Insulators Panel Final A

8/8/2019 Insulators Panel Final A

http://slidepdf.com/reader/full/insulators-panel-final-a 1/84

IEEE T&D – Insulators 101

““Insulators 101”Insulators 101”Section A – IntroductionSection A – Introduction

Presented by Andy SchwalmPresented by

Andy Schwalm

IEEE Chairman, Lightning and InsulatorIEEE Chairman,

Lightning and Insulator

SubcommitteeSubcommittee

IEEE/PES 2010 Transmission and DistributionIEEE/PES 2010 Transmission and Distribution

Conference and ExpositionConference and Exposition

New Orleans, LouisianaNew Orleans, LouisianaApril 20, 2010April 20, 2010




What Is an Insulator?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” mechanicallySecondary function– electrical

Air is the insulator Outer shells/surfaces are designed to increaseleakage distance and strike distance




What Does an Insulator Do?What Does an Insulator Do?

Maintains an Air GapSeparates Line from Groundlength of air gap depends primarily on system voltage, modifiedby desired safety margin, contamination, etc.

Resists Mechanical Stresses“everyday” loads, extreme loads

Resists Electrical Stressessystem voltage/fields, overvoltages

Resists Environmental Stressesheat, cold, UV, contamination, etc.




Where Did Insulators ComeWhere Did Insulators Come

From?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




HistoryHistory

Glass plates used to insulate telegraph line DC toBaltimore

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




HistoryHistory

Wet process porcelain developed for high voltage

applications

Porcelain insulator industry started

Application voltages increased

Insulator designs became larger, more complex

Ceramics (porcelain, glass) still only choices athigh voltages




HistoryHistory

US trials of first “NCIs” – cycloaliphatic based

Not successful, but others soon became interested and a new industry

started up

Europeans develop “modern” style NCI – fiberglass

rod with various polymeric sheds

Now considered “First generation”




HistoryHistory

NCI insulator industry really begins in US with field trialsof insulators Since that time - new manufacturers, new designs, new

materialsNCIs 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.




HistoryHistory

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




Insulator TypesInsulator 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)





Distribution lines

Pin type insulators -mainly porcelain, growing useof polymeric (HDPE – high density polyethylene),

limited use of glass (in US at least)Line post insulators – porcelain, polymericDead end insulators – polymeric, porcelain, glassSpool insulators – porcelain, polymeric

Strain insulators, polymeric, porcelain




Types of Insulators – DistributionTypes of Insulators – Distribution





Transmission lines

Suspension insulators - new installations mainlyNCIs, porcelain and glass now used less frequently

Line post insulators – mainly NCIs for new lines andinstallations, porcelain much less frequent now




Types of Insulators – TransmissionTypes of Insulators – Transmission





Substations

Post insulators – porcelain primarily, NCIs growingin use at lower voltages (~161 kV and below)

Suspension insulators –NCIs (primarily), ceramic

Cap and Pin insulators – “legacy” type




Types of Insulators – SubstationTypes of Insulators – Substation




Insulator Types - ComparisonsInsulator Types - Comparisons

Ceramic• Porcelain or toughened glass

• Metal components fixed withcement

• 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, someline applications

• Metal components normallycrimped

• ANSI Standards C29.11 –C29.19





Ceramic

• Materials very resistant to

UV, contaminant degradation,

electric field degradation

• Materials strong in

compression, weaker intension

• High modulus of elasticity -

stiff

• Brittle, require more careful

handling• Heavier than NCIs

Non Ceramic• Hydrophobic materials

improve contaminationperformance

• Strong in tension, weaker in

compression• Deflection under load can bean issue

• Lighter – easier to handle

• Electric field stresses mustbe considered





Ceramic• Generally designs are

“mature”

• Limited flexibility of dimensions

• Process limitations on sizesand shapes

• Applications/handlingmethods generally wellunderstood

Non Ceramic• “Material properties have

been improved – UVresistance much improved for example

• Standardized product lines

now exist• Balancing act - leakagedistance/field stress – takeadvantage of hydrophobicity

• Application parameters stillbeing developed

• Line design implications(lighter weight, improvedshock resistance)




““Insulators 101”Insulators 101”

Section B - Design CriteriaSection B - Design CriteriaPresented by Al Bernstorf Presented by Al Bernstorf

IEEE Chairman, Insulator WorkingIEEE Chairman, Insulator Working

GroupGroup

IEEE/PES 2010 Transmission and DistributionIEEE/PES 2010 Transmission and Distribution

Conference and ExpositionConference and ExpositionNew Orleans, LouisianaNew Orleans, Louisiana

April 20, 2010April 20, 2010




Design Criteria - MechanicalDesign 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.





Suspension Insulators

• Porcelain- M&E (Mechanical & Electrical) RatingRepresents 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 LoadGuaranteed minimum ultimate strength when new.R.T.L. – Routine Test Load – Proof test applied to each NCI.

- Never Load beyond the R.T.L.





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)





Other Considerations

• Suspensions and Deadends – Only apply tension loads

• Line Posts –- Cantilever is only one load- Transverse (tension or compression) on line post – loadingtransverse to the direction of the line.

- Longitudinal – in the direction of travel of the line- Combined Loading Curve –Contour curves representing various Longitudinal loadsAvailable Vertical load as a function of Transverse loadingManufacturers have different safety factors!!!





6 9 k V P o s t -

0

5 0 0

1 0 0 0

1 5 0 0

2 0 0 0

2 5 0 0

- 3 0 0 0 - 2 0 0 0 - 1 0 0 0 0 1 0 0 0 2 0 0 0 3 0 0 0

T R A N S V E R S E L

,

0 L o n g it u d i

5 0 0 L o n g it1 0 0 0 L o n g

1 5 0 0 L o n g

2 0 0 0 L o n g

L IN E P O S T A P P

C U R V E S

9 - 1 2 - 0 5

C o m pr e s s io n T e n s




Design Criteria - ElectricalDesign Criteria - Electrical

An Insulator is a mechanical support!Air imparts Electrical Characteristics

Strike Distance (Dry Arcing Distance) is theprincipal 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 thestrike distance.

Leakage Requirements do play a role!!!





Dry Arcing Distance –(Strike Distance) – “The

shortest distance through

the surrounding medium

between terminal

electrodes….” 1

1 – IEEE Std 100 - 1992





Define peak l-g kV

Determine Leakage DistanceRequired

Switching Over-voltage

Requirements

Impulse Over-voltage

Chart Courtesy of Ohio Brass/HPS – EU1429-H

69 kV (rms)

41.8 kV (rms)

(line A/1.732)*1.05

59.1 kV (peak)

e=(line B * 1.414)

1

H. INSULATOR LEAKAGE (MIN.)

41.8 inches

I. SSV = (line B) * 3.0 125 kV (peak)

J. PEAK IMPULSE WITHSTAND = (I(t) * R(f))+e

I(t) = 20 kA (typical value = 50 kA)

R(f) = 15 ohm (typical value = 10 - 20 ohm)

e = 59.1 (line C)

K. IMPULSE WITHSTAND = 359 kV

(typic al values ) (inches/(kV l ine-to-ground))

SWITCHING OVERVOLTAGE REQUIREMENTS

IMPULSE OVERVOLTAGE REQUIREMENTS

1.00 - 1.25

1.50 - 1.75

2.00 - 2.50G. HEAVY

UP TO 1.00

A. NOMINAL SYSTEM LINE-TO-LINE VOLTAGE

B. MAXIMUM SYSTEM LINE-TO-GROUND VOLTAGE

C. MAXIMUM PEAK LINE-TO-GROUND VOLTAGE (e)

LEAKAGE DISTANCE REQUIREMENTS

SELECT INSULATOR BASED ON REQUIREMENTS:

(line B)*(inches/kV) =

Enter inches/kV -

PICKING A SUITABLE INSULATOR

ELECTRICAL PARAMETERS

SUGGESTED LEAKAGECONTAMINATION LEVEL

D. ZERO

E. LIGHT

F. MODERATE

POLYMER VALUES

NUMBER OF

PORCELAIN BELLS

K. IMPULSE

WITHSTAND

T. SELECT

INSULATOR

41.8

125

359

SYSTEM

REQUIREMENT

VALUE FROM

PAGE 1H. LEAKAGE

DISTANCE

I. SWITCHING

SURGE VOLTAGE




Design Criteria – Leakage DistanceDesign 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 100 - 1992





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 ESDDPollution MonitorsDummy Insulators

Remove in-service insulators- Evaluate ESDD and select appropriate Leakage Distance





“Application Guide for Insulators in a Contaminated Environment”by K. C. Holte et al – F77 639-8

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 60815 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





Leakage Distance Recommendations

0

0.5

1

1.5

2

2.5

0 0.1 0.2 0.3 0.4 0.5

ESDD (mg/cm^2)

L e a k

( " / k V l -

g )

IEEE V

IEEE I

IEC

Poly. (IEC)

Poly. (IEEE V)

Poly. (IEEE I)




Improved Contamination PerformanceImproved Contamination Performance

Flashover Vs ESD

0

50

100

150

200

250

300

0.01 0.1

ESDD m /cm^2

F

l a s h o v e r V o l t a g e

Porcelain

New EPDM

Aged EPDM

New SR

Aged SR

CEA 280 T 621

SR units - leakage equal to porcelain

EPDM Units - leakage 1.3 X Porcelain





Polymer insulators offer better contamination

flashover performance than porcelain?

Smaller core and weathershed diameter increaseleakage current density.

Higher leakage current density means more OhmicHeating.

Ohmic Heating helps to dry the contaminant layer

and reduce leakage currents.

In addition, hydrophobicity helps to minimizefilming





“the contamination performance of compositeinsulators 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”




Insulator SelectionInsulator 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)





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

69 kV (rms)

41.8 kV (rms)

(line A/1.732)*1.05

59.1 kV (peak)

e=(line B * 1.414)

1

H. INSULATOR LEAKAGE (MIN.)

41.8 inches

I. SSV = (line B) * 3.0 125 kV (peak)

J. PEAK IMPULSE WITHSTAND = (I(t) * R(f))+e

I(t) = 20 kA (typical value = 50 kA)

R(f) = 15 ohm (typical value = 10 - 20 ohm)

e = 59.1 (line C)

K. IMPULSE WITHSTAND = 359 kV

(ty pic al values) (inc hes/(k V line-to-ground))

SWITCHING OVERVOLTAGE REQUIREMENTS

IMPULSE OVERVOLTAGE REQUIREMENTS

1.00 - 1.25

1.50 - 1.75

2.00 - 2.50G. HEAVY

UP TO 1.00

A. NOMINAL SYSTEM LINE-TO-LINE VOLTAGE

B. MAXIMUM SYSTEM LINE-TO-GROUND VOLTAGE

C. MAXIMUM PEAK LINE-TO-GROUND VOLTAGE (e)

LEAKAGE DISTANCE REQUIREMENTS

SELECT INSULATOR BASED ON REQUIREMENTS:

(line B)*(inches/kV) =

Enter inches/kV -

PICKING A SUITABLE INSULATOR

ELECTRICAL PARAMETERS

SUGGESTED LEAKAGECONTAMINATION LEVEL

D. ZERO

E. LIGHT

F. MODERATE

POLYMER VALUES

NUMBER OF

PORCELAIN BELLS

K. IMPULSE

WITHSTAND

T. SELECT

INSULATOR

41.8

125

359

SYSTEM

REQUIREMENT

VALUE FROM

PAGE 1

H. LEAKAGE

DISTANCE

I. SWITCHING

SURGE VOLTAGE





Porcelain – 5-3/4 X 10” bells X 4 units

Characteristic Required Available

LeakageDistance

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




Grading RingsGrading 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




NCIs and RingsNCIs and Rings

Grading (Corona) Rings

• Due to “corona cutting” and water droplet corona – NCIs mayrequire the application of rings to grade the field on thepolymer material of the weathershed housing.

• Rings must be:- Properly positioned relative to the end fitting on which they aremounted.

- 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.




Questions?Questions?



IEEE T&D – Insulators 101 IEEE T&D – Insulators 101

Insulators 101Insulators 101

Section C - StandardsSection 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




American National StandardsAmerican National StandardsConsensus standards

Standards writing bodies must include representatives frommaterially affected and interested parties.

Public review

Anybody may comment .

Comments must be evaluated, responded to, and if found to beappropriate, 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 therequirements of various stakeholders*.

* The American National Standards Process, ANSI March 24, 2005




American Standards Committee

on Insulators for Electric PowerLines

ASC C-29

EL&P Group

IEEE NEMA

Independents

C29 ANSI C29 I l t St d d ( il bl li t )




C29 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)




ANSI C29 Insulator StandardsANSI C29 Insulator Standards

Applies to new insulators

DefinitionsMaterials

Dimensions & Marking (interchangeability)

Tests1. Prototype & Design, usually performed once for a given design.

(design, materials, manufacturing process, and technology).

2. Sample, performed on random samples from lot offered for acceptance.

3. Routine, performed on each insulator to eliminate defects from lot.

ANSI C 29 Insulator StandardANSI C 29 Insulator Standard




ANSI C 29 Insulator StandardANSI C 29 Insulator Standard

RatingsRatings

Electrical & Mechanical Ratings

How are they assigned?

How is conformance demonstrated?

What are application limits?

Electrical RatingsElectrical Ratings




Electrical RatingsgAverage flashover values

Low-frequency Dry & WetCritical impulse, positive & negative

Impulse withstandRadio-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 4-1995 except

test values are corrected to standard conditions in ANSI C29.1.

-Temperature 25° C

- Barometric Pressure 29.92 ins. of Hg

- Vapor Pressure 0.6085 ins. of Hg

- For wet tests: rate 5±0.5 mm/min, resistivity

178±27Ωm, 10 sec. ws




Dry Arcing DistanceDry Arcing DistanceShortest distance through the surrounding medium betweenShortest distance through the surrounding medium between

terminal electrodes , or the sum of distances betweenterminal electrodes , or the sum of distances between

intermediate electrodes , whichever is shortest, with theintermediate electrodes , whichever is shortest, with theinsulator mounted for dry flashover test.insulator mounted for dry flashover test.





Product is designed to have a specified average flashover .

• T his 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≥ Yes

where = 0.95 for Low-frequency Dry flashover tests

= 0.90 for Low-frequency Wet flashover tests

= 0.92 for Impulse flashover tests

l i l i




Electrical RatingsElectrical RatingsDry 60 Hz Flashover Data

0

200

400

600

800

1000

1200

1400

0 20 40 60 80 100 120 140 160

Dry Arcing Distance (inches)

Flashove

r(kV

)

Station Post and Line Post

Suspension Insulator






ANSI C2 Insulation Level RequirementsANSI C2 Insulation Level Requirements ANSI C2-2007, Table 273-1 ANSI C2-2007, Table 273-1

Higher insulation levels required in areas where severe lightning, high

atmospheric contamination, or other unfavorable conditions exist



Mechanical RatingsMechanical Ratings




Mechanical RatingsMechanical RatingsSample & 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 Cantilever 4 quad. cantilever

C29.8 “ Cap & Pin Cantilever TorsionTension

Tension

C29.9 “ Station Post Cantilever Tension

Tension, Cantilever or Bending Moment

C29.12 Composite Suspension SML Tension

C29.13 “ Deadend SML Tension

C29.17 “ Line Post Cantilever Tension

Tension

C29.18 “ Dist. Line Post Cantilever Tension




Mechanical RatingsMechanical Ratings

M&E TestCeramic Suspensions

Bending TestsComposite Posts


Hubbell Power SystemsKinectrics

ANSI C29 High Voltage InsulatorANSI C29 High Voltage Insulator




g gg gStandardsStandards 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

X 10 ≥ R +1.2 S

s10 ≤ 1.72 S

3 sec. tension

at 50% of R

C29.7 Ceramic

Line post

Cantilever strength

of 3 unitsX3≥ 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 eachX

3≥ R

no one xi≮ .85 R

3 sec. tension

at specified value

C29.9 Ceramic Apparatus

Post Type

Cantilever & tension strengths

of 3 units eachX

3≥ R

no one xi ≮ .85 R

Tension

at 50% of R

or

4 quad. bending

at 40% of R

C29.12 Composite

Suspension

Specified Mech. Load (SML)

test of 3 units

xi≥ .R 10 sec. tension

at 50% of R

C29.13 Composite

Distribution Deadend

SML test

of 3 units xi≥ .SML rating

10 sec. tension

at 50% of R

C29.17 Composite

Line Post

Cantilever strength of 1 unit

Tension test of 1 unit

Strength ≥ R 10 sec. tension

at 50% of R

C29.18 Composite

Distribution Line Post

Cantilever strength of 1 unit Strength ≥ R 10 sec. tension

at 50% of R

L A C i i ANSI C29 2L t A t C it i ANSI C29 2




Lot Acceptance Criteria – ANSI C29.2Lot 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 10 -1.2SH

&

s10 ≤1.72SH

s10 is std. dev. of the 10 units

S H is historical std. dev.

If s10 = S H then f or minimally acceptable lot, ~ 11.5% of units

in lot could have strengths below the rated value.


Lot Acceptance Criteria ANSI C29 2Lot Acceptance Criteria ANSI C29 2




Lot Acceptance Criteria – ANSI C29.2Lot Acceptance Criteria – ANSI C29.2

Possible low strengths for ceramicPossible low strengths for ceramic

suspension units in a lot minimallysuspension units in a lot minimally

acceptable according to ANSI C29.2acceptable according to ANSI C29.2Coefficient

of variation, v R

Strength value

at -3σ5% 90% of M&E rating

10% 79% of M&E rating

15% 67% of M&E rating


Lot Acceptance Criteria – CSA C411.1Lot Acceptance Criteria – CSA C411.1




Lot Acceptance Criteria CSA C411.1o ccep a ce C e a CS CPossible low strengths for ceramicPossible low strengths for ceramic

suspension units in a lot minimallysuspension units in a lot minimally

acceptable according toacceptable according toCSA C411.1CSA C411.1

Requirements

Rating ≤ X S – 3s

& X i ≥ 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.


Lot Acceptance Criteria ANSI C29Lot Acceptance Criteria ANSI C29




Lot Acceptance Criteria – ANSI C29Lot Acceptance Criteria – ANSI C29

Possible low strengths for ceramic unitsPossible low strengths for ceramic units

in a lot minimally acceptable according toin a lot minimally acceptable according to

ANSI C29.7, C29.8 & C29.9ANSI C29.7, C29.8 & C29.9Cantilever rating ≤ X Cantilever rating ≤ X 33 & no x & no x i i < 85% of rating< 85% of rating

Coefficient

of variation, v R

Strength value

at -3 σ

5% 85% of Cantilever rating

10% 70% of Cantilever rating15% 55% of Cantilever rating


Lot Acceptance CriteriaLot Acceptance Criteria




Lot Acceptance Criteriap

ANSI C29 –Composite InsulatorsANSI C29 –Composite Insulators

Random samples selected from an offered lot.

Ultimate strength tests on samples.

Requirement is:

x i ≥ Rating

The rated value is assigned by the manufacturer basedon 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.


M h i l R ti A li ti Li itMechanical Ratings Application Limits




Mechanical Ratings – Application LimitsMechanical Ratings – Application LimitsNESC ANSI C Table 277-1NESC ANSI C Table 277-1

Allowed percentages of strength ratingsAllowed percentages of strength ratings

Insulator Type % Strength Rating Ref. ANSI Std.

CeramicSuspension 50%

Combined

mechanical & electrical strength (M&E)

C29.2-1992

Line Post 40%

50%

Cantilever strength

Tension/compression strength

C29.7-1996

Station Post4

40%

50%

Cantilever strength

Tension/compression/torsion strength C29.9-1983

Station

Cap & Pin

40%

50%

Cantilever strength

Tension/compression/torsion strength C29.8-1985

CompositeSuspension 50% Specified mechanical load (SML)

C29.12-1997

C29.13-2000

Line Post 50%

Specified cantilever load (SCL) or

specified tension load (STL)

C29.17-2002

C29.18-2003

Station Post 50% All strength ratings ----------

M h i l R ti A li ti Li itMechanical Ratings Application Limits




Mechanical Ratings – Application LimitsMechanical Ratings – Application Limits

Worst loading case load ≤ (% Table 277-1)(Insulator Rating)

In most cases , % from Table 277-1 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.


Mechanical Ratings Application LimitsMechanical Ratings Application Limits




Mechanical Ratings – Application LimitsMechanical Ratings – Application LimitsComposite Post Insulators – Combined LoadingComposite Post Insulators – Combined Loading


Mechanical Ratings – Application LimitsMechanical Ratings – Application Limits




Mechanical Ratings – Application LimitsMechanical Ratings Application LimitsComposite Post Insulators – Combined LoadingComposite Post Insulators – Combined Loading


Recent Developments for Application LimitsRecent Developments for Application Limits




Component strength cumulative distribution function FComponent strength cumulative distribution function FRR

and probability density function of maximum loads f and probability density function of maximum loads f QQ..


Component Damage LimitComponent 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.






Component Damage LimitComponent Damage LimitDefining 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

l 0




““Insulators 101Insulators 101””

Section D – AchievingSection D – Achieving

‘Quality’‘Quality’

Presented by Tom GrishamPresented by Tom Grisham

IEEE Task Force Chairman, “Insulators 101”IEEE Task Force Chairman, “Insulators 101”

IEEE/PES – T&D Conference and ExpositionIEEE/PES – T&D Conference and Exposition

New Orleans, LANew Orleans, LA

April 20, 2010April 20, 2010

Objectives of ‘Quality”Objectives of ‘Quality”




j yPresentationPresentation

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

‘‘Q li ’ D fi dQ lit ’ D fi d




‘ ‘ Quality’ Defined Quality’ Defined

QUALITY – An inherent, basic or distinguishing characteristic; an essentialproperty or nature.

QUALITY CONTROL – A system of ensuring the proper maintenance of writtenstandards; especially by the randominspection of manufactured goods.

What Is Needed in a Quality What Is Needed in a Quality




Plan?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 workersCommunicating and training

All aspects defined by the company plan

What Documents Should BeWhat Documents Should Be




Included?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 productHandling methods (consult manufacturer)

Installation requirements and techniques

‘‘Proven’ Installation ProceduresProven’ Installation Procedures




Proven Installation ProceduresProven Installation Procedures

Handling of Ceramics – NEMA HV2-Handling of Ceramics – NEMA HV2-




gg

19841984Insulators 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…..

Handling of NCI’sHandling of NCI’s




Handling of NCI sHandling 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 theinstructions 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…”

Li t F ilLi t F il




Line outage FailuresLine outage Failures

Your objective is to find the problem, quickly!

i h iI i T h i




Inspection TechniquesInspection 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

P l i d Gl F ilPorcelain and Glass Failures




Porcelain and Glass FailuresPorcelain and Glass Failures

Failures are ‘typically’ visible or have anew ‘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 failingload and compare to ultimate failing load

• Determine current ultimate strength versus newShould the insulators be replaced?• Establish internal criteria by location

N C i (NCI) F ilN C i (NCI) F il




Non-Ceramic (NCI) FailuresNon-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 newinstallations as future reference! Porcelainand glass, also!

What To Do for an InsulatorWhat To Do for an Insulator




What To Do for an Insulator Failure?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?

Summary of ‘Quality’Summary of ‘Quality’




y Q yy Q y

PresentationPresentationIn today’s environment, this presentation suggests that

the use of a well documented ‘quality’ programimproves long term performance and reduces outages.

Application information that is communicated in the

organization will help to minimize installation issues andreduce costs.

Actively and accurately defining the condition, or

determining the root cause of a failure, will assist indetermining end-of-life decisions.

Source of PresentationSource of Presentation



Source of PresentationSource of Presentation

http://ewh.ieee.org/soc/pes/iwg/

Insulators Panel Final A

Documents

Transcript of Insulators Panel Final A