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 Post subject: Re: 2015 NFPA 70E Changes
PostPosted: Thu Sep 13, 2018 9:32 am 

Joined: Tue Sep 11, 2018 10:26 am
Posts: 1
Hi Jim,
I am new.

In NFPA 70E table method, fault clearing time limits are 0.03 sec, 0.24 sec, 0.33 sec and 0.5 sec. Does the fault clearing time mean short circuit fault clearing time, or it is arc flash fault clearing time? Why?


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 Post subject: Table 130.7(C)(15)(a) Available Fault & Clearing times
PostPosted: Thu Sep 20, 2018 5:19 am 

Joined: Tue Nov 17, 2015 12:40 pm
Posts: 1
PPE categories are given for various tasks and associated max available fault currents and clearing times.

Is the max clearing time determined by the calculated available bolted fault current or the "Arcing" fault current which would likely be less? If so, how would you calculate the arcing current?

What is the intent of these parameters in applying the table method?


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 Post subject: Re: Table 130.7(C)(15)(a) Available Fault & Clearing times
PostPosted: Sun Sep 23, 2018 4:56 pm 
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Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
PA ENGR wrote:
PPE categories are given for various tasks and associated max available fault currents and clearing times.

Is the max clearing time determined by the calculated available bolted fault current or the "Arcing" fault current which would likely be less? If so, how would you calculate the arcing current?

What is the intent of these parameters in applying the table method?


The parameters came from inserting them into IEEE 1584. The intent is CYA but the reality is that the majority of the time that the tables get used the end user won't know those values. If those were known, it would be just as easy and better to apply IEEE 1584.


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