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Equipment damage for wrong sizing

Equipment damage for wrong sizing

Equipment damage for wrong sizing

(OP)
Hello everybody,

I was wondering if some of you may have some information about statistical indexes of:
a) Equipment damage because of being wrong sized, related to circuit breakers, transformers, surge arresters, and so on.
b) As well as some indexes of spurious operations of relays because of wrong settings?

Does anybody have some information related to theses items?
If affirmative,I would thank you to share it.

Best Regards

RE: Equipment damage for wrong sizing

The only place I can think of off-hand is the IEEE Gold Book, "Recommended Practice for the Design of Reliable Industrial & Commercial Power Systems". I don't know if it will help you or not.

Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.

RE: Equipment damage for wrong sizing

(OP)
Hello,

I thank your reply, however, what I am looking for is some updated and real data, based on experiences.

We have some "engineers" that according to their experience it is not needed to size equipment above calculated shortcircuit levels because, a possibility of a fault damaging the switchgears or circuit breakers is very low.

Because of that, I would like to get some feedback coming from experiences of real engineers about some events that may have damaged some equipments.

I hope somebody may provide some data

RE: Equipment damage for wrong sizing

Then I would get me some new "engineers".

Alan

RE: Equipment damage for wrong sizing

Not sure where you are located, but in the US, the NEC requires all equipment be rated for the maximum available SC current.  Violation of that is a serious issue and a major liability in the event of an "event".  

RE: Equipment damage for wrong sizing

I'm glad you put engineers in quotes, because they are not real engineers.

There are so many more issues here than just equipment.  If you undersize equipment and someone dies than you are really going to be up shit creek.   

RE: Equipment damage for wrong sizing

Closest you will come getting such index or historical data would be something like what alehman suggested. Preparing such index is a life time project and even then it would only be as accurate as the input from the people surveyed. Now the people who would be requested to participate in the survey, are no more eager to answer questions than you are when someones calls you up for a phone survey for your house windows!

Regardless of what the index would say, what is important is that you do not become one of those statistics!

 

Rafiq Bulsara
http://www.srengineersct.com

RE: Equipment damage for wrong sizing

"We have some "engineers" that according to their experience it is not needed to size equipment above calculated shortcircuit levels because, a possibility of a fault damaging the switchgears or circuit breakers is very low."

Glad to hear that we can throw away the standards and no longer need to test and rate equipment since none of it matters anyway.

Should make switchgear cheaper and save a lot of money!upside down


 

Alan

RE: Equipment damage for wrong sizing

lume,
If you are in the U.S., the failures you will need to be counting will most likely be reported recorded by OSHA if anyone is injured. Other than that, those statistics are going to be a carefully guarded by manufacturers who track them.

I agree with the other replies. Underrating for fault current is never acceptable.

Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.

RE: Equipment damage for wrong sizing

I was a qc inspector once for switchgears company and the potential problems  I see for underrated equipments aside from actual faults are:

1. Possibility of interchanging CB with different ratings during maintenance.
2. We also take into consideration where the Swgr are to be installed, for the likelihood of incidents like lightning (outdoor swtgr)
 

RE: Equipment damage for wrong sizing

(OP)
Hello everybody,

I thank your comments!

Precisely, what I would like to know is, if you have had some experiences in which because of underrated equipment or incorrect settings some problems have happened and how often.

In Mexico, there is a code like NEC (in fact is a traslation of it) however, some large equipment manufacturers always tend to underrate equipment and it is very difficult to convince them that economical decisions must be based on technical reassons.
In some cases, short-circuit calculation done by the same manufacturer says "minimum value is x" but when you see the equipment name plate shows a value lower than "x".

Of course, there are discussions and so on but, it is very difficult to convince them despite having enough technical data and arguments, simply project managers do not understand technical reassons, only economical ones.

Final clarification: What I am talking about are some specific cases, I mean, it is not the rule to do wrong things in most of the projects, ok?

Best Regards
 

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