On 13/03/18 15:55, NY wrote:
"Tim Streater" wrote in message
.. .
In article , NY
wrote:

"The Natural Philosopher" wrote in message
news On 13/03/18 12:13, NY wrote:
What were the reasons for the UK having its own grid, with a *DC*
connection to mainland Europe? Was it just that the UK wasn't part
of Europe at the time, or was there another more technical, less
political reason?

Well you see its this odd and not very political thing called
GEOGRAPHY. You maye have heard of it although its not as fashoinable
as gay marriage, but what it means is that if you walked all round
the COAST like that ponce on TV you find that is water on every side!

And that means its a long way to string pylons in shipping lanes so
teh GB grid is naturally isolated and always was, since ints
inception in IIRC the 1930s

Yes, that's a very good reason for not having *any* connection
between UK and mainland Europe.

No, you run it on the seabed, or perhaps through the tunnel.

But given that there *is* a connection, is there a reason why it is
DC rather than AC?

Capacitance losses.

Ah. Yes that makes sense. 20 miles of overhead line would be fine (*)
but 20 miles of coaxial cable will have significant capacitance.

Its not coaxial I think, well only in the sense that the sea forms the
outer conductor, together with the armor..

http://www.caledonian-cables.com/pro...es/XLPE-Dc.jpg

is my understanding of a link. I am not sure whether a return cable is
provided or whether the sea does that job





As a matter of interest, how do they avoid the problem when overhead
lines are converted to run underground, eg when passing through an area
of outstanding natural beauty?

Or oustide my door


Do underground lines run as a single cable with three conductors (for
three phases)

yes

surrounded by a common earth,

no. There is no earth on 3 phase usually - ir maybe they use the armour
for that.


or are they three separate
lines, each with its own earth screen? Indeed is it necessary to have an
earth screen as long as the wires are suitably insulated?


Sometimes. It just depends on local conditions



(*) Apart from the "little" matter of suspending the wires across the
Channel :-)


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€œit should be clear by now to everyone that activist environmentalism
(or environmental activism) is becoming a general ideology about humans,
about their freedom, about the relationship between the individual and
the state, and about the manipulation of people under the guise of a
'noble' idea. It is not an honest pursuit of 'sustainable development,'
a matter of elementary environmental protection, or a search for
rational mechanisms designed to achieve a healthy environment. Yet
things do occur that make you shake your head and remind yourself that
you live neither in Joseph Stalins Communist era, nor in the Orwellian
utopia of 1984.€�

Vaclav Klaus