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Topic Title: 47HZ cut-off
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Created On: 28 April 2013 09:20 PM
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 28 April 2013 09:20 PM
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jcm256

Posts: 1792
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Will there be any problems with this


Big brother to switch off your fridge: Power giants to make millions ...
Daily Mail-27 Apr 2013
Fridges and freezers in millions of British homes will automatically be switched offwithout the owner's consent under a 'Big Brother' regime to ...
 28 April 2013 09:30 PM
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leckie

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Keep your old appliances working. And don't let a man into you house if he is carrying a chip and says he wants to look at your fridge!
 28 April 2013 09:36 PM
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slittle

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It was discussed on a larger scale at a recent DNO meeting.

The smart grid could/will by agreement with big users such as supermarkets disconnect their freezers for a period of say 3 hours on the understanding it will only do it once in say 24 hours to allow the freezer to recover.

Makes sort of sense to me, if the grid is struggling with high demand, dump some un-necessary loads.


Stu
 28 April 2013 10:03 PM
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peteTLM

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Originally posted by: slittle

It was discussed on a larger scale at a recent DNO meeting.



The smart grid could/will by agreement with big users such as supermarkets disconnect their freezers for a period of say 3 hours on the understanding it will only do it once in say 24 hours to allow the freezer to recover.



Makes sort of sense to me, if the grid is struggling with high demand, dump some un-necessary loads.





Stu


As far as i know this has happened for years, frozen food distributors, steel works, water treatment plants etc etc. They get compensation for the loss of supply.

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 28 April 2013 10:20 PM
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Legh

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Would it be useful to know what other electrical equipment gets turned off at 'night' or whenever power is at a premium. Security lights, intruder alarms, fire alarms, cctv, access control systems, street lights?

We know that TV's already go into auto shutdown after a period of inactivity .

So a solution might be If we embedded 'chips' in peoples heads we could turn them off at the most 'appropriate' time, then they wouldn't be able to operate electrical equipment?

I'm sure there's much brain storming and 'out of the box' thinking going on somewhere....

Legh .....switching off for the night due to lack of energy......

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 29 April 2013 10:47 AM
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AJJewsbury

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I gather some industrial gas consumers already have a tariff whereby the gas operator can demand they stop using gas when there are distribution problems (e.g. cold snap and domestic usage increases). In return they get a lower unit price for the rest of the time.

The next stage will be a tariff for some consumers to back feed power into the grid at times of high demand/low generation - aimed at electric car owners who could elect to give up some of the power from their car's batteries if it was connected to the charger in return for dosh.

- Andy.
 29 April 2013 11:07 AM
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OMS

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It's not that sinister chaps - just a first step towards demand side management.

As for all the horror stories regarding a big brother spy in your fridge, water heater, heat pump etc then do try to get a grip. It's a fantastic conspiracy theory but in reality it's going to be a frequency monitor factory fitted to new appliances that will drop out the relevant bit of equipment when the frequency is out of spec - frequency being a good indicator of the ratio of demand to available capacity - drooping frequency suggests a lack of generation and thus knocking off a few fridges until the systems recover isn't that much of a drama.

It will not have any reporting or communication facility so all those who think your fridge will be spying on you are blessed with madness.

I think the phrase being looked for here is "firm and interruptible supplies" - the firm supply being available at all times and the interruptible supply being subject to isolation in favour of other consumers in return for a lower cost (or an agreed reduction in demand)

As smart metering rolls out and many more time based tarrifs become available it will be a consumer choice if they wish to add more intelligence and communication to appliances (or even systems) so they can elect to operate when the tarrif is most favourable to them - it won't be imposed on you.

I just love the irony that those who protest most about a breach of privacy are those tweeting about it - on what has to be one of the least secure communications media ever - if you want your identity up in the public domain for everyone to see, well...............

regards

OMS

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 29 April 2013 02:19 PM
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rocknroll

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As we move towards 2016 and various impositions (a few legal) are placed upon us there will probably be a raft of ideas on how to save energy coming about.

Industrial and commercial aside who are used to demands to ease up on energy useage the biggest and most important question yet to be answered which concerns the domestic sector is, how do we in line with EU proposals impose a 2000kwh p.a. maximum on UK households without compromise, for a nation that has enjoyed limitless amounts of energy and probably one of the biggest abusers this is going to be a difficult one, do we mimic the EU and like the french fit a (disjoncteur differential) or will the 'Smart Meter' be the way forward, no-one knows yet.

regards

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leave nothing but footprints!"
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 29 April 2013 02:38 PM
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OMS

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most important question yet to be answered which concerns the domestic sector is, how do we in line with EU proposals impose a 2000kwh p.a. maximum on UK households without compromise,


Have a sliding scale for domestic energy consumption - the second 1000kWh should be double the first thousand and so on.

Then hand out some big demolition contracts and start knocking down the absolutely rubbish housing stock

At the same time, stop giving money to the banks and start spending it on domestic housing with near passiv haus energy performance - at least 1/2 million properties a year - and keep it up for at least 10 years.

With a few checks and balances that should do it.

Failing that - just start building new nuclear and go flat out with gas fracking - plenty of energy down there for sure - and the stone age didn't come to an end for lack of stones did it - so in a few hundred years we'll have new energy sources and it'll be someone elses drama to deal with what base metric our economy has now decided is important - be that carbon, hydrogen or shiny, shiny beads.

Regards

OMS

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Failure is always an option
 29 April 2013 04:30 PM
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Jaymack

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Originally posted by: jcm256
Will there be any problems with this

It's a sensible method for peak lopping, but only one of the possibilities for automatic shedding of loads, not only under routine operation, but in case of emergencies. I don't know the comparative effects with voltage reduction though, and the difficulties in transferring kVAR's for an overall grid reduction, another option is to have control of localised domestic supply transformers. More can be done on the domestic scene. I've got a useage monitor in front of me, connected to the tails using a clamp function, there are warning signs on the icons for high grid useage, and exceeding the daily target, (due to this being a washing day). I imagine that the grid warning signal on the icon, is transmitted by high frequency signals over the incoming the line. I suppose that these useage monitors in households, is a physcological attempt for us all to participate, so that we can export our coal reserves to China.

https://www.wind-watch.org/news/2013/04/28/big-brother-to-switch-off-your-fridge-power-giants-to-make-millions-but-you-must-pay-for-sinister-technology/
 29 April 2013 04:39 PM
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AJJewsbury

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like the french fit a (disjoncteur differential)

Do you mean a disjoncteur-de-branchement? (isn't disjoncteur differential literally a differential disconnector - i.e. a plain RCD to us) - like these: http://www.elec-boutique.fr/di...90-2p-45-a-500-ma.html - as I understand it - an adjustable circuit breaker (plus an RCD in the same box).

Load shedding relays are common (I've never heard of them in anything other than caravans here).

There's a bit of bckground on their 'tarif bleu' & their 'blue days' and 'red days' here: http://www.thegoodlifefrance.c...lectricity-in-france/

- Andy.
 29 April 2013 05:25 PM
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AJJewsbury

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47HZ cut-off

There must be more to it than that surely. Frequency seems like an odd variable to pick. The grid frequency is the one characteristic that's synchronised across the entire country, so if all these millions of appliances have gadgets with identical characteristics then they all switch off at the same moment (so allowing the frequency to recover) and then switch back on again at the same moment (presumably risking dragging the grid frequency down again - possibly below the 47Hz or whatever threshold - so the whole problem just repeats) - that sounds like a recipe for grid instability, not stability to me.

Besides, aren't grid demand/supply problems often regional rather than national? I know it's all interconnected, but the capacities are limited. Will a lack of generation in say the NW really be properly compensated for by reducing load in the SE?

- Andy.
 29 April 2013 05:34 PM
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perspicacious

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My rather simple understanding is that rather than keep less efficient plant running on standby just to keep 50 Hz on the National Grid when peak loads occur, let the applied load slow the frequency to 49.8 Hz and the embedded chips on sensing this, would switch off loads such as freezers (with an overide should the temp rise out of permitted zone) until the peak passed and the frequency returned to 50 Hz.

Now whether the frequency would be allowed to rise to compensate for those with clock points is interesting

Regards

BOD
 29 April 2013 06:05 PM
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OMS

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so if all these millions of appliances have gadgets with identical characteristics then they all switch off at the same moment (so allowing the frequency to recover) and then switch back on again at the same moment (presumably risking dragging the grid frequency down again - possibly below the 47Hz or whatever threshold - so the whole problem just repeats) - that sounds like a recipe for grid instability, not stability to me.


I don't think they'll be identical widgets Andy - you create 26 of them (as an example) and randomly scatter the A to Z's across the manufacturing run of the appliance

Not even the old radio teleswitches had a single response - they were staggered across 15 mins or half an hour(?)

So as BOD suggested, as you start to slip frequency as the spinning reserve drops off, the random load drops out and you start to get get grid recovery.

Regards

OMS

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 30 April 2013 10:02 AM
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jcm256

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Will PV solar grid inverter impossibly gamely try to hold on to 50HZ? When the mains supply frequency decreases to 47HZ. They have a frequency range so they must be able to synchronize with the grid or go pop.

This blog below says that hybrid inverters are expensive

http://giridaran-solar.blogspo...-generators-with.html

Worst of all they are now trying to cover their back (you know the wise ones in government) with disastrous energy policies of intermitting wind power generation by adding to the mix by installing green frog around the country. Diesel fumes belching out to the atmosphere and using up oxygen, that is what the poor and pensioners will be paying for now while been driven into fuel poverty.

http://www.greenfrogpower.co.uk/power_generation.html
 30 April 2013 01:25 PM
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AJJewsbury

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This blog below says that hybrid inverters are expensive

Presumably wouldn't be a problem if the island was big enough - or the local generator could produce a stable output (e.g. incorporated an inverter). I suspect the problem would come trying to re-sync the islanded area with the grid when power returned.

Worst of all they are now trying to cover their back (you know the wise ones in government) with disastrous energy policies of intermitting wind power generation by adding to the mix by installing green frog around the country.

Not a new principle though. Back in the 1980s they built Dinorwig (http://www.fhc.co.uk/dinorwig.htm ) for almost the same purpose - better matching supply & demand - but then the problem was the inability of nuclear (and to some extent thermal stations in general) to respond quickly enough to changes in demand. Now of course both sides of the equation have a bit more variability, but the principle is the same. If such 'backup' systems are only used once in the blue moon, then the quality of their fuel etc is of much less of a worry than if they're running flat out 24x365.

- Andy.
 30 April 2013 01:32 PM
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ectophile

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Grid-tied inverters are designed to monitor the mains frequency and voltage, in order to synchronize themselves.

If the incoming mains goes out of spec, the inverter will shut down for safety - this isn't just to protect the inverter itself, but also to ensure that it doesn't keep generating during a power cut, which could be dengerous for anyone working on the electrical system it's attached to.

The problem I see here is that if the frequency is reduced in order to switch off heavy loads, it could also cause all the micro-generating inverters in the country to suddenly drop out, making the problem worse.

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 30 April 2013 02:45 PM
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impvan

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Another less-well-admitted purpose of Dinorwig was to help restart the Grid in the event of a nuclear attack. It takes a fair bit of power to run a power station, and a cold station has to get its power from somewhere. Dinorwig can act as a bloody big cranking handle.

So long as the bomb didn't drop during half-time in the FA Cup, or an ad-break in a Bond film...

As a wide-eyed youth I was in the control room at Dinorwig a number of times, and observed the frequency changing during peak demand, at that time there was both an analogue needle and an LED display on the wall. On one occasion the frequency was dropping fast and there wasn't any panic "that's Anglesey Aluminium starting a pot line, it'll come back in 5- 4- 3- there you go!" Another time a phone rang, and they started Dinorwig on request for the Fusion research centre at Culham.
 30 April 2013 03:34 PM
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AJJewsbury

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The problem I see here is that if the frequency is reduced in order to switch off heavy loads, it could also cause all the micro-generating inverters in the country to suddenly drop out, making the problem worse.

I agree - some co-ordination is needed - not only should appliances start to cut-out at a higher (below normal) frequency than SSEG generators (47 Hz feels very low), it would be sensible to be able to turn on such appliances to create a short-term increase in load when the frequency increases above normal - but at least both adding loads and turning off SSEG would be pulling in the same direction then (to reduce grid frequency).

- Andy.
 30 April 2013 09:59 PM
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dlane

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Grid requirement is to operate between 49.5Hz and 50.5Hz, frequencies outside of this are regarded as exceptional circumstances.

A power station will only stay connected to the grid for 20 seconds between 47Hz and 47.5Hz so major load shedding will start to occur just before this.

Traditional repsonse to low frequencies is supplied by power stations operating in a frequency response mode where the control system for the turbines monitors the line frequency and adjust the output based on this.

Spinning reserve is usually then called to raise their output, but this is at the request of Grid control and not automatic like frequency response.

Load response after this is from pumped storage and peaking units, usually open cycle gas turbines or diesel engines.

After this, reach for the candles.

There are several forms of 'black start' facilities based around the country that can provide power onto the Grid to allow the larger thermal assets to start generating and restore the Grid system. Some pumped storage facilities offer this as do some gas fired stations and some coal stations that have open cycle gas turbines installed.

Kind regards

Donald Lane
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