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Bluebonnet Electric Cooperative Arc Flash Hazard Mitigation Thomas Ellis, PE Manager of Engineering Serves 81,000 meters across 11,000 miles of power lines within 14 Central Texas Counties What is Arc Flash Arc Flash is a massive energy discharge Similar to the arc obtained during electrical welding Initiated by creation of a conducting path or breakdown in insulation Sustained by the establishment of a highlyconductive plasma Arc fault current is often lower than available bolted fault current Arc Flash Energy System Voltage Fault current magnitude Duration of Fault Enclosures magnify blast and energy transmitted ◦ 2-12 times greater energy Incident Energy Incident Energy measured at the arc potential to the employees face and/or torso cal/cm^2 Incident Energy Incident Energy (cal/cm²) 1.2 Degree Burn 2nd degree burn to bare skin 4 Ignite a cotton shirt 8 3rd degree burn to bare skin Shows the damage that incident energy can impart. Arc Flash Effects Extreme heat, pressure waves, and sound waves ◦ 35,000 degrees Fahrenheit ◦ Molten Metal, Shrapnel, and Vapor ◦ Expansion rate 40,000-1 ◦ Intense light Burns Punctures Concussion Capable of causing severe/fatal injuries Arc Flash Hazards Personnel have exposure to electric arcs: ◦ When working on or near exposed energized electrical conductors or circuit parts. ◦ When interacting with electrical equipment where an electric arc could occur. ◦ Under normal conditions, equipment that is installed and maintained is not likely to pose an arc flash hazard if an personnel are not interacting with the equipment. Racking Breaker National Electric Safety Code (NESC) - 2007 2007 code published August 1, 2006 410.A.3 ◦ “Effective as of 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 lines, parts, or equipment.” Potential exposure greater than 2 cal/cm^2 410-1, 410-2 ATPV less than anticipated arc energy, <1000V arc hazard analysis National Electric Safety Code (NESC) - 2012 2012 code published August 1, 2011 410-A3 ◦ Perform a detailed arc hazard analysis ◦ Alternative – use clothing system tables 410-1- independent of fault current 50V - 1000V 410-2 1.1kV – 46kV 410-3 46.1kV – 800kV Arc Flash Hazards BBEC identified arc hazards over 2 cal/cm². Proactive approach to limit employee arc exposure thru: ◦ Engineering controls ◦ Work rules ◦ Personal Protective Equipment Objectives Reduce potential for personnel injury due to arc flash incidents Electrically safe? ◦ Identify hazards ◦ Provide guidance for performing required duties on or near energized lines and equipment ◦ Determine the best possible PPE To comply with NESC-2007/NESC-2012 Arc Flash Analysis What is Arc Flash Analysis? ◦ A study to determine the anticipated level of incident energy personnel would be exposed to Conducted for the purpose of: Injury prevention Determination of the following: Safe work practices Arc flash protection boundary Effective arc rating of clothing systems Appropriate levels of PPE Training for personnel on hazards of arc flash Appropriate tools NFPA 70E, IEEE 1584 Arc Flash Calculation Variables Voltage Fault current in Amps Duration of Fault in Seconds or Cycles ◦ Protective device clearing time Arc Gap Length Working Distance to Employee ◦ Arc to employee-assumptions vary depending on task Open Air versus Enclosed Space (“Arc in a Box” Arc Flash Analysis Arc Flash Boundary ◦ Personnel inside the arc flash boundary are required to wear the standard work uniform when: Performing work Assisting in work Observing work (1.2 cal/cm^2) Arc Flash Analysis System normal operating mode ◦ Non-Reclose ◦ Abnormal operating mode requires additional caution Proper documentation of changes Reliable update process Arc Flash Analysis Proper equipment operation Coordination study ◦ Proper equipment ◦ One shot Adherence to maintenance plan Identified Work Inside a substation between the transformer low side and the outgoing primary feeders. On energized conductors or circuit parts over 600 volts. On energized conductors or circuit parts under 600 volts. To connect and disconnect meters. Inside Substation Boundary – inside the fence ◦ No rubber gloving Incident energy values may be excessive, the standard work uniform will not provide effective AR protection during rubber gloving procedures. Employees shall use a 15’ switch stick or a telescoping station stick to maintain a minimum of 8’ from the potential arcing source If under extreme conditions, an 8’ working distance cannot be maintained, a hot stick barrier (safety shield meeting ASTM F2522 – 05 standards) and an arc rated face shield shall be worn to provide extra protection against arc flash impacts . Energized equipment over 600V Boundary – 15’ Non-reclose Rubber gloving 15” working distance Hot sticks OH 8’ stick, 6’ working distance URD 6’ stick 4’ working distance Energized equipment under 600V Boundary – 15’ Three Phase Enclosures ◦ Diagnostics only 8’ hotstick 8” probe Single Phase Enclosures ◦ 15” working distance Meters Boundary – 15’ Self contained ◦ Meter pullers ◦ Diagnostics 8” probes Hazard Identification and Risk Assessment Evaluate jobsite Identify hazard Risk reduction ◦ Engineering controls ◦ Work practices ◦ PPE Safe Work Practices Equipment Operation ◦ Unknown conditions Switching and Tagging ◦ Verify/Authorize orders Non-Reclose (HLTG) ◦ Normal mode Cover-up ◦ Properly rated & applied URD ◦ 4 feet minimum Remote Switching When applicable, SCADA operations shall be used to remotely operate switches. Remote operation of switches will reduce, if not eliminate, employee related arc flash hazards. Standard Work Uniform 8.7 cal/cm^2 Shirt 8.7 cal/cm^2 Pants 20 cal/cm^2 Additional items ◦ ◦ ◦ ◦ ◦ Coveralls 20 cal/cm^2 Face shield 12 cal/cm^2 Balaclava 47.9 cal/cm^2 Hood 40 cal/cm^2 Ear Arc Plug Responsibilities Management ◦ Responsible for initiating, overseeing, reviewing and updating a hazard recognition program to identify arc hazards and controls. ◦ Responsible for communicating and training employees on identified arc hazards. ◦ Responsible for implementing and enforcing the arc hazard implementation plan and for regularly reviewing and updating the program an necessary to ensure all arc hazards have been effectively identified and abated. ◦ Responsible for budgeting necessary funds to ensure compliance. Responsibilites Supervisors, Foreman and Lead Technicians ◦ Identifying arc hazards and working with management to develop processes and or procedures to minimize and/or eliminate the hazards. ◦ Ensuring employees have received necessary arc hazard training. ◦ Ensuring only qualified employees work on or near equipment with potential arc hazards. ◦ Enforcing the arc hazard implementation plan requirements including work rules and PPE. Responsibilities Employees ◦ Identifying arc hazards and working with management to develop processes and or procedures to minimize and/or eliminate the hazards. ◦ Following work rules and wearing the appropriate FR clothing and other PPE as required. Training Employees will receive arc flash training initially and every 3 years. Training will include but not be limited to: ◦ – Electric arc hazards ◦ – Identified work practices with arc hazards. ◦ – Engineering controls to minimize arc exposure ◦ – Work rules required to minimize arc exposure. ◦ – PPE use, care and maintenance Safety Rules The arc flash implementation plan does not eliminate any existing safety rules or procedures. All employees are required to follow established safety rules when working on or near energized lines and equipment. All other work must be evaluated for arc hazards before the start of work.
