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Clarification Sought on Operating Sequence of a Circuit Breaker

12/03/2017 11:50 PM

Can a Circuit Breaker assigned with rated operating sequence O-0.3s-CO-3min-CO also be used for an application specifying rated operating sequence O-3min-CO-3min-CO ?

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#1

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/04/2017 12:13 AM

The O-0.3 is the rated time that the breaker is ready to close after being tripped by a short circuit....this would be for a particular application that required minimum interruption time, and the rating class is also relevant...the answer is maybe if it meets the requirements and code...

http://cired.net/publications/cired2015/papers/CIRED2015_0777_final.pdf

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#2

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/04/2017 3:14 AM

What does it say in the manufacturer's information that came with it?

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#3
In reply to #2

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/04/2017 3:54 AM

We are manufacturer of the Circuit Breaker. The end user has specified his requirement for O-3min-CO-3min-CO. Whereas, we have Type Tested our Circuit Breaker for O-0.3s-CO-3min-CO. We know what we produced definitely serves the application. Yet, the end user wants to have a more convincing proof on the same. We don't find any clause in the relevant IEC:62271 series. So, if you can help, please do so.

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#4
In reply to #3

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/04/2017 5:37 AM

Could be a typo. the Client and discuss.

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#5
In reply to #3

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/04/2017 8:57 AM

I do not see a problem with the breaker. I presume it can sit open indefinitely without damage.

But not knowing your whole system, there is a possible problem with the closing power, if the power drain of a fault-tripped breaker depleted the energy reserve for close/trip e.g. capacitor or battery, with a 3 minute break after the fault-trip rather than 0.3s. Being an outsider, I do not know the total drain on the supply, which may feed several breakers or control/protection relays etc, or the recharge time or if the recharge system is disabled by the breaker being open.

Having been a specifier/purchaser, I am aware of the importance of stating what you actually require and of the "weasel wording" sometimes got from suppliers.

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#7
In reply to #3

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/05/2017 6:36 AM

Further to my post #5, I feel that, while your breaker may be designed for automatic reclose after a lightning strike [ a shorter pause 0.3s before reclose being more demanding on the breaker than the customer requirement] this may be a simple ungrounded system with voltage detection of earth fault.

All breakers trip on earth fault, to restore the system it is necessary to manually close each breaker in turn to find the faulted line.

When the faulted line is found, all breakers trip again so it is necessary to reclose all breakers except faulted line.

All this takes a significant time to closing the last breaker, hence the period of 3 minutes possible between closings.

You really need to talk to the customer to understand the requirement.

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#9
In reply to #3

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/06/2017 1:38 PM

The client needs to be edumacated on the specification and what it means, and how that applies to his/her need for a new circuit breaker.

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#10
In reply to #3

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/06/2017 3:34 PM

Just tell them that you asked an anonymous forum, chosen without a single reason, and no assurance anybody on that forum is qualified in any way to answer the question said it would be OK.

This is no way to do business.

What will you tell the customer about your expert advice?

Who is your product engineer?

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#11
In reply to #10

Re: Clarification sought on Operating Sequence of a Circuit Breaker

12/06/2017 4:17 PM

Especially not really cool where safety of people's operation of the equipment is brought to bear, or the safety of people even in the area. This is how some disasters begin.

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#6

Re: Clarification Sought on Operating Sequence of a Circuit Breaker

12/04/2017 7:01 PM

It seems odd that your customer would object. A circuit breaker that can close on a fault that it just cleared 0.3seconds earlier, should be much more robust than one that requires a 3minute lockout period (presumably to allow the contacts to cool); i.e., your breaker could be used for recloser duty while the one as specified could not.

Check with your customer to better understand the exact nature of their objection, it may be in the nomenclature.

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#8

Re: Clarification Sought on Operating Sequence of a Circuit Breaker

12/05/2017 11:10 AM

Sounds like a cost issue. Your 0.3s is more expensive than the 0.3m. You need to tell him it's not better to step over a dollar to pickup a dime.

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