Question for Electrical Engineers & Electricians

[Walt34]

Sitting at my computer today and about to log on here, and the UPS under the desk suddenly came on and stayed on but the lights hadn't so much as flickered. Hmmm.

The software that normally communicates with it to adjust settings and such had been intermittent for a year or so and finally quit working last month. So I crawl under the desk and start pushing the buttons to see if I can get an inkling as to what is going on and one of the readouts says the input voltage is 143v. What!!!

So I go get my Fluke meter and sure enough, it says the wall outlet is holding steady at 140 vac. This is not good, and I'm debating whether to flip the main circuit breaker to shut off all power to the house. Meanwhile, I'm trying to get the UPS to turn off but the only switch that seems to respond is the one that shows different items like input and output voltage, hertz, and such. I call the power company to let them know and decide that the UPS is shot and I'm going to need a new one so I head out to get that. It is a survivor of a nearby lightning strike a couple of years ago that fried a bunch of other stuff and is so old I have only a vague memory of buying it so I guess I got my nickel's worth. The only way to turn it off was take the batteries out.

By the time we get back home with the new UPS there is a recording from the power company acknowledging that there was a failure in a piece of equipment that regulates voltage. Yeah, I had that part figured out. Rechecked voltage and it is now 116, so okay. Oh, and all the clocks had to be reset so power was off for at least a few minutes.

And the new UPS communicates with the software (I bought the same brand/model since it worked so well for so long).

My question is this: Was the voltage high enough at 140 vac that I should have shut down power to the house or can appliances/lights accept that much and not be damaged?

 

[travelover]

Yes, I'd have shut off the power. Sometimes this is caused by a bad neutral wire connection and depending on the load on each side of the transformer, the voltage on one side can shoot up toward 220 volts. I had this happen at a subpanel in my garage and got 170 volts in one outlet.

 

[Walt34]

Okay, something to keep in mind for the future if it ever happens again. Thanks.

 

[MooreBonds]

While on the topic of house electric power.....I'll be building a new house next year. I was going to have the electrical contractor install a "whole house surge suppressor"....but is there anything similar to put on the incoming electrical service to possibly regulate the voltage to prevent a spike like that? Or does it mainly only prevent large surges?

 

[travelover]

Here is a technical explanation of what happens when the neutral wire is broken or has a bad connection.
electrical - Power company's neutral cause surges and brownouts? - Home Improvement Stack Exchange

 

[Walt34]

While on the topic of house electric power.....I'll be building a new house next year. I was going to have the electrical contractor install a "whole house surge suppressor"....but is there anything similar to put on the incoming electrical service to possibly regulate the voltage to prevent a spike like that? Or does it mainly only prevent large surges?

I know you can buy them for individual outlets, the UPS I have has that feature built in (that's what set it off) but you can buy the device separately, so I imagine there are ways to do that for an entire building. Think of large data centers and the like, I'd think they'd have something like that.

The "whole house surge suppressors" do not prevent a low overvoltage like the one I had because I have one installed. Or at least the one I have doesn't prevent it.

 

[gauss]

Not sure if anyone is using incandescent bulbs any more, but their life can be significant reduced by overvoltage. There is an exponential relationship, to the thirteenth power, that has been observed between voltage and lifetime in incandescents.

-gauss

 

[JoeWras]

But at least the shavers and cell phones will be OK. They can take the voltage. Who cares about the fridge anyway, as long as you have the cell phone.

Wow, that sounds like a pretty nasty overvoltage event.

 

[eytonxav]

Sounds like you may need one of these:
https://en.wikipedia.org/wiki/Power_conditioner
but that can be a pretty expensive safety measure, especially for the whole house.
Not sure if the power company may have some liability for such an over voltage situation.

 

[folivier]

I just installed these at my new house and have used them in the past.
DeltaSurgeProtectors.com - Homepage

 

[travelover]

I just installed these at my new house and have used them in the past.
DeltaSurgeProtectors.com - Homepage

There is a difference between a surge or spike and a continuous high voltage. A surge protector is useful, but would not have helped in Walt's case.

 

[Sunset]

Wow totally amazing.
I think I will get some UPS devices to protect my computers and tv. I had not bothered as I figured I wouldn't lose much if a power failure hit , but I never knew of a power increase to an outlet, that's not a spike.

 

[ls99]

There are several brands of Line Voltage Regulators. One I used in Alaska for the seismic recording sytem was a brand named SOLA. This unit was before the 10KW UPS.

In the remote village electric power was poorly regulated and out as often as on.

Be aware full time power regulators tend to be inefficient, run fairly hot. For whole house 220 it would be a very expensive proposition, both in inital cost and operating losses. The Sola unit was a ferroresonat sytem only running on 117 VAC. It regulated very well, ran hot and very noisy with 60 Hz hum.

As for 140 VAC utility, that is high. Agree, better turn off main breaker.

 

[Walt34]

As for 140 VAC utility, that is high. Agree, better turn off main breaker.

If it ever happens again that's what I'll do.

Thanks for all the answers guys.

 

[JoeWras]

Wow, timely. We just endured Hurricane Matthew. Shortly after I posted something here about "mostly rain, only breezy," it all went to heck. I jinxed myself.

Tree fell on a feeder line to the neighborhood and we got all sorts of weird power surges for about 2 minutes. It was like a David Lynch movie here. I was on my way down to trip the breaker, when the electric company's equipment did the deed on their end.

There were casualties. I lost an A/C->D/C power adapter. I lost all the recordings on the DVR, and there may be other latent damage. All computers have backup and surge protectors. It is unknown whether they absorbed anything, although the computers survived fine.