SWEDE Tulsa May 8 th, 2009 Dennis Keilbarth Overhead Distribution Arc Flash at PSO

2 Overview Introduction/Background Technical overview Engineering and policy solutions Ongoing work Conclusion

3 Public Service Company of Oklahoma 527,000 Customers 4405 MW Generation 3700 mi Transmission 21,857 mi Distribution 1712 Employees Headquarters in Tulsa 96 Years Old

4 American Electric Power 5 Million Customers 11 States 38,000 MW Generation 39,000 mi Transmission 208,000 mi Distribution 20,000 Employees Headquarters in Columbus Ohio 102 Years Old

5 PSO’s Arc Hazard Program Dedicated teams Generation Transmission and Substations Network Distribution Metering Overhead Distribution and Underground Residential (URD)

6 Overhead and URD Strategy Purpose Improve safety/reduce hazards NESC National Electric Safety Code compliance Considerations Consistency across distribution operating districts Consistency across GT&D business units Trade-offs: don’t introduce new safety hazards

7 Arc Flash Overview Significant Parameters Fault Current Clearing Time Distance Voltage Measured in cal/cm 2 “Incident Energy” 1.2 cal/cm 2 = 2 nd degree burn on bare skin Image provided by Southern Company

8 Technical Overview Calories/cm 2 Calculations Clearing times 2 to 60 cycles Fault Current 1000 to 20,000 amps

9 Arc Energy as Clothing Curves

10 Fuse Curve vs Clothing Curves

11 Recloser Curves vs Clothing Curves

12 System Summary 4 cal8 cal12 cal25 cal40 cal Reclosers95%100% Fuses98%99%100% Breaker Zones5%20%60%99% Breaker Zones (NRO)*75%98%99% * NRO = Non-Reclose Order

13 Solutions Increase Distance 6ft+ hotstick Reduce Clearing Time Place devices in non- reclose Some electronic relays have fast trip settings (Hot Line Tag) Looking to deploy in high hazard zones

14 Solutions Cover-up Reduce chances of poly-phase faults Watch for damaged equipment while applying PPE Personal Protective Equipment Last line of defense

15 PPE Solutions Traditional PSO Requirements: 4 cal/cm 2 FR shirt, Hardhat, Safety Glasses New Additional Requirements: 8 cal/cm 2 (total) layered FR shirt system Breaker zones require NRO unless a specific analysis has been performed on a breaker without an NRO, with a <= 8 cal result.

16 Ongoing Work Develop internal web resources for arc flash information Training videos Testing Clothing system combinations Effects of reclosing, HLT, and other devices

17 Conclusion Simple, consistent solutions that fit across a wide range of facilities and work practices Achieve the largest safety gains possible while considering the big picture trade-offs Be prepared to refine processes as new information becomes available Always look to “engineer-out” the hazards

18 Questions?