 19 Aug 2013 22:06:50 +0100, Nightjar
wrote:

On 19/08/2013 21:36, Tim Streater wrote:
...
And the cost, 10 times that of pylons. Anyone know the highest voltage
they put underground?


The National Grid provides design data for 400kV underground cables, so
presumably they have some of those.

Quite a few of them, some under major cities.

For instance in London, mainly 400kV cables

http://www.nationalgrid.com/NR/rdonlyres/3C010C53-8431-4B34-A573-5FF88A1BB361/48551/TQNW.pdf


In the UK the highest voltage is 450kV for the BritNed link (submarine +
underground) There are 500kV underground cables in USA & Canada.

There is / was an overhead only line operating at over 1000kV in Kazakhstan and
there are lots of 765kV lines in North and South America, South Africa, India &
China.


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