I remember a few years ago in New York (Long Island) they had a power crisis during a heat wave. Instead of blackouts, they just turned down the juice, so everything got ~75% of normal power. Things still worked, but the A/C just wasn’t as effective. Why isn’t California doing this?
A few million angry PC owners might be a good reason.
Sorry, let me elaborate. A page on the subject states:
Southern California Edison has made a deal with some customers where they can get a break on their bills if they agree to let SCE put a device on their air conditioners that lets SCE turn them off remotely in case the power demand gets too high.
In California they have automatic capacitors at the distribution level that kick in when the voltage goes below a certain level. Although I am not sure at what level that is it is probably above 105 volts. The system tends to run around 115 volts on average.
Detroit Edison here in Michigan does the same thing. I saved a whole $0.25 on my first bill of about $50. And, because it was a separate meter, it was a separate bill with a whole different account number. Needless to say, it was WELL worth it to go back to the “expensive” system, and NOT risk having no A/C during peak demand periods.
Also, lowering the voltage to certain customers wouldn’t have any effect – they have their own substations that could boost the voltage right back up to where it needs to be. If you have a UPS in your home, it probably does the same thing for your computer – it has it’s own rectifier and inverter built in. It wouldn’t cost any more from the power company, either, since you pay for KW/h, which is a function of both the current and the voltage (for the most part).
Lowering the voltage can also damage other things besides your computer – anything with a transformer is at risk – your TV’s, ovens, washers, &tc.
Well, you could raise the voltage back up, but when you raise the voltage, you essentially lower the current. I don’t know the specifics on how sub stations work, but if it were able to send a smaller voltage at the same current, each house would consume less. I think, anyways…
Why is it specifically devices with transformers that would suffer from problems with brownouts? Transformers can stand lower voltages.
Anything with a computer in it wouldn’t work. It probably wouldn’t get destroyed by the low voltage, it just wouldn’t work.
Many other things would work though. However, they would be working at deminished capacity. For example, your lights will be dimmer, and your oven won’t get as hot. (I really don’t see why a brown out would destroy an oven)
The effects of a brownout depend on the loads. Resistive loads such as incandescent lights, heaters, ovens, etc., would be unharmed. Lights would be dimmer. Your oven would take a little longer to get to a certain temperature, and stay on for a higher percentage of time, but you wouldn’t notice while cooking (if you set the thermostat to 450, for example, it will just take a little longer to get there).
In general, if you lower the voltage for resistive loads, you also lower the power consumed. This is not necessarily true for non-linear loads, such as a computer. Most switch-mode power supplies (e.g. the supply in your computer) are (more or less) constant-power supplies- if you lower the voltage, the current it draws will go up, to supply the same amount of power to the computer. Thus, no power savings will result if the power company lowers the voltage (for this type of load). I doubt many PCs would be harmed by 105 volts, and I have seen PCs running with less voltage. Many PC supplies are universal-input (85-264 volts), for use in the US and Europe.
Transformers by themselves wouldn’t be affect by a voltage reduction. However, if a transform is feeding a load (such as a power supply) that increases the current in response to a lower voltage (to maintain constant power), the current in the transformer will increase. Power loss in a transformer is (mainly) due to resistive heating loss (current causing the transformer wires to heat up), which would increase if the current increased (and the heat goes up as the square of the current!) This could cause a transformer to overheat, although you’d need somewhat of an extreme situation.
Many industrial motors with smart controllers will be unaffected by a lower voltage, unless they shut down altogether, since the controller will maintain a constant power output (by changing conduction angles, etc.)
If you lower the nominal 120V value by 10%, for example, some loads will draw less power (lights, mainly), while others won’t heaters (sure, while they’re on they draw less power, but they’ll be on for longer to maintain the thermostat setting, so it’s a wash), computers, TVs, etc. So it may not save much power. On top of that, there’ll always be someone at the end of a distribution line who was already 10% low, so now they’re too low, and something fails- now you’ve got an angry customer with broken equipment, or a lawsuit if it was something life-critical. On top of that, you’ll get the multitudes who think the power company caused something to fail, and call in to complain.
Arjuna34
Brownouts don’t do damage to anything that is just using resistance doing a job. Example electric heating elements, incadesents lights. Anything using a tranformer, electric motor, compressor, or newer electronics which are much more sensitive than an old tube televisions, are at great risk of burnout. Anything less than a temporary brown out can over heat the later, and cause a dead appliance.
Think of electricity in these terms , if helpful. A filled and pressurized water tank is the available power to do work or wattage. The pressure on the water line is voltage, and the amount of flowing water is the amps. Opening a lot of valves will alow a larger amount of water to flow, at a lower pressure to do less individual work. Opening only some of the valves and maintaining a higher pressure, will allow the opened valves to do a greater individual amount of work.
An electric line can carry only so much current. Utilities try to mantain voltages at about 120 volts. Your appliances use a certian wattage to run. To keep it simple I will use power conversion for DC. The total power consumed is amps (current) times volts (push)to give you watts (power). A utility sending power to you at 120 volts can send more watts over the grid than if they drop to 110 volts. The grid can still only support the same amount of amps. A utility with not enough power, can send out the power that they have available as more amps and less voltage.
A brownout will mean less voltage going over the transmission lines. By dropping the voltage transmitted and maintaining the same watts over the grid more amps are available. All electrical items on the grid will have more amps available, but the will not be getting the proper amount of voltage (push) to get through the appliance. The current going through an appliance is less because there is not as much push through it.
The end result is lights and ovens are ok. Transformers, compressors, motors, and modern electronics will burn out from over heating due to not enough watts (power). A rotating black out, is better than a brownout.
any PC supplies are universal-input (85-264 volts), for use in the US and Europe Yeah, but the power supplies have a switch on the back to switch between 120 or 240V input.
Maybe I should check it. I have a spare power supply in the basement, and a variable transformer thingie (0-150VAC about) and a multimeter. Maybe I’ll be pleasently surprised. But, maybe not…
I don’t think it’s as bad as that. Modern switching power supplied will draw more current to compensate for the lower voltage. The water analog starts to break down here, but you could think of it like this- the water pipe represents the “load”, and the diameter of the pipe represents the resistance. If there’s less pressure available, the power supply circuitry in effect “widens the pipe” so the load draws more current, thus keeping the total water flow constant.
I’ve been in areas with the line voltage down around 100 volts or so, with no noticeable problems (once this was at a power quality trade show convention hall!!) The problem with lower the voltage, though, is that the people at the end of the line who were already low are now too low, plus the savings aren’t as great as you might think, since heating loads aren’t really affected.
Arjuna34
You’re right- I was thinking of my laptop, which switches automatically. My Dell desktop (here’s a sample spec) is rated at 90-135V, or 180-265, depending on the switch setting. So, it could withstand a 25% drop from the nominal 120 volts, but like I said, the power consumed would be the same.
Arjuna34
Do the California electric utilities warn consumers of a scheduled black out? Something along the lines of: “At 11:30 AM we will cut the power in the area bounded by Main Street on the east, First on the south, … The power will be off for two hours. At 1:30 PM, power will be cut …”
Or is it just one big SURPRISE party? Just hope you’re not in an elevator when its your turn to be surprised. If they aren’t warning their customers, the execs of these utilities should be used to complete the circuit.
As I understand it:
Everyone is in a “block”. I’ve heard that these blocks are approx 77K consumers, but I could be wrong.
Up here, the only blocks that they do the rolling BOs on are 1-14. Others are exempt for certain reasons, don’t ask me what. I know hospital over 100 beds are exempt as are some police stations and fire stations. I do NOT know if they’re in the same blocks as everyone else or they have a block of their own.
I am in block 3. Monday, blocks 12, 13 and 14 went out (14 for only a partial amount). The next time they need to do rollind BOs, they’ll start with 14 again (for the remainder of their time, I’m not sure of the timing on each BO) then go to Block 1 and proceed consecutively. Every night on the news, they’ll tell you which blocks went out, so you can kinda guage your position.
There are all sorts of extraneous problems too, like plants going off-line and other plants ready to go on-line, but can’t get power because no one will sell the energy to them due to the amout of money already owed.
It’s a disaster.
Arjuna34
I was trying to explan in terms that people who don’t understand electricity could get something out of this. Anybody that knows how power works, will see problems with the anologies, but they get the point across to a lot of people.
Sidenote: I had to turn off the main breaker one night for a few hours. Imagine the gas furnace trying to run. the flames would kick on, the furnace would over heat, because the fan didn’t work. The furnace would shut down due to over heating. I had about 75 volts coming in. This was a transformer problem at a substation, six months after lightening struck it.
Wisconsin has come very close for a couple years to having rolling blackouts. We got lucky and made it through with few problems during the summer, which haws been mild. The big problem is that there is no area with huge amounts of electricity that is surplus, and the transmission grids in place are not extensive enough.
Last summer during a heat wave half of Wisconsin lost power for about six hours. The tranmission lines which bring in the power melted. Yet we have been trying to install new power grids for years, and get nowhere, because everybody starts a lawsuit against having a power plant or transmision line built in this state.
For the lawsuit happy, please disconect from the electric lines so we can get by with what power we still can get.
My county wanted to know what the residents thought we needed to develope. I sent back the letter with build a power plant. You can build it in my back yard.
“Do the California electric utilities warn consumers of a scheduled black out?”
Not yet. We are trying to get them to though. Dunno how they would do it.
Each person is on a block & they rotate them. We are on 01 for example & the business district is 05.
Re warning of blackouts: I read in the L.A. Times (I believe; too lazy to look up cite) that they don’t do this for safety reasons. Think about it: When the power’s off in a block, that means no burglar alarms, no security cameras, no electric fences. Why would you want to tell the thieves an area will be safe to raid?
Like I said, though, I’m only going by what I saw in the paper. If this reason isn’t true, please let me know. I don’t want to be responsible for spreading ignorance…
That’s exactly why they don’t tell everyone in advance. They do tell the police, fire stations, big employers, hospitals etc. so they can get prepared, though.