Siemens 34.5 KV Breaker

[wpaul29]

Just wandering if anyone has ever come across something like this.

34.5KV feed from power company goes into a packaged dead front switchgear to a Siemens Vacuum type circuit breaker and back out to the transformer. When opening up the front door compartment to check different metering and control equipment you can hear a distinct noise. It sounds some what like arcing but I'm really not for sure. There is another packaged switchgear with the same setup and it to sounds almost definitely like something is arcing.

During the commissioning of this installation Siemens was contacted and said that there is nothing to worry about. A qualified technician working for the power company told me that he has not heard medium voltage breakers sound like that before. We do have other 12.5 KV breakers and there is no noise noticed there.

I don't think this is normal but maybe I am wrong. Siemens did not even send anyone out to inspect it.

 

[charlie tuna]

Re: Siemens 34.5 KV Breaker

i would schedual a power shutdown and have siemans on site to inspect the gear! i would have a crew there to clean the gear while seimans does a full inspection. you don't get a second chance with that voltage. we worked on a chiller plant that had seimans 4160 volt starters and we could never get any manufacturer information or parts -- we had to improvise everything!

 

[rcwilson]

Re: Siemens 34.5 KV Breaker

At 34.5 kV, corona can become as issue. Corona sounds like continuous hissing or arcing. It can be fine for a while, even for years. Or it might get wet and go tomorrow.

As suggested above, I would take the gear down to clean and inspect it. Look for tell-tale corona tracks on the edges of insulation.

Bring out an experienced High Voltage electrician or NETA technician to look at the gear. I think there are some corona detection devices available that might give an indication of any problems.

Good Luck,

Bob Wilson - "Don't let the smoke out!"

 

[Nick]

Re: Siemens 34.5 KV Breaker

I belive a partial discharge test would pinpoint the problem. Alot of medium voltage gear comes with instructions how to insulate the buss after you land the cables to it. Maybe that wasn't done and it is tracking across a dirty insulator.
I agree with Bob. Have it checked out by a NETA certified testing outfit.

[ August 01, 2005, 06:29 PM: Message edited by: Nick ]

 

[zog]

Re: Siemens 34.5 KV Breaker

A few NETA companies (Mine included) can provide on-line partial discharge testing that can find your problem without a shutdown, rcwilson nailed it on the head about the corona.

 

[mrford]

Re: Siemens 34.5 KV Breaker

Whenever we go into unit subs, or vaults and work on switchgear as such we always use a ultrasound probe
on the equipment to listen for any corona, tracking,
arcing, basic fault finding before we shut it down and maintain the equipment. On the low voltage side we use a flir camera to check for the hot spots but the probe lets us here everything that is going on without it dissipating enough heat for the camera to pick up. You should get someone to have a listen to the equipment before you shut it off to see if you can isolate the problem, and bring some backup parts for repair while you down. Always best to go in the problem with as much info as you can .