On 20/08/13 13:40, Tim Watts wrote:
On Tuesday 20 August 2013 13:32 The Natural Philosopher wrote in uk.d-i-y:

On 20/08/13 09:03, Tim Streater wrote:
In article ,
Andy Burns wrote:

Tim Streater wrote:

And the cost, 10 times that of pylons. Anyone know the highest voltage
they put underground?
"Murphy is one of the UKs leading tunnelling
contractors with a wealth of experience in the design,
construction and fitting out of cable tunnels. We have
successfully delivered a number of high-profile
infrastructure power projects, including the Olympic
Park (132/400kV Cable Tunnels)"


http://www.murphygroup.co.uk/uploads...er%20Brochure/
Power%20Brochure.html#/8/zoomed
So 400kV underground has to be in a tunnel rather than buried?
I wouldn't be surprised

Is that AC? Not sure I'd like to be walking along next to it.

yes, HVDC is only worth doing for seabed or very long cables.


And more importantly, where you cannot phase lock both ends...


No. in the case of seabed stuff the capacitance to ground gives them a
lousy power factor. They need to be DC to avoid that.

Plenty of offshore HVDC links are done within one grid phase area.

phasing could easily be solved by reconverting AC to AC through an
inverter. That's not the reason to go DC which is PURELY to reduce long
line/high capacitance cable losses.

--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.