Ideal electrical systems (just idle curiosity)

[John Williamson]

Don't confuse him with facts, or it'll all end in tears.

[John Williamson]

There is a niggling, and mostly insignificant loss in that the insulation isn't a *perfect* dielectric, but yes, the main losses are in the conductors.

[Tim Watts]

Are they phased locked? I don't know.

If they are, then they have relatively long borders which means lots of interconnections.

You aren't going to hold 2 disparate grids in sync with one or two cross channel links - National Grid has enough trouble holding the UK grid in phase between Scotland and the South (they have (or had at Bankside at least) a phase indicator colloquially known as the "scottish wobblemeter".

If it started oscillating, a certain amount of panic ensued...

Yes. There's an interesting document that you can google for which outlines the Nat Grid Blackstart procedure. Rather involved...

[jgh]

Sorry, I still don't understand this. We're talking cables not capacitors. How does a 16mm2 PVC insulated cable have a higher resistance if it's immersed in water than if it's in a vacuum?

jgh

[Nightjar]

Exactly the type I used for the computer stack at my factory. I still have much of a reel of 16mm flex that I used for the plug. I keep meaning to use some of it to replace the bit of 10mm cable that connects to the back of my cooker.

[The Natural Philosopher]

It doesn't. BUT it has a higher out of phase current flowing through it due to greater capacitance to earth.

[The Natural Philosopher]

No, They said that once they had switched off each end, that was what they did to discharge the cable

[The Natural Philosopher]

Its not. It is plain WRONG because 'dielectric' losses are losses incurred IN a dielectric due to it having e.g. resistance.

[The Natural Philosopher]

That I can agree with..

[The Natural Philosopher]

Most of Europe is phase locked.

There is an interesting situation also in that Germany's neighbours are actually being forced to balance the N-S parts of Germany's grid because Germany itself has loads of solar power in the south and wind power in the north and there are significant power flows between N and S in excess of what the German grid alone can handle.

The cost of handling the excess is borne by e.g. Czech republic which has made serious noises about disconnecting itself from Germany as the whole power flow is destabilising its own grid.

[Tim Watts]

It doesn't. It has a lower Line-Earth reactance (capacitative) - at least that is what's being claimed.

However, the cables are all armoured so it does not really matter if they are in a dry tunnel or under the sea.

The big difference is a cable vs overhead lines.

[Tim Watts]

Fascinating. I would have thought they would have avoided that due to the buggeration factor.

Is there a supergrid organisation that manages this euro-grid at the top level then?

[John Williamson]

All the mainland European networks are phase locked by necessity, as they move power from one to the other on a regular basis in all directions.

They do.

[John Williamson]

The *resistance* doesn't change. When transmitting AC, however, the

*impedance* does change, both due to the capacitance to earth, and, if the frequency is high enough, "skin effect", which is where the current flow is restricted to the areas near the surface of the strands also starts to come into play.

[John Williamson]

You could say that. Or you could just call it huge.

[harryagain]

All AC circuits have resistance, inductance and capacitance. With long cables, the resisatance and capacitance effects become more important.

Capacitance depends on the nature of the insulation, the surface area of the conductors and the distance apart they are. With overhead cable, the distance apart is much greater than with underground cables. So capacitance is much more with the latter. Also the permitivity of air is much less than plastic insulation.

[harryagain]

There is a small amount of energy taken to reverse the electric field.

[The Natural Philosopher]

Mmm. Not sure that is so, but cant put a finger on why I feel its different..

Yes.

[The Natural Philosopher]

I really don't know.

I think each nation has its own but presumably they have to phase lock with each other before they start interconnecting

[Graham.]

In the TV repair trade, getting a painful belt was almost a daily occurrence and elicited little comment, other than ones swear word of choice. I'm perplexed how the ESC managed to catalouge what was never reported.