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 Post subject: IEC 61641 "Arc Free" vs NFPA 70E / IEEE 1584
PostPosted: Sat Mar 20, 2021 5:15 pm 

Joined: Fri Jan 15, 2016 12:45 pm
Posts: 1
All,

I'm posting this here as it is really this new question of IEC 61641 in my North American world of NFPA 70E/IEEE 1584. I've done various studies based on the latter for my US clients.

To the best of my knowledge, North American standards like NFPA 70E and IEEE 1584 regarding arc flash have no equivalent to IEC 61641 for "arc ignition protected zones". I understand the IEC used to refer to this as "arc free".

In Section 1 (Scope) of the IEC 61641, it ends with the sentence, "This is a voluntary test made at the discretion of the manufacturer." At the very end of the standard in Annex B, it has this very curious note (that is suggested to need inserted right after the Section 1 last sentence):

"NOTE 2 The recommendations of this report are not acceptable in the USA, nor in Canada, nor in the United Kingdom."

Can anyone speak to why this was inserted. I have seen some misgivings in posts elsewhere regarding IEC 61641. This note appears to have actually written into the standard some sort of significant split. I can't help wonder if it is the "arc ignition protected zones" versus the rest of the standard's testing to something similar to IEEE C37.20-7.

Thanks in advance for any potential help.


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 Post subject: Re: IEC 61641 "Arc Free" vs NFPA 70E / IEEE 1584
PostPosted: Mon Mar 22, 2021 8:03 am 
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Joined: Thu Jul 07, 2011 6:03 am
Posts: 66
Location: Netherlands
First: I don't know the exact reason why it has been inserted in that way. My guess is that the standard, like IEC 61439 for LV switchgear, is performance based and doesn't specify any design parameters like ANSI standards. As long as the tests are passed it doesn't matter *how* they were passed and that could be a reason the standard has not been adopted in these jurisdictions.

The benefits of arc ignition protection zones are fairly limited as the testing conditions (such as closed panel doors) typically fall under the "no likelihood of occurence" in NFPA 70E Table 130.5(C). Work that happens where the testing conditions are invalidated, for example after opening a door or removing a barrier to do voltage testing, still require a risk assessment like for any other type of switchgear. So the hazard is the same, the likelihood of occurrence is lower for conditions that already had a low likelihood. You would need a very mature and detailed electrical safety program for this to make a meaningful difference in working procedures.

There are useful exceptions like LV switchgear that maintains the arcing class while racking breakers but I've never seen those in the wild.


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 Post subject: Re: IEC 61641 "Arc Free" vs NFPA 70E / IEEE 1584
PostPosted: Thu May 13, 2021 2:55 am 
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Joined: Tue Oct 13, 2009 3:59 am
Posts: 7
Location: Brighouse, West Yorkshire, UK
I have been told (over the years) various reasons why IEC/TR 61641 was not accepted in the UK:-

1. It has been very difficult to predict LV arcing in order to make the tests repeatable. [I was told maybe only 1 out of 10 tests passed, guess which got published...].

2. Most arc faults happen with the doors open so all tests are invalid anyway. [This is also my experience and I heard of one yesterday].

3. The approach in the rest of Europe has been to deal with the arc after it happens, very pragmatic, whereas UK tries to prevent it happening at all (greater emphasis on insulation/segregation).

4. If you buy "arc protected" or "arc certified" switchgear you can tick a box and go back to sleep.

I don't know whether any/all of these are true, but the tick box attitude to purchasing strikes a chord with me (speaking as a switchgear manufacturer based in UK). One of the drivers for change in many areas of the UK are the insurance companies so if people (specifiers) think they can reduce their risk by ticking a box they will, even if they don't really understand what they are asking for.


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