I suspect it's an idea originating from the bean counters, rather than qualified, experienced engineering staff.
Reducing the mains voltage to save energy
- Thread starter John D v2.0
- Start date
I suspect it's an idea originating from the bean counters, rather than qualified, experienced engineering staff.
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That's OK. We don't have a water meter!
Seriously, if the water companies are concerned about wasting water, I think they'd do well to repair all their leaks.
All of this talk of reducing mains voltage leads me to ask whether doing that is likely to affect the accuracy of our 50Hz frequency?
I ask because I have an old mains clock, powered by a synchronous motor. The type which used to be popular perhaps half a century ago (I remember my dad had one then, anyway). Despite its age, it keeps very good time. Naturally, the frequency will often dip below, and rise above the nominal 50Hz, but over time the one compensates for the other.
I ask because I have an old mains clock, powered by a synchronous motor. The type which used to be popular perhaps half a century ago (I remember my dad had one then, anyway). Despite its age, it keeps very good time. Naturally, the frequency will often dip below, and rise above the nominal 50Hz, but over time the one compensates for the other.
I don't think it's anything like as simple as you imply ...
... at any particular point in time (when the reduction in voltage effected) a substantial proportion of thermostatically-controlled loads would be 'getting close to being switched off (by the thermostat)', so the effect of the voltage reduction would be to extend the period for which those currently 'on' loads remained 'on' (at lower voltage). On the other hand, those loads which were already 'off' (by virtue of thermostatic control) when the voltage reduction occurred would know nothing about that voltage reduction, and therefore would not 'come on' again any later than if the voltage had not been reduced. I'm not convinced that that would necessarily represent a reduction in overall power consumption.
Kind Regards, John
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'Dynamic demand appliances would react to this very same signal. When the needle is to the left, they would be more likely to switch off, reducing the load on the grid and helping to restore the balance.'
..and if badly designed, it could set up a see-saw action, causing the mains frequency to vary rapidly.
Their 'live' grid frequency value seems to be at odd with this one- http://www.gridwatch.templar.co.uk/
Thanks. I have one of those web-based meters somewhere lurking on my computer. It is quite interesting to watch and, as has been stated, the frequency variation very rarely extends far from the ideal.
That Dynamic Demand website hasn't been updated in well over a decade.
But equally, there will be many loads which have only just turned on, so they will reduce load and the extra on time won't happen until other measures can kick in.
Take a simplistic case where a large number of loads are working on a 1 minute on, one minute off cycle. At any point in time, around 1/4 of them will be in the first half of an on period - so cutting the voltage will give you about 30s before half the savings are gone.
In practice, many loads have much longer cycle times, so the change could give at least several minutes which is long enough to trigger other mitigation measures - calling on interruptible loads, dispatching STOR, opening the taps at Dinorwig, etc (depending what & where the problem is).
I wasn't clear enough. What you say is true but, in that example, another quarter of them will (if things are random) remain 'on' for more of that 30 seconds than they would have done without the decrease in voltage - thereby at least partially cancelling the 'savings' to which you refer.
Don't forget that with thermostatic (or whatever) control, the cycle will not remain at "1 minute on, 1 minute off" if the voltage chages.
Maybe - but, as you say, any appreciable saving would be very short term. With the sort of loads we are talking about, if the thermostatic (or whatever) control were 'perfect', then the energy consumption over any number of whole cycles would be unchanged.
Do not periods of extreme demand automatically result in end-user voltage reductions, anyway, due to transmission losses ('VD')?
Kind Regards, John
As I said, this all relies on the length of cycle times being longer than the time needed to get other measures "fired up". Immersion heaters have cycle times of at least several minutes, as do (IME) fan heaters - I'd say at least an order of magnitude longer than it takes to (for example) open the taps at Dinorwig or call up some diesel gennys.
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