Smell of ozone from MV switchgear 7

[Thedroid]

We recently had our GE Magne-blast 1200A breakers serviced during our annual outage. It's been about 3-4 weeks, and we're starting to notice the smell of ozone coming from the back of one of the switchgear cabinets.This breaker provides power to a transformer and also a MV motor through a parallel feed. The original set of cables is shielded, and the other set was added on at a later date and is unshielded. They run through seperate conduits, and are pretty close to the same length. I'll say within 10ft. They both terminate on the bus of the load break switch, and another run of shielded cables to feed the mill soft-starter is also connected to the same bus.

Today we racked out the breaker and removed the back cover to look for any sign of corona effect or tracking. We could not find any obvious damage to any of the insulation, but did notice that some of the cables were bent sharply, and also contacting the switchgear cabinet.

The unshielded cables were the ones contacting the enclosure, so we shortened the cables by about a foot, and made a support for them out of a fiberglass insulator to keep them away from any metal. The original terminations were real sloppy. The ends looked like the had been wittled instead of stripped, and the fabric material under the insulation had been left hanging at the termination. We redid these terminations, and wrapped the cables with scotch 70 about 8 inches back. We inspected everything that was visible, and could not find any signs of the insulation deteriorating.

We then inspeceted the breaker, for any signs of tracking or powder, or anything out of the ordinary, and could not find anything. This breaker was just hi potted and ductor tested a month ago, and was found to be ok.

After our inspection, we put the breaker back in service and noticed the smell of ozone coming from the back vents with about 5 minutes. The smell is there even with no load on the circuit.

Are there any other areas I can check, and how big of deal is this. I feel that it's a definate sign of a failure coming, and also the smell of ozone is choking.

 

[oldfieldguy]

Checking the 'spouts' or 'jugs' is not convenient with the MagneBlast, but it can be done. Remove the breaker from the cubicle and rack the mechanism as if you were installing the breaker. The shutters should open. It this point you can look up into the jugs. I'd recommend a full set of Nomex and a hood, just in case...

I'm thinking, though, that you really want to have the breaker looked into, including removing the arc chutes. It wouldn't be the first time that a preventive maintenance effort messed stuff up I've found tools, broken parts, incorrect reassembly. Some of these weren't found until the NEXT preventive maintenance.

MagneBlasts are notorious around here for problems with arc chutes, but that's here on the Louisiana Gulf Coast where humidity IS an issue. Still, that's where I'd start looking.

old field guy

 

[Zogzog]

I agree 100% with OFG. And want to add that the pole peices are also common failure points omn Mangeblasts, I have replaced hundreds of them, we actually build replacement poles for those. The insulation could have been damaged from testing (Hipot) or cleaning (Chemical damage).

Maybe I missed it in a post but have you tried swapping this breaker with a spare yet?

 

[Thedroid]

Yes we have swapped the breaker, and so far the smell is less intense, but still there. This is what's leading me to believe that the problem is in the gear, specifically the spouts. I'm thinking that if the breaker is not the problem, then the only thing that would change would be the connection up in the spouts. Will the racking mechanism activate without the breaker in place, or will I have to defeat some of the interlocks? I will remove the chutes on both breakers also, because we have not checked this area yet.

 

[Thedroid]

I looked into the Drager test kits and they were $500+. Was I looking at the wrong model?