Pilot Program on the Application of Electronic Resettable Sectionalizers to Improve Reliability

1. Pilot Program on the Application of Electronic Resettable Sectionalizers to Improve Reliability SWEDE Conference May 1, 2008 Van Nguyen Thu-Van.Nguyen@CenterPointEnergy.com

2. Pilot Program Review • Circuit History on Hockley (HK) -04 and -06 • Circuit Demographics • Reliability Performance • Root Cause Analysis on Circuit Operations and Fuse Outages • Review of Outage Data in Early 2005 • Potential Solutions • Course of Action for Electronic Resettable Sectionalizers (ERS ) • Functions • Advantages • Safety Concerns • Implemented by Early 2006 • Education • Performance Results for 2006 and 2007

3. Circuit History • Circuit Demographics on HK-04 and HK-06 • 12 kV circuits • Rural, agricultural areas • No static construction • Low customer count • HK-04 – 1,000 customers • HK-06 – 465 customers

5. HK-04 Lateral

6. Circuit History (con’t) • Reliability Performance on HK-04 • 10% SAIDI circuit in 2003, 2004 and 2005 • Excessive circuit operations in 2004 • 9 specific fuses accounted for 60% of total circuit SAIDI minutes from potential temporary events (lightning, wind, wildlife, etc…) in 2004 • Similar performance in 2003 and 2005

7. Circuit History (con’t) • Reliability Performance on HK-06 • 10% SAIDI circuit in 2004 and 2005 • Excessive circuit operations in 2004 • 5 specific fuses accounted for 58% of total circuit SAIDI minutes from potential temporary events in 2004

8. Root Cause Analysis • Review of Outage Data in Early 2005 • 60% (HK-04) and 58% (HK-06) of total circuit SAIDI mins from potential temporary events in 2004 • Excessive circuit operations in 2004 • HK-04 – 27 operations • HK-06 – 36 operations • Source of excessive operations unknown • Fault current data ( < 1kA to > 4kA ) from relays indicated activities may be at multiple points

9. Root Cause Analysis (con’t) • Review of Outage Data in Early 2005 • Lightning analysis investigation • No static construction • Flat, grasslands, agricultural areas • Temporary events such as lightning and wind • Erratic fault current values • Correlation between outages and lightning strikes

10. Mapping of Hockley Circuits

11. Lightning Data Plot for 2004

12. Root Cause Analysis (con’t) • Investigation of Potential Solutions • Installation of lightning arresters • Effective but costly • Installation of static neutral • Effective but costly • Remote controlled equipment • Limited effectiveness • Electronic resettable sectionalizers (ERS) • Effective and economical

13. Course of Action • Functions of ERS Devices • Works in conjunction with upstream reclosing protective device • Similar in operation as a typical sectionalizer • Registers current greater than its actuating level • Registers loss of voltage • Device opens on predetermined number of counts of fault current AND loss of voltage • 1, 2 and 3-count devices can be placed in series

14. Course of Action (con’t) • Advantages of ERS Devices • Allow temporary faults to clear without experiencing a sustained interruption • Less expensive alternative to reclosers to isolate faulted (sustained) sections of conductor • Fits into standard fuse cutout body • Simple to install and implement • Ideal for replacing existing fuses

15. Course of Action (con’t) • Safety Concerns on ERS Devices • Must be used in conjunction with an upstream reclosing protective device • Cannot be blindly used to replace fuses • Detailed engineering analysis must be performed prior to implementing • Lack of familiarity by line crews on the operation of ERS devices

16. Course of Action (con’t) • Implemented by Early 2006 • Protection analysis conducted by engineering • Breaker coordination with hydraulic reclosers • HK-04 • 3 hydraulic reclosers installed • 9 fuses replaced with ERS devices • HK-06 • 1 hydraulic recloser installed • 5 fuses replaced with ERS devices

17. Hockley-04 Oneline

18. Recloser 127Z

20. Sectionalizer 112N

22. Hockley-06 Oneline

23. Course of Action (con’t) • Education • Line crews trained on application • Article published in company-wide newsletter • Stenciling nomenclature (###N or N###)

24. Stenciling Nomenclature

25. Performance Results for 2006 • HK-04 and HK-06 • 47% combined decrease in SAIDI values • Neither repeated as 10% SAIDI circuits • Pilot program deemed successful • CPE approved the deployment of ERS devices on other circuits

26. Performance Results for 2007 • HK-06 was not a 2007 10% SAIDI circuit • HK-04 was a 2007 10% SAIDI circuit • 16% of total circuit SAIDI mins from potential temporary events behind line fuses • Trees, collisions, material failures and unknown causes also contributed to SAIDI mins

27. Questions?