Arc contacts for switch gear?

If you have below 33kV then VCBs are fine, if voltages are over then SF6 type CBs can be taken into account. Aux. contact can not assist the main contact, they are only use for interlocking purpose or status monitoring etc..

There is a several manufacturers in the world who have excellent products out on the market which use some of the ideas of principles you mentioned in your initial question. That might also be a reason why you should not expect to get to much information in CR4 official forum.

But I would like to recommend to look here, because they have world leading products:

http://www.abb.de/product/ge/9AAC30200091.aspx

There is also an english site, but I don't have the time to search for it in this moment.

Most medium-voltage, load-break switches include replaceable, arcing contacts. Contact S&C

Friend,

Yes! I don't have catalog data at the moment, but your approach is used by many manufacturers for this purpose. The "auxiliary" contacts are mounted very close to the power contacts, but spring loaded so they close slightly earlier than the power contacts and open slightly after them. They take the sparking and pitting, and at higher voltages will create those long plasma arcs which are extinguished in a variety of ways. Because they only have to carry the current for a very brief period of time, they do not have to be physically as large as the power contacts.

My personal experience is with low-voltage switchgear (600V or less), and I have run across them many times.

--JMM

Thanks a million-Newton and Mueller! I will vote good for both and follow up on the info you dug up.

As stated by jmueller the "punishment" or "auxiliary" contacts, which we call arcing contacts are supposed to take the arc until it can be extinguished respectively the next zero crossing of the current. Under normal conditions it is possible to decrease the current through circuit breakers before the are supposed to interrupt but in failure conditions the breakers have usually to interrupt a multiple of the nominal current. Thus they are rated for a certain amount of current and time (kA*s) which is dependant on the erosion capabilities of the arcing contact. One should monitor the integral of arc current and put the switch gear into service if only one full interruption is left.

If this service is forgotten the other, main contact system might take over the arc, because the arcing contact is become to short and opens, before the main contact opens. Since the main contact is designed to make very good contact it cannot withstand arcing for a long time and it usually does not have any means for arc extinguision installed.

The switchgear might fail in this case, which is really serious if it is located between a generator and a block transformer. This fireworks will last as long as the generator needs to come to a complete stop or any part of the current path disappeared completely.

BTW, I'm working in the test laboratory for such switches and we have a generator and several other means to simulate failure scenarios.

I wish you two--JMueller and Newton2k1 would give each other a good answer vote so that they will get logged as good answers ---when people seach for this information they will find this here.

Thanks to all who participated--I have done my part and I appreciate the answers.

Kilgore Trout's footer: Those who believe in telekinetics, raise my hand --- Attention! Off-topic comment: Haha, I like this footer a lot but I don't believe in telekinetics at all :-( Maybe I can get you to rise your hand my way?: "Who would like to have a free beer?"

MY HAND JUST RAISED! IT WORKS!

And in no uncertain Irish terms:

Brilliant!