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'-~+J~ <br />Elk River -~= <br />Municipal Utilities <br />13069 Orono Parkway • P.O. Box 430 <br />Elk River, MN 55330-0430 <br />March 4, 2008 <br />To: Elk River Municipal Utilities Commission <br />Jerry Takle <br />Jerry Gumphrey <br />John Dietz <br />From: Bryan Adams <br />Subject: Arc Flash Assessment <br />Phone: 763.441.2020 <br />Fax: 763.441.8099 <br />The arc. f.7ash issue has raised its head again. Approhimately 20 years ago arc flash became a <br />discussion point with the adoption of OSHA 1910.269.. Arc flash. is the light and heat energy <br />given off in an unintentional electrical contact between two energized conductors or an energized <br />conductor and ground. This is analogous to the light and heat energy given off as in arc welding <br />only much more interise due to the higher voltage involved. This is not electrical burns from <br />contact to an energized conductor where the current flows through the body. <br />OSHA 1910269 states that the clothes worn by linepersons cannot make the injuries wur~:e from <br />arc flash. At this point, linepersons could only wear clothes of natural fabrics such as cotton, <br />silk, wool, etc.; not synthetic materials like rayon, nylon, etc. that can melt and cause further <br />injury from burning fabric. <br />Section 410 of the National Electric Safety Code (NESC) requires employers to do an arc flash <br />assessment by January f, 2009. The employer shall require employees to wear clothing or a <br />clothing system that has an effective arc rating not less than the anticipated level of arc energy. <br />The NESC has an exception which states that for secondary systems below 1 OOOv, applicable: <br />work rules required by this part and engineering controls shall be utilized to limit exposure. In <br />other words, we are not required to follow the arc flash assessments below 1000v. Unfortunately <br />this is the area where many hazards are. The National Electric Code (NEC) which generally <br />applies to voltages less than 600v (covers electricians, not electric utilities) and the National Fire <br />Frotection Agency (NFPA) do not include the NESC exception. The NFPA does not apply to <br />electric utilities. <br />