Mains power voltage drop to reduce usage?

[Commander Kinsey]

Instead of rolling blackouts when there's a power shortage, why don't we just allow (or deliberately) the voltage and frequency to drop? Wouldn't that make a lot of devices use less?

[Commander Kinsey]

Instead of rolling blackouts when there's a power shortage, why don't we just allow (or deliberately) the voltage and frequency to drop? Wouldn't that make a lot of devices use less?

[danny burstein]

In the US that's a common technique the utilites use called a "brownout" [a]. They'll drop the voltage by five or even ten percent.

As to whether this makes any difference with power demand these days, given the types of loads, is another story.

[a] that term is often misused to refer to "shedding load", where a power company will black out some sections of the grid to keep everything else up and running.

[hubops]

The large thermal plants are very sensitive to system frequency deviations - so that isn't an option.

In Ontario the grid operations use 3 % or 5 % voltage reductions as part of their emergency load reduction plans. It's tested regularly - link below for a local municipal utility.

Also :

Typical voltage reduction is: A 3% voltage reduction will lead to about a 1.5% reduction in total energy consumption (for a load of 20,000 MW this represents about 300 MW) A 5% voltage reduction will lead to about a 2.6% reduction (for a load of 20,000 MW, this represents about 520 MW

file:///C:/Users/USER_ONE/Downloads/ORGuide.pdf

John T.

[danny burstein]

[snip]

Thanks for the link to real world data. I'm not so sure this will continue to be the case as the load mix changes...

[Commander Kinsey]

The UK is predicted to be 5% short this winter. Would a 10% drop in voltage cause problems? I doubt it since the legal rule is I get 230V+/-10% anyway, which is a 23V drop.

[Commander Kinsey]

The other answers disagree, some loads would reduce, resistive heating for example (including washing machine heaters).

Note, since yourself and others keep dropping off the crossposts (idiots), you might not have seen the other replies, they're in alt.home.repair and uk.d-i-y

[Commander Kinsey]

A device getting damaged by not enough power is screaming of bad design.

[hubops]

The voltage reduction tests - 2 per year ? will chart the effectiveness - and also serve to identify and iron-out problems. The effectiveness hasn't changed significantly since my time - mid 1970's. One major change in the grid and distribution in more recent years is the abundance of wind and solar - big and small - - I have no idea how that affects things. John T.

[David Wade]

Recent research suggests "no" or perhaps not enough. At one time you could buy transformers to reduce the houshold voltage with the aim of reducing consumption. In the past where devices had conventional PSUs and we had incandescence lights this worked.

With modern devices it doesn't really work well. Many devices have switched mode PSU's which simply ramp up the input current to compensate for the lack of voltage so you don't save any power.

So TVs, computers, USB chargers and many LED lighting systems. Even a modern fridge has in effect a switched mode PSU so a variable frequency inverter drive to the motor.

or

so that will simply increase the power input to maintain the motor speed. I guess microwaves ovens are similar, and my hob is an induction hob so I expect that adjusts its power depending on voltage.

That leaves devices which actually heat. Kettles simply take longer to boil, washing machines longer to heat up (they also have inverter driven motors, so again, essentially a switched mode PSU) so not much scope there.

Dave

[Commander Kinsey]

What a ridiculous way to reduce power. Why not just turn less lights on, or use lower wattage bulbs? And turn the heating thermostat down instead of artificially throttling it?

Yes, but a lot of stuff would use less - washing machine water heater, electric water or house heating for example.

I've heard of that but never owned one, I doubt many have those yet. I assume a lower voltage would lower the consumption of most motors.

But it would make people use less at that precise moment. The problem is not overall usage, but peak demand.

[SteveW]

Not necessarily. We have a "guaranteed" minimum and maximum supply voltage. Why should a company spend extra designing and installing protection against supplies (not temporary aberrations) outside them?

[Commander Kinsey]

Because other things could cause lower voltage, like a wiring fault in the device or the building. Especially in dual voltage countries like the US where you can lose one live.

And all you need is thicker motor windings surely? Or a better cooling fan? Everything is designed to just manage to work, no safety margins like there used to be with "over engineering".

I recently broke a brand new strimmer simply by it jamming for precisely 1 second. Seriously? No thermal cutout? No over-current cutout? These devices are very simple and cheap to add. My £10 fan heater has a thermal cutout. It probably cost 50p.

[Max Demian]

The first two and possibly the latter have thermostats so will just be on for longer.

Even without that the motor would be on for longer as they have thermostats.

Actually my fridge freezer might as well not have one as it rarely turns off. Ice forms inside the fridge part and you can just about freeze vodka in an ice cube tray so it must be about -25C.

[Jim Joyce]

I don't think any of us is going to be able to access a file on your computer.

[Cursitor Doom]

Yes, all sorts of issues if a power company messes around with the voltage and frequency. If a consumer wants to attempt saving money in this way then the obvious thing to try would be a variac. It won't change the frequency but does enable one to reduce the supply voltage easily to whatever device you wish to reduce the power to.

[hubops]

Sorry about that - it seems that their files are stored on a google cloud or something and automatically download & open ? Dunno .. see if this link works :

John T.

[Tim+]

Have you measured how much that is costing you? Fridges are potentially a fairly major household power consumer these days now that lighting has become so much more efficient. You really don’t want a fridge that’s working harder than it needs to 24/7.

A power monitoring plug can be had for less than £15 and is a useful tool.

Tim

[Carlos E.R.]

Those with switching supplies would compensate, taking more current, and eventually burning when the voltage goes below design margins. Otherwise, they would take the same power, so no gain.

[Commander Kinsey]

Not the same thing at all. If you want to reduce usage, you turn things down or off. If the whole country wants to do that over a short period due to high demand, they can't very well phone everyone up and tell you to delay your coffee for half an hour, they have to lower the voltage.