# Arcing Fault



## lishaji (Aug 11, 2010)

Attached is a arc damage at line side 3ø 480V 1600 Main Breaker (Westinghouse PCF31600), hopefully corner grounded delta, not sure may be ungrounded delta. I am still wondering whether its a breaker failure, as the arc flared upward out of the breaker looking at the arc damage on cable. Or its a phase to phase & ground high impedance arcing fault.


----------



## ampman (Apr 2, 2009)

what is it feeding


----------



## lishaji (Aug 11, 2010)

2 300kW Compressors. Both were shutdown/off when the fault occured


----------



## wildleg (Apr 12, 2009)

so what steps are you taking to determine ? megging everything, having breaker tested ?


----------



## lishaji (Aug 11, 2010)

now I am hunting for the breaker and down grading it to 1200A, but it looks like its not in stock. if some thing is available, i would megger the bus or else gut it all. Its old 1981.


----------



## lishaji (Aug 11, 2010)

I meggered the bus and downstream breakers, everything tested fine.


----------



## MDShunk (Jan 7, 2007)

lishaji said:


> I meggered the bus and downstream breakers, everything tested fine.


Wouldn't be the first time an old breaker just took a notion to fizzle out. A bit of PM testing might have avoided the blow-up, but that repair would have had to be done eventually, I feel sure. 

For heaven's sake, DLRO everything before you put it back into service also. Megger those compressors too.


----------



## brian john (Mar 11, 2007)

IR
EPM

and you minimize expenses on repairs.


----------



## Zog (Apr 15, 2009)

lishaji said:


> now I am hunting for the breaker and down grading it to 1200A, but it looks like its not in stock. if some thing is available, i would megger the bus or else gut it all. Its old 1981.


I should have plenty of those, you want the 1200 or 1600A?


----------



## RIVETER (Sep 26, 2009)

Zog said:


> I should have plenty of those, you want the 1200 or 1600A?


Hey, Zog, what do you say...Arc fault...or arc flash? I would say loose connection. It would destroy the equipment at a low current not sensed by the OC device.


----------



## Zog (Apr 15, 2009)

RIVETER said:


> Hey, Zog, what do you say...Arc fault...or arc flash? I would say loose connection. It would destroy the equipment at a low current not sensed by the OC device.


Impossible to tell with the limited info, but looks like a breaker failure. Could be imporper AIC rating for the available fault current (My best guess at this point) or another failure due to lack of maintenence of the breakers. Who knows? Send me PO and I will go and find out.


----------



## gold (Feb 15, 2008)

wow, first time I ever heard of a hopefully corner grounded delta ...


----------



## RIVETER (Sep 26, 2009)

Zog said:


> Impossible to tell with the limited info, but looks like a breaker failure. Could be imporper AIC rating for the available fault current (My best guess at this point) or another failure due to lack of maintenence of the breakers. Who knows? Send me PO and I will go and find out.


I'll have my people call your people.


----------



## lishaji (Aug 11, 2010)

Thank you so much for all the responses. We are in a middle of restructuring and no one is ready to put a dime in these equipment. I guess, as for the compressors, they would be renting a couple of diesel units for couple of months. I kind of agree with Zog, may be its breaker failure, as I won't be surprised if someone would say the breaker was never operated since installed. However, there was so fault to be found anywhere down stream of the breaker. Still wondering, maybe its just the cobweb across the phases!


----------



## lishaji (Aug 11, 2010)

Today I got confirmation that the secondary is an ungrounded delta. Since the transformer was on no-load, my suspicion is ferroresonnance. But then, why didn't the compressor motor controller electronics didn't blow out due to any transient overvoltages caused by ferroresonnance, and still was able to sustain an arcing fault?


----------



## RIVETER (Sep 26, 2009)

You should have said that in the first place. For ferroresonance issues you should go to the DIY site.


----------



## HAND (Jul 15, 2010)

Well at the diy site they are going to say that this guy sounds like an insurance investigator or somebody who is looking for info to testify in court as to what happened to that old piece of ****, where to get the best answer than from the people who installed it, and free to boot.


----------



## lishaji (Aug 11, 2010)

HAND said:


> Well at the diy site they are going to say that this guy sounds like an insurance investigator or somebody who is looking for info to testify in court as to what happened to that old piece of ****, where to get the best answer than from the people who installed it, and free to boot.


:laughing:

You are rt about being the investigator, because this is the second time such thing has happened without any rhyme or reason. Also the poor electrician incharge was being ridiculed by his supervisor of doing it for some extra overtime.


----------



## Shorty Circuit (Jun 26, 2010)

lishaji said:


> Attached is a arc damage at line side 3ø 480V 1600 Main Breaker (Westinghouse PCF31600), hopefully corner grounded delta, not sure may be ungrounded delta. I am still wondering whether its a breaker failure, as the arc flared upward out of the breaker looking at the arc damage on cable. Or its a phase to phase & ground high impedance arcing fault.


I'm going out on a limb and guess that the arcing was caused by dust and dirt similar to tracking. The arc was phase to ground. Once it started on the left end ionized airborne particles extended to the middle phase. It was quenched before it reached the right side which appears to have sustained much less damage. I'm surprised there isn't more evidence of scorching. What's missing must have vaporized in the arc. I'll bet this facility hasn't seen any maintenance in a very long time. Pay me now or pay me later.


----------



## RIVETER (Sep 26, 2009)

Shorty Circuit said:


> I'm going out on a limb and guess that the arcing was caused by dust and dirt similar to tracking. The arc was phase to ground. Once it started on the left end ionized airborne particles extended to the middle phase. It was quenched before it reached the right side which appears to have sustained much less damage. I'm surprised there isn't more evidence of scorching. What's missing must have vaporized in the arc. I'll bet this facility hasn't seen any maintenance in a very long time. Pay me now or pay me later.


You are describing the arc flash phenomena.


----------



## Shorty Circuit (Jun 26, 2010)

RIVETER said:


> You are describing the arc flash phenomena.


Yes that's right. Once the arc is initiated by say airborne particles of dust or a foreign object, it's hard to put out because the ionized air becomes the path and it can remain ionized for awhile. It is particularly dangerous on the primary side of a delta wye transformer. I once had it happen on a tranformer for an entire building where one phase on the primary side was lost because of tracking. The voltage on the secondary side on one leg was very high and we had to shut the building down immediately to avoid extensive damage to everything and we sent everyone home for the day. The next day when we fixed it it was a Saturday and it was 19 degrees outside. This is why sooner or later lack of PM always catches up with you but business models just don't get it.


----------



## McClary’s Electrical (Feb 21, 2009)

Shorty Circuit said:


> Yes that's right. Once the arc is initiated by say airborne particles of dust or a foreign object, it's hard to put out because the ionized air becomes the path and it can remain ionized for awhile. It is particularly dangerous on the primary side of a delta wye transformer. I once had it happen on a tranformer for an entire building where one phase on the primary side was lost because of tracking. The voltage on the secondary side on one leg was very high and we had to shut the building down immediately to avoid extensive damage to everything and we sent everyone home for the day. The next day when we fixed it it was a Saturday and it was 19 degrees outside. This is why sooner or later lack of PM always catches up with you but business models just don't get it.


 


I had one short phase to phase in a machine shop due to airborne metallic filiings working their way into the MCC. Went off like a shotgun


----------

