1. “Insulators 101” Presented by Andy Schwalm President – Victor Insulators, Inc. IEEE Life Member Presented to: SWEDE May 8, San Antonio, TX

2. Who Developed Insulators 101?
Insulator Working Group 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
length of air gap depends primarily on system voltage, 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 to present Glass plates used to insulate telegraph line DC to Baltimore
Types of Insulators Distribution, 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
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 – Electrical What’s an appropriate Leakage Distance?
“Application Guide for Insulators in a Contaminated Environment” by K. C. Holte et al – F
ESDD (mg/cm2)
Site Severity
Leakage Distance
I-string/V-string
(“/kV l-g)
0 – 0.03
Very Light
0.94/0.8
0.03 – 0.06
Light
1.18/0.97
0.06 – 0.1
Moderate
1.34/1.05
>0.1
Heavy
1.59/1.19
IEC Standards
ESDD (mg/cm2)
Site Severity
Leakage Distance
(“/kV l-g)
<0.01
Very Light
0.87
0.01 – 0.04
Light
1.09
0.04 – 0.15
Medium
1.37
0.15 – 0.40
Heavy
1.70
>0.40
Very Heavy
2.11

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

16. Design Criteria – Insulator Selection
Select the 69 kV Insulator shown at right.
I-string – Mechanical
Worst Case – 6,000 lbs
Suspension: ≥ 12k min ultimate
Leakage Distance ≥ 42”
Switching Surge ≥ 125 kV
Impulse Withstand ≥359 kV

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

18. ANSI C29 Insulator Standards (available on-line at nema.org).1
Insulator Test Methods .2
Wet-process Porcelain & Toughened Glass - Suspensions .3
Wet-process Porcelain Insulators - Spool Type .4
“ Strain Type .5
“ Low & Medium Voltage Pin Type .6
“ High Voltage Pin Type .7
“ High Voltage Line Post Type .8
“ Apparatus, Cap & Pin Type .9
“ Apparatus, Post Type
.10
“ Indoor Apparatus Type
.11
Composite Insulators – Test Methods
.12
“ Suspension Type
.13
“ Distribution Deadend Type
.17
“ Line Post Type
.18
“ Distribution Line Post Type
.19
“ Station Post Type (under development)

19. 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.

20. Ceramic Spools and Strains
Standards
STD. No.
Insulator Type
Sample test
Routine test
C 29.2
Ceramic Suspension
M&E
Tension
C29.3, C29.4
Ceramic Spools and Strains
None
C29.5
Pin Type
Puncture
Electrical
C29.6
“ Pin Type
Cantilever
C29.7
“ Line Post
4 quad. cantilever
C29.8
“ Cap & Pin
Cantilever, T, To
C29.9
“ Station Post
Cantilever, T
Cantilever, T or BM
C29.10
Indoor Apparatus
C29.12
Composite Suspension
SML
C29.13
“ Deadend
C29.17
“ Line Post
C29.18
“ Dist. Line Post

21. 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

22. Standards – NEW C29.2 ANSI Class Connection type Dimensional Values
Mechanical Values
Electrical Values
Radio-influence Voltage
Leakage distance, inches (mm)
Spacing, inches (mm)
Shell diameter, inches (mm)
M&E strength, pounds (kN)
Impact strength, inch-pounds
(N-m)
Tension proof, pounds (kN)
Low-frequency dry flashover, kV
Low-frequency wet flashover, kV
Critical impulse flashover, positive, kV
Critical impulse flashover, negative, kV
Low-frequency puncture voltage, kV
Low-frequency test voltage, kV
Maximum RIV at 1,000 kHz, µV
52-3-L
B&S Type B
11-1/2 (292)
5-3/ (146)
10-3/4 (273)
15,000 (67)
55 (6.0)
7,500 (33.5) 80 50
125
130
110 10
52-3-H
20,000 (89)
10,000 (44.5)
52-4-L
Clevis
52-4-H
52-5-L
B&S Type J
(279)
25,000 (111)
60 (7.0)
12,500 (55.5)
52-5H
30,000 (133)
15,000 (66.5)
52-6-L
52-6-H
52-8-L
B&S Type K
11-3/4 (298)
36,000 (160)
90 (10)
18,000 (80)
52-8-H
40,000 (178)
52-10-L
6-1/ (165)
52-10-H
52-11
(381)
6-1/ (155.5)
12-1/4 (311)
50,000 (222)
140
52-12
(178)

23. 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.

24. Standards – Implications Example C29.2 M&E Test
Coefficient
of variation, vR
Strength value
at -3σ 5%
90% of M&E rating
10%
79% of M&E rating
15%
67% of M&E rating

25. Standards – Implications Example C29.7, 8, 9 Cantilever Test
Coefficient
of variation, vR
Strength value
at -3 σ 5%
85% of Cantilever rating
10%
70% of Cantilever rating
15%
55% of Cantilever rating

26. NESC ANSI C2 Table 277-1 Allowed percentages of strength ratings
Insulator Type %
Strength Rating2
Ref. ANSI Std.
Ceramic3
Suspension
50%
Combined
mechanical & electrical strength (M&E)
C29.2
-1992
Line Post
40%
Cantilever strength
Tension/compression
Strength
C29.7
-1996
Station Post4
Tension/compression/torsion strength
C29.9
-1983
Station
Cap & Pin4
C29.8
-1985
Nonceramic5
Specified mechanical load
(SML) C C
Specified cantilever load (SCL) or
specified tension load (STL) C C
Station Post
All strength ratings

27. 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.

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

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

30. Sources

31. Domestic Manufacturing
Transmission
Porcelain, Glass – NONE
NCIs- full lines (changing)
Substation
Porcelain – full lines (for now)
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

32. Supply Chain NON CERAMIC CERAMIC US (3 main plants): US:
No transmission suspensions
No spools
No strains
Pin Type – 1 Plant
Line Post – 1 Plant
Station Post – 3 Plants
Housings – 2 plants
All remaining plants are importing as well as manufacturing. Sources are China, Romania, Thailand, etc.
NON CERAMIC
US (3 main plants):
Transmission suspensions
Transmission line posts
Distribution suspensions
Distribution line posts
Station Class
Now importing as well as manufacturing. Sources are China, Germany, Canada,

33. Market Size DATE TOTAL LVPOST HVPOST LVSUSP HV SUSP STATION SALES 2005
$162,659,854
$9,175,541
$50,689,720
$21,321,445
$37,249,650
$44,223,498
2006
$186,134,838
$8,764,774
$56,879,248
$21,326,689
$42,944,457
$54,341,020
2007
$178,871,136
$8,148,902
$54,370,706
$19,123,333
$41,294,116
$55,934,079
2008
$184,703,067
$9,033,449
$55,328,125
$20,249,198
$45,963,460
$54,128,835
2009
$199,346,541
$7,212,093
$55,796,547
$16,462,470
$64,840,398
$50,381,412
2010
$204,434,456
$5,631,635
$57,686,263
$19,853,611
$57,254,895
$64,008,052
2011
$265,809,282
$8,490,867
$82,247,066
$21,663,012
$78,483,176
$74,925,161
2012
$275,534,244
$8,761,597
$81,904,852
$21,427,918
$91,549,038
$71,890,839

34. 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

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

36. 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≥ k
Want 30 ≥ 1
M&E s 2
M&E s 3
M&E s