143 volts in the house

We lost power last night in some awesome storms that rolled through. 
I called in the outage around 4:30. 
At 9, it came on but the ac unit was sounding strange and the lights were brighter than normal. 
The outlet showed 143-145 volts. 
I killed the main and called the power company (using the gas hotline to get a human). 
They were very nice and are heading back out. 
Then the main power from the pole clicked back off again as I was killing the power around the property  

I never have done much with household current than the handy homeowner stuff...I assume the voltage is regulated off the transformer?  And...I live in the country so the transformer is only supplying my house. Maybe there is a settings for more draw on the transformer itself?

If the service tech is friendly, I will ask some questions but thought I would ping the hive as I sip on coffee and breakfast in the bus while I wait. :)

I think the transformer steps the current down to something higher than 240, so that regardless of how long the cable runs are or how many people are requiring power everyone still gets at least 220 to the house, and 110 to the wall plugsplugs'. So perhaps you were among the first reconnected and you got all the powers for a while.

Something tells me that it's either 7200v or 14400v before it gets stepped down, depending on how they have the local grid set up.  It's been a while.

143 sounds weird, it isn't an even division of anything I can think of.

Either the main voltage is 15% high, or the transformer has a short in the windings.

And that is pure guesses based on no ac knowledge.

The transformer steps down the voltage, not the current.  It is center tapped so it produces two legs of nominally 120VAC RMS, 180 degrees out of phase so the two legs will supply current at a nominal 240VAC RMS to the load.  The isn't any regulation at the transformer.  It is a fixed ratio and is selected depending on the voltage being distributed by the grid.  If the output voltage is reading high, and assuming the transformer is operating properly, then the voltage being supplied by the power company is also high.  If you measure 143VAC at an outlet that is pretty odd.  What are you measuring it with?  If you have a true RMS meter you may read weird values, especially if there is some load on the line that is not operating properly and is causing a distortion in the AC waveform causing it not to be sinusoidal.  The storm might have surged the grid supply and damaged your transformer, or possibly something in your house like HVAC.

Another thing that can happen is if you have an open (or high resistance) shared neutral, the 240v doesn't get split evenly between the two phases. So, you might end up with 140v on one phase and 100v on the other, depending on the loads connected to each phase. (It essentially becomes a series 240v circuit with the voltage at the floating neutral dictated by how much current each leg is drawing)

143v is pretty high but shouldn't make things act funny.  Still, you were smart to be safe.

Voltage drops over distance.  For that reason, distribution happens at very high voltage.  Every so often on a utility pole you'll see a transformer.  That transformer supplies multiple residences in the vicinity.  If you're the closest house, you see more than 120v.  If you're the last one in the row, you might see 110v.  My house has a pretty consistent 127-128v at the outlets.

You might also notice that your voltage changes depending on load on the rest of the houses that draw from your transformer.  If everyone's A/C is on at the same time on my street I might see 122v.  At the remote campground where I spend the summers, I have seen it as low as 90v because it's a LONG way to the transformer, and everyone is sharing a modest amperage supply.  I can tell when my neighbors turn on their coffee pot (which is a handy tidbit of info... tells me when to go knocking with cream and sugar)

The voltage doesn't need to be exact.  Heck, most appliances these days are designed to operate in multiple countries and they maybe could take anywhere from 100-260v.  Even a 120v-only appliance can operate on a range of (depending on the appliance) 100-130v.

143v is pretty excessive, though, and you're smart to call someone.  Bad transformer is my guess.  Not much else it could be except higher voltage spike from the generation plant.  The plant spits out generic 14,400v juice and sends it out to transformers to be stepped down to whatever you need.  Pretty foolproof and analog.

If it's a bad transformer, it can be fixed in a matter of minutes.  Most power companies have redundant transformers already installed on the pole so they can switch over in a heartbeat and replace the bad transformer without any real interruption in your service.

In reply to Curtis73 (Forum Supporter) :

You are correct!  Bad transformer...these guys thought 145 was bad, and I am happy to have a new transformer out front. It took a few hours because of a rural setting...they had to fetch it out. But I am right on 123V inside, my AC unit stopped making strange sounds and my bulbs are glowing appropriately. One lamp switch fried...that's the only damage found so far. 
I'm glad to know it was no big deal...it's funny that it let in the higher voltage then knocked itself out after a few minutes. 
cold beer in the fridge. All is well with the world. 
 

Better get the connections in your breaker panel checked, especially the neutral bonding connection to ground. Like flat4_5 spd said in an earlier post, bad neutral/ground connections will give you some weird readings. Voltage on the neutral is bad, and will f*ck some stuff up.

I service commerical/industrial equipment, one particular manufacturer specifies a range of 200-240v AC for their 220v equipment, which is a pretty wide range. Still, there's been plenty of times when I get to a site, measure the voltage, and it's 242, 243, etc, or worse. I'm forbidden to even touch the equipment until the customer gets the voltage back within range - usually by having an electrician install a buck/boost transformer inline to bring down one leg of the 220v from 110v to 95v or so. Not ideal (the voltage should be the same on both legs, measured to ground), but it puts the total down under 240v, so it's "within range".    

Just a little more color...so when the first truck showed up, I told the tech what I was reading in my house and in the shop before it popped for the 2nd time. He threw the breaker to live and it made the same loud hum that it made previously. He measured the voltage and got the same high reading I did. He pulled the plug and called for a replacement transformer.  A four truck crew came out and the made it happen. If you guys think that higher voltage could have done some damage at the boxes, I will call in an electrician.  

jh36 said:

In reply to Curtis73 (Forum Supporter) :

You are correct!  Bad transformer...these guys thought 145 was bad, and I am happy to have a new transformer out front. It took a few hours because of a rural setting...they had to fetch it out. But I am right on 123V inside, my AC unit stopped making strange sounds and my bulbs are glowing appropriately. One lamp switch fried...that's the only damage found so far. 
I'm glad to know it was no big deal...it's funny that it let in the higher voltage then knocked itself out after a few minutes. 
cold beer in the fridge. All is well with the world. 
 

Glad to hear it's fixed... and about the beer.

143v wouldn't have fried a switch.  There was some kind of voltage spike (or amperage spike from undervolting) that would have caused that.  Voltage doesn't kill switches, in fact, higher voltage like you saw probably made it easier on the switch because it was carrying fewer amps.  I only mention that because I agree with earlybroncoguy... check other stuff too. 

I have accidentally run 240v through a switch before (my dumb ass grabbed the wrong wire in the box) and it was fine after a few hours until I realized that the 15w bulbs in my outdoor lights were remarkably bright, so I highly doubt that 143v killed your switch unless it was desperately on the verge of dying anyway.

I saw something like this back in 2003. Lights flickering so I checked the voltage with my Fluke and saw 140 volts before I could kill the breaker the power for the East Coast went out for several days. 

So I was smart to throw the main breaker in the house the one time I noticed everything seemed weird, and my voltmeter said there was only 80v at the outlet?

I mainly did it because I didn't feel like unplugging every electronic device manually.  Why do that when there is a handy lever in the basement?

Glad you figured it out.

I had a weird electrical problem that took me quite a while to figure out, though some of that time was my fault. I was getting crazy voltage numbers, like 600V to ground, or from neutral to the ground of a machine or steel work bench, from 240 single phase coming in to the shop. I walked into the shop one day and smelled wood burning. The bottom steel foot of a saw was arcing to a nail in the wooden floor, burning the wood. And I once grabbed a machinist vice off the floor which somehow had become energized and I got a shock that hit so hard I thought it was going to kill me.

Any guesses what it was?

None of my electrician coworkers had a clue, though one of them told me how to figure it out

DrMikeCSI said:

I saw something like this back in 2003. Lights flickering so I checked the voltage with my Fluke and saw 140 volts before I could kill the breaker the power for the East Coast went out for several days. 

AH HA! So it was YOU who took down the east coast power grid! 

:)

In reply to Peabody :

Did someone nail through one leg of phased 240 below the floor?

jh36 said:

In reply to Curtis73 (Forum Supporter) :

cold beer in the fridge. All is well with the world. 
 

Pro tip, keep at least one frozen 2 liter bottle of water in the freezer. If power goes out move all beer and mixers for liquor to the freezer. It's better than a cooler and you should have cold drinks for up to 3 days.

In reply to Stampie :

Keeping the freezer "full" is good for energy savings, anyway.  Gallon jugs full of ice makes a great thermal battery.

Now I want to see a rapper named 143 Volts perform

143 Volts... in da house

Curtis73 (Forum Supporter) said:

Voltage drops over distance.  For that reason, distribution happens at very high voltage.  Every so often on a utility pole you'll see a transformer.  That transformer supplies multiple residences in the vicinity.  If you're the closest house, you see more than 120v.  If you're the last one in the row, you might see 110v.  My house has a pretty consistent 127-128v at the outlets.

You might also notice that your voltage changes depending on load on the rest of the houses that draw from your transformer.  If everyone's A/C is on at the same time on my street I might see 122v.  At the remote campground where I spend the summers, I have seen it as low as 90v because it's a LONG way to the transformer, and everyone is sharing a modest amperage supply.  I can tell when my neighbors turn on their coffee pot (which is a handy tidbit of info... tells me when to go knocking with cream and sugar)

If it's a bad transformer, it can be fixed in a matter of minutes.  Most power companies have redundant transformers already installed on the pole so they can switch over in a heartbeat and replace the bad transformer without any real interruption in your service.

Utility service voltage is regulated by the state code or Public Utility Commission.  In the case of PA, the allowed range depends on the type of service.  For services that are primarily for lighting, such as a residential service, the allowed range is nominal +/- 5%.  That works out to 114-126V for a residential single phase service.  Services primarily for power are allowed a range of nominal +/- 10%.  Variations outside of that range are allowed for periods under 1 minute.  The OP is located in MD which sets a range of +/-5% of nominal regardless of secondary voltage.  If you're seeing a consistent 127-128V in your home that is excessive. Likewise a sustained 110V to a customer would be quite low.  

Also I can assure you we don't have spare transformers installed on the system for failures. 

Campgrounds can be some of the absolute worst voltage complaints to resolve, especially once they start stringing wires everywhere.

GhiaMonster said:

In reply to Peabody :

Did someone nail through one leg of phased 240 below the floor?

I got a bunch of 8' fluorescent fixtures from work and my nephew, a first year apprentice, installed them for me. A couple of them did not get grounded properly (old two conductor with no ground wire) which the ballasts, apparently, do not tolerate well.

I first noticed a little tingle on the toggle switch of my belt sander, which I suspected was a problem with the machine. Then the drill press did the same thing, then the smoke incident and the zap I got from the vise. It was a bitch to figure out but I found it before the barn burned down.

Of course, all the electricians I'd asked previously figured it was something like that...

I had something similar happen in my other house.  The voltage was creeping up slowly.  I initially noticed it when my drill would work fantastic at my house but seemed slower and not as strong when I used it in other places.  I could also use 60-watt bulbs in most lights and have more than enough light. (these were old incandescent bulbs) I tested the voltage at my friend's house about a mile down the road and he only saw 115 or so. 

When I tested mine it was at 130 and I called it into the electric company but they did nothing.  over the course of about 6 months It slowly crept up to close to 140 and I called it in again this time they came out and the test by their lineman was 147 at the meter.  They pulled my meter immediately and changed the transformer in front of my house that night and that fixed it. 

What I did not expect was a letter in the mail saying that they accepted responsibility for any damage it may have caused and if we had to replace any electrical appliances or other electrical items in the last 6 months to send them a copy of the receipts and they would reimburse me.  We had a refrigerator, electric range, PC and an electric dryer all fail.  Other than the PC I really think the other stuff was just old.  Maybe the increase in voltage killed them?  I never checked the voltage at the dryer.  I can say that after the transformer was replaced things took longer to dry.   I had the receipts and submitted them and they sent a check for the full amount. 

It was a pleasant surprise.  I remembered lamenting to my wife that it was crazy that we were having to replace all these appliances in such a short period of time.  I never connected the two until they sent the letter.   

220, 221, whatever it takes. 

In reply to dean1484 :

That is very stand up of them. Nice.
Based on that, I feel pretty good that we noticed it in pretty short order...I have a feeling if we hadn't, we might be replacing appliances. By the way, the unhappy fridge has put itself back in line and has had no further issues. 
All the tips on ice in fridge and keeping the beverages cool are also appreciated.