Mains power voltage drop to reduce usage?

[Carlos E.R.]

LOL.

[Max Demian]

I don't have one personally, but the supply to the common areas of my block does and the supplier erroneously turned it off a couple of weeks ago. It was three days before they could be persuaded to turn it back on, so we lost the door entry system, porch and flood lights, lights in the stairways and passages - the emergency lighting failed after a few hours: before nightfall, the TV aerial distribution system and the fire brigade were ringing up the management agents complaining that the fire alarm was out of action.

[John Larkin]

A SMPS usually has a negative input impedance. As the line voltage drops, the current increases.

[John Larkin]

Right. It's inefficient to take an hour to heat a kettle to boiling.

Mandatory staggering of tea times would help.

We heat our kettle with gas. All that heat winds up in the house, which usually needs it. An open flame is a more efficient heater than a gas furnace; no heat is vented.

[Max Demian]

I'm not in a position to replace it as it came with the flat. And it's a bit of a squeeze to fit in the alcove. I can't clean the fridge part properly as the door doesn't open past 90 degrees or so I can't remove the shelves or drawer.

I tried to measure the consumption by timing the spinning wheel of the meter: I used 104W with it on and 58W with it off so I suppose the FF uses 46W or so.

[Max Demian]

It's set to 1, which is next to off, so I assume that's the minimum refrigeration.

[Max Demian]

Do you really want Big Brother telling you when you can eat? I suppose we could all eat in communal dining halls and drink Victory (ersatz) Coffee.

They could ban adverts on TV to stop everyone from switching the kettle on at the same time.

[Max Demian]

What's that, a ZX81 with a 16kB RAM pack?

[Carlos E.R.]

LOL :-DDD

Or they could stagger the adverts on different stations :-)

[hubops]

There are always fuses < or breakers > - sometimes they are a little slow or sometimes the nature of the fault is such that catastrophic damage occurs regardless. I've seen the aftermath of a 500 kV ~750 MVA transformer splitting open and spilling it's guts .. poop happens. The solution for your high voltage vs low end-voltage can be complicated and expensive to resolve - involving installing in-line regulating transformers or capacitor banks .. possibly on more-than-one feeder .. John T.

[hubops]

Are you sure it isn't 1 primary phase ? plus neutral - which feeds center-tapped transformers that provide 2 hots + neutral to the customer. < that is the North American way >

.. which would save many millions of miles of primary conductor and insulators ... compared to 2 primary lines. John T.

[upsidedown]

Was this in the US with "pigs" in the poles ?

To my understanding the medium voltage feed is three phase open wire in delta configuration (no neutral). The "pig" is a single phase transformer with the primary connected between two phase wires in the medium voltage feed. The third phase wire is not used by this transformer, but most likely in the next pig. The secondary is center tapped with 2 x 120 V. The cent re tap is connected to neutral and ground.

Are you sure that the wire between pig secondary CT to your house neutral was broken ?

Your description sounds more like a phase wire of the open wire medium voltage feed was broken. If your pig did not use this phase, you would not observe anything strange on your low voltage side, you would have well balanced 2 x 120 V.

Note that the third wire on the medium voltage side is not neutral, but the third phase connector.

[Martin Brown]

Yes. UK HT distribution is all lines are hot and three of them. Neutral is derived as the centre tap at the step down transformer.

Very large villages do have a full sub station and all three phases present but I only discovered comparatively recently that my village has just two out of the three phases. This arose out of walking the cable routes when we had an MFU with no power for days (thanks to Northern Powergrid's inadequate maintenance and storm Arwen).

In rough terms where I am there are two full 3 phase spines carrying mains at 33kV running north south and the spurs come off that.

There is a slight difference in appearance of most poles. Convention here is horizontal mounted is HT and vertical mounted consumer mains.

3 phase ._i_. where dots are cables

2 phase .__. you have to be quite close to see the difference.

It is also confirmed by the fact that if a single phase goes down we some some very strange voltages.

If it was one driven phase and neutral then it would be all or nothing.

[NY]

No.

Reducing the frequency will cause mains-referenced clocks to run slow. And that is many clocks with digital displays (which I thought until recently used quartz crystals like a watch) and not just older clocks with synchronous motors. Reducing the frequency too far may affect the efficiency of transformers: I think reducing the frequency makes it more likely that the magnetic core will saturate (though I may have got that the wrong way round!). (*)

Reducing the voltage will reduce the power consumption of resistive loads such as immersion heaters and cooker hobs/ovens, but may have little difference to switched-mode power supplies as used in electronic equipment because they will drawn proportionally more current to maintain the rated output (eg 5V for phone or 20 V for laptop).

And if the temperature of an oven reduces, or the power output of a kettle reduces, the appliance will need to be on longer to cook the food or boil the same amount of water, so there will be no saving. In most cases you are interested in the transfer of a certain amount of energy to do a given job, and it doesn't matter whether that is transferred as high power for a small amount of time or a lower power for a longer period of time.

(*) I've heard it said that transformer-driven devices from the US don't necessarily work efficiently in Europe (even if you correct for the different voltage) whereas European devices run OK in the US (having corrected for voltage) because of the difference between 60 Hz (US) and 50 Hz (UK). Or maybe it's the opposite way round.

[JNugent]

That sounds more likely to be right than wrong in an extreme case.

Applying a high-enough-voltage DC supply to the primary side of a transformer can eventually overheat the coil and burn off the winding wire's insulation coating. Reducing the frequency isn't the same as supplying DC, but the lower the frequency, the more like DC it becomes.

Charging units work more or less just as well when transplanted from the USA to the UK and vice-versa. Reducing frequency by about a fifth or a sixth shouldn't have a disastrous effect.

We like induction hobs. There's no power wasted heating the environment

- just the cooking vessel - and they are so efficient that they can work off a 13A power point. Same point as above regarding Hz change, though.

See above re phone and laptop chargers.

[Cindy Hamilton]

It's in the U.S.

I could see both ends of the break. The entire bundle of wires is one of these:

The uninsulated "messenger" line was broken. The power company came by yesterday evening and repaired the break.

[Scott Lurndal]

Note that the neutral is also known as the "Grounded Conductor", and it is tied to earth at the service entrance. This would explain why the two 120VAC legs in the home would still look balanced as they'll use the earth directly rather than indirectly through the grounded conductor from the pig to the service entrance.

[John Larkin]

We don't have tea time in the USA, and we're un-manageable anyhow.

I'm sipping Peet's French Roast now. They will have to pry that out of my cold dead hands.

[John Larkin]

That happened to me once. We had 90 and 135 vrms on various outlets. The PG&E guys didn't want to believe me but I finally convenced them (some of the lights were BRIGHT) and they fixed a splice on the wires outside.

That's weird because neutral here is usually multiply earth grounded too.

[John Larkin]

I'm working on a photo album of hideous poles and wiring in San Francisco. I'll post a link eventually.