Power failure - residual power

The other night, the power went off at my place. It was a dark and stormy night. (Cue a thunder clap.)

So, we sat and waited for the power to come back on, and it did about half an hour later, and everything was good. But I noticed some unusual things that I can’t fathom. Perhaps someone here can offer an explanation.

So, suddenly we’re in darkness as the lights and telly go off. That’s what you’d expect. Right? The TV is run through a Foxtel box, by the way. I wouldn’t think that significant, but who knows.

So, sitting there chatting in the dark, and waiting, I become aware of the on-light (LED) on the TV and it’s still shining like it thinks it’s on. That’s weird. Then as my eyes become accustomed to the darkness, I can see a general dim luminance from the TV screen. That’s odd – some sort of capacitor keeping power to it, maybe. I grabbed the remote and pressed a button at random, and blow me down if a message wasn’t flashed on the screen, which disappeared so quickly that I couldn’t read it. I had to wonder why it displayed in the first place. The power was off, after all.

At that point, I realised there was a light down the passage way. Checking it out, I find the toilet light is on. Not very bright, but on. It’s one of those twisted fluro tube bayonet fit lights that you see everywhere. It was very dim but was putting out some light.

I have solar panels on the roof. I have no battery associated with the panels. I’m on a feed-in tariff arrangement (I just mention that for completeness), but I find this so puzzling.

So where was this power coming from?

As well as Blackouts there are sometimes instances of "Brownouts" in electrical grids, this is where there is still power but not at the full grid voltage. In these cases some lights and appliances may continue to operate in some form.
Leaving appliances running during a brownout can cause significant damage particularly with inductive loads where a reduced voltage will usually result in a higher current draw resulting in overheating.

Your service provider may be able to advise if there was a particular event as they have monitoring to check voltage supply installed at particular locations. If your unsure or concerned you should have an electrician check your installation.

when things like that happen around here they say power is coming down one of the phases, as opposed to all of em.
if that makes sense.
just the grid doing grid things and not usually a fault at your house.

The thing that got me, and perhaps I should have mentioned earlier, was that while the toilet light was putting out some light for a while, and while the TV still seemed 'active' for a while, they both eventually gave out and went dark.

Things that occurred to me were:

a) The wiring in this house is really stuffed up,

b) The solar panels, while not producing output (because it was night) had retained a charge, and like a capacitor, were slowly releasing it to the inverter, then when that charge disappeared, the light went out, or

c) When the supply went out, my neighbours (but I have no idea of this) might have had a battery with their solar panels, and with the power failure, their battery began feeding the whole street, which included me.

I can't say I have experienced any brownouts. I've heard of them, obviously. But my experience of power failures, to date, has generally been that everything is shut off. I imagine a brownout experience might be that everything essentially stays on, but as you said, at a lower voltage. And my access to power is single-phase only. It was my belief that with 3-phase that a connection to one of them would be sufficient to supply the house. Therefore, if two of them dropped out as suggested, depending on how things were wired, the property would either have full power or none at all.

Perhaps next time I might grab a torch and check what is on vs off. Certainly, the street lights were off.

In a brownout it is not uncommon for some devices to stay on but others go out.
In the day of incandescent lights it would be a yellow or orange glow but with fluorescent and LEDs there is a cutoff point where the supporting gas discharge or electronic drivers cutout. This cutoff point will be different for individual devices, eg all lights off except for some different brand led light that has a lower cutoff voltage to all the others in your home.

With three phase your 240v devices will be spread across phases, meaning some lights or outlets will be powered and running, devices on the missing phase will be off and unpowered. The devices will not get power from the other working phases.
It is possible to have 3 phase and have a brownout on individual phases without affecting the others.

Supply in the street may be 3 phase with different houses or the street lights on separate phases, meaning with the loss, or brownout on one phase only affecting alternate houses differently.

I can't help explain the TV, but once at work (office tower) a fluro started "staying on", staying on so long after the power was off a co-worker had time to take it down and bring it to show us. And it was in a comms room on a different floor and he needed to wait for the lift. Pretty crazy. Not "explaining", just that it can and does happen to that tech

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Originally Posted by ErrolFlynn

The thing that got me, and perhaps I should have mentioned earlier, was that while the toilet light was putting out some light for a while, and while the TV still seemed 'active' for a while, they both eventually gave out and went dark.

Things that occurred to me were:

a) The wiring in this house is really stuffed up,

not really


b) The solar panels, while not producing output (because it was night) had retained a charge, and like a capacitor, were slowly releasing it to the inverter, then when that charge disappeared, the light went out, or

solar panels have zero ability to "hold charge" besides your invertor had no grid AC signal due to being off and has zero abilty to "island" off your house and keep supplying charge, no moonlight can't supply your panels either.

c) When the supply went out, my neighbours (but I have no idea of this) might have had a battery with their solar panels, and with the power failure, their battery began feeding the whole street, which included me.

no, not in the slightest

I can't say I have experienced any brownouts. I've heard of them, obviously. But my experience of power failures, to date, has generally been that everything is shut off. I imagine a brownout experience might be that everything essentially stays on, but as you said, at a lower voltage. And my access to power is single-phase only. It was my belief that with 3-phase that a connection to one of them would be sufficient to supply the house. Therefore, if two of them dropped out as suggested, depending on how things were wired, the property would either have full power or none at all.

Perhaps next time I might grab a torch and check what is on vs off. Certainly, the street lights were off.

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brown outs mean the proper voltage and frequency can't be supplied for a short-ish period, normally temporarily because some large generator in the grid can no longer do its job, which can happen pretty suddenly. so inbetween the grid authority is trying to work out out who to shut off to keep the rest of the grid stable. always remember you can't make anymore electricity then whats actually being used.


so if all the generators are suddenly making too much electricity or not enough some weird stuff is going to happen until the power is actually cut