Low Volatge Circuit Breaker Reliability 2

[gordonl]

I'm looking at replacing an old 600V switchgear lineup with a new or refurbished lineup. My question: Is there any sourcs of data that compare ANSI breakers from different manufacturers for reliability? IE trip unit failures, false trips, breaker failures, etc.

Our first foray into the market for the modern lines of withdrawable power circuit breakers was a disaster, we had Merlin Gerin breakers which nuisance tripped when the load was below 15%. We also had a couple of trip unit failures in the 7 years they have been in service. (we ended up sending all of these brekers back to be out fitted for external power supplies)

Personal experience with any of the recent lines of LV Power CB's would be appreciated, positive or negative. As well I would be interested if anyone has experience with SACE CB's, particularly the Emax or Megamax lines.

 

[CHDean]

Product reliability information is typically a closely guarded secret with most manufactures. I'm not aware of any means of comparison based on field failure rates.

Depending on the number of breakers you have in service a couple of failures may be within the average, I wouldn't think it unusual if you have >50 installed.

ABB-SACE breakers are going to be similar in basic design as the Merlin-Gerin. The only ANSI breakers of similar types are the SACE,SqD/Schneider/Merlin Gerin "Masterpact" and Cutler-Hammer "Magnum DS". I think all of the other ANSI manufactures are still using a steel frame design. The composite frame gives these three manufactures an edge on short circuit ratings which is a function of the frame. Trip units are another matter. Manufactures periodically tweek their electronics. The majority of high failure rates I've seen have been new or "improved" products that haven't got all of the bugs out of them. If you stick with a trip thats been on the market for a couple of years you should have good luck. Be cautious of the latest greatest releases, being first to buy is seldom a pleasant experience

 

[peebee]

I've also had bad experiences with the Merlin Gerin Masterpact breakers (specifically, those sold in the US under the Square-D name but sourced in France and with French abbreviations on the trip units), including severely high rates of trip unit failures and lots of nuisance tripping on functioning breakers. The typical trip unit failure mode was that the breakers would completely fail to trip, they essentially turned into electrically operated switches. And to add insult to injury, replacement of the trip units took something like 14 weeks each time as they don't stock spares here in the US.

Sorry, I've got no other information on breaker reliability.

 

[alehman]

My company does electrical commissioning. We see more failures of new products from all manufacturers than I would think should be acceptable. I don't know that any one is better or worse than any others. GE issued a large recall on certain power circuit breaker trip units last year (due to failure to trip). As far as I know this problem was traced to a bad component and has been corrected.

 

[gordonl]

Thank You all.

What does the nuclear industry do to ensure switchgear reliability? Would the above mentioned products meet these standards?

 

[peebee]

I can't speak for the nuclear industry. But in general, if you're looking for a reliable Air Power Breaker, I'd stay away from the new plastic ones and stick with the traditional metal ones. I have no data to back that recommendation up, it's mostly just a gut feeling. . . .

 

[alehman]

Just to clarify, there are three classes of "plastic" circuit breakers in the U.S. This discussion relates to power circuit breakers per ANSI and UL 1066. Examples of plastic power breakers are the Cutler-Hammer Magnum DS and MG Masterpact.

The second class of plastic breaker are called insulated case and are rated per UL 489 with much lower fault withstand ratings. Examples would be SquareD SE, GE PowerBreak and MG Masterpact (the Masterpact is available with either rating). They have double action operating mechanisms similar to a power breaker.

Molded case breakers are the third class are also rated by UL 489.

 

[Shortstub]

The US nuclear industry would not condone wholesale replacement of their switchgear. The prices paid to keep spares of the original manufacturer are unreal. But then, that's what it's all about!

 

[peebee]

Re: "The US nuclear industry would not condone wholesale replacement of their switchgear."

I'm not quite following you -- it'd seem they must attach some expected lifespan, say 30 or 50 years, to the switchgear, after which they replace it -- no? Or is the whole nuclear plant expected to be decommissioned at about the same time as the switchgear, under the assumption that the whole thing has reached its expected lifespan?

 

[gordonl]

What does class 1E equipment mean in reference to nuclear industry? What does C37.82 and IEEE-323 require for LV switchgear above and beyond C37.13 & C37.20.1.

 

[Shortstub]

Peebee,
I believe your latter remark is true, except for your order of events. Switchgear age is not the motivating factor. The reactor is. In general, parts availability for the "useful" life of a nuke plant,i.e., typically 40-years, are a requirement. The question of decommissioning has not been adequately addressed. If you abandon the reactor in place, then continued use of the facilities are not possible. As you probably know, that 40-year limit is approaching.

For plants seeking life extension licenses, and there are a few, then, such extension considers replacement ancilliaries, but not on a piece-meal basis, nor on an original OEM basis.

Gordonl,
I do not work, per se, in the nuclear industry, at least not on the nuclear-side. I have supplied, although not lately, ESD systems for generators and feedpumps, on the non-nuclear side.

 

[cuky2000]

There are few data in the enclose generic publication

http://www.usace.army.mil/publications/eng-tech-ltrs/etl1110-2-560/entire.pdf