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 Post subject: When to Perform an Arc Flash Study?
PostPosted: Fri Mar 16, 2012 5:29 am 
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A University is asking me if they are now required to have arc flash studies performed on all their buildings. It's a smaller University with about 10 buildings on campus and no renovation work has been done lately. I know how to perform the study, but I'm not sure how to answer their question...

Thanks,

Tom


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PostPosted: Fri Mar 16, 2012 6:58 am 
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Location: Wisconsin
Every employer needs to be able to identify the hazards in the workplace and provide their employees with the appropriate PPE. While they do not have to provide PPE to 'outside contractors' they still must advise the contractors of potential hazards.

Arc flash is only one of several work place hazards.


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PostPosted: Mon Mar 19, 2012 1:29 pm 
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tmillard wrote:
A University is asking me if they are now required to have arc flash studies performed on all their buildings. It's a smaller University with about 10 buildings on campus and no renovation work has been done lately. I know how to perform the study, but I'm not sure how to answer their question...

Thanks,

Tom

The short answer is "Yes", at least assuming you are in the US.
Even if the system consisted of 1 service per bldg, fed from transformers < 112.5 KVA, at 120/208, you would still be "performing a study" to determine that, and to print appropriate labels.

But in the more likely case where they have MV switchgear, MV distribution, and MV/480 V transformers at each building, and then 480 distribution, heck yes they are required to do one.


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PostPosted: Mon Mar 19, 2012 2:06 pm 
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Thanks for the response, but let me re-phase the question...

How do I answer the question "Am I (a university) required to have an arc flash study performed and if so, why? Our employees don't work on any energized (live) equipment and we hire electrical contractors to do all our maintenance, etc???"


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PostPosted: Mon Mar 19, 2012 7:55 pm 

Joined: Fri Apr 01, 2011 5:00 pm
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Location: Minnetonka, MN
I hate to be wordy....but here's an answer that I often used when asked why do we have to have a study performed..
A common question posed by organizations concerned about electrical safety is – What can I do to protect my workers? Very common follow-up questions would be – What regulations do I follow? What is the hierarchy of the regulations? Those organizations that are aware of the NFPA 70E document often ask the questions – Is NFPA 70E Law? Is compliance with NFPA 70E mandatory per OSHA?
As an electrical industry, perhaps we should not focus so much on the question -should we follow NFPA 70E or not, but ask – Since OSHA requires us to protect our workers against known electrical hazards (such as shock and burn) if we are not following procedures such as those contained within NFPA 70E – what are we using? Perhaps we should take a quick look at some of the regulations that presently exist, and decide whether we are progressing along a path that will protect our workers.
Let’s start with OSHA, then weave in pertinent sections of certain NFPA documents that apply to electrical safety:
OSHA:
General Duty ClauseSection 5(a)(1) states, “Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.”
In a July 25, 2003 OSHA Standard Interpretation letter signed by Russell B. Swanson, Director, Directorate of Construction, it states, “With respect to the General Duty Clause, industry consensus standards may be evidence that a hazard is “recognized” and that there is a feasible means of correcting such a hazard.”
It further states that “Industry consensus standards, such asNFPA 70E, can be used by employers as guides to making the assessments and equipment selections required by the standard. Similarly, in OSHA enforcement actions, they can be used as evidence of whether the employer acted reasonably.
What should a prudent employer do? Hazard assessments are important, but so are alerting techniques; considering PPE; providing Electrical Safety Training:

[color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3]Then I think one should look to NFPA 70 Art 110.16 - where electrical equipment ....that is likely to be examined, adjusted, serviced or maintained while energized shall be field marked....to warn of an arc flash Hazard.[/size][/font][/color][/size][/font][/color]

[color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3]And NFPA 70E Art 110.1 which defines the responsibilities of the host and contractor in situations where there is a known electrical hazard.[/size][/font][/color][/size][/font][/color][/size][/font][/color][/size][/font][/color]

[color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3][color=#4b6183][font=Arial][SIZE=3]Just because your own employees may not be exposed to electrical hazards, your contractor may be exposed, and they ( at least those who understand the hazards) will ask you to help quantify those hazards, that is why a study can be very helpful.[/size][/font][/color][/size][/font][/color][/size][/font][/color][/size][/font][/color][/size][/font][/color][/size][/font][/color]

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Steven T Rasmussen CESCP
Zone Safety Rep


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PostPosted: Tue Mar 20, 2012 8:50 am 
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At a minimum, you should have a short circuit and protective study done. Before the contractor can determine the arc flash energy level or Hazard Risk Category, they'll need to know the available short circuit current at the equipment and the time that it takes the upstream device to operate. Determining the hazard level is not an easy task. Having these studies increases the chance that the contractor will correctly calculate the arc flash energy level and determine the appropriate ppe.

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Robert Fuhr, P.E.; P.Eng.
PowerStudies


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PostPosted: Wed Mar 21, 2012 3:44 am 
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There is at least 3-4 relatively simple methods for getting to an arc flash hazard study that does not require a large amount of money or time.

The first requirement is to do the short circuit study. You MUST do this these days. It is required by the National Electrical Code for labelling, and it is not possible to safely install equipment without it (because you could end up with underrated equipment that can fly apart if a fault happens...not good). If you have single line drawings (which if you don't have them are pretty easy to create from scratch), this is one of the few studies that can be done by hand with a pen and calculator if necessary.

The second requirement is to do a coordination study. This one is not really required by any code but you end up gathering the same data that is needed for the arc flash study (trip times).

Third is to perform the arc flash calculation. There are 3-4 relatively simple methods. They will tend to produce "overprotected" results but get you to where you need to be. The first is the table method. Take your trip times (calculated in the coordination study...use SCCR as well as approximately 85% of SCCR for fault current to determine trip time) and compare to the 70E table specifications. If they are lower, use the 70E table results.

The second method is detailed on the "brainfiller" web site. Google it. It is a refined version of the above.

The third method is to use one of the methods listed in the appendix of 70E. Some such a Lee method require very little data but again, may lead to overly conservative results. Others (IEEE 1584) take a lot more data and get to the point where although a spreadsheet can be used for some relatively simple cases, a full blown power analysis software package (EasyPower, EasyTAP, SKM for example) becomes necessary...along with the training to use it.

Although I work in a multimillion dollar chemical/mining company believe it or not we still use these "simplified" methods infrequently because sometimes it is more important to get to an answer than to get the third decimal right.


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PostPosted: Wed Mar 21, 2012 5:48 am 

Joined: Mon Nov 19, 2007 5:25 am
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Location: Titusville, Fl.
All good info above concerning protection of employees per OSHA 5A1, General Duty Clause, and how the host employer should protect contracted employees per NFPA70E. The three methods for Arc Flash calculations, w/r to the Short Circuit Study (required), and the Coordination Study (preferred), also good info. Regarding the NFPA70E tables it was eluded to verify your electrical equipment/system meets the criterion to allow you to use such Tables. Hence, make sure once all information has been gathered (trip time and available fault currents) you comply with the Notes at the end of the NFPA 70E table,

"Table 130.7(C)(15)(a) Hazard/Risk Category Classifications and Use of Rubber Insulating Gloves and Insulated and Insulating

Hand Tools-Alternating Current Equipment (Formerly Table 130.7(C)(9)."

One question that comes into mind, has the University adopted NFPA 70E? It's consensus standard referenced by OSHA, but not mandated. However, if not adopted, then what type of Electrical Safety Program (ESP) has been established at the University to be in compliance with the OSHA General Duty Clause. Hate to bring up this bigger issue, but your ESP should be established, in order to drive your efforts such as arc flash studies and labeling. Something to think about...


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PostPosted: Wed Mar 21, 2012 10:23 am 
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You don't adopt the 70E, it goes in to effect the day it is released. Not the same as the NEC which gets adopted.


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PostPosted: Wed Mar 21, 2012 3:51 pm 
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Yes, you do adopt 70E in a particular edition. 70E is an industry consensus safety standard. It is not a regulation. That makes a big difference. We're free to write our safety standards. We can choose to recognize 70E, some other standard such as NESC, or some other standard such as CSA Z462 (not that this matters...Z462 and 70E are 99% word-for-word identical except for the annexes in which Z462 has more). It does not go "into effect" unless the individual company safety standards say "latest edition". I highly doubt that many utilities have adopted 70E since NESC is vastly more comprehensive and useful in their industry. And in a similar approach, the RUS standards supercede many sections of the NESC standard. Even non-rural utilities often use the more restrictive RUS standard. And most of them have been pretty slow to adopt the arc flash requirements in the NESC.

Even if we recognize 70E, we don't even have to recognize it exactly the way it is written. Article 90 clearly states that 70E is a guidance document, nothing more, and that everything in it is more or less a suggestion.

The major reason for not writing your own standard is that then in court you have the burden of proof of proving that your standard meets the general duty clause requirements. If you adopt a consensus safety standard, an affirmative defense is that you are using recognized and generally accepted good engineering practices (RAGAGEP) which means that you have a defense against arguing the technical specifics. This leaves only two remaining hurdles in the defense. First is whether or not the specific implementation details meet the standard that is claimed, and the second is whether or not the standard being cited is indeed RAGAGEP. The second case would occur for instance if a company adopted a very early 1980's edition of 70E and that the issue at hand is addressed in later years of the standard. In this case there is clearly a recognized hazard and relying on the old standard simply doesn't meet RAGAGEP criteria.

A grey area is if a company is 3-5 years behind the current standard. It is frequently the practice to delay by one revision cycle and see if any of the new and controversial changes are adopted, dropped, or modified in the next Code cycle. A good example of this is the recent inclusion of the new "disconnects" exception in 130.2, as well as including both shock and arc flash hazard boundaries to "trigger" safe working conditions. It is highly likely that this section is going to undergo changes in the next code revision if for no other reason than that the new exception is written extremely poorly from a readability point of view.


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PostPosted: Fri Mar 23, 2012 10:00 am 

Joined: Wed Aug 31, 2011 5:26 am
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tmillard wrote:
Thanks for the response, but let me re-phase the question...

How do I answer the question "Am I (a university) required to have an arc flash study performed and if so, why? Our employees don't work on any energized (live) equipment and we hire electrical contractors to do all our maintenance, etc???"

NEC 110.16 states "...other than dwelling units,..."


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