Internal circuit breaker failure

[jnaas2]

Any body ever had a 100 amp main fail between phases

 

[cowboyjwc]

Any body ever had a 100 amp main fail between phases

Don't remember if it was specifically a 100 amp main, but I've had a couple go bad.

And I don't know why I can never remember, but I know what it is when I see it, but you either get 220 across but 110 on only one leg or if you get 110 and 110 but not 220.

 

[kwired]

Don't remember if it was specifically a 100 amp main, but I've had a couple go bad.

And I don't know why I can never remember, but I know what it is when I see it, but you either get 220 across but 110 on only one leg or if you get 110 and 110 but not 220.

If you have one pole fail to close you get 120,120 but no 240.

I guess I thought when he said fail between phases, I was thinking you get a lot of fault current, and hopefully on load side of contacts and magnetic trip mechanism.

 

[cowboyjwc]

If you have one pole fail to close you get 120,120 but no 240.

I guess I thought when he said fail between phases, I was thinking you get a lot of fault current, and hopefully on load side of contacts and magnetic trip mechanism.

That makes sense and you may have cleared that up for me before.

Well now also, I may have assumed that I knew what he was talking about. He said "fail between phases".

 

[kwired]

If you have one pole fail to close you get 120,120 but no 240.

I guess I thought when he said fail between phases, I was thinking you get a lot of fault current, and hopefully on load side of contacts and magnetic trip mechanism.

That makes sense and you may have cleared that up for me before.

Well now also, I may have assumed that I knew what he was talking about. He said "fail between phases".

Actually you will only have 120,120 but no 240 if there is a 240 volt load connected to the supply. Turn off all double pole breakers and you will only have 120 on the good line.

 

[jnaas2]

Sorry I didnt get back sooner, The reason I posted this question is that I was working on a 50 year old building that was empty for 5 years and the needed an electrical inspection to get power back on. Checked panel and all wiring and everthing looked good, called for inspection and waited for vectren to show up, Just to be safe i disconnected all circuits from breakers and turned all breakers off

I also double checked the neutral wire and marked it for vectren to connect to, they show up and reconnected to transformer thats also been off for 5 years and come inside and verify 120 and 240 are correct in meter socket and go to install meter and boom, burns one stab on meter socket

Pulls meter backout looks at me and says something is wrong with your wiring and says we need to takes this meter, jump in there truck and are gone. So I pull out all wiring from overhead and verify correct wiring marked and wire is in good shape, also pull wire from meter socket, which is 2 inches under meter base everything looks good but there are burn marks on the feed wires to 100 amp breaker which was turned off but nothing else is damaged

Since nothing else was connected I cant figure out what happened except that the 100 amp main failed internally phase to phase and caused the melt down or it was the smart meter that they installed that caused the problem

 

[kwired]

Do you own an ohmmeter? Check for any continuity line to line and each line to ground. If main is open you should not have any continuity at all.

Not sure of just exactly what you all checked, but make sure you didn't have a cross over between meter and main disconnect and end up landing an ungrounded conductor on the neutral lug in the disconnect. If you had correct voltages at meter line side then the problem was not on the line side and you need to focus harder on the load side. If only one stab of the meter is burned, there is even greater chance this was a line to neutral fault and not line to line, otherwise you would likely have burned both meter stabs.

I suppose there is some risk that there was a malfunction in their meter.

 

[jnaas2]

I checked all that, the only reason I think it was a meter malfunction or main is that both sides of the 100 amp breaker had arc damage but the neutral wire was in perfect shape. If a ungrounded wire was hooked to the neutral lug in panel it would, have showed damage like the 2 line wires did. And the one meter stab that burned had more arc damage on the 100 amp breaker then the other one

One other thought, I know when you have a loose neutral the voltages will do strange things but I havent dealt with these smart meters much, could that have caused a issue even though there was no load applied to either phase at panel but maybe by the meter, just a thought

 

[kwired]

I checked all that, the only reason I think it was a meter malfunction or main is that both sides of the 100 amp breaker had arc damage but the neutral wire was in perfect shape. If a ungrounded wire was hooked to the neutral lug in panel it would, have showed damage like the 2 line wires did. And the one meter stab that burned had more arc damage on the 100 amp breaker then the other one

One other thought, I know when you have a loose neutral the voltages will do strange things but I havent dealt with these smart meters much, could that have caused a issue even though there was no load applied to either phase at panel but maybe by the meter, just a thought

If the connections are all secure you will not see any damage, unless maybe the fault current was really high, I'm talking the kind of incident where the guy plugging in the meter is going to the hospital if he had little or no protective gear.

There may have been a layer of conductive dust or a foreign object across the terminals of the breaker that have vaporized during the incident, or if there was a fault within the breaker you may have soot deposits on conductors from any venting that escaped around the line side lugs area. Do you have melted metal at the line side terminations or just a layer of film deposited there?

I guess only one meter plug could be burned if contact was not made simultaneously. Say Line 1 was made first with no fault, than line 2 closes into a fault - line 2 would be the one that has burn marks

 

[jnaas2]

Yes there was dust deposits on both sides and a small amount of melted metal on both, the side that melted the stab was worst but both screws backed backed out . I saved all 3 wires to show they were connected right since they are only a foot long they were removed with the original bends still there

 

[cowboyjwc]

If the connections are all secure you will not see any damage, unless maybe the fault current was really high, I'm talking the kind of incident where the guy plugging in the meter is going to the hospital if he had little or no protective gear.

There may have been a layer of conductive dust or a foreign object across the terminals of the breaker that have vaporized during the incident, or if there was a fault within the breaker you may have soot deposits on conductors from any venting that escaped around the line side lugs area. Do you have melted metal at the line side terminations or just a layer of film deposited there?

I guess only one meter plug could be burned if contact was not made simultaneously. Say Line 1 was made first with no fault, than line 2 closes into a fault - line 2 would be the one that has burn marks

Have seen that before, and I was kind of wondering the same thing before I read your post. That's why we require an idle meter inspection, before we will release a meter to a panel that has been shut off for any time.

 

[jnaas2]

Never heard of the term Idle meter inspection,

 

[cowboyjwc]

Never heard of the term Idle meter inspection,

We use the term here and even issue a permit for it. It's for anything that had a meter, but hasn't had one for any length of time, like 1+ year(s). Never know what's been done, what's gotten into the equipment, why it was turned off in the first place, issues like that. You had a building that I believe you said hadn't had power for 5 years. I would have been doing a very thourgh check for things as simple as copper theft or equipment theft or even rodents.

 

[kwired]

Some POCO have a device they plug into the meter socket and it tests for faults, incoming voltage, and maybe a few other things. If it fails a fault test they will not plug the meter in to prevent exactly what happened in the OP or even worse.

 

[jnaas2]

They may call it that here, when I go in for the permit I just tell them I need a electrical permit for service reconnect and its a year here to. Then the owner cant understand why you need to go thru the whole electrical system when all they want is a meter, aggravating as %###@#