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View Full Version : Arcing,sparking,burning electrical question?



wierdscience
08-21-2006, 10:44 PM
Friend recently had an event at his shop,he does blueprint detailng and uses computers extensively.

The otherday,for no good reason a surge protector suddenly went up in flames.The following morning none of his computers would startup and run save one that was on a UPS.
Three hard drive power supplies fried and all seven surge protectors,a four line phone,one copy and one fax machine along with other things like a microwave all toast.
Luckily he had his files backed up on an external drive so they lived.

The odd one was the control x-former on the ac unit was burnt also,but not the unit.This tells me that it most likely wasn't a lightning hit.

After checking the incoming voltage,it was found to be high,280 volts to be exact.Also witnessed lights flickering when a drill motor was used to check wall outlets.

Power company was called they checked the incoming power and also checked the distribution panel and the only thing they found was a loose ground connection both on the pole and on the pigtail coming in from the stack.Once they fixed that eveything seems okay.

They have offered to pay for half the r&r cost which has me wondering if they shouldn't pay for the whole thing,but are trying to weasel out.

The other thing I am wondering is,what exactly happened to cause this?

darryl
08-21-2006, 11:32 PM
A loose neutral anywhere in the power delivery chain after the pole pig (transformer) would allow the voltage on the hot legs to vary. If both hot leads are equally loaded down, then there will be no voltage variations unless the power company feeds a varying voltage to the pole pig. However, if one hot leg is loaded more than the other, the voltage on that leg will drop, and that on the other leg will rise. This is what I think happened. I had a situation where my outbuilding had 220 wired to it, and 110 was taken between either hot and the neutral. If I loaded down one hot, the voltage on the other rose. I could start up the table saw, and the lights would brighten. I had a solid neutral, but the wire was too small of a gauge, and the run too long. I could measure 115 vac on the light circuit, and when I started the saw, it rose to 130, then settled lower, but still above the original voltage.

In your case, if the neutral was lost completely, even momentarily, you could see nearly the full value of the combined voltage from two hots, which usually would be from 220 to 250 or so vac. Anything above about 150 or so ac volts will start the movs in the surge protectors conducting to control the surge. What gets me is that this voltage is already too high for many devices to withstand, and they burn out. The fuses blow to protect from fire, but by that time the device has already cooked.

My feeling is if the power company found a fault before the wiring enters your building, they should be fully responsible for the damages.

By the way, what's this 'loose ground connection on the pigtail coming in from the stack'? This sounds like their butt covering story to avoid having to pay the full damages.

ASparky
08-21-2006, 11:41 PM
Guessing here ... but It is likely that some other customer on the same line as your friend but further away from the grid, was drawing a lot of power. With no ground this can raise the apparent voltage to above normal volts.

When momemntarily high enough, I suspect that the surge protector or protectors triggered. They trigger at a voltage well above the supply so should not trigger accidentally.

However they are designed to kill off brief overvoltage and blow a fuse. With a full time overvoltage with lots of amps if the fuse doesn't blow, they will short and smoke. The first one to go can let the voltage rise to where the next one blows and so on. Sometimes the bounce back when it gives up can cause a transformer to send a spike back and cause other devices to blow. All of which fits with what has happened here.

I think they are being fair in going halves. I would also recomend that your friend look at the fusing. I suspect that there is a missing fuse somewhere between the surge protectors and the panel plus transformer or whatever.

wierdscience
08-21-2006, 11:44 PM
By the way, what's this 'loose ground connection on the pigtail coming in from the stack'? This sounds like their butt covering story to avoid having to pay the full damages.

Thats just it,it's in the top of the meter socket which is covered and sealed with they're lock.My feeling is it's on thy're side of the meter,then it's they're baby.

Could someone explain how those surge protectors work,I have never looked inside so I am blind as to what's inside.

ASparky
08-22-2006, 12:16 AM
This link for a general overview of protectors installation etc.

http://www.nemasurge.com/help.html

and for a overview of how they work see

http://computer.howstuffworks.com/surge-protector.htm

Note that there are different types Gas dicharge MOV etc, usually combined.

Also yep if the fault is pre the meter it is the power co job and costs to fix. Damage resulting is more ambiguous. They can and do argue that if the "house" side is not adequately fused and protected or incorrectly wired then the damage is not (entirely) their responsibility. I do not know in this case, but I would wonder why a fuse did not blow well before the disaster let alone during.

J Tiers
08-22-2006, 12:40 AM
If it did that much damage, there is a strong possiblity that the grounding of the business was poor.

We had a tree fall on out lines in the recent storms, breaking the neutral. Had the two legs, but no neutral. We ran for 10 days like that, I monitored the voltage and all was well, onlt 2 volts change.

We had up to 7 or 8 amps ground current, measured by an Amprobe clamp-on on the pipes, but no problems.

After they fixed the neutral, we still had 2 or 3 amps ground current, so the neutral drop is not a be-all and end-all. I know of others with a similar situation, known to have OK neutrals that ALSO have current flow.

I figured that our neighbors were supplying us with ground thru the water pipes and back on their neutral. The earth would have been too high a resistance, especially with the drought.

With good ground, there shouldn't have been such a high voltage.

CCWKen
08-22-2006, 12:43 AM
Fuses blow with amperage overload not voltage. You could run 10,000 volts through a 3A fuse. I'd make them pony up for the full amount. Check shop insurance policy too. It may be covered so let the insurance company hack it out with them.

It could have been a line regulator that went bizerk too. Happened here. Check with the neighbors. Kept getting high readings one day then low for a week. Called CPS and they came out and replaced some regulators up the road.

dicks42000
08-22-2006, 12:46 AM
OK, others have described what happens well enough. The condition is called a "floating neutral" and can occur from a number of causes. If it happens between the pole & your service entrance, say due to resistance at an oxidized neutral connection, or a broken neutral conductor; the utility should be to blame, since it's their wire...
Yes, they might argue that your wiring, protection etc. was deficient...but stand your ground & see what happens. However, if it happenned on a sub-feed to another building, say; That's your problem. Surge protection is OK, but critical branch circuits could be better protected by panel-mounted surge protection, GFCI's or arc-fault breakers. (Now a code-requirement on some circuits according to the latest revision of the BC Electrical Code/ CEC. For instance circuits supplying bedroom lights/ outlets.)
As far as voltage variation due to circuit loading. The panel should be balanced as close as possible. (Amp draw between each line & neutral.) Sometimes this is a worthwhile exercise. Motor starting loads will cause some momentary variation, as you know. Also check the integrity of your ground & neutral connections in the panel & at the ground rods/ electrodes/ UFER ground plate. (Should be accessable).
Also, if you have ANY aluminum conductors in the panel (service conductor, heavy branch circuits etc. Clean, Penetrox & retighten them.....
(Turn off the power first, goes without saying. Or hire an Electrician.)
Hope that helps.
Rick

MikeHenry
08-22-2006, 01:57 AM
What brand was the surge protector?

We've been inspecting non-UL listed devices at work lately and have found a fair number of problems with Tripp-Lite products.

Mike

J Tiers
08-22-2006, 09:01 AM
There isn't a plug-in surge-protector made that will take the overvoltage and live.

But, they SHOULD be fused so at least they are not incendiary devices.


Yes, current , not voltage, blows fuses, but excess voltage drives excess current through the circuit.


That said, fuses of the normal branch circuit protecting type would not have any effect whatever. If teh current is under the 20A or 15 A, the breaker or fuse won't open.

Does not matter if that is being drawn by your shaver, or an electric clock (with flames), or a vacuum cleaner (might be ok). All same-same, the fuse won't care.

Facility grounding was insufficient. It happens that code ALLOWS insufficient grounding, and now almost REQUIRES it, since a ground rod is OK (even though it is a stupid high resistance ground), but a water pipe ground is not.

But, as our experience shows, water pipe grounding has its good points....

Wareagle
08-22-2006, 06:20 PM
Facility grounding was insufficient. It happens that code ALLOWS insufficient grounding, and now almost REQUIRES it, since a ground rod is OK (even though it is a stupid high resistance ground), but a water pipe ground is not.

But, as our experience shows, water pipe grounding has its good points.... The reason that a water pipe is no longer accepted as the sole grounding means is the use of plastic water pipes serving the structure. Too many times there has been electrical services grounded to a copper water pipe that is adapted from a PVC pipe in which the water is plumbed into the building. This is definately a poor ground!

The NEC requires a driven ground rod for an electrical service.

J Tiers
08-22-2006, 06:38 PM
The reason that a water pipe is no longer accepted as the sole grounding means is the use of plastic water pipes serving the structure. Too many times there has been electrical services grounded to a copper water pipe that is adapted from a PVC pipe in which the water is plumbed into the building. This is definately a poor ground!

The NEC requires a driven ground rod for an electrical service.

Yes, the driven rod is accepted as "sufficient".

However, it may have as much as 25 ohms resistance and still be accepted. That is sufficiently high that a short to ground will NOT open a protective device (fuse or breaker).

Then also, in a drought, the rod may "bake out" and be essentially "open", if the soil it is driven into is dry.

And even if it is over 25 ohms, it is only required to drive and bond one more, regardless of the resulting resistance.

So the rod is "legally sufficient" and so the service is "defined" as grounded. But it may not REALLY be grounded.

And don't forget that in SOME jurisdictions, supply water pipes may be plastic inside the house as well as at the mains. Then there is really nothing to ground to.

But all that does not change the fact that WITH metal piping, and grounding to that, the ground your facility is missing for some reason may be supplied elsewhere via the piping.

If I had not had metal piping, almost certainly appliances would have soon been burning all over my house when the tree cut the neutral. I would not have liked that, perhaps the code authorities think it would be fine.

As it is, it was several hours before we even realized there was a cut neutral, and we never even had much light blinking.

Thank you very much, but I'll keep my ground to the pipes.... my house does not even HAVE a ground rod. It's grandfathered as-is since 1934.

Mcostello
08-22-2006, 11:26 PM
Question------ If a 25 ohm resistance ground is not the best, would 2 ground rods make the situation any better? My ground rod top is about 3 or 4' from ground level. Would the earth dry out clear down to the point? Would a lower resistance save any money on lectric bill?

J Tiers
08-23-2006, 12:21 AM
Question------ If a 25 ohm resistance ground is not the best, would 2 ground rods make the situation any better? My ground rod top is about 3 or 4' from ground level. Would the earth dry out clear down to the point? Would a lower resistance save any money on lectric bill?

It must be driven in a full 8 foot. if that can't be done due to bedrock, it can go in at an angle.

If you mean its 3' underground, well......

If it isn't at or below 25 ohms, a second rod is required.

It likely won't save you a nickle on electric, it is a safety feature.

dicks42000
08-23-2006, 03:11 AM
J. Tiers et al;
I can't comment on the States you live in, but up here in BC, the use of 2 "ground rods" is no longer code-compliant. (Latest edition of BC Electrical Code, CEC) Yes, we still have the requirement of bonding metallic water services & a ground connection to metal gas piping at the furnace or water heater. (Just did that on a new installation today.)
What are accepted are buried plate electrodes (greater surface area) or Uffer grounds (buried under the footing wall). All this is an attempt to minimize the resistance to ground, as has been said by others. The greater surface area, depth, & superincumbant weight of the concrete footing all serve to hopefully make a better ground "connection".
That's about all I know.

J Tiers
08-23-2006, 09:03 AM
Use of gas piping for grounding is strictly forbidden in all the code issues I know of.

Buried rebar in concrete is allowed and encouraged, but if course is not applicable unless new construction.

Plates are allowed also, but usually the standard is a ground rod. Mostly I think because it is a known item with a history. Code people like that.

At the end of the day, you are only getting as good a conductivity as the earth provides, wet or dry etc. And, it goes back to a "butt ground" on the pole, which is either a rod, or a coil of wire wound on the pole butt.

So as good as you make your end, you cannot change dry ground (Arizona) or other conditions which make it a poor return path.

Mike W
08-23-2006, 12:53 PM
I once used a ground resistence tester to test the ground rods for a new tower installation in Phoenix. I was quite surprised to find a reading of about 0.8 ohm. I checked the rods before they were bonded to the tower and rebar.

gundog
08-23-2006, 04:28 PM
What you had is what in the utility industry calls an "Open Neutral" Voltage goes high on one leg and low on the other. This happens because you have other appliances connected 220 V to both hot legs and the leg needs a return path it has lost the neutral and returns on the other hot leg do to the current imbalance. The problem can be in your equipment or on the utility side. Your equipment is defined as any part of the meter base excluding the meter that belongs to the utility. The lugs the meter plugs into are part of the meter base and belong to the customer. If the service is fed over head the wire inside the mast is the customers and only the service drop connectors and meter belong to the utility. If fed under ground the wire and meter belong to the utility and the panel including the landing lugs are yours. There is a little rub here if the utility did not properly tighten the lugs an argument over responsibility could arise. I hope this helps.

One more note on surge protectors they almost always burn up and sometimes catch fire with open neutrals. The surge protector is looking for a raise in voltage between phase and neutral so guess what happens when the neutral is lost they do not see it as a surge even though the voltage goes much higher than their trip rating.

One more note if the problem was on the utility company side they are responsible but be ready for them to depreciate the damaged appliances. They will most likely not give you replacement cost. It is best to turn it in to your insurance and let them deal with the utility company.
GD

wierdscience
08-23-2006, 11:16 PM
Thanks for all the replies.

Got some good news today,when he rented the building the power company came out a stabbed the meter in,but didn't check the connection on the lead in copper LIKE THEY WERE SUPPOSED TO.

They have now offered to pony up about 2/3's of the loses and the guy said "he would see if he could do better with his supervisor",I smell blood in the water now:D