The Missing Link In Arc Flash Analysis - Risk Assessment

By Charles Helmick, Training Manager, AVO Training Institute

In the fall of 2001 the 2002 National Electric Code (NEC) introduced a new requirement. Article 110.16 required electrical equipment to be field marked, to warn qualified persons about the arc flash hazard associated with exposed energized conductors. The equipment required to have this field marking (warning label) has been more clearly defined through subsequent editions of the NEC. Basically the only electrical equipment which is excluded from this requirement is in dwelling occupancies. Fine Print Note (FPN) no.1 to that article listed the NFPA 70E-2000 Electrical Safety Requirements for Employee Workplaces as a source of information that would aid in determining severity of potential exposure, planning safe work practices and selecting personal protective equipment. FPN no. 2 listed ANSI Z535.4-1998, Product Safety Signs and Labels as a guide for designing labels (field marking). Normally new requirements in the NEC are only applicable to installations built after the implementation of that edition. This is known as “grandfathering”. In this case, because of the possibility of an imminent hazard in the workplace, the Authority Having Jurisdiction (OSHA) only allows a reasonable amount of time to get into compliance. According to the 2000 Edition of the NFPA 70E Part II Safety-Related Work Practices, Chapter 2 General Requirements for Electrical work Practices 2-1.3.3 The Flash Hazard Analysis must be done before a person approaches an exposed electrical conductor or circuit part. To perform a flash hazard analysis an electrical engineer must know the:

1. Short circuit current available at each piece of equipment
2. Clearing time of the upstream overcurrent device
3. The working distance for each task to be performed. (Usually the working distance at 600 volts and below is 18 inches and above 600 volts should be 3 feet.)