NFPA 70E archflash

[living2learn]

I have a generator room and was wanting to set the Instantenous portion very high or not at all to coordinate better with my downstream devices and the alternative to that is very high arc flash. So here is my thought I tie the door contacts and motion sensor for the room into the instantenous portion of the circuit breakers. My thought is while nobody is in the room then arc flash is irrelevant.

My concern is while somebody's in the room and the generators aren't on therefore the instaneous portion is on and the generators fire up I just have to coordinate any inrush with my temporary instaneous.

Any other concerns?

 

[rbulsara]

Arc flash is only relevant when someone is working on the energized gear. Just being in the room is not the problem. Just keep the distance from the breaker, when it is energized.

As it is, it is very inconvenient to stay in the gen room when the generator is running.



Rafiq Bulsara

http://www.srengineersct.com

 

[jghrist]

I would use a labelled maintenance switch to implement the instantaneous. Safety training would then include the procedure to close the maintenance switch anytime that live maintenance was performed.

 

[alehman]

And several manufacturers offer systems that can do what jghrist suggests.

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

 

[Zogzog]

I recommend a maintenence switch also, I had posted that earlier but for some reason my post was deleted. This is a common issue and the maintenence switch is an excellent solution.

 

[ASimmons23]

We also use maintenance switches on each switchgear lineup which arms the 50 Elements of the main relays before any work is done on the gear.

I highly recommend this solution opposed to not using an instantaneous element in situations where the inst. element interferes with downstream coordination.

 

[Maak]

"Arc flash is only relevant when someone is working on the energized gear."

I strongly disagree. Don't you think about a) damage to the equipment and b) costs due to interrupted processes? Safety first, but it is definitely not the only issue.

There are better solutions than maintenance switch.

 

[rbulsara]

Maak:
That comment was in context of the topic of the original thread only. Perhaps a read of Preface to 2009 NFPA 70E would help.

While your concerns are valid, equipment damage due to arc flash is not covered by NFPA 70E or IEEE 1584. NFPA 70E primarily deals with work practice related safety of personnel and generally enforced by OSHA (vs. say electrical inspectors). Until 2000, it only dealt with shock hazards, now it also has included arc flash hazard (to personnel).

Rafiq Bulsara

http://www.srengineersct.com