12kV fuse contactor

[victa1288]

I am working on an international project. One of our engineers insists on using 12kV contactor instead of breaker. There are a couple of manufacturers available for 12kV contactor, such as ABB, Siemens, and Areva. I am not feeling comfortable with using 12kV contactors. My concern is as follows,

12kV contactor might not be used in the industry long enough, so I need to contact the end users to find out what their experiences are about 12kV contactor.

There may be crone effect issue for 12kV contactor.

 

[swn1]

the distinctions in design between breakers and contactors have very little to do with the voltage level.

Contactors are designed to operate frequently (100's of thousands of operations) and NEVER to interrupt fault current.

Breakers are designed to interrupt fault currents occasionally and to operate infrequently - no more than a few thousand between overhauls, modern designs good for maybe 30,000 operations total.

Use the right tool for the job. 15KV-class contactors based on a proven vacuum interrupter should work just fine. I can't recall having worked on any 15KV-class air-magnetic starters - we don't see a lot of 15KV motors in our service area - and you aren't likely to buy them for a new installation. But if you do, go with a proven design and get service history information from somebody who really uses them at least as hard as you will.

Crone effect? Do you mean corona?

Keep them clean and you won't have a problem. Make sure the cables are terminated properly, of course. Evaluate the switchgear for adequate termination space and good design and workmanship on interument transformers, bus jumpers, etc. Those are your corona (partial discharge) problem areas - whether you use a breaker or a contactor.

 

[victa1288]

Actually, we are at 10kV level. I am waiting Some manufacturers to give me the reference list so that I can be convinced.

 

[rcw retired EE]

In my experience fused contactors work well on smaller motors. (>5,000 HP). Larger motors start running into fuse coordination problems with the contactor interrupting rating.

If the motor is only going to start once a month then a breaker will give better service.

On smaller motors we ran into a problem with cable size when the client specified circuit breakers. The breaker clearing time was much longer than the typcial fuse. Cable size had to be increased 150-200% to get the required short circuit withstand.

If it was my plant - I would use fused vacuum contactors along with a good supply of spare contactors, fuses and an infared inspection program.

Circuti breakers cost more and take more room. Except it is a toss up at 6 kv IEC.

 

[victa1288]

Rcwilson, in our case, we will have enough short circuit to clear the fuse within 100ms before the contactor drop out. So contactor can be protected.

Cable sizes for the circuit breaker could be a problem. I will do a quick calculation to size the cable based on short circuit thermal withstand.

Is there any crona problem with 10KV contactor?

 

[tulum]

We use Toshiba 15kV contactors for transformer switching and have never had a problem...

Toshiba (houston) has available fused combinations to bring SC level up to acceptable levels. ...just another option.

Regards,
TULUM