Electrical Systems / Electrical Safety / Arc Flash

Electrical safety experts answer your questions

Our panel of industry experts answers your arc flash hazard questions about NFPA 70E, PPE and much more.

Arc flash hazard mitigation is at the top of every plant's electrical-system-safety list. Help ensure your electrical-system workers go home at night by understanding the risks and the latest technologies designed to minimize them.

During a recent webinar, Chief Editor Mike Bacidore spoke with Joe Weigel, owner of Electrical Safety Works, and Mark Ackerson, safety maintenance instructor for AVO Training Institute, about how regulations such as NFPA 70E impact the plant. Here are answers to your questions from that webinar.

Question: Is PPE required for resetting a breaker?

Answer: It really depends on the size of the breaker. In small, low-voltage (less than 480-volt) lighting and circuit feeder panels, with the panels dead front covers all in place, PPE is not necessary to switch or reset a circuit breaker. But power circuit breakers such as 600 Amps and larger at any voltage, it would be prudent to wear PPE. I would recommend PPE to switch any breakers that are 1000V AC or higher voltage.

Question: Besides PPE, are there any alternative methods?

Answer: Yes. Turn off all the power and lock it out. Once an "electrically safe work condition" is confirmed by a qualified person wearing PPE (no voltage) work can be done without PPE.

Question: What about remote racking and remote switching for "tools for safe work"?

Answer: Remote racking and remote switching are both very useful safety options, if these options can be utilized. Not all circuit breakers can be remotely operated unless they are electrically operated. Racking breakers always requires PPE unless the person doing the work is outside of the hazard area by using a remote racking device.

Question: Who can deem an employee qualified? This is in a maintenance setting.

Answer: The employer is responsible for making sure that the employee has been trained, that the training is documented in writing, and that the employee has demonstrated proficiency in working safely. The employer/supervisor determines who is qualified and is also responsible for that decision.

Question: Where is it written that a PE must perform the arc flash calcs?

Answer: As far as I know, there is no written requirement in the standards that state that only a PE can perform arc flash analysis. However, IEEE1584 says that a properly executed arc flash analysis consists of a combination of several electrical studies (short circuit study, time-current coordination study, and the arc flash analysis itself). Typically, only licensed electrical engineers are trained and capable of performing these studies, so the inference is that only licensed electrical engineers should perform these system studies. If someone is comfortable with doing this kind of work without being an EE or PE, and is willing to take the legal risk of doing it, doing so would not violate any written requirement.

Question: What is considered ''work''?  Is simply opening a cabinet and looking inside considered work?   

Answer: Yes. This is called "non-contact inspection" and PPE is required if the covers are removed or there are any exposed conductors or circuit parts. IR inspection falls into that category. Look at tables 130.7(C)(15)(a) in NFPA 70E and you will see some PPE recommendations for this kind of interaction.

Question: What is considered to be up to date on single line drawings?   

Answer: The single line drawings are considered up to date if they show every change that has been made in the electrical system. If you replace, for example, a 225A circuit breaker with another 225A circuit breaker in a panel, that is not a change. If you add a safety switch or other device or add circuits or equipment, that will require the drawings to be modified to show those changes.

Question: New version of NFPA 70E does not mention date on the label. Why the change?   

Answer: You are right! Article 130.5(C) describes what must be on the equipment label, and it does not show the date. It is common practice, however, for most engineering companies who do arc flash analysis to put the date of the AF analysis on the label. The feeling is that the date will indicate how recent the arc flash study is. The NFPA 70E requires the arc flash studies to be reviewed periodically, so the date could be useful in that regard.

Question: How do you make workers put on their PPE?

Answer: Management must understand and support the company's electrical safety policies. Employees must conform to those policies, including wearing PPE. Those employees who constantly violate the policy should be counseled and terminated if they continue to violate the rules. They are a liability to themselves, to the company, and to others.

Question: If commercial software is being used to determine the arc flash calculations, does a licensed professional engineer need to be the person entering the data in the program and running the program, or does it just need to be supervised by the licensed professional engineer?

Answer: There is a lot of judgment required, based on experience and training, that determines how to input the data into the software. Bad data in results in bad data out. An example is arc fault propagation in three phase systems. If the operator doesn't understand this phenomenon, they will make bad decisions. Often, a less experienced engineer will enter the data and run the calculations, but the results are reviewed and "stamped" by a more experienced engineer.

Question: How do you protect employees from complacency?

Answer: I know that can be a problem. People who have years of experience working without PPE on energized equipment feel that they know what they are doing and are resistant to change. Training and management oversight are important to enforce the electrical safety program.

Question: What about an engineer who just surveys the switchgear?

Answer: The survey is commonly called "data collection". If that process does not required any equipment covers to be removed, breakers racked out, etc., PPE is not required. In fact, it doesn't require a "qualified person" to do the survey.  However, often a cover has to be opened to check a large circuit breaker setting or other visual inspection. That will require a qualified person wearing proper PPE.

Question: What percentage of the industry would you say have completed their arc flash studies?

Answer: Based on talking to tens of thousands of people over the past ten years, my best estimate is that only 10% of facilities have completed AF studies. That’s a lot of facilities that still need this work done.

Question: When does a spark become a larger arc flash?

Answer: All faults begin as small arcs; the key is making sure the upstream over current protective clears the fault in the quickest amount of time to limit the arc. Using modern current limiting fuses is one of the most cost-effective methods to do so. A spark can only become a dangerous arc flash hazard if there is sufficient voltage and fault current to cause the arc to form in the air and to sustain itself long enough.

Question: What is the minimum NRR hearing protection for a typical arc flash PPE?

Answer: The NFPA 70E 2012 simply says "hearing protection (canal inserts)”.  In searching the 70E, I could not find any reference to a specific level of hearing protection.

Question: Our firm provides maintenance and construction services on numerous Department of Defense bases. Who is responsible for providing the short circuit study and arc flash hazard analysis? Is it the company or the owner?

Answer: Generally, the owner of the equipment is required to provide the analysis, and the labeling of the equipment. Usually, the owner will contract with an engineering company to do that work, and pay for it.

Question: Are the requirements the same for communications techs running Ethernet, fiber-optic cables for switchgears as for electricians in general regarding PPE?

Answer: Ethernet and FO cables do not carry hazardous voltage and current levels. However if they are running these as a communication system inside electrical switchgear (i.e. metering, breaker controls, etc.), PPE is required, and qualified people must do the interconnection work that is inside of the switchgear or other power distribution equipment, if it is energized.

Question: What is the hazard level of plugging in a buss plug? 100-Amp buss, 20-CB plug, 208 volts.

Answer: Bus plugs can be hazardous from an arc flash hazard perspective. It has been common practice for many years for workers to "hot plug" these devices into and out of overhead distribution bus ducts. It was thought to be safe until people saw how many arc flash accidents involving injuries and fatalities have occurred. Even a 100-Amp plug can be very hazardous, especially on 480-V bus duct because of very high fault currents that can be delivered through the bus duct. At 208 V, the hazard is much less, but still an arc flash analysis should be done to determine exactly what PPE would be required to perform this operation.

Question: I know that government facilities are not "required" to follow OSHA. I also know, if you read further in OSHA, it states that you must develop a standard that meets or exceeds OSHA standards. What is that standard?

Answer: OSHA has jurisdiction only over private sector employers/workplaces, not Federal/State/or Municipal Government facilities. However, I have consulted to many Federal Government agencies, and they are all aware of NFPA 70E and electrical hazards, and want to comply with it. Most government agencies follow NFPA 70E because it is the right thing to do for their employees, and they don't want the lawsuits from accidents.

Question: What is the minimum voltage (AC and DC) level applicable to arc flash safety?

Answer: The NFPA 70E 2012 states that arc flash and shock hazard only exists if the equipment operates at "50 Volts or greater" (AC or DC), so that level defines a minimum hazard level. Lethal shock can occur even at 120 volts or more. Arc flash really doesn't become a serious potential hazard until the voltage levels exceed 120 volts (208V and higher).

Question: Can an individual be within the arc blast boundary if not performing work on the equipment?

Answer: The arc flash boundary doesn't exist until the energized equipment is opened (covers removed, etc.). With enclosed equipment operating normally, there is no requirement for PPE to be near the equipment. However, if the equipment is opened and people in PPE are working on it, no one may be in the work area except qualified workers wearing PPE. In some cases the arc flash boundary can be a hundred feet or more from the equipment. That's unusual, but we have seen it.

Question: Why does NFPA 70E start arc at 240V and IEEE 1584 starts at 208V?

Answer: IEEE 1584 is mostly written by electrical engineers who tend to be very conservative and look for the "worst case perfect conditions". NFPA 70E committees include engineers, electricians and others who are a little less conservative and tend to see things in a more pragmatic way. This is my "informed opinion".  But the differences between hazard levels at 240V and 208V are pretty small where arc flash hazard is concerned.

Question: Do people in the power generation maintenance need to be safety trained?

Answer: Yes, absolutely. An electric utility power generating plant looks exactly like a large industrial facility in the type of electrical equipment inside, and the hazard levels that are present. Where utilities overhead and underground distribution systems and outdoor substations are involved, the work tasks are quite different and most utility workers use different safety practices such as the NESC (National Electrical Safety Code). For that kind of work environment, NFPA 70E is not usually used.

Question: Is PPE required when operating breakers with the doors closed?

Answer: Again, operating circuit breakers (On - Off - Reset) won’t usually require PPE if the equipment is closed up and operating normally. However, for larger power circuit breakers above 600A and medium voltage breakers 1000 volts or higher, prudence would indicate wearing PPE to do CB operation, and PPE is absolutely required to do breaker racking. For electrically operated breakers, it would be pretty easy to provide a remote switch to operate the breaker from outside of the hazard area.

Question: Can a panel fail on its own or does it have to be caused by human error?

Answer: Panels and other electrical equipment do occasionally fail "spontaneously", without anyone present, but it is pretty rare. Usually it's caused by poor maintenance/dirt buildup on bus, a loose cable orb bus connection, or a rat or other critter that gets into it. Whenever someone is injured, it is almost always due to an unsafe act by that person.

Question: Do we really need to do the arc flash study for outdoor AIS substation?

Answer: Mostly, these outdoor substations are owned by electric utilities, although some are owned by larger industrial customers. We have seen some arc flash studies done on outdoor AIS substations that are privately owned. The study process is a little different than what would be done for a typical indoor system. I think utilities have their own requirement to do these, and electric utilities actually are exempted as a "special industry" from the requirements in NFPA 70E.

Question: Why is an arc flash likely to propagate?

Answer: Arc flash usually starts between a single phase conductor and ground, although they can go to another phase (rarely). Once the phase to ground arc initiates, it is full of hot arcing plasma and gases that are fairly conductive. That causes the second and third phase to immediately fault, so engineers always assume that every arc flash in a three phase system will be a three phase arcing fault. Once the three phase arc forms, it tends to travel upwards if it can, towards the source of the incoming feeders (in switchgear, towards the main breaker) where there is more energy to feed the fault. This will not happen if sufficient barriers are present in the equipment to block the arc fault propagation. So the propagation is more common in switchboards, MCCs and panel boards, than in compartmentalized switchgear construction.

Question: The NFOA 70E FPN I referenced is for the need to wear arc flash rated PPE to operate switchgear even when the gear is enclosed with all covers.   

Answer: I see where the answer we gave you during the live webinar Q&A was wrong. You mentioned 130.7(C)(9) FPN No. 1 in NFPA 70E 2009 and we were looking in NFPA 70E 2012 edition, where those FPN's are now called "Informational Notes". I think where the confusion is, is when using the "task tables" 130.7(C)(9) in your older NFPA 70E, the PPE recommendations are estimates, and they tend to be very conservative to cover worst case situations. Normally operating switchgear breakers or switches with doors closed should not require PPE (however racking breakers in drawout gear definitely does require PPE). Having said that, if I were going to switch a 4000 A 480V breaker in dirty old switchgear that was 40 years old and had never been maintained in a nasty old steel mill, I think I would be putting on a category 4 blast suit to do it.

Question: Who is responsible for the cost of the hazard 2 FR clothing?

Answer: OSHA requirements state that the employer must provide and the employee shall use the PPE (all categories of PPE and other safety equipment such as insulated tools, etc.).

Question: Any opinions regarding using fused test leads when using a multimeter - as opposed to relying on a fuse that is internal to the multimeter?

Answer: Not a fan of fused leads. I think we are creating another hazard when we try to fuse leads for protection. A blown fuse in a meter will give you no reading, and a blown fuse in a test lead will give you a false reading.

Question: What sources should be referenced for DC arc flash analysis?

Answer: NFPA 70E table 130.4 (C) (b)