The National Electrical Safety Code - NESC

The National Electrical Safety Code (NESC) or ANSI Standard C2 is a United States standard of the safe installation, operation, and maintenance of electric power and communication utility systems including power substations, power and communication overhead lines, and power and communication underground lines. It is published by the Institute of Electrical and Electronics Engineers (IEEE). "National Electrical Safety Code" and "NESC" are registered trademarks of the IEEE. NESC rules cover supply and communication lines, equipment, and associated work practices employed by a public or private electric supply, communications, railway, or similar utility in the exercise of its function as a utility. The purpose of the NESC is the practical safeguarding of persons, and utility facilities during the installation, operation, and maintenance of electric supply and communication facilities, under specified conditions. 

Who NESC covers

NESC is specific to the electrical utility industry and "covers the electric supply conductors and equipment . . .(including) electric supply stations, that are accessible only to qualified personnel." NESC basically applies to all electric utility work performed at investor-owned utilities, electric co-ops and municipalities.

What NESC requires

The NESC Rule 410A3 governing the use of flame-resistant, arc-rated clothing for electrical utilities, requires the following:

• Effective January 1, 2009, the employer shall ensure that an assessment is performed to determine potential exposure to an electric arc for employees who work on or near energized parts or equipment. The 2012 rule added low voltage equipment to the >1000V equipment requirement in 2007. 
• If the assessment determines a potential employee exposure greater than 2 cal/cm² exists, the employer shall require the employee to wear clothing or a clothing system that has an effective arc rating at least equal to the anticipated level of arc energy. 
• When exposed to an electric arc or flame, clothing made from the following materials shall not be worn: Acetate, nylon, polyester, or polypropylene unless arc rated in a blend. 
• The effective arc rating of clothing or a clothing system to be worn shall be determined using Tables 410-1, 410-2, and 410-3 or performing an arc hazard analysis. 
• When an arc hazard analysis is performed, it shall include a calculation of the estimated arc energy based on the available fault current, the duration of the arc (cycles), and the worker distance from the potential hazard.
• EXCEPTION : If the clothing required by this rule has the potential to create additional and greater hazards than the possible exposure to the heat energy of the electric arc, then clothing with an arc rating or ATPV less than that required by the rule can be worn. This is normally allowed for uncommon work methods such as helicopter work on live power lines.

Summary

For electric utilities, NESC: 

• Specifies that employers conduct a hazard risk assessment to determine the potential arc exposure for employees who work on or near energized parts or equipment. 
• Requires employees to wear flame-resistant clothing with an ATPV, or cal rating, equal to or greater than the determined arc hazard.

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