utility power supply interrupted

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Check whether it was an ordinary strip or contained surge protection. When MOVs or other protective elements are exposed to a prolonged hard overvoltage (usually more than just double) they can fail in a way that generates a lot of heat. Especially if the protection is not fused.


Tapatalk...
 
131125-2343 EST

I think there is missing information. For the damage that has been described, there was a considerable amount of energy available. At 240 V this would be more than just the time to sever the wires that were hit by the tree limb. At a much higher voltage the time could be much shorter.

A clean drop out of voltage and a clean restoration of power is not a likely cause. When we had the great eastern blackout the power dropped, and came back a couple times. Might have even exceeded nominal voltage. I was home in the basement and saw the occurrence. At the shop some machine fuses were blown, and one Ethernet router had some damaged channels. No equipment damage at home.

At the shop some years back we had arcing connections on both hots terminals, and the neutral on the pole transformers. Had problems with UPS clicking and some machines with phase loss detection. Some lights dimmed and some brightened. At least one floor stand fan was heard to speed up. No real damage, just annoying.

Much more than these kinds of incidents occurred at the home in question to cause the damage described. And why not the other neighbors? What information about the circuit is missing?

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gar said:
Much more than these kinds of incidents occurred at the home in question to cause the damage described. And why not the other neighbors? What information about the circuit is missing?

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As well as what was all damaged when the tree fell? We don't know the layout of the distribution between the transformer and all the services it supplies, what was broken and what remained intact, or if there was any primary conductors involved in the incident. You have to recreate exactly what happened, then some of the results may make a lot more sense.
 
kwired said:
As well as what was all damaged when the tree fell? We don't know the layout of the distribution between the transformer and all the services it supplies, what was broken and what remained intact, or if there was any primary conductors involved in the incident. You have to recreate exactly what happened, then some of the results may make a lot more sense.
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True, you guys are right on, there is information missing. The very tall tree fell across and broke all 3 of the high voltage lines leading to and very close to the transformer. The tree continued down and broke all 3 of the single phase 240volt lines leading from the transformer to only 6 houses, big boom and big flash at 9pm. The high voltage service lines were going up the street and the 240v lines in reverse direction back down the street. When the high voltage lines were cut, that severed the line sides of the transformer and removed power from the load side. The broken high voltage lines were still live and likely contacted the now defunct 240v service lines, sending a high charge through the the load side. But still, why did it effect my customer so much more than others? Turns out the others have not all been questioned and those that have are still mostly in 1980 and before, very little electrical upgrades, though it turns out at least a few light bulbs were lost. So my customer lost Diva dimmers, newer GFI recepts, surge suppressors, 12volt plug in transformers, new furnace, tankless water heater, and all light bulbs that were on. I think the neighbors did lose a few things but not so many as my customer.

I have yet to open POCO seal to the main meter section and check the condition and secure fit of the original 200amp service wires. I doubt there will be anything notable but what else should I look for and what would it indicate?
 
I would really consider replacing ALL GFCIs. This is in an abundance of caution. It sounds like a serious overvoltage, one of the primaries touching the secondary while still energized. There appears to be too much damage for a simple loss-of-neutral. In the case of a cross between a primary and secondaries (or 23kV with 12.7kV) the POCO here usually springs for the repairs / replacements.

We had a school experience a 23kV to 12.7kV cross on the primary to the distribution transformers. It welded a 1200A main breaker and a 400A feeder breaker CLOSED. We were single-phased and motors were grumbling. I called the POCO for an emergency disconnect since I couldn't turn off some of the motors. After about 10 minutes I got out our switch stick and started to open primary disconnects. Then the POCO arrived and we had a short chinfest:rant: and I loaned him the stick to complete the disconnect. They paid for a lot of damage.
 
kevlar54 said:
True, you guys are right on, there is information missing. The very tall tree fell across and broke all 3 of the high voltage lines leading to and very close to the transformer. The tree continued down and broke all 3 of the single phase 240volt lines leading from the transformer to only 6 houses, big boom and big flash at 9pm. The high voltage service lines were going up the street and the 240v lines in reverse direction back down the street. When the high voltage lines were cut, that severed the line sides of the transformer and removed power from the load side. The broken high voltage lines were still live and likely contacted the now defunct 240v service lines, sending a high charge through the the load side. But still, why did it effect my customer so much more than others? Turns out the others have not all been questioned and those that have are still mostly in 1980 and before, very little electrical upgrades, though it turns out at least a few light bulbs were lost. So my customer lost Diva dimmers, newer GFI recepts, surge suppressors, 12volt plug in transformers, new furnace, tankless water heater, and all light bulbs that were on. I think the neighbors did lose a few things but not so many as my customer.

I have yet to open POCO seal to the main meter section and check the condition and secure fit of the original 200amp service wires. I doubt there will be anything notable but what else should I look for and what would it indicate?
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Tried to fish that kind of information out of you earlier as I was suspecting maybe there were primary to secondary fault all along. Why did it effect one customer more than others? Very well could be in the details of exactly what broke first and what was still connected when this contact from higher voltage happened. This is a little like a lightning strike though the current paths are a little more predictable as the voltage is not nearly as high as it is in a lightning event, but is still high enough to be able to flash over places where 120 volts wouldn't.
 
131127-1837 EST

Now the damage is beginning to correlate with the event. Appears primary voltage got to the secondary circuit for a short time. Customer should have seen lights get bright.

If this is a Y primary source with neutral common between high and low voltage, then is there some way that the fault current produced a higher voltage on the neutral at the end of the line customer?

Also how much unnoticed damage has occurred to all the customers on this transformer? What more can learned about other damage, and exactly what were the possible current paths for the fault current? Is there good evidence that both sides of neutral had a comparable density of failures?

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There are many variables that could answer as to why the neighbors didn't take as much a hit as this house did.

here are just a few:

The other houses had a better bonded water main that also connected to other services via it.

The secondary drops were severed to the point that the neutrals at the pole were apart thus the one coming into this house only made contact with the primary.

As far as losing a neutral on a service only causing higher voltage on only one leg is a myth, remember the see-saw effect of a lost neutral, as loads on the higher voltage leg burn out the balance can shift the higher voltage to the other leg so damage can occur on both legs conning into the house, I've seen it happen.

I have also seen the lamp filaments get hot enough to melt right through the glass on the lamp from just a lost neutral so it is still possible that thats what happen, like was said, its the first conductor to pull free in a tree fall event since it is the supporting conductor, so it is common for this to happen.

If the primary came into contact with the drop to this house there would have been arcing everywhere, but it would not make sense that it would flow through appliances that had no other path to earth or return to the MGN since if it only contacted the neutral which is in most cases bare it would have brought the neutral and grounding up to the same potential with the MBJ in the panel, the only things that would not follow this is anything connected to phone lines, cable which could provide another path back to the MGN, the furnace hot water heater could also provide a path through the water and gas lines but this would not explain the lamps blowing out??

But it could have been a combo of both happening or a timing that the primary made contact to the neutral while the hots were still connected to the transformer thus giving a return through all the appliances in use just before the hots were severed.

If primary voltage did enter the house you should see signs of it like arc marks in the panels, cable/phone drop showing signs of over heating or burn marks at the demarks and such.

Things happen so fast in events like this that can make it hard to pin point exactly what happened and why but if you think about current paths that would have to have taken place sometimes it can jump right out at you, just look at which appliances were damaged and then look at what common current paths they share that makes sense to the damage you see, lamps would have to had the over voltage to happen between the hot and neutral, if the hots were severed then how did this happen, my first thought is the hots had to have still been connected but the neutral severed, this explains the over voltage that first was just a lost neutral that could have see-sawed from one leg to the other, or the primary came into contact with the severed neutral just for a brief moment which is all it would take.

In the end you customer still has to catalog all that was damaged and submit it to their insurance, carefully wording it as storm damage and not using the term electrical damage as most insurance wont cover damage from bad house wiring and they will try to wiggle out of it if you say anything that could be interpreted as damage from an electrical issue, let the insurance company go after the POCO as they have the money to do so.
 
hurk27 said:
As far as losing a neutral on a service only causing higher voltage on only one leg is a myth, remember the see-saw effect of a lost neutral, as loads on the higher voltage leg burn out the balance can shift the higher voltage to the other leg so damage can occur on both legs conning into the house, I've seen it happen.
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It all depends on how the burned out loads fail.
If they fail open, then the leg which already has the higher resistance will just increase the resistance more, raising the voltage still further.
But if one of the stressed loads fails shorted (at least for awhile) then it can drop the voltage on that leg close to zero and thus start burning out loads in the other leg.
Since the loads on the two legs are in series, a short in one load will not be likely to trip the main and may not even trip its own branch breaker. If the branch breaker trips, the stress will flip back to the original leg, and as you say can keep bouncing back and forth from that mechanism.

But if all of the loads fail open or increase in resistance, then only the loads on the initial high voltage leg will fail.

If the open neutral stays undetected long enough (as a result of current returning to the transformer through the GES, for example) then additional loads could easily be turned on or off, either manually, or via a timer or thermostat, making the forensic analysis really tricky.

If you look at the video on Open Neutrals which Mike posted, it is possible to have an open utility neutral raise the neutral in one part of a building or set of buildings on a common secondary to the point where current will arc from grounded/bonded parts to earth grounded parts within the building, creating low voltage arcs or glowing connections even though the voltage differential is not enough to be noticed based on burning out loads.
 
Thanks again to all who replied with good information including "electricity is weird"

kwired -
Yes, I entered this forum before I had more info because my curiosity was itching at a rate much faster than I was able to scratch. I was also hoping that your feedback would provide me with better insight as to what might have happened thus making future information more relevant. All is proving correct, your input is both gracious and valuable, thank you for your patience. I have not concluded a perfect picture and I might never but the very fuzzy picture is now a lot more clear. More info is coming. I will check the main breaker and meter socket for compromise.

I also appreciate the advice for changing all of the GFI receptacles. Some had already failed, the remaining few had either tripped and could reset or had no symptom. Of those, all tested good with my simple plug-in trip tester.
 
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