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 Post subject: European Arc Flash Study
PostPosted: Wed Jul 08, 2015 11:12 am 
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Hello,
My previous question was based on curiosity but now has become reality as we have been hired to perform an arc flash study in a European facility of a USA based company. Seems that it is the corporate policy to do at all facilities.

So if anyone has any advice on working in the IEC world or anything else in Europe, I would appreciate any insights, hints, suggestions, etc.

Both the software I have, EasyPower and SKM, have IEC functionality and haven't decided which one to use yet.

Thank you in advance.

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 Post subject: Re: European Arc Flash Study
PostPosted: Wed Jul 08, 2015 12:09 pm 
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The last couple of 'overseas' projects we performed involved equipment and wiring sourced from the US so the actual study location did not have much impact.

Arc flash calculations per IEEE1584 are based on North American power analysis procedures and bolted fault currents. But, IEC device short circuit evaluations need to be based on European procedures and values.
I believe the standard software packages can handle these differences.


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 Post subject: Re: European Arc Flash Study
PostPosted: Wed Jul 08, 2015 1:02 pm 
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Other than the obvious voltage, frequency and equipment differences, the concept is pretty much the same. I've taught how to perform arc flash studies at a lot of global locations and they are not that much different than in the U.S. Except Europe/U.K. have called them "Arc Flash Risk Assessments" since the beginning. My Colleague Mike Frain from the U.K. and I presented an IEEE paper in 2012 about the risk assessment approach. This approach made it's way to this side of the Atantic with the next edition of NFPA 70E (2015 Edition)

A European View of Arc Flash Hazards and Electrical Safety 2012


A few other articles that Mike and I co-authored that discuss arc flash overseas can be downloaded below:

U.K. Fear of Flashover 2007

Part 1 U.K. Arc Flash Article 2009

Part 2 U.K. Arc Flash Article 2009

Part 3 U.K. Arc Flash Article 2009

In keeping with the forum rules, I won't post my email or phone info here, but you can PM me if you have any other questions or wish to discuss the details.


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 Post subject: Re: European Arc Flash Study
PostPosted: Wed Jul 08, 2015 3:34 pm 
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Thank you Jim. I thought might provide some useful information!

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 Post subject: Re: European Arc Flash Study
PostPosted: Thu Jul 09, 2015 4:30 am 
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Jim, the link for Part 2 of the article, takes one to something that says You do not have permission to view drafts.

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 Post subject: Re: European Arc Flash Study
PostPosted: Fri Jul 10, 2015 11:34 am 
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Speaking from working for a European company with U.S. plants,

The big difference I've noticed is that the focus in Europe is on the ANSI Z10 Hierarchy. Where in the U.S. there is a tendency to go right for the bottom of the hierarchy (just wear PPE) in Europe the focus seems to be on preventing/eliminating the hazard (ALARP...as low as reasonably practicable). This has generated more interest in arc resistant gear, arc termination devices, and various arc flash relays (reduction). When it comes to PPE, there seems to be a tendency at that point to true to ignore the issue altogether as opposed to North America where the tendency seems to be to go towards PPE without even considering alternatives.

The second big difference is that IEC has a group of methods for doing short circuit analysis compared to just one (ANSI) for North American markets. However at least with SKM, this is where things get bizarre. The majority of short circuit analysis methods apply various empirical tricks to make it tractable to do the analysis by hand, although very few people still do it that way. The end result is "conservative" (over-estimates) for short circuit estimates which is usually not an issue. However for arc flash if we overestimate the short circuit current, due to the fact that it results in a faster trip time, it under-estimates arc flash hazards. Thus the software mentioned (SKM, ETAP at least) use the IEC "comprehensive" (most accurate) method of estimating short circuit faults for arc flash calculation purposes, no matter which model generates the short circuit study results. So whether you knew it or not, you've been using the IEC model all along.

And the third big difference is that European market requirements for LOTO are often very different from those in the U.S., and this stems again from the concept of risk assessments. In the U.S. in some markets (utilities) ONLY a visible break disconnecting means is accepted for lockouts. In almost all others, ONLY a mechanical means of locking out closing the power conductors is accepted. And a handle where the axis of rotation is parallel to the face of the cabinet and where the cabinet has to be able to be opened without removing the lock is the only accepted lock out handle in certain U.S. markets that follow NFPA 79 as opposed to the IEC rotary handles where the axis of rotation is perpendicular to the cabinet face. European countries seem to accept the idea that as long as the lockout mechanism meets the risk assessment criteria, any equivalent mechanism will work without limitations. Also European countries seem to actually set absolute standards for risk (frequency of occurrence of accidents) whereas there are no clear government-endorsed standards in North America.

Thus it seems to me like a mixed bag. The general approach and concepts that arise out of ALARA/ALARP and the hierarchy of controls is much more advanced whereas basic PPE requirements seem much more relaxed when comparing European approaches to North American ones.

In terms of IEC itself, it is exasperating. NEMA standards for starters tend towards much heavier duty starters. Generally if you design to IEC standards, increase the rating by one class to get equivalent results. Whereas NEMA standards are one-size-fits all with a rating roughly equal to "AC-3.5", IEC standards are more flexible resulting in cheaper, lighter duty starters unless you specify AC-4 which actually exceeds NEMA slightly. The overall design philosophy though seems to be to jam all the starters in one big cabinet with very little protection except for maybe an overall fuse or circuit breaker. With no way to isolate controls, power wiring, or even one starter from another, arc flash is a much more difficult challenge in terms of implementation. It also extends to electric room layouts. I have actually worked on European equipment with medium voltage starters with 24" of clearance in front of the starter.. The "two second" rule probably does not apply in those conditions.


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 Post subject: Re: European Arc Flash Study
PostPosted: Fri Jul 10, 2015 6:15 pm 
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wbd wrote:
Jim, the link for Part 2 of the article, takes one to something that says You do not have permission to view drafts.


Thanks Barry, I fixed it.


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