How will you meet new code requirements for arc reduction?: Q&A Session

Arc flash incidents occur all too often and impact many lives. To address the problem in the industry, NEC 240.87 was developed to ensure arc flash safety in the electrical industry. Three industry experts weigh in through an extensive Q & A.

04/30/2014


Eaton sponsored the custom Webcast that originally aired on April 24. Courtesy: EatonThomas Domitrovich, PE, LEED AP, Eaton, Ken White, retired, Olin Chlor-Alaki, and Jim Dollard, safety coordinator, IBEW Local 98, answered the following Webcast-viewer questions related to NEC 240.87 code requirements:

Q: To what extent are foremen/supervisors responsible for following arc-fault safety, procedure for calculating safety distance?

  • A: Jim: Everyone is responsible for safety. See NFPA 70E 2012 105.3 and 110.3.

Q: How should PPE selection be approached with respect to NFPA 70E Annex H vs. Table 130.7(C)(16)? Why do the two tables differ for the same energy levels? Should we not be using hazard/risk categories when an analysis has been performed?

  • A: Jim: Excellent question! The HRC tables and Annex H are different because doing a study and using the tables are two completely different approaches. The tables are based on empirical data from industry and the collective experience of the committee. A study is based on formulas and data gathered by the engineer. The tables are built conservatively and a study that identifies an exposure at 7.5 cal cannot be classified as an HRC 2. An understanding of the definition of "arc rating" is essential. The user must fully understand ATPV and EBT. Perhaps the 2018 edition of 70E will get that done.

Q: Can you discuss why the NFPA 70E has different methods of PPE selection and why they are different for the same incident energy? i.e. Annex H vs. Table 130.7(C)(15)(a)

  • A: Jim: Excellent question! The HRC tables and Annex H are different because doing a study and using the tables are two completely different approaches. The tables are based on empirical data from industry and the collective experience of the committee. A study is based on formulas and data gathered by the engineer. The tables are built conservatively and a study that identifies an exposure at 7.5 cal cannot be classified as an HRC 2. An understanding of the definition of "arc rating" is essential. The user must fully understand ATPV and EBT. Perhaps the 2018 edition of 70E will get that done.

Q: Have adequate and functional auto-darkening hoods been developed yet?

  • A: Jim: I am not certain about "auto-darkening," but the tint on the shields has progressed to allow more light to see the task at hand.

Q: Jim or Tom, Please explain how the NEC-2014 requirements for 1200A breakers affects existing equipment. What about overcurrent protection such as fuses?

  • A: Thomas: The National Electrical Code applies to new construction but this technology can be applied to existing locations. Section 240.87 does not apply to fuses.

Q: There must be a slightly increased risk of actuating the overcurrent device when using the "reduced arc energy maintenance switch." Do you have to wear the appropriate FR clothing for the arc flash rating prior to adjustment of the switch - and then reduce your arc flash clothing to meet the new level?

  • A: Thomas: The attractive feature of the Arc Reduction Maintenance Switch is that the switch can be activated remotely and with doors closed.

Q: Is there a code that requires the labeling of arc flash hazards or is it just a best known practice based on NFPA 70E?

  • A: Jim: Labels are addressed in NFPA 70E 2012 in 130.5(C). The 2015 edition of 70E will clarify that the owner of the equipment is responsible for the label.

Q: What type of clothing must be worn underneath the Arc Flash Suit?

  • A: Jim: Natural fiber clothing only, no meltables. See 130.7.

Q: [Are] programmable trip breakers with Arc Flash Mitigation going to be addressed by NFPA 70E in the future?

  • A: Jim: NFPA 70E is a workplace safety standard and not an installation standard. There is a good chance that CB's and other equipment equipped with a means to ensure arc energy reduction gets addressed in 70E with respect to how justified energized work is approached.

Q: What safety gear should we be using to protect ourselves prior to opening up switchgear equip ment, and is there any specific type of safety gear such as the thickness of rubber/leather gloves, shoulder wear, eye wear, etc? Thank you.

  • A: Jim: PPE, other protective equipment, insulating and shielding materials must be selected for the equipment on which justified energized work will be performed. This is after a shack hazard analysis and an arc flash hazard analysis is performed. For examples see the HRC Tables in 130.7(C)(15)(a) with Table 130.7(C)(16) and Table H.3(b) in  Annex H NFPA 70E 2012.

Q: Live work and OSHA's stance?

  • A: Jim: See 1910.333 where OSHA mandates that energized work is justified as done in 70E.

Q: There's seems to be a conflict between A/F and selective coordination (in '14)?

  • A: Thomas: This technology is meant to reduce incident energy. Should an event occur, selective coordination would have been lost as well. This technology, especially when using the Arc Reduction Maintenance switch, damage is limited and the facility can be up and running very quickly just as in the success story documented in the presentation today.

Q: Your discussion seemed to address maintenance more than normal run time. Do the injury stats - perhaps - include mere out-of-the-blue accidents that might include end users?

  • A: Jim: Normal operation of properly installed and maintained equipment does not expose the employee to hazards. When energized work is performed, the likelihood of an incident is exceptionally higher.

Q: What is the fundamental difference between the IEEE 1584 AND NFPA70E requirements.

  • A: Jim: See NFPA 70E 2012 Table D.1 in Annex D. 1584 is one of several calculation methods available. NFPA 70E does not mandate the calculation method used. 

Q: Can you identify specific language in NEC & NFPA70E that requires FM's to conduct an AF Study?

  • A: Jim: The requirement is that an arc flash hazard analysis be performed. It can be achieved through a study or the use of the HRC Tables. See NFPA 2012 130.5.

Q: It seems the tables in 70E for PPE are nearly worthless after you read the fine print. Basically, without doing an arc fault study, it still a guess if they apply. How do you use them?

  • A: Jim: The tables work. When we look at all of the legacy equipment in the world there is an extremely minute amount that has a study performed. The tables work where we can determine an assumed amount of available fault current and clearing time. When you get into larger devices such as LVPCB's the user may not be able to determine an assumed clearing time and they cannot use the table.

Q: Any 70E updates?

  • A: Jim: There are a lot! Maybe that could be another Eaton webinar!

Q: Mandatory changes to arc flash labeling system per the latest NFPA 70E. How do we standardize the method of calculations in various plants with different installation contractors? What the areas of the world that currently have mandatory arc flash labeling systems?

  • A: Jim: There are multiple excellent questions here! We could build a webinar on your question. It is just too much to do at this time.

Q: How do I contact the presenter(s)?

  • A: Thomas: Please visit Eaton.com/electrical and there are also references if you download a PDF of the slides under "Event Resources" on the left side of your screen.

Q: What is the change in stringent requirement between 2009 70E and 2012 70E?

  • A: Jim: There are so many we could do a webinar on that alone.

Q: Do we need to install hazard level for all equipment above 50 volts or only for equipment between 50 volts and 240 volts with transformer rating above 112.5 KVA??

  • A: Jim: That was deleted in the 2012 70E. There is no longer an exception for given sizes of kVA and voltage.

Q: Is a maintenance switch a standard feature for breakers greater than 1000A, such as for all major manufacturers?

  • A: Thomas: I would not say it is a standard feature. Specify Arc Reduction Maintenance Switch on your next design.

Q: Arc Flash protection for Line Side 480 VAC installations and use (and problems) with utilizing the NFPA-70E Tables?

  • A: Jim: Use of the HRC tables mandates that the user determine an assumed maximum available fault current and clearing time. While one may be able to determine an assumed maximum available fault current by determining the maximum fault current on the secondary of a utility owned transformer assuming an infinite primary, there is no clearing time. The parameters of the tables cannot be met in service equipment unless the line side of the main OCPD is enclosed.

Q: 240.87 does not appear to actually "require" that circuit breakers be used. It also does not seem to "require" that solid-state trip units are necessary; it says, "Where the highest current rating... is installed." What about if "Fuses" are provided?

  • A: Jim: Section 240.87 does not apply to fuses. It falls under the section entitled "Circuit Breakers".

Q:  What is the OSHA interpretation of live? Especially in Lockout/Tagout off confirmation operations, how realistic is it to reduce hazard areas and still have selective coordination?

  • A:  Jim: Where exposure to energized conductors or circuit parts exists, the worker is exposed to live parts. Your second question is one that owners must seriously ponder. If you have a system that is selectively coordinated, do you really want to enetertin energized work? You could take the enetire system down. If a fault occurs you will have an outage, that is a given. It is prudent to apply a means of arc energy reduction which will limit the energy, reduce exposure to workers and reduce equipment damage to your selectively coordinated system.

Q: Referring to NFPA 70E-2012, article 130.5, I've encountered many people who believe arc flash hazard analysis now has to be done to circuits below 240v, fed by 125KVA and lower, just because NFPA 70E doesn't have the statement anymore. Is this correct?

  • A: Jim: Yes, that is correct. Perhaps the collaborative efforts of NFPA, IEEE and many major players in the industry will provide the data we need to address this issue.

Q: Tom, With the maintenance switch in place, is it a good idea to provide two different arc flash hazard labels for the two different time curves?

  • A: Thomas: I have seen this done in the past. I do not see any harm in doing so and more information, I would think, is better than less. 

Q: Any 70E 2012 changes?

  • A Jim: There are far too many changes in the 2012 and 2015 editions of NFPA 70E to comment at this time.

Q: Ken White, In the case study, was the breaker in Cubicle 4 a feeder or main? How much of the electrical system was interrupted? Voltage, ground system?

  • A: Ken: The main is in cubicle 1 cubicle 4 feeds an air compressor.

Q: What role does OSHA play regarding these requirements?

  • A: Jim: OSHA requires that employers protect their employees from recognized hazards. Utilizing a means of arc energy reduction is a significant step to reduce exposure where justified energized work must be performed.

Q: How do you handle a situation where you cannot get below a CAT4?

  • A: Jim: When incident energy is in that range there is an extremely high amount of thermal and explosive energy. In the past there were proposals to go to an HRC 5 at even higher levels of energy. The 70 E committee rejected that idea because science can tell us how to predict an protect against the thermal energy but not the exposed arc blast and associated shrapnel. See NFPA 70E 130.7(A) Informational Note No. 3 where the committee suggests that in excess of 40 cal/cm2 a greater emphasis on reenergizing is necessary.

Q: Can you discuss the arc flash 208v and nfpa 70e requirement?

  • A: Thomas: NFPA 70E 2012 requires a shock and arc flash hazard analysis for all voltages 50 volts and higher. Systems less than 50 volts must also be evaluated for capacity and overcurrent protection to determine exposure to arch flash and the hazards associated.

Q: What is the most economical and effective arc flash reduction strategy?

  • A: Thomas:  The Arc Reduction Maintenance switch is your fastest, easiest to employ and specify.  The ARMs solution will come as part of the equipment and can be wired at the manufacture for local indication to meet the NEC requirements. 

Q: What is the consultant's role in meeting the code requirement?

  • A: Thomas: A consultant's role in system design and the Code is to design a system that meets the Code or exceeds it. 

Q: Why is there no time reduction in seconds as indicated in 240.87? By how much should clearing time be reduced?

  • A: Thomas: By implementing these technologies, reduced clearing times are implemented. The code currently does not have a maximum clearing time for arcing current.

Q: Can you discuss the trade-offs between arc flash mitigation and selective coordination?

  • A: Thomas: Achieving selective coordination places intentional delays in upstream overcurrent protective devices. This can be the cause of increase incident energy, arc flash values higher up in the system.  Section 240.87 addresses this issue by requiring arc reduction techniques up stream in the system. This requirement will hopefully educate many on the cost effective solutions available so that it is applied even further downstream in the system.

Q: Clarification: Does 240.87 apply to non-adjustable breakers?

  • A: Thomas: It applies to ALL circuit breakers 1200Amps and above. And that can be adjusted to 1200Amps. It does not provide any relief for non-adjustable circuit breakers.

Q: Please discuss the implications of arc flash hazard reduction vs. protective device coordination.

  • A: Thomas: Achieving selective coordination places intentional delays in upstream overcurrent protective devices. This can be the cause of increase incident energy, arc flash values higher up in the system. Section 240.87 addresses this issue by requiring arc reduction techniques up stream in the system. This requirement will hopefully educate many on the cost effective solutions available so that it is applied even further downstream in the system.  The implication here is that reliability of the power distribution system can be increased with this section of the NEC as after the event, the distribution system has a faster re-energizing time than those that do not employ these technologies and have to be replaced after the event.

Q: Ken, was there a safety observer during the work who was not participating in the work? If not, why not?

  • A: Ken: The second electrician was considered as the safety person.

Q: Are arc fault breakers required to be installed when gfci receptacles are to replace conventional receptacles in kitchen?

  • A: Thomas: Although not a part of this program, I can address this question. The act of replacing a receptacle 406.4(D)(4) is your code reference. If you are NEC 2014, this section of the NEC says you can put a breaker in or put an OBC AFCI device at the first outlet. But if you are on NEC 2014, it did add kitchens to the list of protected rooms and so a kitchen receptacle replacement would trigger AFCI protection as well.

Q: What methods are available for arc flash reduction in older switchgear? How does the size of the upstream transformer affect arc flash calculations?

  • A: Thomas: Always keep in mind that the incident energy heavily relies on the amount of current and time it is permitted to flow. The challenge with existing older systems is to get them to respond faster to arcing faults. Upstream transformers can reduce the available fault current but it doesn't help an overcurrent protective device respond faster. You must model the system and review ways to reduce clearing times. Retrofitting technology into existing equipment is possible in many cases.

Q: Please recommend software for arc fault calculations.

  • A: Thomas: SKM software is a good resource but you can always look at others like EDSA.

Q: Can you discuss employing arc reduction strategies in existing facilities, retroactively? And also how to convince owner/managers to have arc flash studies performed in order to implement arc reduction strategies?

  • A: Thomas: Arc reduction strategies and the work it takes to convince owners and managers to make the decisions necessary to address is and probably always will be difficult. Unfortunately it takes fines and events to convince some individuals who say it can never happen hear or it never happens to us. Now that we are seeing National Electrical Code changes in this area, more will be aware of how simple it really can be to address incident energy. Education and codes will change some people's minds but unfortunately for many it will take time. Retrofitting these technologies into existing systems is possible. 

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Anonymous , 05/01/14 02:09 PM:

Is no one going to answer the question with regard to whether conventional instantaneous-trip breakers comply with this regulation?
MAHENDRAKUMAR , IA, India, 06/13/14 01:33 PM:

very good article
Raymond , NC, United States, 06/18/14 11:20 AM:

IEEE has published data indicating that 96% or therebouts of all arcflash incidents are ground fault related. They further state that the use of a resistance grounded system can reduce the hazard by 96%. Why then is there never a mention of this in discussions of AF hazard reduction?
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