As stakeholders revisit arc-flash hazards, the obvious question is, where are the biggest risks? Experts site the removal or installation of circuit breakers or fuses, the racking of circuit breakers in and out of switchgear and the removal of electric equipment panel covers as tasks that have the highest injury rates. Arc flashes can occur almost anywhere an electric utility line worker, trouble-call technician or maintenance worker is working around energized lines. Uninvolved workers and the public may also be at risk when an arc fault occurs. Of special concern are tasks on the system where additional equipment such as switchgear, transformers and fuses are involved. Most interesting is the fact that low-voltage testing and system analysis is a task where high numbers of arc-flash injuries are occurring.

Safety advocates point out that standard NFPA 79E was originally written to protect firefighters, and an arc-flash section happened to be included in the standard. It makes a blanket calculation in setting protective standards, but does not address any work methods or the way an electric system is operated.

PSE&G's Tom Verdecchio is a member of the National Electric Safety Code (NESC) Subcommittee 8, which addresses work methods. He reports that the committee is working on several rule revisions related specifically to arc-flash hazards. NESC codes are revised every five years. New rules will be proposed for the 2007 code stating that employers must perform an arc hazard study on any task exposing workers to an arc flash.

The proposed new rule adds tables to the code, which will allow the employer to choose the right level of protection without having to perform a study or do tedious calculations. These tables, based on fault current and clearing time, are the result of studies being done by utilities like PSE&G and PECO.

PSE&G has spent the past 24 months “engineering out the heat hazards” related to arc flash, says Verdecchio. The utility started with the highest risk areas, for example, linemen gloving on 13 kV. The two-year-old initiative includes analyzing the clearing time and distance to employees for each task.

PSE&G's field studies are showing that by reducing the clearing time of a circuit, the heat that an employee is exposed to will be reduced. In one case, the target was to keep the heat exposure to less then 5 cal/cm² and less than second-degree burns to expose skin. Several utilities are now expanding the study to other exposure tasks related to arc-flash hazards. They hope to have collaborative results available by September 2006.

Another area where PSE&G is making changes is in FR clothing. For example, the utility has gone to a “Level 2 Clothing” applies to shirts, pants and T-shirts for overhead linemen. The utility is now studying FR levels and other preventative procedures on other tasks where arc flashes may occur.

It is worth repeating that when an arc-flash incident occurs, enormous amounts of concentrated energy explode through the air, through cabinets and circuits, and through anything or anyone in the vicinity. It is often unpredictable, but is always capable of doing serious damage to a person's hearing, eyesight and body. Depending on the voltage level, a ball of combusting heat is dispersed that can melt metal and severely burn a worker or anyone in the area. Pieces of metal and material may also be released like a bullet toward workers close and even not so close to the arc fault. The National Institute for Occupational Safety and Health (NOSH) has reported that from 1992 through 2001, there were 44,363 electrical-related injuries involving days away from work. Of those injuries, 17,101 were caused by electric arc-flash burns.

As we have heard from the industry, the final word on increased standards for arc flash is still being written. Everything from increased labeling requirements to more comprehensive exposure calculating practices may be on the horizon. But one thing everyone is in agreement on: Increasing the awareness and understanding of arc-flash hazards is one of the best ways to prevent arc-flash injuries.