SWEDE Tulsa May 8th, 2009 Dennis Keilbarth

Overhead Distribution Arc Flash at PSO

Overhead Distribution Arc Flash at PSO

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OverviewOverview

• Introduction/Background

• Technical overview

• Engineering and policy solutions

• Ongoing work

• Conclusion

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Public Service Company of Oklahoma

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

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American Electric PowerAmerican 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

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PSO’s Arc Hazard ProgramPSO’s Arc Hazard Program

• Dedicated teams • Generation

• Transmission and Substations

• Network Distribution

• Metering

• Overhead Distribution and Underground Residential (URD)

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Overhead and URD StrategyOverhead 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

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Arc Flash OverviewArc Flash Overview

• Significant Parameters• Fault Current

• Clearing Time

• Distance

• Voltage

• Measured in cal/cm2

• “Incident Energy”

• 1.2 cal/cm2 = 2nd degree burn on bare skin

Image provided by Southern Company

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Technical OverviewTechnical Overview

Calories/cm2 Calculations

Clearing times 2 to 60 cycles

Fault Current 1000 to 20,000 amps

Fault Current (kA) Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2 Cal/cm2

20 2.49 4.99 7.48 9.97 12.47 24.93 37.40 49.87 62.33 74.8019 2.31 4.62 6.93 9.24 11.55 23.10 34.65 46.20 57.75 69.3018 2.13 4.27 6.40 8.54 10.67 21.34 32.01 42.68 53.35 64.0217 1.96 3.92 5.87 7.83 9.79 19.58 29.37 39.16 48.95 58.7416 1.79 3.58 5.37 7.16 8.95 17.89 26.84 35.79 44.73 53.6815 1.63 3.26 4.88 6.51 8.14 16.28 24.42 32.56 40.70 48.8414 1.47 2.95 4.42 5.90 7.37 14.74 22.11 29.48 36.85 44.2213 1.33 2.65 3.98 5.31 6.64 13.27 19.91 26.55 33.18 39.8212 1.18 2.36 3.54 4.72 5.90 11.81 17.71 23.61 29.52 35.4211 1.05 2.10 3.15 4.19 5.24 10.49 15.73 20.97 26.22 31.4610 0.92 1.83 2.75 3.67 4.58 9.17 13.75 18.33 22.92 27.50

9 0.79 1.58 2.38 3.17 3.96 7.92 11.88 15.84 19.80 23.768 0.67 1.35 2.02 2.70 3.37 6.75 10.12 13.49 16.87 20.247 0.56 1.13 1.69 2.26 2.82 5.65 8.47 11.29 14.12 16.946 0.46 0.92 1.39 1.85 2.31 4.62 6.93 9.24 11.55 13.865 0.36 0.72 1.08 1.44 1.80 3.59 5.39 7.19 8.98 10.784 0.27 0.54 0.81 1.09 1.36 2.71 4.07 5.43 6.78 8.143 0.18 0.37 0.55 0.73 0.92 1.83 2.75 3.67 4.58 5.502 0.10 0.21 0.31 0.41 0.51 1.03 1.54 2.05 2.57 3.081 0.04 0.07 0.11 0.15 0.18 0.37 0.55 0.73 0.92 1.10

Clearing Time (cycles): 2 4 6 8 10 20 30 40 50 60

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Arc Energy as Clothing CurvesArc Energy as Clothing Curves

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Fuse Curve vs Clothing CurvesFuse Curve vs Clothing Curves

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Recloser Curves vs Clothing CurvesRecloser Curves vs Clothing Curves

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System SummarySystem Summary

4 cal 8 cal 12 cal 25 cal 40 cal

Reclosers 95% 100%

Fuses 98% 99% 100%

Breaker Zones 5% 20% 60% 99% 99%

Breaker Zones (NRO)* 75% 98% 99% 99% 99%

* NRO = Non-Reclose Order

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SolutionsSolutions

• 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

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SolutionsSolutions

• Cover-up• Reduce chances of

poly-phase faults• Watch for damaged

equipment while applying

• PPE • Personal Protective

Equipment• Last line of defense

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PPE SolutionsPPE Solutions

Traditional PSO Requirements:• 4 cal/cm2 FR shirt, Hardhat, Safety Glasses

New Additional Requirements:• 8 cal/cm2 (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.

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Ongoing WorkOngoing Work

• Develop internal web resources for arc flash information

• Training videos

• Testing• Clothing system combinations

• Effects of reclosing, HLT, and other devices

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ConclusionConclusion

• 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

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Questions?Questions?