In general you have a few different organisations involved in supplying power to your house. Some may be embodied by the same entity depending on where you live.
The company or corporation that runs the power plant, windmill, solar panel field, etc.
A consolidator or wholesaler of electricity, linking the generation with the transmission.
The company or corporation that runs the transmission lines, getting the power from plant X to a substation in city Y. They have technicians and trucks for this.
A national or regional body such as NERC, in charge of making sure the nation’s transmission grid has some reliability and redundancy. Multiple organisations may be involved.
A regional public utilities commission, a regulatory body with involvement in billing practices, reliability standards, regional planning.
The distribution company or corporation or cooperative, that runs the physical network from the local substation to your street and actually has employees and trucks and spare poles and transformers.
The company that bills you for power. In some cases, especially in parts of the U.S., this can be different from the distribution entity.
There are cases in the U.S. where a single company provides transmission and distribution but regulations require these two sides of the company to be kept deliberately separate, with different office buildings, different-coloured badges, very limited information sharing, etc. to preserve competition.
Like I said, in some places this is very consolidated. Here in Québec, production, transmission, distribution and billing are mostly done by a government-owned corporation called Hydro-Québec, with a nominally separate government commission for examining rate increases etc., and participation in outside bodies such as NERC.
All of this to say: normally brownouts are a very local thing involving your neighbourhood, your street or the transformer that serves the 3-4 houses around you. Only your distribution company or corporation or co-op would be involved.
Also, note that brownouts in only half the house described in the OP are a consequence of the center-tap arrangement to supply 240V and 120V to the same meter, which isn’t done outside North America.
Roughly 10 years ago, in either Santa Fe or central CA where my mom was living, the power in her house was in a brownout / under-volt situation for on the order of a day or two. They weren’t sure what was happening, so they didn’t unplug their appliances.
This situation destroyed most of her plugged in electronics. They needed a new TV, Tivo, and I think a microwave. Something about the low voltage caused the electronics to destroy themselves.
Interesting. I’ve learned my one thing for the day.
When you say 3-phase being split out, is that 3 phases voltage wrt ground, or wrt to each other (LHS of the transformer diagram)? So if one phase “browns” can it affect the other two?
So if there is a brown-out, it’s unlikely that only one leg (say, V1) is lower voltage in your diagram, unless everyone on the street has their oven turned on and they are mostly connected to V1 not V2, for example? (Except ovens and other heavy draw are 240V) Ovens should still work, just less power, like incandescent bulbs - not as bright/hot? (Of course modern ovens tend to have electronic controls and relays not simple switches, so there’s the risk your controls won’t function - in the appliance showroom the ovens had a 120V adapter that allowed the electronics to work for demonstrations, but not the heating elements; I presume it simply only fed one leg and ground)
I know for regular fluorescents, they won’t operate below a certain voltage. Never seen what happens with CFL, or with LED. Do they require a minimum voltage near 110V to even light up?
(Anecdote - I worked in an industrial plant with 3-phase.A salesman tried to sell the company a system for dimming old fluorescent (tube) lights using clipping of the waveform. The head electrical engineer had a fit - can’t do that because 3 phases have a common neutral, the dimming would change the phase of the power, possibly creating an additive load on the neutral that would cause overheating. )
I too am curious as to how too low voltage could fry electronics. I’ve designed a LOT of audio electronic equipment, and the working mains range was always an important parameter. In every case if the mains dropped too much the equipment would just sit there doing nothing, or doing its usual thing badly with a lot of hum.
NB This was usually with transformer-rectifier supplies, not switch-mode PSUs.
I have a very elementary understanding of electronics - but as I gather, most solid-state devices are basically diodes with a gate or some such to control flow, so need a basic voltage (~1.5V?) to even function. If the power supply design can’t provide that, then some things don’t work. Power on process, however, usually relies on an RC circuit or such to hold the voltage low on the chips’ reset line long enough for the voltage to get up to operating voltage so the system can go through its startup process. If the system is stuck in a limbo situation where there is no detectable off-to-on on the reset line after when the voltage finally reaches operating levels (I.e. with turn on during brownout, slow/delayed voltage rise) then the complex microprocessor type operations may instead hang in an uncertain state.
I’ve read somewhere around 90% of normal voltage, so below 99V for a normal 110 house, or below 198 for a 220V circuit.
If I had to guess why things react differently, it’s because some can function just fine at lower voltages and/or have built-in circuitry to drop the voltage anyway, and others require the full voltage to work correctly.
I’ve read that most white LEDs operate around 3V, so they have circuitry in the bulb to drop down from 110 anyway, so they’re probably ok if the voltage drops to 99v.
As far as the effects on things, computers get weird if the voltage gets wonky. I don’t know how much actual damage is done, but voltage drops can flip bits, etc… ending up with different states internally than you started with before the brownout, and that makes programs go haywire.
That’s the point - most switched power supplies, and definitely transformers, assume an input voltage at a certain level. That switched power supplies (which seems to be almost everything electronic today) can operate fine whether Euro-240V or US-120V, suggests they could be fairly forgiving, but it’s unclear what happens below, say, 99V. Obviously, you can’t power a 120V unit with 12V automobile input - not just the DC vs. AC, but that then the necessary power would involve 10 times to amperage, and some components probably are not intended to handle that?
I’ve not seen nor heard of that ever being the case. Not saying it isn’t, but there’s a reason that North American residential service is called “split phase” instead of “2 phase”. Here in Cincinnati I see exactly what @engineer_comp_geek describes, 3 phase primary distribution on main streets, with single phase branch taps going down side streets to transformers that provide 120/240 secondary distribution to the homes and street lights.
In the OP’s scenario of a small retail business, they’re most likely on a 3-phase 208 service to the building, probably a strip mall or some sort of multi-tenant building. In that case, a lost phase (which the power company would never cut intentionally, that can happen due to a lightning strike, or someone crashing into a utility pole) will cause the symptoms described. Commercial breaker panels have bus bars connected to the different phases, so if one phase is lost, some lights go out, some stay on, and others go dim because it’s backfeeding power through the other phase at half the voltage.
Just to expand a bit further, in a typical commercial (or apartment) 120/208 3 phase service, you get 208 volts between each leg and 120 volts between any leg and neutral. So the electrical outlets and lighting will be at 120 volts and the A/C will be 208 3 phase with a triple breaker (resistive loads like stoves and water heaters might just be 208 single phase with a double breaker). If one phase goes out, then one third of the lighting and plugs will go out while the rest will be unaffected.
It’s also very possible that the service is 480/277 3 phase, with the lighting running on single phase 277 volts and a separate on-premises transformer to step down the 480 3 phase to 120 3 phase for convenience outlets. In that case, losing a leg would lead to the same situation with outlets, one third would go out. However for lighting, since that’s phase-to-phase, it would act weird with one third working ok and the rest either not working at all or running dim. If you lost two phases then you’d still have a third of your outlets working, but only a third of the lights would get any power, and it would be partial power. Not sure if it would be 0.5 or 0.58 or what, but it’d be rough. Good thing the HVAC has safety disconnects because single phasing can ruin motors very quickly.
Just to nit-pick or clarify: I think that most heavy appliances - oven, dryer - are 240V with optional center neutral. So even in apartments, like houses, the power distribution should be 240V; the breaker panel has a center neutral and 2 side bars, each 120V wrt neutral and 240V to each other. Last time I was shopping for a new oven (Previous one died due to power surge frying controller electronics) nobody made a distinction between “house or apartment” or asked “120 or 240”? Higher voltage means less amperage, which in a high power situation is safer.
Nope. Many larger buildings are three phase and each unit has 2 phases going to each so you have 208/120 instead of 240/120. Unfortunately, 208V leads to much slower heating of devices like ovens.
Right, it works OK for ovens, dryers, and water heaters, just not great. Usually they’re simply de-rated for 208 volt but they still work. Motors, pumps, and A/C units may be rated for 208/240 but they could need some control circuitry and transformers rewired for the actual voltage (a 24 volt transformer for thermostats that’s tapped for 240 would be badly undervolted on 208 equipment), but if they’re only rated for 240 then they’re most likely going to overheat and burn out the motor windings.
Well-designed electronics will not be fried. But, quite a lot of stuff is badly designed.
The primary mechanism I can think of is that a switch-mode power supply (the dominant kind used today by computers, USB chargers, etc.) will compensate for decreased input voltage by increasing the current draw. Generally speaking, this is what you want, so that the output can have constant power. But if the voltage dips too much, then the current may rise beyond what the components are rated at. They’ll overheat or fail in some other way.
These supplies should have some kind of undervoltage protection, but they may not. And even if they do, it may be that degradation due to age or some other reason will cause them to fail when they’re pushed to the edge of their rating.
Many LEDs sold these days are capable of dimming, though the mechanism is different. They usually “work” on incandescent dimmers, but the range of dimming is small and non-linear, and you’re supposed to replace the switch with an LED dimmer. Plus it’s supposed to be better for the bulbs’ lifespan.
LED light on a standard switch in a brownout, I’m not sure.
In our apartment building, the only stuff that operated during our brownouts were things that pulled very little juice. Nite lights and the light in the fridges mostly. So I’d say they cut the power almost all the way off, but left a trickle going. This would surely vary depending on where someone lived and how they got their power.
In Texas, a place where not one single thing made sense to me, we got our power from one company, but they used another company’s poles and lines to deliver it. Which might explain why our electric bills were sky high. If you tried to call them abut stuff, you had a statistically better chance of getting the President in Wash D.C. on the phone. At midnight.
There are a few places in the USA with 2 phase power. 2 phase power requires 4 wires. 2 seperate wires for each phase. A home will have single phase power with 3 wires. 2 hots and 1 neurtal line.
With 480/277 3 phase power if one leg is lost 1/3 of the lights will go out. The lights are 277 vac powered off one leg and the neutral, the lights are not phase to phase to phase, that would be 480 vac.
But loosing one high side leg would cause one low side leg to be normal, but 2 low side legs would be under voltage.
Oops yeah you’re right. That’s not a setup I’m really familiar with (I’m not an EE or anything), and that’s probably what happened at my last office when a car crash cut off (I think) two phases. Most of the fluorescent lights went out, but some were still on and very dim and flickery, kind of like they were struggling to start in a cold room. The most interesting were our computer workstations. Because of the way they ran the integrated power, some people’s whole computer went down, some stayed up, some lost the computer but not the monitors, some lost one monitor, etc. depending on how they plugged everything in. There was also a scramble to shut down all the A/C units, because they did not have any sort of single-phasing protection, and they started growling like angry beasts.