Electric utility workers face complex, high-risk electrical hazards nearly every day. Information about shock hazards – which may come from impressed voltage, residual energy, induction, objectionable current flow in a grounding system or stored energy – has been taught to many of us for quite some time, as have the methods of assessing them.
On the other hand, arc flash hazard assessments are still relatively new to us. In the past, most of us knew that an arc flash could potentially occur during the course of performing our tasks, but the level of the flash and the PPE requirements – other than wearing 100 percent cotton – were not seriously considered in our day-to-day activities until approximately 15 to 20 years ago. To provide more concrete guidelines, OSHA published new regulations in April 2014, with more recent enforcement dates. Instead of making a best guess about PPE, the industry now has a reasonable approach to providing adequate PPE for utility employees who are tasked with performing open-air work. Once a utility completes the required arc flash analysis, develops a policy based on the analysis results and adequately conducts training for affected field personnel, the job of assessing risk and determining PPE levels can easily be incorporated into the daily job briefing. The goal is to make the assessment data easy to access and understand in order to provide effective protection for all workers.
Causes and Severity Levels of Arc Flash Events
An arc flash is the result of either a short circuit during which two energized parts of different potentials (phases) make contact, or a ground fault where an energized part and a grounded conductive part of a different potential make contact. An arc flash event may be caused by a failure of electrical apparatus, potentially due to lack of maintenance, or by worker error, perhaps due to an employee moving conductive parts near energized parts or leaving conductive tools in an energized work area. It’s important to note that differences in potential must always be effectively isolated by distance (air) or insulated barriers.