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 Post subject: Definition of What is "Normal Operation"
PostPosted: Wed Mar 27, 2013 9:09 am 
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It appears that the expression "Normal Operation" is going to remain in the new 2015 revision of the NFPA 70E WITHOUT a detailed explanation of what it really means.

It refers to the normal operation of the equipment (proper voltage, enclosed, dry,) in other words, proper (normal) conditions of operation EXCLUDING any actions from humans, like opening or closing overcurrent protection devices or switches, pushing buttons, etc).

Or does it refer to normal actions that humans do when interacting with the electrical equipment, like the action described in the previous paragraph.

The standard does explain in detail the concept of proper installation and proper maintenance but not the concept of proper operation.

Or maybe it does, and I have not yet found it. Any input regarding this issue. It is important because depending the interpretation of this expression, maintenance procedures could change considerably.

Thanks.


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PostPosted: Thu Mar 28, 2013 2:11 pm 
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I would say that "Normal operation" means that the system operates at or below the full (current limited) load conditions of each system component (including allowances for the across-the-line inrush current which is initially drawn at start-up) and operation that does not exceed timed current overload parameters while running. Normal operation also implies operating with current load conditions that do not exceed amperage rating of wire, circuit breaker, fuse, overload and transformer sizing with no unintended paths to ground.


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PostPosted: Fri Mar 29, 2013 6:41 am 
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Operating the equipment. See the owner's manual/instructions that came with the equipment. This would be opening/closing disconnects, breakers, etc. Pushing buttons to operate starters. That kind of thing. Anything in the manual that refers to maintenance/repair or only doing it in an emergency such as opening a safety disconnect under load clearly counts as not normal operation. Also operating equipment that is not properly maintained wouldn't be "normal operation".


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PostPosted: Mon Apr 01, 2013 7:20 am 
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That is the challange when the expression NORMAL OPERATION is not precisely defined. Some will interpret it like PaulEngr and others like Larry.

Both are different. One is relating to normal operation relating human interaction with the electrical equipment, the other normal operation relating to the rating of the equipment.

Some will argue that normal operation could mean both interpretations at the same time.

I believe we should have from NFPA a precise explanation of what is NORMAL OPERATION.


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PostPosted: Mon Apr 01, 2013 8:21 am 
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RECS wrote:
That is the challange when the expression NORMAL OPERATION is not precisely defined. Some will interpret it like PaulEngr and others like Larry.

Both are different. One is relating to normal operation relating human interaction with the electrical equipment, the other normal operation relating to the rating of the equipment.

Some will argue that normal operation could mean both interpretations at the same time.


Both interpretations absolutely can be applicable at the same time.

If you operate equipment outside the manufacturer specifications, you certainly void the warranty for abnormal operation. In the Technical Specification section of an equipment manual, you will see an outline indicating what is normal (or allowable) for a wide range of specifications including enviromental conditions, input parameters, and output parameters.


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PostPosted: Mon Apr 01, 2013 8:52 pm 
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Larry:

By your comments, I understand that you main interpretation of Normal Operation as being a rating issue, something related with environment (i.e. temperature, water exposure, dust, etc.), withstand rating, ampere rating, interrupting rating, etc. Not a human interaction with the equipment.

But do you consider Normal Operation to close or open a 2,000A main circuit breaker? This is an action, a human interaction with the equipment. Others could be depressing a start pushbutton, resetting an overload, etc.


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PostPosted: Tue Apr 02, 2013 5:06 am 
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I look at the term as a way of qualifying "interacting with the equipment in a manner which could cause an arc flash".


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PostPosted: Tue Apr 02, 2013 6:27 am 
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RECS wrote:
Larry:

By your comments, I understand that you main interpretation of Normal Operation as being a rating issue, something related with environment (i.e. temperature, water exposure, dust, etc.), withstand rating, ampere rating, interrupting rating, etc. Not a human interaction with the equipment.

But do you consider Normal Operation to close or open a 2,000A main circuit breaker? This is an action, a human interaction with the equipment. Others could be depressing a start pushbutton, resetting an overload, etc.


I agree with Paul, but also that the operator not interact with the equipment in any manner which would cause any component to exceed its designed specifications. This includes arc flash, but is a somewhat more encompassing definition to include not intentionally trying to push the equipment beyond the limits at which it was designed to operate. Any typical operation that the equipment is designed for would be deemed "Normal Operation"


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PostPosted: Thu Apr 04, 2013 6:14 pm 
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The draft already mentions environmental, installation, and maintenance concerns. That leaves operating it. Certain operations such as opening and closing disconnects or circuit breakers, taking readings, operating buttons, and so forth should be included. Where I would draw the line based on actual experience is inserting buckets into cells. Another example would be opening and closing hinged inspection doors but not for instance bolted panels on the backside, especially in MCC's with molded case breakers, overload relays only accessible internally, fuses, and the low voltage compartments of medium voltage gear, all of which are clearly intended for routine access. And yes, it should be spelled out. A manufacturer of MCC's lists removing and inserting buckets while deenergized but not while energized for instance.


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