NESC-2007 Update

The 2007 edition of the National Electrical Safety Code may pose significant work rule changes for electric utilities. The updated code, which is detailed in the NESC-2007 handbook, covers the following areas.

Effective January 1, 2009, the updated code requires each employer to perform an arc hazard assessment for employees who work on or near energized parts or equipment.
If the assessment determines a potential employee exposure greater than 2 cal/cm2, the employer will be required to provide clothing/clothing systems that have an effective arc rating not less than the anticipated exposure.
The arc rating called the Arc Thermal Performance Value (ATPV) expressed in calories per square centimeter represents the maximum capability for arc flash protection of arc flash clothing, which may include clothing systems. Employers are required to determine the ATPV value and perform an arc hazard analysis when employee exposure is 1 kV or greater so an effective clothing or clothing system can be determined. Employees who have exposure to secondary systems less than 1 kV (meter technicians, etc.) may wear clothing or clothing systems with a minimum effective arc rating of 4 cal/cm2 to limit exposure. The code does recognize that energy levels can be excessive with secondary systems so it requires utility safe work rules and engineering controls to be utilized to reduce the levels. This may be accomplished by either performing an arc hazard assessment or by using the tables in the code.
Clothing systems, according to the code, include multiple layers with the outer layer being of flame-resistant materials. This requirement poses a significant change for electric utilities that have designed clothing or clothing systems so they would not contribute to the extent of the burn. This takes a more proactive role in the design of clothing and clothing systems and ensures that employers provide clothing to protect employees from the hazards of electric arcs.

The code updates requirements for safety signs and tags to comply with the provisions of ANSI Z535.1-2006 through ANSI Z535.5-2006. The 2006 ANSI standards address three types of safety messages: grouped safety messages, section safety messages and embedded messages. The grouped safety messages appear with the words "Danger," "Warning," "Caution," and "Notice." Many utilities may already be required to update their signage to comply with the changes in the new ANSI standards.

Changes have been made with regard to qualification of employees who are now required to be qualified prior to operating mechanical equipment. "Qualified" employees must be able to identify electric and communication lines and equipment, know approach distances that must be maintained for safety, understand conditions that could occur if contact with lines and equipment occurs, and understand the safety action plan that must be initiated for employee and public safety if a contact occurs. The code also addresses qualification of employees who do not normally work on or in the vicinity of electric lines or equipment but their work brings them into these areas. These employees may only proceed with their work when authorized by a qualified person. This change aligns the NESC code with OSHA standards.

Changes in underground line operating procedures include boring and directional drilling methods, the use of mechanical equipment, and requirements for hand digging near buried energized cables. Under the new code, existing utility facilities must be exposed prior to performing a boring operation. Additionally, mechanized equipment should not be used to excavate close to buried electric cables and nonconductive handles should be used on hand tools when digging near energized electric cables. This may require buried electric cables to be uncovered by hand digging.

The code update requires insulating cover-up to be rated for phase-to-phase voltage if a determination shows that phase-to-phase exposure may exist. If not, cover-up used may be rated for phase-to-ground voltage exposure. When determining exposure and type of cover-up required, the utility may use work rules, conductor spacing and worker position.

The AC live work minimum approach distances, commonly referred to as MAD, changes slightly for both distribution and transmission voltages in the new code. The changes represent the most up-to-date developments in MAD research and will pose a change from current OSHA regulations.

For 2007, the NESC code changes relative to multiple ground cables connected to the same grounding point. The code states, "All phase connections shall be removed before removing any of the ground connections." An exception to this rule allows grounds to be removed individually from each phase and ground conductor if the application of the rule produces a hazard such as contact of the ground with ungrounded parts.ip

Pam Tompkins, a Certified Safety Professional and Certified Utility Safety Administrator, is President of SET Solutions in Lexington, South Carolina. The company specializes in helping small to medium size electric utilities comply with safety and training requirements. Prior to forming SET in 2000, Tompkins worked in the electric utility industry for over 20 years.

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Tuesday, 17 October 2017

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