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newshound newshound is offline
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Default *Five* wire overhead mains cables

On 21/04/2021 09:07, The Natural Philosopher wrote:
On 20/04/2021 21:40, newshound wrote:
On 20/04/2021 14:08, The Natural Philosopher wrote:
On 19/04/2021 16:09, newshound wrote:
On 17/04/2021 11:11, The Natural Philosopher wrote:
On 17/04/2021 09:11, Andy Burns wrote:
ARW wrote:

Andy Burns wrote:

ARW wrote:

insulating spacers to stop the phases getting too close in the

Yep. I see it when I look further down.
And a customer sent me this last week

But those "X" spacers which the commentator says are to stop them
shorting the system, are on wires of the same phase!

they are to stop wires *chafing*,when on the same phase.

No, the X spacers for the four conductors on each phase of supergrid
lines give the overall conductor an electric field distribution more
like a larger diameter conductor, reducing the corona losses.

No, that's what 4 wires instead of 1 does... the spacers are to
*keep* them 4 wires...:-) imagine 4 wires that close in a gust of

I guess
they also reduce the conductor temperature at a given current from
the level if all the aluminium conductor was wrapped around a single
steel (load carrying) core.

Mmm. greater surface to volume? nah. I think that works the other way
cross section goes up as radius squared but area only goes up as radius.

Have I got that right - the cross section of 4 wires is the same as a
single wire twice the diameter so surface area of single wire is 2 pi
D whereas its 4 x pi x D for 4 wires...-oh ok, you are right. All
other things being equal that should run cooler - although from
memory they don't mind them getting hot, its the resistance they
don't like.

Conductor temperature has other significance. They can (and do) carry
more current in the winter than the summer while staying within the
"sag" allowance from thermal expansion. A rare example of Sod getting
it wrong.

Also factor in the mundane. Nice to stock just one kind of overhead
cable and get 4 x current carrying capacity with a few spacers and
different insulators.

You could be right although I suspect that each supergrid voltage has
its own optimised cable. I'm pretty sure the individual insulator
elements in 275kV and 400kV are different (as well as the stringers
being longer for 400).

That is a straw man. times 4 conductors increase powwer capacity *at the
same voltage*

Its a neat way to up the power without having to increase voltages which
would probably in the end cost more

No, it would be cheaper to do that with one fat wire, which would need
slightly more conductor to reduce the heating effect. THE REASON FOR