CBF , Circuit Breaker Fauiler

[alivip]

In protection system we usually consider CBF protection for each circuit breacker. If CBF operates in one CB ,it sends trip to all other adjacent CBs.
The question is whether the CBF function in other adjacent CBs which received this trip must be activated or not? why?

Do you have any opinion?

Regards,

 

[davidbeach]

Of course it must. What happens when you have a common failure mode in the breakers and get multiple simultaneous breaker failures? This used to poo-pahed until one utility suffered a rash of simultaneous breaker failures due to using the wrong grease during maintenance. It really adds nothing to the complexity of the scheme to have cascading breaker failure initiate.

 

[alivip]

it must!? but i think we can not talk about it certainly.

1-I read the spec of two famous power engineering consultant co. in my country. Both of them indicate that the CBF must not initiate CBF in adjacent CBs.

2- I don't know exactly, but i guess breaker failure in other CBs will be cleared by the other protection relating to those CBs.

3- In all schemes I have seen the CBF initiate CBF of adjacent CBs just when for each CB, two CBF were considered. i think it is because of that considering two CBF makes high reliability for protection system and prevents malfunction of CBF. and make us sure , CBF just initiate when both CBF of main CB initiate it and CBF does not send trip because of malfunction.

 

[submonkey]

Alivip,

Breaker failure should always cascade. If it is correct
for the protection to trip the breaker, it is also correct
for the breaker-fail scheme to be initiated.

Thanks,
Submonkey

 

[bacon4life]

David, do you have any more information on when/where that happened? Having recently had an inadvertent CBF operation on our system, I am hesitant to cascade the signal. I agree cascading adds hardly any wiring, but the impacts of an inadvertent operation expand from just a couple of pieces of equipment to potentially limitless assuming that remote tripping also activates CBF.

The Guide for Breaker Failure Protection of Power Circuit Breakers C37.119 suggests in section 8.3 that two CBF scheme problems are more likely than two failed breakers.

 

[davidbeach]

Not off hand. It was talked about at the last WPRC, but it wasn't my year to go, so I've just heard it second hand.

 

[alivip]

bacon4life,
i read the same that two probability of two cbf malfunction operation is higher than probability of two breaker failure, so it is suggested do not cascade cbf.

what is C37.119?

 

[DTR2011]

C37.119=IEEE Std

 

[bacon4life]

Finally found the paper David mentioned from the 2009 WPRC, "Protection Engineer Campfire Tales" by Ralph Barone from BC Hydro. They do routinely cascade BF and had two separate incidents of slow operating breakers just months apart.

It was interesting that the original breakers did eventually trip. It would be interesting to find out about the fault clearing ability of a breaker is when it operates slower than expected.

 

[Samiyoussif]

I am working on Areva P122, why there is >I setting beside the breaker position? is it for not fully opened CB?
and if i must not cascade it should i send the trip directly to the breakers or depend on the other breakers protection to see the fault?
bacon4life please send me the link of this paper

 

[bacon4life]

One of my coworkers had a copy of the conference proceedings, so you would probably need to contact the WPRC to get a copy.

Welcome to the forum, but you are much more likely to get an answer about the P122 if you start a new thread instead of hijacking this one.

 

[Samiyoussif]

I didn't mean to, I was searching about the CBF and the title of the thread appeared I thought it is general.
Sorry!