Who Developed Insulators 101?

1. “Insulators 101”Presented by Andy SchwalmPresident – Victor Insulators, Inc.IEEE Life MemberPresented to: SWEDEMay 8, 2014- San Antonio, TX

2. Who Developed Insulators 101? • Insulator Working Group 15.09.09 of the (then) L&I Subcommittee – Now OHL Subcommittee • Tony Baker – Vice President – Technology – K-Line Insulators USA • Al Bernstorf – Principal Engineer – Insulators – Hubbell Power Systems • Tom Grisham – Consultant – Griscut Ltd • Andy Schwalm – President – Victor Insulators, Inc.

3. What Is an Insulator? What does it do? • An insulator is a “dam***” poor conductor! And more, technically speaking! • An insulator is a mechanical support! • Primary function - support the “line” mechanically • Secondary function– electrical • Air is the insulator • Outer shells/surfaces are designed to increase leakage distance and strike distance • Maintains an Air Gap • Separates Line from Ground • lengthof air gap depends primarily onsystemvoltage, modified by desired safety margin, contamination, etc. • Resists Mechanical Stresses • “everyday” loads, extreme loads • Resists Electrical Stresses • system voltage/fields, overvoltages • Resists Environmental Stresses • heat, cold, UV, contamination, etc.

4. History • Where Did Insulators Come From?Basically grew out of the needs of the telegraph industry – starting in the late 1700s, early 1800s • History from approx. 1840 to present Glass plates used to insulate telegraph line DC to Baltimore • Types of InsulatorsDistribution, transmission, substation, porcelain, glass, NCI, cycloaliphatic, HDPE etc. • Comparison of types (materials) The “plus and minus” of the multitude of designs and materials in use today

5. Insulator Types - Comparisons • Ceramic • Porcelain or toughened glass • Metal components fixed with cement • ANSI Standards C29.1 through C29.10 • Non Ceramic • Typically fiberglass rod with rubber (EPDM or Silicone) sheath and weather sheds • HDPE line insulator applications • Cycloaliphatic (epoxies) station applications, some line applications • Metal components normally crimped • ANSI Standards C29.11 – C29.19

6. Insulator Types - Comparisons • Ceramic • Materials very resistant to UV, contaminant degradation, electric field degradation • Materials strong in compression, weaker in tension • High modulus of elasticity - stiff • Brittle, require more careful handling • Heavier than NCIs • Non Ceramic • Hydrophobic materials improve contamination performance • Strong in tension, weaker in compression • Deflection under load can be an issue • Lighter – easier to handle • Electric field stresses must be considered

7. Insulator Types - Comparisons • Ceramic • Generally designs are “mature” • Limited flexibility of dimensions • Process limitations on sizes and shapes • Applications/handling methods generally well understood • Non Ceramic • “Material properties have been improved – UV resistance much improved for example • Standardized product lines now exist • Balancing act - leakage distance/field stress – take advantage of hydrophobicity • Application parameters still being developed • Line design implications (lighter weight, improved shock resistance)

8. Design Criteria - Mechanical • An insulator is a mechanical support! Its primary function is to support the line mechanically Electrical Characteristics are an afterthought Will the insulator support your line? Determine The Maximum Load the Insulator Will Ever See - Including NESC Overload Factors.

9. Design Criteria - Mechanical • Line Post insulators • Porcelain • Cantilever Rating • Represents the Average Ultimate Strength in Cantilever – when new. • Minimum Ultimate Cantilever of a single unit may be as low as 85%. • Never Exceed 40% of the Cantilever Rating – Proof Test Load • NCIs (Polymer Insulators) • S.C.L. (Specified Cantilever Load) • Not based upon lot testing • Based upon manufacturer testing • R.C.L. (Reference Cantilever Load) or MDC or MDCL (Maximum Design Cantilever Load) or MCWL or WCL (Working Cantilever Load) • Never Exceed RCL or MDC or MDCL or MCWL or WCL • S.T.L. (Specified Tensile Load) • Tensile Proof Test=(STL/2)

10. Design Criteria - Mechanical • Suspension Insulators • Porcelain • M&E (Mechanical & Electrical) Rating • Represents a mechanical test of the unit while energized. • When the porcelain begins to crack, it electrically punctures. • Average ultimate strength will exceed the M&E Rating when new. • Never Exceed 50% of the M&E Rating • NCIs (Polymer Insulators) • S.M.L. – Specified Mechanical Load • Guaranteed minimum ultimate strength when new. • R.T.L. – Routine Test Load – Proof test applied to each NCI. • Never Load beyond the R.T.L.

11. Design Criteria - Electrical • Design criteria - electrical focus on the importance of strike distance as the primary characteristic for determining electrical properties, with consideration given to leakage (creepage) • Strike and Leakage • Dry 60 Hz F/O and Impulse F/O – based on strike distance. • Wet 60 Hz F/O - Some would argue leakage distance as a principal factor. At the extremes that argument fails – although it does play a role. • Leakage distance helps to maintain the surface resistance of the strike distance.

12. Design Criteria – ElectricalWhat’s an appropriate Leakage Distance?

13. Design Criteria – ElectricalWhat’s an appropriate Leakage Distance?

14. Design Criteria - Electrical • Impulse Withstand If only Critical Impulse Flashover is available – assume 90% (Take Positive or Negative Polarity, whichever is lower safe estimate for withstand) • Importance of corona (grading) rings

15. Dry 60 Hz Flashover Data 1400 1200 Suspension Insulator 1000 800 Flashover (kV) Station Post and Line Post 600 400 200 0 0 20 40 60 80 100 120 140 160 Dry Arcing Distance (inches) Insulator Electrical Ratings

16. Standards • Focus on ANSI Standards • Review of mechanical and electrical ratings • Analysis of ratings vs. design for in service load requirements

17. Standards

18. Standards • ANSI Standards apply to NEW Insulators and Cover: • Definitions • Materials • Dimensions & Marking (interchangeability) • Tests • Prototype & Design, usually performed once for a given design. (design, materials, manufacturing process, and technology). • Sample, performed on random samples from lot offered for acceptance. • Routine, performed on each insulator to eliminate defects from lot.

19. Standards

20. Standards – NEW C29.2 C29.2A and C29.2B • For transmission classes (C29.2B) now TWO ratings class for each “level” • E.g. previously only Class 52-3 • Now: 52-3L and 52-3H

21. Standards – NEW C29.2

22. Standards – NEW C29.2 Combined mechanical and electrical-strength test Ten assembled insulators shall be selected at random from the lot and tested in accordance with 5.2 of ANSI C29.1. The criteria for determining conformance with the standard are as follows: All insulators subjected to the combined mechanical and electrical-strength test shall equal or exceed the rated combined mechanical and electrical strengths as given in Table 2 of this standard.

23. Standards – Implications Example C29.2 M&E Test

24. Standards – Implications Example C29.7, 8, 9 Cantilever Test

25. NESC ANSI C2 Table 277-1 Allowed percentages of strength ratings

26. Strengths – More In Depth Discussion 2 New IEEE Papers • IEEE TF on Insulator Loading, “High voltage insulators mechanical load limits –Part I: Overhead line load and strength requirements,” IEEE Transactions on Power Delivery, Vol. 27, No. 3, July 2012 • IEEE TF on Insulator Loading, “High voltage insulators mechanical load limits –Part II: Standards and recommendations,” IEEE Transactions on Power Delivery, Vol. 27, No. 4, October 2012.

27. Inspection & Evaluation – Have the insulators deteriorated in service?

28. Inspection & Evaluation – Have the insulators deteriorated in service?

29. Sources

30. Domestic Manufacturing • Transmission • Porcelain, Glass – NONE • NCIs- full lines (changing) • Substation • Porcelain – full lines (for now) • NCIs- full lines (changing) • Distribution • Porcelain – only 1 plant left • NCIs – full lines • Glass – NONE • Porcelain: • Spools, strains – NONE • Cut Out Porcelain – NONE • Line posts – mixed • Pin types – 1 plant

31. Market Size

32. Market Distributions • Distribution – still mainly porcelain below 35 kV, except for dead ends – 90% NCI, growing use of HDPE • Transmission – mainly NCI below 345 kV, >50% ceramic above that

33. Economics • Transmission Lines – insulators typically <3% total cost of line • Distribution Lines – insulators typically 1% - 3% of cost of line

34. Inspection & Evaluation – Inspection Techniques and Evaluation of Results • Visual Inspection- • Individual insulators from a bucket truck or helicopter • Binocular assist • Video Imaging- • Daytime (DAYCOR) • Night time (thermal imaging) • Evaluating corona activity • RIV measurements • Established basis of good and bad • Replacement of Insulators- • Do not “HOT” work any line with known failures. • Procedures to work “HOT” lines is no different for ceramic or NCI’s. • Uncertain if we should replace insulators in the “HOT” mode! • Select a random sample, n= 30. • Subject to M&E test and determine 30 & s • Would like (30 – ks) ≥ M&E Rating • Use student’s t statistic • For α = .05 (95% confidence), want t≥ 1.699.