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Lightning Arrester Initiative for Improved Distribution System Reliability

Learn about a pilot project enhancing lightning protection for better reliability in distribution systems. Presented by Tim Constanzo, PE. Dive into root cause analysis, maintenance strategies, and proposed solutions.

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Lightning Arrester Initiative for Improved Distribution System Reliability

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Presentation Transcript

  1. Distribution Lightning Protection Pilot Projects Reliability Engineering TeamLightning Arrester InitiativePresented byTim Constanzo, PE

  2. Where it all started Corporate initiative to improve reliability • Reliability Summit • Root cause analysis methodology • Relay philosophy/settings • Maintenance, allocation of resources • Backbone initiative (distribution system design) • Lightning arresters (LA’s)

  3. Problem Statement Lightning arresters (LAs) are believed to be the cause of an unacceptable frequency and duration of customer interruptions and outages.

  4. Probing Questions • How bad is it? • Why/how are LA’s failing? • How effective is current application of LA’s on system?

  5. How bad is it? • Estimated population: 39,000 35kV line LAs 300,000 35kV equipment LAs Total 35kV LAs: 339,000 • 35kV LAs issued for maintenance FYE 2005: 500 • Ratio of replacements to total population: 0.15% • Circuit outages in FYE 2005 LA related: 135 • LA related rate of circuit outages: 8.7%

  6. How/why are LA’s failing? • Fishbone and Pareto graphs/Root Cause • LA failure categories: • Proper isolator operation (not a failure!) • Design/Manufacturing defects • Installation Design/Practice • Thermal Runaway

  7. Normal Operation • Isolator designed to operate when capacity of LA is exceeded • Lightning • TOV • No outage caused • Loss of protection until replaced • Reduced BIL/CFO until replaced

  8. LA Design/Manufacturing Issues • Poor design/manufacturing • Poor seals • Voids under sheds • Recommendation: Revise LA standards to eliminate designs with poor seal and voids under sheds.

  9. Failure due to moisture ingress

  10. Installation Design • Current installation design/practice • Long leads wrapping around primary • Reduced Insulation/BIL after isolator operates • Recommendations: • Shorter leads • Eliminate insulating bracket

  11. Tracking Failure of Bracket

  12. Installation T & E Option

  13. Thermal Runaway • Cause: • Aging zinc oxide block material • Moisture ingress (most common) • Effect: High leakage current • Marginalized MCOV • Elevated temperature • Recommendations: • IR patrol • removal when +10°C/18°F above ambient

  14. Current Application of LA’s • Line arresters • 27 kV/22 kV MCOV (Heavy Duty) • ¼-mile spacing, all phases • Equipment arresters • 27 kV/22 kV MCOV (Heavy Duty) • All equipment

  15. Evaluating LA Application TFlash modeling cases: • Baseline: no arresters • Arresters @ ¼ mile, 3 phases • Every pole, center phase only • Every pole, raised center phase only • Every pole, 3 phases

  16. TFlash Results

  17. Conclusions/Recommendations • Discontinue current application: “¼-mile” • Let attrition remove line LAs • Maintain LAs protecting equipment • Apply only when/where lightning is an issue • Circuits requiring higher reliability • High exposure • Use higher voltage rated LA (27 -> 30 kV)

  18. Lightning Arrestor Initiative Going Forward • T&E lightning arrestor installation arrangements • Static wire (no arresters) • LA’s center phase only, every pole • Further modeling in TFlash • Evaluate costs of various arrangements

  19. Questions?

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