1. “Insulators 101” Section A – Introduction Presented by Andy Schwalm IEEE Chairman, Lightning and Insulator Subcommittee IEEE/PES 2010 Transmission and Distribution Conference and Exposition New Orleans, Louisiana April 20, 2010
IEEE T&D – Insulators 101

2. And more, technically speaking!
What Is an Insulator?
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
IEEE T&D – Insulators 101

3. What Does an Insulator Do?
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.
IEEE T&D – Insulators 101

4. Where Did Insulators Come From?
Basically grew out of the needs of the telegraph industry – starting in the late 1700s, early 1800s
Early history centers around what today we would consider very low DC voltages
Gradually technical needs increased as AC voltages grew with the development of the electric power industry
IEEE T&D – Insulators 101

5. History
Approx 1840
Glass plates used to insulate telegraph line DC to Baltimore
Glass insulators became the ”norm” soon thereafter – typical collector’s items today
Many, many trials with different materials – wood – cement – porcelain - beeswax soaked rag wrapped around the wire, etc.
Ultimately porcelain and glass prevailed
IEEE T&D – Insulators 101

6. Approx 1893 - 1897 Approx 1902 - 1920 History
Wet process porcelain developed for high voltage applications
Porcelain insulator industry started
Approx
Application voltages increased
Insulator designs became larger, more complex
Ceramics (porcelain, glass) still only choices at high voltages
IEEE T&D – Insulators 101

7. Approx 1960 Approx 1960 - 1965 History
US trials of first “NCIs” – cycloaliphatic based
Not successful, but others soon became interested and a new industry started up
Approx
Europeans develop “modern” style NCI – fiberglass rod with various polymeric sheds
Now considered “First generation”
IEEE T&D – Insulators 101

8. Approx 1970 - present History
NCI insulator industry really begins in US with field trials of insulators
Since that time - new manufacturers, new designs, new materials
NCIs at “generation X” – there have been so many improvements in materials, end fitting designs, etc.
Change in materials have meant changes in line design practices, maintenance practices, etc.
Ceramic manufacturers have not been idle either with development of higher strength porcelains, RG glazes, etc.
IEEE T&D – Insulators 101

9. Approx 1970 - present History
Domestic manufacturing of insulators decreases, shift to offshore (all types)
Engineers need to develop knowledge and skills necessary to evaluate and compare suppliers and products from many different countries
An understanding of the basics of insulator manufacturing, design and application is more essential than ever before
IEEE T&D – Insulators 101

10. Insulator Types
For simplicity will discuss in terms of three broad applications:
Distribution lines (thru 69 kV)
Transmission lines (69 kV and up)
Substations (all voltages)
IEEE T&D – Insulators 101

11. Insulator Types Distribution lines
Pin type insulators -mainly porcelain, growing use of polymeric (HDPE – high density polyethylene), limited use of glass (in US at least)
Line post insulators – porcelain, polymeric
Dead end insulators – polymeric, porcelain, glass
Spool insulators – porcelain, polymeric
Strain insulators, polymeric, porcelain
IEEE T&D – Insulators 101

12. Types of Insulators – Distribution
IEEE T&D – Insulators 101

13. Insulator Types Transmission lines
Suspension insulators - new installations mainly NCIs, porcelain and glass now used less frequently
Line post insulators – mainly NCIs for new lines and installations, porcelain much less frequent now
IEEE T&D – Insulators 101

14. Types of Insulators – Transmission
IEEE T&D – Insulators 101

15. Insulator Types Substations
Post insulators – porcelain primarily, NCIs growing in use at lower voltages (~161 kV and below)
Suspension insulators –NCIs (primarily), ceramic
Cap and Pin insulators – “legacy” type
IEEE T&D – Insulators 101

16. Types of Insulators – Substation
IEEE T&D – Insulators 101

17. 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
IEEE T&D – Insulators 101

18. 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
IEEE T&D – Insulators 101

19. 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)
IEEE T&D – Insulators 101

20. “Insulators 101” Section B - Design Criteria Presented by Al Bernstorf IEEE Chairman, Insulator Working Group IEEE/PES 2010 Transmission and Distribution Conference and Exposition New Orleans, Louisiana April 20, 2010
IEEE T&D – Insulators 101

21. 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.
IEEE T&D – Insulators 101

22. 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.
IEEE T&D – Insulators 101

23. 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. (Rated 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)
IEEE T&D – Insulators 101

24. Design Criteria - Mechanical
Other Considerations
Suspensions and Deadends – Only apply tension loads
Line Posts –
Cantilever is only one load
Transverse (tension or compression) on line post – loading transverse to the direction of the line.
Longitudinal – in the direction of travel of the line
Combined Loading Curve –
Contour curves representing various Longitudinal loads
Available Vertical load as a function of Transverse loading
Manufacturers have different safety factors!!!
IEEE T&D – Insulators 101

25. Design Criteria - Mechanical
IEEE T&D – Insulators 101

26. Design Criteria - Electrical
An Insulator is a mechanical support!
Air imparts Electrical Characteristics
Strike Distance (Dry Arcing Distance) is the principal constituent to electrical values.
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.
Leakage Requirements do play a role!!!
IEEE T&D – Insulators 101

27. Design Criteria - Electrical
Dry Arcing Distance – (Strike Distance) – “The shortest distance through the surrounding medium between terminal electrodes….” 1
1 – IEEE Std
IEEE T&D – Insulators 101

28. Design Criteria - Electrical
Define peak l-g kV
Determine Leakage Distance Required
Switching Over-voltage Requirements
Impulse Over-voltage
Chart Courtesy of Ohio Brass/HPS – EU1429-H
IEEE T&D – Insulators 101

29. Design Criteria – Leakage Distance
What is Leakage Distance?
“The sum of the shortest distances measured along the insulating surfaces between the conductive parts, as arranged for dry flashover test.” 1
1 – IEEE Std
IEEE T&D – Insulators 101

30. Design Criteria - Electrical
What’s an appropriate Leakage Distance?
Empirical Determination
What’s been used successfully?
If Flashovers occur – add more leak?
ESDD (Equivalent Salt Deposit Density) Determination
Measure ESDD
Pollution Monitors
Dummy Insulators
Remove in-service insulators
Evaluate ESDD and select appropriate Leakage Distance
IEEE T&D – Insulators 101

31. Design Criteria - Electrical
“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
IEEE T&D – Insulators 101

32. Design Criteria - Electrical
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
IEEE T&D – Insulators 101

33. Design Criteria - Electrical
IEEE T&D – Insulators 101

34. Improved Contamination Performance
IEEE T&D – Insulators 101

35. Improved Contamination Performance
Polymer insulators offer better contamination flashover performance than porcelain?
Smaller core and weathershed diameter increase leakage current density.
Higher leakage current density means more Ohmic Heating.
Ohmic Heating helps to dry the contaminant layer and reduce leakage currents.
In addition, hydrophobicity helps to minimize filming
IEEE T&D – Insulators 101

36. Improved Contamination Performance
“the contamination performance of composite insulators exceeds that of their porcelain counterparts”
“the contamination flashover performance of silicone insulators exceeds that of EPDM units”
“the V50 of polymer insulators increases in proportion to the leakage distance”
CEA 280 T 621, “Leakage Distance Requirements for Composite Insulators Designed for Transmission Lines”
IEEE T&D – Insulators 101

37. Insulator Selection Where do I get these values?
Leakage Distance or Creepage Distance
Manufacturer’s Catalog
Switching Surge
Wet W/S
((Wet Switching Surge W/S)/√2) ≥ 60 Hz Wet Flashover (r.m.s.)
Peak Wet 60 Hz value will be lower than Switching Surge Wet W/S
Impulse Withstand
Take Positive or Negative Polarity, whichever is lower
If only Critical Impulse Flashover is available – assume 90%
(safe estimate for withstand)
IEEE T&D – Insulators 101

38. 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
IEEE T&D – Insulators 101

39. Porcelain – 5-3/4 X 10” bells X 4 units
Insulator Selection
Porcelain – 5-3/4 X 10” bells X 4 units
Characteristic
Required
Available
Leakage Distance
42”
46”
Wet Switching
Surge W/S
125 kV
240 kV
Impulse W/S
359 kV
374 kV
M & E
12,000 lbs
15,000 lbs
IEEE T&D – Insulators 101

40. Grading Rings Simulate a larger, more spherical object
Reduce the gradients associated with the shielded object
Reduction in gradients helps to minimize RIV & TVI
Porcelain or Glass –
Inorganic – breaks down very slowly
NCIs
Polymers are more susceptible to scissioning due to corona
UV – short wavelength range – attacks polymer bonds.
Most short wavelength UV is filtered by the environment
UV due to corona is not filtered
IEEE T&D – Insulators 101

41. NCIs and Rings Grading (Corona) Rings
Due to “corona cutting” and water droplet corona – NCIs may require the application of rings to grade the field on the polymer material of the weathershed housing.
Rings must be:
Properly positioned relative to the end fitting on which they are mounted.
Oriented to provide grading to the polymer material.
Consult the manufacturer for appropriate instructions.
As a general rule – rings should be over the polymer – brackets should be on the hardware.
IEEE T&D – Insulators 101

42. Questions?
IEEE T&D – Insulators 101

43. Insulators 101 Section C - Standards
Presented by Tony Baker
IEEE Task Force Chairman, Insulator Loading
IEEE/PES 2010 Transmission and Distribution
Conference and Exposition
New Orleans, Louisiana
April 20, 2010
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101 43

44. American National Standards
Consensus standards
Standards writing bodies must include representatives from materially affected and interested parties.
Public review
Anybody may comment.
Comments must be evaluated, responded to, and if found to be
appropriate, included in the standard .
Right to appeal
By anyone believing due process lacking.
Objective is to ensure that ANS Standards are developed in an environment that is equitable, accessible, and responsive to the requirements of various stakeholders*.
* The American National Standards Process, ANSI March 24, 2005
IEEE T&D – Insulators 101

45. American Standards Committee on Insulators for Electric Power Lines
ASC C-29
EL&P Group
IEEE
NEMA
Independents
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

46. 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)
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

47. ANSI C29 Insulator Standards
Applies to new insulators
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.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

48. ANSI C 29 Insulator Standard Ratings
Electrical & Mechanical Ratings
How are they assigned?
How is conformance demonstrated?
What are application limits?
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

49. Electrical Ratings Average flashover values Impulse withstand
Low-frequency Dry & Wet
Critical impulse, positive & negative
Impulse withstand
Radio-influence voltage
Applies to all the types of high voltage insulators
Rated values are single-phase line-to-ground voltages.
Dry FOV values are function of dry arc distance and test configuration.
Wet FOV values function of dry arc distance and insulator shape, leakage distance, material and test configuration.
Tests are conducted in accordance with IEEE STD except
test values are corrected to standard conditions in ANSI C29.1.
-Temperature 25° C
- Barometric Pressure ins. of Hg
- Vapor Pressure ins. of Hg
- For wet tests: rate 5±0.5 mm/min, resistivity 178±27Ωm, 10 sec. ws
IEEE T&D – Insulators 101

50. Dry Arcing Distance Shortest distance through the surrounding medium between terminal electrodes , or the sum of distances between intermediate electrodes , whichever is shortest, with the insulator mounted for dry flashover test.
IEEE T&D – Insulators 101

51. This is the manufacturer’s rated value, R.
Electrical Ratings
Product is designed to have a specified average flashover.
This is the manufacturer’s rated value, R.
Samples are electrically tested in accordance with standard
This is the tested value, T.
Due to uncontrollable elements during the test such as atmospheric fluctuations, minor differences in test configuration, water spray fluctuations, etc. the test value can be less than the rated value.
Does T satisfy the requirements for the rating R?
If T/R≥ 𝝃 Yes
where 𝝃 = 0.95 for Low-frequency Dry flashover tests
= 0.90 for Low-frequency Wet flashover tests
= 0.92 for Impulse flashover tests
IEEE T&D – Insulators 101

52. Dry Arcing Distance (inches)
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
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

53. Electrical Ratings ANSI C2 Insulation Level Requirements ANSI C2-2007, Table 273-1
Higher insulation levels required in areas where severe lightning, high atmospheric contamination, or other unfavorable conditions exist
IEEE T&D – Insulators 101

54. Electrical Ratings - Application
Customer determines needs and specifies electrical requirements:
60 Hz Dry & wet flashover
Impulse flashover and/or withstand
Leakage distance
Does offered product meet customer’s specification S?
If R ≥ S and T ≥ 𝝃R
yes, otherwise no.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

55. Mechanical Ratings
Sample & Routine Mechanical Tests are based on the primary in-service loading conditions
STD. No.
Insulator Type
Sample test
Routine test
C 29.2
Ceramic Suspension
M&E
Tension
C29.6
“ Pin Type
Cantilever
-----
C29.7
“ Line Post
4 quad. cantilever
C29.8
“ Cap & Pin
Torsion
C29.9
“ Station Post
Tension, Cantilever or
Bending Moment
C29.12
Composite Suspension
SML
C29.13
“ Deadend
C29.17
“ Line Post
C29.18
“ Dist. Line Post
ilever
IEEE T&D – Insulators 101 55

56. Mechanical Ratings Bending Tests Composite Posts M&E Test
Ceramic Suspensions
Bending Tests
Composite Posts
Hubbell Power Systems
Kinectrics
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

57. ANSI C29 High Voltage Insulator Standards
Std.
No.
Insulator
Type
Ult. Strength
QC Test
Lot Acceptance
Criteria
Routine
Test
C29.2
Ceramic
Suspension
Combined M&E strength
of 10 units
Ave. Std. dev. = S
X10 ≥ R +1.2 S
s10 ≤ 1.72 S
3 sec. tension
at 50% of R
C29.7
Line post
Cantilever strength
of 3 units
X3≥ R
no one xi ≮ .85 R
4 quad. bending
at 40% of R
C29.8
Ceramic Apparatus
Cap & Pin
Cantilever, tension, & torsion strength
of 3 units each
no one xi ≮ .85 R
at specified value
C29.9
Ceramic Apparatus
Post Type
Cantilever & tension strengths
Tension
at 50% of R or
at 40% of R
C29.12
Composite
Specified Mech. Load (SML)
test of 3 units
xi ≥ .R
10 sec. tension
at 50% of R
C29.13
Distribution Deadend
SML test
of 3 units
xi ≥ .SML rating
C29.17
Line Post
Cantilever strength of 1 unit
Tension test of 1 unit
Strength ≥ R
at 50% of R
C29.18
Distribution Line Post
Strength ≥ R
IEEE T&D – Insulators 101

58. Lot Acceptance Criteria – ANSI C29.2
Lot acceptance according to ANSI C 29.2.
Select ten random units from lot and subject to M&E test.
Requirements are:
M&E rating ≤ X SH
&
s10 ≤1.72SH
s10 is std. dev. of the 10 units
SH is historical std. dev.
If s10= SH then for minimally acceptable lot, ~ 11.5% of units in lot could have strengths below the rated value.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

59. Lot Acceptance Criteria – ANSI C29
Lot Acceptance Criteria – ANSI C Possible low strengths for ceramic suspension units in a lot minimally acceptable according to ANSI C29.2
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
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

60. Lot Acceptance Criteria – CSA C411
Lot Acceptance Criteria – CSA C Possible low strengths for ceramic suspension units in a lot minimally acceptable according to CSA C411.1
Requirements
Rating≤ XS – 3s
&
Xi ≥ R
On a -3 sigma basis , minimum strength that could be expected in a lot is the rated value regardless of the coefficient of variation for the manufacturing process that produced the lot.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

61. Coefficient of variation, vR Strength value at -3 σ 5%
Lot Acceptance Criteria – ANSI C29 Possible low strengths for ceramic units in a lot minimally acceptable according to ANSI C29.7, C29.8 & C29.9 Cantilever rating ≤ X3 & no xi< 85% of rating
Coefficient
of variation, vR
Strength value
at -3 σ 5%
85% of Cantilever rating
10%
70% of Cantilever rating
15%
55% of Cantilever rating
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

62. Lot Acceptance Criteria ANSI C29 –Composite Insulators
Random samples selected from an offered lot.
Ultimate strength tests on samples.
Requirement is:
xi ≥ Rating
The rated value is assigned by the manufacturer based on ultimate strength tests during design.
However for a lot minimally acceptable according to the standard, statistical inference for the strength distribution for entire lot not possible.
Composite Insulators have a well defined damage limit providing good application direction.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

63. Mechanical Ratings – Application Limits NESC ANSI C Table Allowed percentages of strength ratings
Insulator Type %
Strength Rating
Ref. ANSI Std.
Ceramic
Suspension
50%
Combined
mechanical & electrical strength (M&E) C
Line Post
40%
Cantilever strength
Tension/compression strength C
Station Post4
Tension/compression/torsion strength C
Station
Cap & Pin C
Composite Suspension
Specified mechanical load (SML) C C
Specified cantilever load (SCL) or
specified tension load (STL) C C
Station Post
All strength ratings
IEEE T&D – Insulators 101

64. Mechanical Ratings – Application Limits
Worst loading case load ≤ (% Table 277-1)(Insulator Rating)
In most cases , % from Table is equal to the routine proof -test load.
Bending tests on a production basis are not practicable in some cases, (large stacking posts, cap & pins , and polymer posts) and tension proof-load tests are specified.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

65. Mechanical Ratings – Application Limits Composite Post Insulators – Combined Loading
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

66. Mechanical Ratings – Application Limits Composite Post Insulators – Combined Loading
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

67. Recent Developments for Application Limits Component strength cumulative distribution function FR and probability density function of maximum loads fQ.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

68. Component Damage Limit
DAMAGE LIMIT Strength of a component below ultimate corresponding to a defined limit of permanent damage or deformation. For composites the damage limit is fairly well understood.
IEEE T&D – Insulators 101
IEEE T&D – Insulators 101

69. Component Damage Limit
Defining Damage Limit for ceramics more difficult to define as shown by comparing stress-strain curves for brittle and ductile materials. L&I WG on Insulators is addressing this problem now
IEEE T&D – Insulators 101

70. “Insulators 101” Section D – Achieving ‘Quality’ Presented by Tom Grisham IEEE Task Force Chairman, “Insulators 101” IEEE/PES – T&D Conference and Exposition New Orleans, LA April 20, 2010
IEEE T&D – Insulators 101

71. Objectives of ‘Quality” Presentation
Present ideas to verify the supplier qualification, purchasing requirements, manufacturer inspections of lots, shipment approval, material handling, and training information for personnel
Routine inspection of the installation
Identify steps to analyze field complaints
To stimulate “Quality” improvement
IEEE T&D – Insulators 101

72. ‘Quality’ Defined
QUALITY – An inherent, basic or distinguishing characteristic; an essential property or nature.
QUALITY CONTROL – A system of ensuring the proper maintenance of written standards; especially by the random inspection of manufactured goods.
IEEE T&D – Insulators 101

73. What Is Needed in a Quality Plan?
Identifying critical design parameters
Qualifying ‘new’ suppliers
Evaluating current suppliers
Establishing internal specifications
Monitoring standards compliance (audits)
Understanding installation requirements
Establishing end-of-life criteria
Ensuring safety of line workers
Communicating and training
All aspects defined by the company plan
IEEE T&D – Insulators 101

74. What Documents Should Be Included?
Catalog specifications and changes
Supplier audit records and lot certification
Qualification testing of the design
Utility-specific testing
Additional supplier testing for insulators (vibration, temperature, long-term performance, etc)
ANSI or equivalent design reports
Storage methods
Installation records (where, by whom, why?)
Interchangeability with other suppliers product
Handling methods (consult manufacturer)
Installation requirements and techniques
IEEE T&D – Insulators 101

75. ‘Proven’ Installation Procedures
IEEE T&D – Insulators 101

76. Handling of Ceramics – NEMA HV2-1984
Insulators should not be dropped or thrown…..
Insulators strings should not be bent…..
Insulator strings are not ladders…..
Insulators with chips or cracks should be discarded and companion units should be carefully inspected…..
Cotter keys should be individually inspected for twisting, flattening or indentations. If found, replace keys and retest the insulator…..
The maximum combined load, including safety requirements of NESC, must not exceed the rating…..
Normal operating temperature range for ceramics is defined as –40 to 150 Degrees F…..
IEEE T&D – Insulators 101

77. Handling of NCI’s
NEMA is working on a ‘new’ application guide for NCI products. It will likely include……………………
“Insulators should not be dropped, thrown, or bent…”
“Insulators should not be used as ladders…”
“Cotter keys for ball sockets should be inspected identically to the instructions for ceramic insulators…”
“The maximum combined loads should not exceed the RTL…”
Normal operating temperature is –40 to 150 Degrees F…”
“Insulators should not be used as rope supports…”
“Units with damaged housings that expose the core rod should be replaced and discarded…”
“Units with cut or torn weathersheds should be inspected by the manufacturer…”
“Bending, twisting and cantilever loading should be avoided during construction and maintenance…”
IEEE T&D – Insulators 101

78. Line outage Failures Your objective is to find the problem, quickly!
IEEE T&D – Insulators 101

79. Inspection Techniques
Subjective: What you already know
Outage related
Visual methods from the ground
Previous problem
Thermal camera (NCI – live line)
Objective: Answer is not obvious
Leakage current measurements
Daycor camera for live line inspections (live)
Mechanical and electrical evaluations
IEEE T&D – Insulators 101

80. Porcelain and Glass Failures
Failures are ‘typically’ visible or have a new ‘history’ or upgrade on the site?
New products may not be your Grandfather’s Oldsmobile, however!
Have the insulators deteriorated?
Perform thermal-mechanical test before failing load and compare to ultimate failing load
Determine current ultimate strength versus new
Should the insulators be replaced?
Establish internal criteria by location
IEEE T&D – Insulators 101

81. Non-Ceramic (NCI) Failures
Cause of failures may NOT be visible!
More ‘subjective’ methods used for live line replacement
Some external deterioration may NOT be harmful
Visual examples of critical issues are available to you
Imperative to involve the supplier!
Evaluate your expertise to define ‘root’ cause condition
Verify an ‘effective’ corrective action is in place
Utilize other sources in the utility industry
Establish ‘subjective’ baselines for new installations as future reference! Porcelain and glass, also!
IEEE T&D – Insulators 101

82. What To Do for an Insulator Failure?
Inspection of Failure
What happened?
Extraordinary factors?
Save every piece of the unit!
Take lots of pictures!
Inspect other insulators!
Supplier Involvement
Verification of production date?
Available production records?
Determination of ‘root’ cause?
Recommended action?
Safety requirements?
IEEE T&D – Insulators 101

83. Summary of ‘Quality’ Presentation
In today’s environment, this presentation suggests that the use of a well documented ‘quality’ program improves long term performance and reduces outages.
Application information that is communicated in the organization will help to minimize installation issues and reduce costs.
Actively and accurately defining the condition, or determining the root cause of a failure, will assist in determining end-of-life decisions.
IEEE T&D – Insulators 101

84. Source of Presentation
IEEE T&D – Insulators 101