I've just been doing a bit of surfing for power cable specs on the Net, when this site popped up.
As you may remember, Auckland was crippled by a catastrophic failure of it's 110kV feeders into the city in the early part of 1998, blacking out most of the CBD.

http://www.cs.auckland.ac.nz/~pgut001/misc/mercury.txt

BTW, watch out for the jokes at the bottom of the page!.

Heck Trumpy - that is one interesting article! Thanks!!

What a faff the oil/gas-filled lines are.

The author is obviously no fool .

No problems, UK sparky!.
Also, here's a related file that goes into the causes of the faults that caused the blackout.
There is a rather interesting part at the end of this PDF file that talks about cables moving inside thier conduits, this concept was discovered by the UK Post Office as far back as 1921!.

http://www.med.govt.nz/inquiry/failtech.pdf