Understanding and Reducing Arc Flash Hazards
Littelfuse POWR-GARD Products
Des Plaines, IL
USA

Although arc hazards have existed since man began using electricity, increasing deaths, injuries, and property loss from arcing faults have led to increased study into the causes, effects, and methods of protection. The studies are not complete, and the scientific community has not reached complete accord on the methods used to calculate the hazards. However, these studies serve as a starting point for improving worker safety. While much work remains to be done, in the interest of improved safety, several national codes and standards have been revised. These revisions are intended to reduce worker exposure to arc hazards and establish safer work practices when approaching or working on energized equipment. Since the changes affect every person involved in the design, installation, service, and maintenance of electrical systems and all machinery, mechanical equipment, and devices powered or controlled by electricity, applicable codes and standards should always be followed.

While parts of the Standards, Regulations, and Codes especially relating to arc flash hazards are quoted or summarized herein, readers are cautioned that only the complete Standards constitute the law or regulation and all parts must be followed where applicable. In addition, some critics take the position that calculating methods contained in the standards greatly understate the incident energy for systems under 600 volts. Because the standards and regulations attempt to establish minimum requirements for improving safety, these minimums may not be adequate, and it may be necessary to use an increased level of personal protective equipment.

The principle regulations that address arc hazards are:
National Fire Protection Association (NFPA) Standard 70 “The National Electrical Code” (NEC).
By definition the NEC is an installation standard although to some degree its requirements impact on maintenance and repair.
NFPA 70B 2002 “Recommended Practice for Electrical Equipment Maintenance.”
NFPA 70E 2000 “Standard for Electrical Safety Requirements for Employee Workplaces.” NFPA 70E 2000 is referenced by the Occupational Safety and Health Administration (OSHA) and forms part of their “Safety Related Work Practices.”
OSHA Standards 29-CFR, Part 1910. Occupational Safety and Health Standards. 1910 sub part S (electrical) Standard number 1910.333 specifically addresses Standards for Work Practices.

OSHA Regulations apply to every worker that may approach or be exposed to electric energy. Failure to conform to these regulations frequently causes serious worker injuries, expensive downtime, and costly lawsuits.

閱讀全文，請訪問http://www.littelfuse.com.hk/data/zh/Technical_Articles/Arc_Flash_Whitepaper_8-18-03.pdf