On April 11, 2014 the Occupational Safety and Health Administration (OSHA) announced the final rule to improve workplace safety and health for performing electric power generation, transmission and distribution work.  “The types of installations covered include the generation, transmission, and distribution installations of electric utilities, as well as equivalent installations of industrial establishments.” OSHA 29 CFR parts 1910 and 1926 adopt revised approach-distance requirements and add new requirements to protect workers from electric arcs while better aligning with the construction and maintenance standards.  A summary of the major changes relative to arc flash hazards are as follows:

• Incident Energy & Approach Distances
  • After April 1, 2015, incident energy calculations and new OSHA Minimum Approach Distances (MAD) must be determined for work on energized electrical equipment.
  • OSHA does not explicitly call out voltage ranges where incident energy estimates are required; however OSHA chose 50 volts as a widely recognized threshold for hazardous electric shock.
• Calculation Methods
  • OSHA studied various methods for calculating incident energy levels and determined where each method returns reasonable results.  Appendix E of section 1910.269 details appropriate methods for “assessing the workplace for flame and electric-arc hazards.”  The most versatile method is the IEEE-1584 method, which can be used up to 15 kV.
  • Above 15 kV, OSHA found that only ARCPRO, a commercially available software package, is acceptable for determining incident energy levels.  Above 15 kV, IEEE and NFPA 70E methods are only acceptable for determining where incident energies are below 2 cal/cm2.  Due to the overly conservative methods at higher voltages, the resultant incident energy calculations using IEEE and NFPA 70E are typically very high and would require employees work in safety equipment that far outweighs the true hazard.
• Working Distances
  • OSHA mandates the “employer shall ensure that no employee approaches or takes any conductive object closer to exposed energized parts than the employer’s established MAD.” They do however offer the following exceptions to this mandate:
    1. The employee is insulated from the energized part.
    2. The energized part is insulated from the employee.
    3. The employee is insulated from any other exposed conductive object in accordance with the OSHA’s requirements for live-line bare hand work.
  • When any of the three above exceptions are made, OSHA uses 15 inches as its standard for a comfortable working distance. However, “employers may use other distances if those distances reasonably resemble the actual exposures faced by employees.”
  • OSHA also concludes that the distances in IEEE Std 1584-2004 are reasonable estimates for the distance from the employee to the electric arc. These are typically 18, 24, and 36 inches depending on the voltage, type of equipment, and the likely task being performed by the employee.
• Estimates Over Multiple System Areas
  • OSHA allows estimates to be made over multiple systems.  They state “the employer need not estimate the heat-energy exposure for every job task performed by each employee.  Paragraph 1926.960(g)(2) permits the employer to make broad estimates that cover multiple system areas provided that: (1) the employer uses reasonable assumptions about the energy-exposure distribution throughout the system, and (2) the estimates represent the maximum exposure for those areas.  For example, the employer can use the maximum fault currents and clearing time to cover several system areas at once.”
• Probability of Exposure
  • “OSHA will consider an employee exposed to electric-arc hazards if there is a reasonable likelihood that an electric arc will occur in the employee’s work area, in other words, if the probability of such an event is higher than it is for the normal operation of enclosed equipment.”
  • OSHA is not nearly as detailed as the NFPA-70E with regards to guiding an employer on choosing risks/hazards.  OSHA does not allow the use of the NFPA tables as an acceptable method of estimating incident-energy levels and thus caution should be taken when using NFPA table 130.7(C)(15)(A)(a) in lieu of actually estimating incident energy for any generation, transmission, or distribution facility.
• PPE Selection
  • Paragraph 1910.269(l)(8)(v)(A) requires that arc-rated protection cover the employee’s entire body, with limited exceptions for the hands, feet, face, and head.
  • In general, review commenters had issues with OSHA’s PPE standards as much of industry has adopted 4, 8, 25, and 40 cal/cm2 flame-resistant systems.  OSHA does not appear to have an issue with these standard levels as long as the employee is properly protected.  OSHA merely mandates that protective clothing meet or exceed the estimated incident energy levels expected.