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 Post subject: Maximum Arcing Times in Easy Power
PostPosted: Tue Apr 23, 2019 6:39 am 

Joined: Thu Sep 06, 2018 11:12 am
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I'm looking to see what the general consensus is for the Maximum Arcing Times people are using in Easy Power since the release of IEEE-1584, 2018. Obviously 2 seconds is well published, but has anyone lowered the max time for <0.25kV to something below 2 seconds?


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 Post subject: Re: Maximum Arcing Times in Easy Power
PostPosted: Tue Apr 23, 2019 7:34 am 
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Since there is no consensus document for other than 2 seconds that is what I use and probably most people also.

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 Post subject: Re: Maximum Arcing Times in Easy Power
PostPosted: Tue Apr 23, 2019 11:30 am 
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erockvan wrote:
I'm looking to see what the general consensus is for the Maximum Arcing Times people are using in Easy Power since the release of IEEE-1584, 2018. Obviously 2 seconds is well published, but has anyone lowered the max time for <0.25kV to something below 2 seconds?


2 Seconds is reaction/response time and not dependent on voltage. That is the only number referenced in IEEE 1584 for this so WBD is certainly correct and that is what most would use if they cut off the time.

I always felt it was a bit conservative because using 2 seconds implies that a person is standing in the same spot at a fixed working distance and taking the entire 2 seconds of energy.

In reality, I believe the person is rapidly increasing the working distance (i.e. jumping/running/being blown back) which would decrease the energy (unless they are trapped or incapacitated). However, this is not accounted for and I don't believe anyone has studied it.


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 Post subject: Re: Maximum Arcing Times in Easy Power
PostPosted: Mon Apr 29, 2019 9:33 am 
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Joined: Tue Jan 19, 2010 2:35 pm
Posts: 138
I agree with Jim, 2 seconds is conservative however I'd want you to consider the situation. If you do decide to lower the time, you might want to insure those using and relying on the arc flash information understand that the calculation is less than 2 seconds. Using Easy Power you can add language to the label that says as much. Regarding the actual working situations; consider if a person needs a ladder to access the device in question? Evening stepping off the bottom step of a ladder adds time to escape the arc flash. What about the room where the equipment is located? We know electrical rooms never have stuff stored in them. The truth is, large mop buckets, mops, cardboard boxes filled with supplies and other things are often stored in electrical equipment rooms. Although the electrician should, expecting him to remove any non electrical stuff isn't entirely reasonable. Before lowering the 2 second time, I'd want to have fully considered some of the other options to get the upstream over current device to open faster. There maybe changes you can make that can get the time and arc flash energy lower.


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 Post subject: Re: Maximum Arcing Times in Easy Power
PostPosted: Mon May 13, 2019 7:31 am 

Joined: Mon Nov 25, 2013 8:03 am
Posts: 5
If a person is trapped then the arc level will be far higher than listed on the label. Also, using the 2 seconds or less does not reduce the damages, even if the person involved gets out of the arc. I use 5 seconds to see where the protection is inadequate and then try to fix it. If it cannot be fixed then I believe the actual arc level should be used. I am strongly opposed to using the 2 second rule. If you fail, you die. I call it the "electrician jump test rule". The 2 second rule seems to imply that if an electrician cannot get out of the way in time you really do not need him anyway.


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