Big Changes Coming Concerning Arc Flash
Dealing with arc flash hazards and arc blast protection has become one of the most important—and confusing—issues developing in the wake of changes made to the 2002 edition to the National Electrical Code. According to George Farrell, a long-time CSE contributor and co-author of the Protecting Electrical Systems series, protection against arc flash hazard, which was revised unde...
Dealing with arc flash hazards and arc blast protection has become one of the most important—and confusing—issues developing in the wake of changes made to the 2002 edition to the National Electrical Code.
According to George Farrell, a long-time CSE contributor and co-author of the Protecting Electrical Systems series, protection against arc flash hazard, which was revised under section 110.16, "Flash Protection," in the 2002 edition, is creating a big buzz in more ways than one.
"The most recent revision to NFPA 70E dealt with personnel protective equipment requirements," says Farrell, who adds the action was really minimal as far as arc-flash hazards are concerned. "But now, higher standards for actually disconnecting the devices that protect switches downstream are being considered."
Arc flash is primarily found in circuits of 208 and higher voltages in commercial and industrial facilities. Protection from arc flash is primarily a personnel safety issue. The 2002 edition of the NFPA Code handbook summarized it thusly: Field markings that warn electrical workers of potential electrical arc flash hazards are now required because significant numbers of electricians are being seriously burned or killed from accidental electrical arc flash while working "hot" (energized) equipment. Most of these accidents could be prevented, or their severity significantly reduced, if electricians wore the proper type of protective clothing. Requiring switchboards, panelboards and motor control centers to be individually field-marked with proper warning labels will raise the level of awareness of electrical arc flash hazards and thereby decrease the number of accidents.
But Farrell thinks there are bigger issues beyond labels and protective clothing.
"The NEC now only requires a warning label," he says. "Proposals to require that the label include the calculated incident energy level and the level of personal protective equipment (PPE) required have been submitted for the next NEC revision (in 2005) and are being looked on favorably, although the decision has not been made."
Furthermore, despite the fact that current NEC wording places responsibility on the installer, it is highly probable that the responsibility will shift to the engineer "as few contractors have the expertise to make the necessary calculations," he says.
Confusing the issue even further is the fact that several other standards bodies, including NFPA itself, also address the issue in other offerings. For example, NFPA 70E-2000, Electrical Safety Requirements for Employee Workplaces , provides assistance in determining severity of potential exposure, planning safe work practices and selecting personal protective equipment.
Another is ANSI Z535.4-1998, Product Safety Signs and Labels , which, according to Farrell, provides guidelines for the design of safety signs and labels for application to products.
The condition is also covered by IEEE Guide 1584, Arc Flash Calculations , and by OSHA under its safe work practices.
"This subject is highly complex," says Farrell. "And there are a number of proposals right now to revise NFPA 70E."
But this is really just the tip of the iceberg in his opinion, as insurance costs will eventually force plant and factory operators, in many cases, to install parallel electrical systems.
"Before all this [arc flash] discussion, when calculating short circuits, the protective device only had to interrupt that circuit. And with arc flash, specifically, it was always the minimum, never the maximum," says Farrell.
That attitude's changing, he adds, as the Australian equivalent of IEEE is challenging what the maximum discharge should be.
The NFPA Foundation, he says, is seriously considering this as a research project, and word from the NEC camp is that major changes will also be coming to section 110.16.
What those changes will be, exactly, remain to be determined. "At the least, equipment needs to be altered so it's safer to work on or so it can at least be de-energized more easily," says Farrell.
While such electrical system upgrades may prove quite expensive to end users, Farrell sees this as the real future, as in practice, too many people work hot. OSHA, he says, will be the agency that enforces this cultural change, and he says the agency will require documentation when employees have to work in such situations and that they, indeed, have protective gear on.
In the meantime, many manufacturers are already acting. For example, Square D/Schneider Electric, this past summer, held a day-long seminar on the subject in Cedar Rapids, Iowa, where the company has a major testing lab. Besides a number of expert speakers (see "Researchers Sharpen Their Focus on Arc Flash Fault" in the news archive at csemag.com ), the company also demonstrated its lower voltage circuit breaker, which product managers noted won't necessarily stop arc flash from occurring, but will mitigate the flash so it's not as dangerous.
High-resistance grounding device manufacturer Post Glover, Erlanger, Ky., will also conduct a symposium later this month that will also include a discussion of arc flash hazard.
The subject also surfaced on the floor of last month's IEEE/PES T&D conference and exhibition in Dallas. In fact, you couldn't help but hear it, as exhibitor S&C regularly set off a mock arc flash explosion at its booth to demonstrate its line of arc-resistant switchgear.
Fuse manufacturers, including Ferraz-Shamut and Cutler-Hammer, also discussed the issue and noted how some of their products can or will be able to help mitigate the problem. Cooper-Bussmann already has arc flash calculation software available.
"It's definitely an issue," says Ferraz-Shawmut's Doyle Anderson. "And it's not new, but much more is being done about it because of OSHA," he says.
But fundamentally, Farrell believes plant operators will have to upgrade their electrical systems themselves, as obviously, that's the surest way to keep employees safe.