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The Low-Voltage Distribution Equipment (LVDE) section of the National Electrical Manufacturers Association (NEMA) has published a white paper on arc-flash analysis that highlights the need for utility system parameters in the selection of personal protective equipment (PPE).
NFPA 70E, Electrical Standard for Safety in the Workplace, defines an arc-flash hazard as “a dangerous condition associated with the release of energy caused by an electric arc.”
It is an explosion involving an electric arc operating at temperatures of several thousand degrees Celsius and the pressure wave created by the arc. Within a few milliseconds, the energy from this explosion can cause severe burns and loss of hearing, eyesight, taste and smell. Molten metal particles, equipment parts and other loose items are expelled from the arc area.
Extensive equipment damage frequently results in downtime for an installation. More devastating are the trauma, hearing and eyesight loss, and burns to personnel, and arc flash can result in major injuries or death.
The increasing awareness for the need to perform arc-flash analysis is driven by the changes to the 2002 National Electrical Code, which added requirements for markings to alert qualified personnel on the potential of arc-flash hazards. NFPA 70E provides tables for determining the level of PPE. These tables apply only to specific parameters, whereas an arc-flash analysis will permit the selection of PPE suitable for each location.
Utilities have traditionally provided a conservative fault current value, but this may not provide the worst-case arc-flash condition. The white paper identifies parameters that utilities should provide so an accurate analysis can be conducted. By providing these and notifying users of system changes, utilities can assist users in ensuring that safe practices consistent with NFPA 70E are maintained. To view the white paper, visit www.nema.org.
