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Pantex Plant Electrical Arc Flash at Automatic Transfer Switch 68 December 2005

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Pantex Plant Electrical Arc Flash at Automatic Transfer Switch 68 December 2005

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    1. 1 Pantex Plant Electrical Arc Flash at Automatic Transfer Switch 68 December 2005 Carlos Alvarado DOE/NNSA Pantex Site Office

    2. 2 Pantex Arc Flash Pantex M&O Contractor was performing studies of plant electrical circuits Automatic Transfer Switch 68 (ATS 68) services multiple facilities (12.47kV) ATS 68 services the buildings being studied and also services building 12-118

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    4. 4 Pantex Arc Flash Three 40 Amp Fuses were removed at ATS 68 to isolate downstream transformers serving the buildings being studied ATS 68 remained energized Power to the buildings being studied was locked out, power to building 12-118 remained energized because it was assumed 12-118 was a critical load Work was performed LOTO was removed in anticipation of restoring power

    5. 5 Pantex Arc Flash Electrician donned PPE (40 calorie suit and hood, gloves,boots, hardhat) Electrician re-installed fuses on the load side of the ATS (“A” Phase, “B” Phase, “C” Phase) Electrician removed barriers that isolated the fuses from the feed side of the ATS Using a 6 ft long “hot stick” the electrician began reinstalling the fuses on the feed side of the ATS

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    9. 9 Pantex Arc Flash “A” phase fuse was inserted successfully During “B” phase fuse installation, a 4 foot arc flash was generated This resulted in a ground fault trip at the main substation and a phase to phase trip on the “B” phase of the feeder circuit The ATS opened and disengaged as designed

    10. 10 Immediate Consequence Sixteen facilities lost main power The electrician was unharmed, the 40 calorie suit was scorched The ATS cabinet was slightly damaged

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    14. 14 Root Cause:Energized Switching Conducted for Operational Convenience

    15. 15 Contributing Causes Roles and responsibilities were not defined for coordination of outages It reduced the need for coordination of outages between support groups Approval process for high voltage switching orders was not adequately formalized

    16. 16 Contributing Causes Organization accepted the perception that the ATS was designed for energized switching Adequate High Voltage electricians and engineering support was not available on site ATS safety interlocks were easily defeated

    17. 17 Corrective Actions Develop a formal approval process for switching orders and associated work packages that requires:

    18. 18 Corrective Actions Justification for Energized Work Senior Management approval to authorize energized work System engineering approval of switching procedures

    19. 19 Corrective Actions Incorporation of Engineering and vendor recommendations into switching operations Incorporation of the intent of NFPA 70E Annex J Positive Control of Safety Interlock Keys for ATS Not sure if this is a continuation from the last slide. Not sure if this is a continuation from the last slide.

    20. 20 Corrective Actions Establish requirements for and confirm: High Voltage Distribution System Configuration Control

    21. 21 Corrective Actions Establish criteria and a process for: Clear roles and responsibilities in coordinating building outages Integrate Outages with Master Production Schedule Characterizing the impact of building shutdown & identifying alternatives to energized switching.

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