Power cut

[Brian Gaff]

You should read the previous thread before starting a new one? Brian

[Brian Gaff]

Later estimates put the number higher once it transpired how much of the rail network it had affected. Brian

[Brian Gaff]

Well I'm not sure where you were, but a friend was on a boat in the estuary of the River Fal, and five foot waves meant they had to go back.

I think the problem with the weather may well be a contributory factor for the wind turbines, the suggestion is where the power comes ashore. Anyone know how this is done?

Brian

[Brian Gaff]

I don't thin you can blame Winds Turbines on the EU. I can remember many years ago that Tomorrows World reported on a company on the Isle of Wight making them for export. I under stand that operation has shut down though. We are not very good in holding on to our technology and exploiting it. Brian

[charles]

I was in my car !

when a transmitter goes off, the power failure may easily not affect the entire service area

[Andy Burns]

Only going by what I saw reported ...

Actually today I've heard 1 million *premises* reported, so several times that in terms of people

[Steve Walker]

Some of the current DAB sets are not too bad on batteries, they have improved tremendously. They obviously can't match the longevity of the pocket fm radio that I sometimes have on when I'm doing DIY ... that'll run for many weeks before needing new bateries.

SteveW

[tony sayer]

Invisible hidden windy mills:)

Their half way up but done tell anyone:!..

[Bob Eager]

The main radio I use for DIY (i.e. needs to be portable) is a Bosch PRA Multipower. We have at least 5 rechargeable batteries that fit it!

Not DAB, but it'll Bluetooth from my phone.

[harry]

I heard it's to do with asynchronous generators and wind turbines.

[Vir Campestris]

The paper mentioned that there was a National Grid tweet about record wind power.

Half an hour before it all went bang... Paper didn't seem to think this was ironic.

Andy

[Max Demian]

I don't understand all this frequency business. Do all generators on the grid have to be synchronised exactly? If not, how does it all work?

[Andy Burns]

Yes.

[Max Demian]

How do that with sodding great dynamos all round the country that all work in different ways?

What about wind turbines that go fast or slow depending on the wind?

[Chris Green]

Yes, they do.

[Andy Burns]

They're only coupled via rectified/inverted electronic links, that's why they don't count as spinning mass as far as the grid is concerned,

[Andy Burns]

By all running at 50Hz, and getting them into sync before joining them to the grid.

[Chris Hogg]

If they weren't, imagine what would happen if one generator was at the peak of it's positive half cycle, and another at the peak of its negative cycle, both connected together via the grid. Bang! (I know it's all three phase and that's probably a gross oversimplification, but it satisfies me!).

[NY]

I've seen a design for a very simple phase indicator for use in getting a generator in phase with the mains before switching over. It involves a few diodes and a tungsten light bulb, but I forget the details. I think the lights go out (or to minimum brightness) when the two generators are in phase and it is safe to switch over.

Once a generator is in phase with the grid, it tends to stay in phase because any departure from phase causes the rotor to speed up or slow down (negative feedback) until phase lock is resumed.

[Martin Brown]

They synchronise them into phase match frequency before they join the grid. Otherwise they would be fried to a crisp. Once they are a part of the grid the entire lot are rotating in lock step. Load tries to slow down the frequency acting as a drag on the system and power input from gas/coal/PV/wind tries to speed it up. They keep it in close balance.

If the load is too much then the frequency and voltage drop until either it balances again naturally or active countermeasures (load shedding) is triggered. Typically you find the mains runs slower at times of peak load and a bit fast in the middle of the night. They have a duty to maintain it to nominal 50Hs averaged over 24 hours so that classical mains synchronous motor based clock mechanisms keep good time.

It gets typically converted into DC and then into matched frequency AC by a grid tie converter. A scaled up much beefier version of the inverter that is used to tie a domestic PV setup to the grid. eg.

Brochure for a 12MW unit.