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 Post subject: Electric Generator Exposed Power Leads & Arc Flash Concerns
PostPosted: Thu Aug 02, 2018 7:29 am 

Joined: Thu Aug 02, 2018 6:44 am
Posts: 2
Location: New Hampshire
Hello – Need help with a question on arc flash on 480V/3ph generator. We’re OEM manufacturer of pre-packaged generators. The generator and electrical cabinet are mounted on a baseframe. The three-phase power leads from the generator are connected to a circuit breaker (mounted inside the electrical cabinet 2ft away from the generator). The generator has no TB or conduit box, but when the generator is running the package panels cover the power leads section all the time. The exception is when the user needs to remove some panels to replace package filters while the unit is running. This exposes the generator non-drive end and the 2ft section of the power leads from the generator to the back of the electrical panel. Some engineers raised concerns about arc flash hazards in this situation and the need to install a barrier or some other solution to protect personal. We’re not sure why applies and how to address these concerns.


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 Post subject: Re: Electic Generator Epxosed Power Leads and Arc Flash Conc
PostPosted: Thu Aug 02, 2018 11:59 am 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
Keeping it really simple, in general, employees should not be exposed to energized electrical conductors.


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 Post subject: Re: Elect Generator Exposed Power Leads and Arc Flash Concer
PostPosted: Thu Aug 02, 2018 12:08 pm 

Joined: Thu Aug 02, 2018 6:44 am
Posts: 2
Location: New Hampshire
Agree, but note that the generator leads are actually insulated. No copper is exposed, just the leads themselves are within site and are not inside a TB or conduit box.


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 Post subject: Re: Elect Generator Exposed Power Leads and Arc Flash Concer
PostPosted: Thu Aug 02, 2018 8:22 pm 
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Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
MTE wrote:
Agree, but note that the generator leads are actually insulated. No copper is exposed, just the leads themselves are within site and are not inside a TB or conduit box.


The word exposed doesn't mean you can see copper and this is a very common misconception. Shock protection is not required where energized conductors are insulated, guarded (visible but behind some kind of barrier that prevents inadvertent contact), or not exposed. Exposed is sort of a catch all that captures things such as conductors that are not accessible such as overhead power lines, or behind some kind of panel where blind reaching is either not being done or not possible. Inside modern MCC buckets when you open the door even though there are clearly power and control cables plainly visible if they are properly terminated, nothing is exposed. All of it is either guarded, insulated, or not exposed by covers. Exposed also has to be evaluated by distance. For instance if I'm working outside the restricted approach boundary (which also includes additional distance to account for inadvertent movement...hence 480 VAC has a 12" boundary with a little under 1" of arcing, and 11" of buffer space for inadvertent movement).

Most generators have a lot of little control wires running around them and a few power conductors where the ends are terminated with little to no gaps. MCC buckets are the same way, and with either one with the doors open everything is guarded, insulated, or not exposed, at least when it comes from the factory. What the end users do to a piece of equipment is an entirely different story. I don't mind...more business for me to repair the stuff that blew up.


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 Post subject: Re: Electric Generator Exposed Power Leads & Arc Flash Conce
PostPosted: Thu Nov 29, 2018 11:30 pm 

Joined: Tue Nov 06, 2018 12:38 am
Posts: 2
It is really common that there are wire running aroung <deleted link to commercial website>, such as electromagnetic switch, PT fuel pump on the unique model. oil refueling port, and so on.


Last edited by wbd on Fri Nov 30, 2018 5:37 am, edited 1 time in total.
Link embedded to commercial website


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