There was someone on another group in the past few months, maybe uk.railway? I think the poster was possibly German, and they were claiming that on the German grid, the system frequency during the loss of 1.5 - 2GW of generation (this was a one trip, one site event) with a system loading of 50GW was about 0.05Hz.
Yes you read that right zero point zero five hertz. So that's a larger loss than the Sizewell B Longannet incident of 2008 that resulted in a frequency of around
48.8Hz. No, I didn't believe it either!
Not got any measurements in Germany but the frequency moves about in Italy about the same as the UK.
People can use that little a day? We sit at around 20 units/day but then we aren't wage slaves so normally "in" so the daytime base load is about 1 kW, compared to the 300 W overnight norm. Still that only accounts for about five units of the twenty.
which are a visually redesigned proper fan storage heater like the commerc ial range. There will be a Smart Switch where that whirling (giggle) wind t urbine can dump electricity into it at suitable times as essentially a larg e dump resistor bank when the wind is blowing, generating electricity, when no-one wants it :-)
smart actual temperature regulation, fan only rather than leak output, ultr a high value insulation, they have a) created silly prices (£650 or so fo r 3kW) and b) forgot you need about 65mm+ Celotex on every wall in a 3 bed semi for it to have a chance of heating. Ok, 50mm XPS will do, but it is th e big stumbling block.
Whr limit, far below the typical 8-10 units per day people use (ignoring st orage heaters, electric chair for the wife / kids / bank staff).
y are not part of the recall. Quality is going to the dogs broadly, ironica lly surprised at Legrand French outlets & parts recently - highest end mode ls at eye watering prices on a house scale tho re NF100 requirements. Legra nd sockets seem to have a low plug retention compared to MK. Things might h ave peaked in quality, sadly :-(
Well I use less than that now and I have no gas and an electric car.
I've never understood why a load on the grid _must_ affect frequency. (and yet it does...)
A generator is shoving out a certain amount of power into a load. If the load increases (reduces its resistance) either the power goes up, or the voltage comes down.
I can see why the easiest way for the voltage to come down is for the generator to slow down. The coils aren't going through the fields as fast, so you get less power consumed. In the case of the grid, where all the generators are synchronously locked, if they all slow down then the grid frequency drops.
But why can't you just control the current into the field coils to keep the frequency spot on, and let the volts go up and down?
When the load increases, the generator output voltage will decrease, because of the resistance of the armature windings. However, this will probably be a minor effect compared with the voltage drop on the power distribution cables, and I'm pretty sure that somewhere down the line, at the sub-stations, there is some tap-switching equipment which tries to maintain a more-constant voltage at the customer. Unfortunately, this will result in a further increase of the load on the generator.
Also, as the load on the generator increases, it will slow down, and the guys at the power station will try to maintain its speed by (literally) putting more coals on the fire in order to increase the drive power to the shaft of the generator, and to apply more voltage to the field windings (to increase its current, and thus maintain the output voltage).
Unfortunately, if the load is so great that not enough coals can be put on the fire quickly enough, something has to give - and there are only two things that can happen. One is that the load has to be reduced (and I guess that this is usually done by switching the customers to a slight lower voltage - although in some cases, this may mean that some will then try and draw more current to compensate). Alternatively, the output voltage of the generator itself could be allowed to fall by reducing the field current (although this might cause complications at the tap switchers). The other alternative is to allow the generator to slow down. In practice, in the home, we usually see both effects, ie that the voltage is lower that we normally get, and frequency is less than 50Hz.
Reminds me of my mock Physics practical A level back in nineteen canteen.
I'd been given the problem of measuring the cubic coefficient of expansion of a liquid, using a precision flask with a capillary stopper. The liquid smelled strongly of paraffin, but a whispered conversation about my result with the chap next to me suggested that the liquid was in fact water.
When the teacher handed out the results (I got good marks) he admitted that it was water with an added drop of paraffin.
And further thought has suggested that even really dousing yourself in petrol might not help - the taser-armed person might assume it was water with a drop of petrol...
Germany doesn't have a grid - it's part of a much larger sychronisation zone which covers all EU countries between Portugal and Romainia, and is controlled from Switzerland. (Also includes some north african countries via a Gibraltar link, but I doubt that passes a large amount of energy in relative terms.)
Originally all the eastern (political) european countries were part of the USSR synchronisation zone, but they've been gradually moving across. It was an interesting issue when the Berlin Wall came down - the West was 50Hz +/-0.1Hz, and very short of power, and the East was 50Hz +/-1Hz (but often a larger drift), and with a surpless of power, but very poluting power generation.
reach a new level and the power goes off !!!!!!...
Now it would bypass the UPS as it would be direct to yuor computer, it would be a chipmon the mother board. And as UPS are basically inefficient the'y be the first to be switched off if teh tech was available.
Should have said "Not an independent grid", I think.
The German grid is tied into other European countries by direct wiring, so the whole of that zone works as a "grid". The UK is only linked to the mainland by DC links, and the inverters at each end are locked to their respective grids, so our internal transmission frequency and phasing can and does vary from the mainland grid.
Oops, 'EU' should have said Europe. (It's nothing to do with the EU.)
The post was talking about 50Hz stability, but Germany doesn't control that - it's part of a single synchronisation zone covering lots of countries (including Italy which was also mentioned), which have a single supply infrastructure. This is the zone over which supply and demand are matched using directly connected sychronised generation.
We are also connected to this, but not sychronised - we are our own synchronisation zone and separate grid, and our 50Hz can drift against the Europe 50Hz.
2GW loss is a much smaller proportion of the European zone than it is of our zone.
It is a grid, but covers all the countries in the Zone, not just Germany.
Which doesn't negate the fact that the freezer effort will depend on the ambient temperature, which could be very different between a heated kitchen and a cold pantry, even if they are both constant.
Whilst I'm inclined to believe the latter part I don't think the first is quite right. Agreed the early "smart meters" may have been not much more than a meter with built in energy monitor but I think the ones going in now are the proper "smart" ones with remote reading that doesn't require visit or even a van driving down the street polling the meters.
So switching a running fridge pot is 'harmless'? Off is OK but if the pot has been running for some time, so that the pressure in it it high and is then turned off for a minute or two and then back on, it's starting on load. If I need to turn off my freezer I always try to do it when the pot isn't running. If there's a supply fault that's on-off, the freezer then any computery things are first to be switched off. Lights and heaters are OK to greater or lesser extent (oh dear, blown a CFL, what a pity).
The frequency of the alternator depends on it's speed which depends on the speed of the driving device. To vary power output/maintain voltage, the excitation current is varied.
This means that the mechanical input torque has to be increased if excitation is increased. If this fails to happen the frequency will fall.
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