My name is Günther Müller, I have 20 years of experience in electrical engineering, and I work for a Consultant in Germany. I currently work on the extension of the electrical installation of a site in Europe, owned by a large American industrial group.
In this context, we were asked to evaluate the risk related to Arc Flash, in compliance with NFPA 70E standard and the IEEE1584 calculation methodology. It was the first time I had to do this evaluation, as this is a US standard which I did not know about and which has no equivalent here.
First, we had to make the audit of the existing installation, and the dimensioning of the extension. Then, we had to make the estimation of the Arc Flash risk level for every electrical switchboard, in order then to choose the category of PPE (Personal Protection Equipment) which electrical maintenance people should wear when operating on or near these equipments.
But now I really wonder: will this really help to protect the maintenance operators against arc flash risks?
First, I doubt it is realistic in practice to ask maintenance teams to wear different types of protections depending on the switchboard they work on. And I doubt they will even wear these protections, considering they seem to make it really hard to work with (impossible to do precise work with your fingers, lack of visibility, heat, etc …)
Second, I wonder why the standard calculates the Arc Flash energy at a distance of 18 inches (~50 cm): what about the possible damages to the hands and arms of a worker who is at the origin of the short-circuit, for example due to a mistake when checking that the power is down?
Third, as the results give a PPE category = 0 for 400V switchboards with a short-circuit level of 20kA, isn’t there a risk that some maintenance people will consider that there is no risk, when in reality if they are at the origin of a short-circuit with their tool they will be at minimum seriously burnt?
Also, as I found this standard somewhat questionable, I searched for more information about it on the web, and found this article and survey done in Australia and published in Industrial Electrix issue of April/June 2011, which I found on this website:
http://www.flipemag.com.au/APT/emagIE_secondquarter_2011/)
(click the link and go to page 44)
This is an abstract from the article:
So I even wonder if the calculations and estimations of this IEEE 1584 are realistic, or if the real risk is in some cases underestimated, which makes the standard almost worse than no standard at all, as people following the rules will feel safe with their PPE when they may risk more than 2nd degree burns.
Finally, even though my first thought was that it was a good thing there was an existing standard in the US, I feel that the current situation worldwide is:
* in the US, there is an existing standard but it is potentially dangerous
==> Contradict me if you disagree
* outside US, there is no Arc Flash risk specific analysis or recommendations
==> Tell me if you know about existing surveys or standards in your countries
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Hi Günther,
Your comments and shared experience with arc-flash hazard analysis is very interesting for me. I have no experience with the NFPA 70E standard but I work for electrical engineering company, manufacturer of LV and MV switchboards.
What I can comment is that testing of LV switchboards under arcing conditions is considered as special test in accordance with IEC 61641. Unfortunately this is destruction test and tested switchboards can not be used any more. So in Bulgaria we try to implement type tested switchboards and rely on real test to prove the personnel protection under arc conditions.
Hi Krum
Thanks for your comment.
Which real test do you pass to prove personnel protection under arc condition ?
Does it help to define Personal Protection Equipment (PPE) to be used ?
“I doubt it is realistic in practice to ask maintenance teams to wear different types of protections depending on the switchboard they work on”
You make a very good point. Most teams don’t want to lug around extra gear or stop to change between projects. They will make do with whatever PPE they have. Unfortunately it may not always be the most appropriate gear and then safety becomes an issue.
Hi Gunther,
You raise some very good questions and I certainly am not qualified to answer all of them but I would like to take a stab on several of these issues.
* First off, I can confidently say that it is better to have the NFPA 70 E rather than no standard at all and we see evidences of this all the time. For example, a crew of ours was asked to do some data collection at a large paper mill. They had not yet had their arc flash evaluation, the equipment was old, and the data model needed to be built from the ground up. We did initial estimate of the level of arc flash where the technicians were working and outfitted them accordingly ( category 2). At the time they were measuring voltage on a 600 V MCC and something triggered an arc flash The worker most directly involved received a second degree burn on the crook of his arm in a first degree burn on the side of his neck. He was back to work that day. In contrast to this, a few months previous to his experience, one of the facilities own electricians was doing some similar work and triggered an arc flash. He was badly burned and was off work for many weeks. there will workers were working without knowledge of the NFPA 70E and it's requirements and that ignorance was directly responsible for this worker's injuries. Indeed this accident underscored to the management that they needed to pursue immediately becoming compliant with the NFPA 70E.
* I believe one of the missing components in your discussion of the NFPA 70E is theneed for training. You can do all calculation, and paste all the labels you like, but if the electricians are not trained to understand and use the information correctly it will do them no good and indeed may do them some harm. They may think that because they are wearing some sort of PPE that it will be effective in all situations which as you remarked is simply a dangerous conception.
*Beware of placing too much stock in a single article which would seek to overturn a large bulk of experimentation and practical application.
*On the issue of wearing different types of PPE (personal protective equipment), I don't see any other way to deal with the situation. The only other option would be to take the worst-case scenario and wear the maximum PPE all the time, but that is ridiculous. No one is going to wear the full arc flash suit all the time. What most facilities are doing is going to a modified two category PPE scenario to minimize the need for multiple PPE changes and to provide adequate protection for all workers. Electricians are outfitted in arc-rated uniforms that meet the category 2 standard (minimum of 8 cal per centimeter squared thermal protection). This allows them to do the bulk of their work without dragging around extra equipment on category 0, 1, 2 arc flash hazards. On the few times that they be required to work on category 3 or 4, they would then put on a category 4 arc flash suit (minimum of 40 cal per centimeter squared thermal protection) to accomplish the work.
*The NFPA 70E covers the need for extra protection on parts of the body that are closer to the arc source than the 18 inch working distance. It requires gloves sufficient to meet the extra thermal demands. At the time of his arc flash, our technician was wearing voltage rated rubber gloves covered by the leather protectors. They did an excellent job protecting his hands which were very close to the source of the arc.
*I don't know about other countries, but the Canadians also have their own standard, CSA Z462, which is so close to the NFPA 70E as to be virtually indistinguishable.
Best regards,
Roger
Whilst inaccuracies may lead to workers underestimating the risks involved, a standard like the NFPA 70E is, as Roger mentioned, as much about improving awareness, training, knowledge and understanding of the potential risks and industry best practice on minimising the dangers.
For crews to completely disregard the safety standards, carry around inadequate PPE, refuse to change it accordingly or work on systems without the correct hazard analysis, they’re risking their own lives and others.
The UK has an equivalent but also uses the IEEE1584 to calculate the degree or arc flash hazard.
IEEE 1584 is like every other standard, a recommended minimum requirement to limit the severity of injuries due to an arc flash should one occur.
There has been much research on the subject of arc flash and the standards like IEEE 1584 and NFPA 70e give guidance to the designer, engineer and others to help limit the dangers to maintenance personnel.
There are no absolutes when dealing with arc flash hazards.
The hazards are very real and staff need to be aware of the dangers of arc flash and the possible injuries when working on electrical supplies.
PPE can and does limit injuries in the event of an arc flash but staff must be made aware of the limitations of the various PPE categories, hence the requirements of signs of Arc Flash Hazards and PPE categories.
Commonsense and mental alertness by trained maintenance staff will go a long way in preventing arc flashes.
In Australia live electrical testing is not classed as work from a safety point of view, so skirts around some of main safety requirements normally placed on “live work” so live testing can be performed.
I’ve come to the conclusion that the cost for some companies to upgrade to state of the art test equipment, which could reduce test time or eliminate some procedures, could be prohibitive possibly until an incident occurs or full tests as specified are not performed reducing risk.
Its all well and good for management to inform technicians to wear restrictive ppe,to monitor much harder,if this is the case, common sense does not dictate.
What is needed is more engineered solutions, not letting technicians be test dummies.
What i’ve picked up regarding incidents, natural reactions is for your hands to save your face, then you can be unlucky enough to suck in the ionised air from a gasp in sudden shock.
I apeprcaite you taking to time to contribute That’s very helpful.
Hi rford
I understand what you explain but as an engineer i prefer measurement than examples to validate if standards, calculations and PPE are useful on not.
Did some survey really measure that arc flash injuries decreased in the US thanks to arc flash risks calculation and PPE real usage ?
What are real differences between US and Europe explaining that arc Flash risk is an issue there and globally not managed here ?
we know arc is affected from what but how to protect from it If the way of protection as eng and the experience man says in the first page that is first step of idea but the second step must have aprotection things like element or subject which help the person or isolation .
we know it connected through the air so . how we solve this problem?
Brilliant article, Where has this website been all of my life
Does any one have soft copy of latest IEC:::Please share it.
Thanks
Many years ago we developed a Computer-Based Training course entitled Earthing for Electricians in which we explain Arcing Faults in very graphical terms using animations with audio narration. Should there sufficient interest from engineers & trainers, we would be happy to extract the relevant micro-lessons and make them available free-of-charge. Please visit http://www.matra.co.za and mail me at dave@matra.co.za for further information etc.
Hi Gunther
I’d have to agree with rford.
Until future engineered solutions are available to remove or majorly decrease risk, technician specific training in arc risk is needed and appropriate standard cal available to be worn with the restrictive higher cal available for the higher risk kA jobs and management needs to constantly monitor the the work systems and procedures.
Additionally, i think all electrical equipment worked on, where arc risk is associated, should be assessed as to maximum fault kA condition and stated on that equipment and the category of protection required.
There also needs to be an associated register to be updated as to changes in kA ratings due to installation upgrades.
From a technician’s point of view I am generally interested, these days, primarily in risk analysis and then getting the job done. If an incident occurs it will be extremely costly and embarrassing.
1. If i get injured or killed many people and procedures will be affected.
2. Equipment damage and down time will also cause the above.
From an engineering view, over engineering the safety requirements would be adviseable because measurement of such fault conditions contain too many variables.
Regards