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ELECTRIC POWER RESEARCH INSTITUTE Field Guide: Visual Inspection of Polymer Insulators 1013283 Effective December 6, 2006, this report has been made publicly available in accordance with Section 734.3(b)(3) and published in accordance with Section 734.7 of the U.S. Export Administration Regulations. As a result of this publication, this report is subject to only copyright protection and does not require any license agreement from EPRI. This notice supersedes the export control restrictions and any proprietary licensed material notices embedded in the document prior to publication.

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ELECTRIC POWERRESEARCH INSTITUTE

Field Guide:Visual Inspection of Polymer Insulators

1013283

Effective December 6, 2006, this report has been made publicly available in accordance with Section 734.3(b)(3) and published in accordance with Section 734.7 of the U.S. Export Administration Regulations. As a result of this publication, this report is subject to only copyright protection and does not require any license agreement from EPRI. This notice supersedes the export control restrictions and any proprietary licensed material notices embedded in the document prior to publication.

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Please note that this field guide is the public version of EPRI product 1020289, which is available for download only and contains updated content.

Field Guide: Visual Inspection of Polymer Insulators

1013283

Technical Update, May 2006

EPRI Project ManagerA. Phillips

ELECTRIC POWER RESEARCH INSTITUTE3420 Hillview Avenue, Palo Alto, California 94304-1395 • PO Box 10412, Palo Alto, California 94303-0813 • USA

800.313.3774 • 650.855.2121 • [email protected] • www.epri.com

DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIESTHIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM:

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNEDRIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'SCIRCUMSTANCE; OR

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES,EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOURSELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT.

ORGANIZATION(S) THAT PREPARED THIS DOCUMENT:

EPRI

NOTEFor further information about EPRI, call the EPRI Customer Assistance Center at 800.313.3774 or e-mail [email protected].

Electric Power Research Institute and EPRI are registered service marks of the Electric Power Research Institute, Inc.

Copyright © 2006 Electric Power Research Institute, Inc. All rights reserved.

iii

CITATIONS

This report was prepared byElectric Power Research Institute (EPRI)1300 W.T. Harris Blvd.Charlotte, NC 28262

Principal InvestigatorsA. PhillipsT. Shaw

This report describes research sponsored by EPRI.

The report is a corporate document that should be cited in the literature in the following manner:

Field Guide: Visual Inspection of Polymer Insulators. EPRI, Palo Alto, CA: 2006. 1013283.

CONTENTS

1. Anatomy of a Polymer Insulator . . . . . . . . . . . . . . . .1

2. Definition of Dimensions . . . . . . . . . . . . . . . . . . . . . .5

3. Maintenance Priority Rating . . . . . . . . . . . . . . . . . . .9Maintenance Priority Rating . . . . . . . . . . . . . . . . . . .10

4. Sheds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Splits and Punctures . . . . . . . . . . . . . . . . . . . . . . . . .14Torn or Damaged . . . . . . . . . . . . . . . . . . . . . . . . . . .16Gunshot Damage . . . . . . . . . . . . . . . . . . . . . . . . . . .18

5. Sheath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21Exposed Rod (Electrical Activity) . . . . . . . . . . . . . . .22Exposed Rod (Mishandling) . . . . . . . . . . . . . . . . . . .24Unclipped Sections . . . . . . . . . . . . . . . . . . . . . . . . . .26Splits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28Gunshot Damage . . . . . . . . . . . . . . . . . . . . . . . . . . .30

6. Sheds and Sheath . . . . . . . . . . . . . . . . . . . . . . . . . . .33Whitening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36Animal Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38Undermining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Alligatoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44Erosions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48Crazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50Fungus or Mold Growth . . . . . . . . . . . . . . . . . . . . . .52Insect Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54Hydrophobicity Loss (SIR) . . . . . . . . . . . . . . . . . . . .56Silicone Grease on Surface . . . . . . . . . . . . . . . . . . .58

v

7. Corona Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61Flashover Damage . . . . . . . . . . . . . . . . . . . . . . . . . .62Incorrect Position . . . . . . . . . . . . . . . . . . . . . . . . . . . .64Loose Ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66Gunshot Damage . . . . . . . . . . . . . . . . . . . . . . . . . . .68

8. End Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71Flashover Damage . . . . . . . . . . . . . . . . . . . . . . . . . .72Degraded Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

9. Failure Mode Guide . . . . . . . . . . . . . . . . . . . . . . . . . .79Failure Mode Distribution . . . . . . . . . . . . . . . . . . . . .80Brittle Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82Flashunder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84Destruction of Rod by Discharge Activity . . . . . . . . .86Mechanical Failure: Rod Failure . . . . . . . . . . . . . . . .88Mechanical Failure: End Fitting Pullout . . . . . . . . . . .90

Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . .93

11. POLYMER INSULATORS

1. Anatomy of a Polymer Insulator

Anatomy of a Polymer Insulator

ELECTRIC POWERRESEARCH INSTITUTE

31. POLYMER INSULATORS

End Fitting Fiberglass Rod

Sheds Sheath

Sheath

Sheds

End Fitting

Anatomy of a Polymer Insulator

ELECTRIC POWERRESEARCH INSTITUTE

Corona Ring (Installed Incorrectly) Corona Ring

52.DEFINITION OF DIMENSIONS

2. Definition of Dimensions

Dimension Definition Properties Influenced

Connection Physical location Length of conductors and

hardware in configuration

Dry Arc Power frequency, Distance lightning, and (with no switching surge corona ring) performance

Definition of Dimensions

ELECTRIC POWERRESEARCH INSTITUTE

Dimension Definition Properties Influenced

Dry Arc Power frequency, Distance lightning, and (with corona switching surgering) performance

Leakage Contamination(Creepage flashoverDistance) performance

72.DEFINITION OF DIMENSIONS

93. MAINTENANCE PRIORITY RATING

3. Maintenance Priority Rating

Maintenance Priority Rating

ELECTRIC POWERRESEARCH INSTITUTE

Each polymer insulator condition illustrated in this Guide has been assigned a Maintenance Priority Rating which indicates the severity of the problem.

The Maintenance Priority Ranking below is only a recommendation provided by EPRI.

Maintenance Priority Rating

113. MAINTENANCE PRIORITY RATING

MaintenancePriority Rating Definition

A Good or like new. No action required.

B Low degree of damage, wear, decay.Monitor for future damage.

C Moderate degree of damage, wear, decay.Consider replacement.

D High degree of damage, wear, decay.Remove polymer insulator from service.

Maintenance Priority Rating

134. SHEDS

4. Sheds

Sheds

Sheds

ELECTRIC POWERRESEARCH INSTITUTE

C C

Splits and Punctures

B C

154. SHEDS

What You See: Splits or punctures in sheds (splits often along mold line).

Possible Cause: Aging and/or poor design or manufacture, mishandling.

Resulting Failure Mode: Exposure of rod � Brittle Fracture, Flashunder, Rod Destruction by Discharge Activity

Rating Observation Action

B Split localized to sheds Monitor for growth ofsplits and possibleprogression to sheath

C Split progressingtowards or close tosheathPuncture through shed

Remove polymer insulator from serviceat next opportunity

Splits and Punctures

C

Sheds

ELECTRIC POWERRESEARCH INSTITUTE

Torn or Damaged

B B

174. SHEDS

Torn or Damaged

What You See: Torn/damaged sheds – damage does not extend to sheath; rod not exposed.

Possible Cause: Mishandling during shipping, storage, or installation.

Resulting Failure Mode: Tear extends to sheath � Exposure of rod � Brittle fracture, Flashunder,Destruction of rod by discharge activity

C

Rating Observation Action

B Tear is across shed Monitor for growth of splitsand possible progressionto sheath

C Tear has progressed or is progressing to the sheath

Remove polymer insulator from serviceat next opportunity

Sheds

ELECTRIC POWERRESEARCH INSTITUTE

Gunshot Damage

BB

194. SHEDS

Gunshot Damage

What You See: Sheds punctured/broken by gunshot.

Possible Cause: Gunshot.

Resulting Failure Mode: Discharge activity from lodged bullets � Shed/sheath damage � Exposure of rod �Brittle Fracture, Flashunder, Destruction of rod by discharge activity

B or C

Rating Observation Action

B Damage to sheds only Monitor for growth of splitsand possible progressionto sheath

C Bullets lodged in sheds Monitor for discharge activity, remove polymerinsulator from service atnext opportunity

215. SHEATH

5. Sheath

Sheath

Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Exposed Rod (Electrical Activity)

D D

235. SHEATH

What You See: Severe degradation of rubber and rod is exposed to elements.

Possible Cause: Excessive electrical activity, harsh environment, poor design and/or manufacturing.

Resulting Failure Mode: Exposed rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

D Exposed rod Remove polymer insulatorfrom service

Exposed Rod (Electrical Activity)

D

Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Exposed Rod (Mishandling)

D D

255. SHEATH

Exposed Rod (Mishandling)

What You See: Exposed rod and damage to rubber sheath.

Possible Cause: Mishandling during shipping, storage, or installation.

Resulting Failure Mode: Exposed rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

D Exposed rod Remove polymer insulatorfrom service

D

Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Unclipped Sections

D D

275. SHEATH

Unclipped Sections

What You See: Rubber sections unclipped from one another or end fitting; rod may be exposed.

Possible Cause: Mishandling during shipping, storage, and installation.

Resulting Failure Mode: Exposed rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

D Exposed rod- between end fitting and

sheath sections- between sheath sections

Remove polymerinsulator from service

D

Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Splits

D D C

295. SHEATH

What You See: Splits along sheath sections.

Possible Cause: Excessive discharge activity and/or weathering of material.

Resulting Failure Mode: Splits extend to rod � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

SplitsRating Observation Action

C Silicone gel present; rodnot exposed

Monitor for growth of splits,remove at next opportunity

D Exposure of rod Remove polymer insulatorfrom service

C

D

Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Gunshot Damage

D DD

315. SHEATH

What You See: Sheath punctured/damaged by shot. Bullet maybe lodged in rubber.

Possible Cause: Gunshot.

Resulting Failure Mode: Discharge activity � Increased sheath damage � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

C Sheath damaged – rodNOT exposed

Remove polymer insulator from service at next opportunity

D Exposure of rod or bullets lodged in sheath

Remove polymer insulatorfrom service

Gunshot Damage

C

336. SHEDS AND SHEATH

6. Sheds and Sheath

Sheath

Sheds

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Whitening

A

A

356. SHEDS AND SHEATH

What You See: Whitening/white powder or film all along sheath surface. More prevalent closer to end fittings and on surfaces facing the sun.

Possible Cause: Exposure of filler compound due to normal weathering.

Resulting Failure Mode: N/A

Rating Observation Action

A White powder or film on surface

No action necessary

Whitening

A

Note: Adjacent sections may have different levels ofwhitening – not an issue.

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Tracking

D

D

Severe Tracking* Severe Tracking

376. SHEDS AND SHEATH

What You See: Electrically conductive paths along the surface of sheds and/or sheath.

Possible Cause: Leakage currents on highly contaminated polymer insulator surface.Resulting Failure Mode: Tracking � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by

discharge activityTracking � Flashover

Rating Observation Action

D Conductive path along surface Remove polymer insulator from service

Tracking

*Images Courtesy of EskomResult of Severe Tracking*

D

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Animal Damage

C

D

Rodent Damage Bird Damage

396. SHEDS AND SHEATH

What You See: Sheds and sheath have been eaten by birds or rodents.

Possible Cause: Birds or Rodents.

Resulting Failure Mode: Damage extends through sheath � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

A Minor shed damage No action necessaryB Shed damage only Monitor and leave in service

C Sheath damage, rod notexposed

Remove polymer insulator fromservice at next opportunity

D Rod exposed Remove polymer insulator from service

Animal Damage

Image Courtesy of Powerlink

B

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Undermining

C

D

416. SHEDS AND SHEATH

What You See: A puncture hole through sheds, usually at the shed/sheath interface.

Possible Cause: Excessive discharge activity.

Resulting Failure Mode: Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

C Sheath damage,rod not exposed

Remove polymer insulator fromservice at next opportunity

D Rod exposed Remove polymer insulatorfrom service

Undermining

C

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Cracking

B-C

C

436. SHEDS AND SHEATH

What You See: Surface Cracks on rubber sheds/sheath greater than 0.1 mm (0.004 in) in depth.

Possible Cause: Harsh environment or poor polymer insulator design/manufacture.

Resulting Failure Mode: Cracks extend through sheath � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

B Only sheds cracked Monitor for future damageC Sheath and sheds cracked Consider replacement

D Sheath cracked and moisture penetration possible

Remove polymer insulator from service

Cracking

D

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Alligatoring

A

C Shed Top

456. SHEDS AND SHEATH

What You See: A roughening of the surface resembling the texture of alligator skin. Material is brittleto the touch. The condition is due to loss of filler material.

Possible Cause: Aging of material, harsh environment, or poor design.

Resulting Failure Mode: Excessive material loss � Exposure of rod � Brittle fracture, Flashunder, Destructionof rod by discharge activity

AlligatoringRating Observation Action

A Limited to surface, material is not brittle

No action

B Significant depth Monitor for increased degradation

C Severe embrittlement Consider removal from service

Shed Bottom

A

Shed Bottom

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Erosions

D

C

476. SHEDS AND SHEATH

What You See: Loss (erosion) of material on either sheds or sheath, often close to end fittings.

Possible Cause: Excessive discharge activity, leakage currents, harsh environment, poor design and/or manufacture, incorrect application of corona ring.

Resulting Failure Mode: Excessive material loss � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

B Shallow surface erosion Monitor for progressionof damage

C Deep surface erosion Consider removal from service

D Excessive surface erosion Remove from service

Erosions

B

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Contamination

B

C

496. SHEDS AND SHEATH

What You See: Contamination on polymer insulator sheds and/or sheath.

Possible Cause: Pollutants from marine, agricultural, or industrial sources.

Resulting Failure Mode: Excessive contamination and critical wetting conditions � Flashover

Rating Observation Action

A-C Varying levels of contamination

Depends on level andtype of contamination

ContaminationC

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Crazing

A

A

516. SHEDS AND SHEATH

What You See: Shallow cracks on shed surface 0.1 mm (0.004 in) or less in depth.

Possible Cause: Weathering.

Resulting Failure Mode: N/A

Rating Observation Action

A Shallow surface fractures None

Crazing

A

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Fungus or Mold Growth

A

A

536. SHEDS AND SHEATH

What You See: Fungus contamination on polymer insulator sheds and/or sheath.

Possible Cause: Fungal or mold growth.

Resulting Failure Mode: N/A

Rating Observation Action

A-B Fungus or mold accumulation None

Fungus or Mold Growth

A

Note: Current research indicates that fungus or moldgrowth is not an issue in most cases; there may be aconcern in contaminated environments. Continuedresearch is underway, and specific situations mayrequire special actions.

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Insect Activity

A

A

556. SHEDS AND SHEATH

What You See: Insect activity.

Possible Cause: Spiders, caterpillars, or moths make nests, webs, or cocoons on sheath or shed rubber surfaces.

Resulting Failure Mode: Excessive insect activity and critical wetting conditions � Flashover

Rating Observation Action

A Webs, nests, or cocoons present None

B Excessive webs, nests, or cocoons Consider removal or washing

Insect Activity

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Hydrophobicity Loss (SIR) (Silicone Rubber Insulators only)

B A

Total Loss of Hydrophobicity

576. SHEDS AND SHEATH

What You See: Silicone rubber polymer insulator only – Insulator wets out (water does not bead);effect may be localized at live end.

Possible Cause: Aging due to electrical and/or environmental stress.

Resulting Failure Mode: In a contaminated environment, the risk of flashover may increase.

Rating Observation Action

A Localized loss of hydrophobicity None

B Complete loss of hydrophobicity Monitor for damageor contamination

Hydrophobicity Loss (SIR)

Localized Loss of Hydrophobicity

A

Sheds and Sheath

ELECTRIC POWERRESEARCH INSTITUTE

Silicone Grease on Surface

A A

596. SHEDS AND SHEATH

What You See: Silicone grease on polymer insulator sheds and/or sheath. Mainly at shed/sheath interface.

Possible Cause: Natural aging of polymer insulator. Happens with certain polymer insulator designs.

Resulting Failure Mode: N/A

Rating Observation Action

A Grease on sheds and/orsheath

Check to see if shedsand/or sheath are split

Silicone Grease on SurfaceA

617. CORONA RINGS

7. Corona RingsCorona Ring (Installed Incorrectly) Corona Ring

Corona Rings

ELECTRIC POWERRESEARCH INSTITUTE

Flashover Damage

B

D

Remove from Service

Leave in Service

637. CORONA RINGS

What You See: Corona ring broken/punctured by flashover.

Possible Cause: Flashover due to lightning and/or power arc follow-on currents.

Resulting Failure Mode: Damage to corona ring � Corona activity � Audio noise, Radio Interference

Rating Observation Action

B Damaged but no AN/RI complaints Leave in service

C Damaged with AN/RI complaints Replace at next opportunityand check for other damage

D Serious damage Remove from polymer insulator

Flashover Damage

Leave in Service

B

Corona Rings

ELECTRIC POWERRESEARCH INSTITUTE

Incorrect Position

Correct Position Backwards Installation Correct Position

C

657. CORONA RINGS

What You See: Corona ring installed backwards or in incorrect position.

Possible Cause: Incorrect installation. Check manufacturer’s recommendations.

Resulting Failure Mode: Damaged sheds/sheath � Exposure of rod � Brittle fracture, Flashunder, Destructionof rod by discharge activity

Rating Observation Action

C Corona ring backwards or inincorrect position

Reinstall corona ring correctly;check for degradation of rubber material

Incorrect Position

Incorrect Position

C

Note: Refer to EPRI Guide 1008741, Field Guide: Corona Rings forPolymer Insulators.

Corona Rings

ELECTRIC POWERRESEARCH INSTITUTE

Loose Ring

C

C

677. CORONA RINGS

What You See: Grading ring is loose or not perpendicular to polymer insulator.

Possible Cause: Poor installation or falling ice.

Resulting Failure Mode: Damaged sheds/sheath � Exposure of rod � Brittle fracture, Flashunder, Destruction of rod by discharge activity

Rating Observation Action

C Corona ring is loose Reinstall corona ring correctlyand check for damage toinsulator

Loose RingC

Corona Rings

ELECTRIC POWERRESEARCH INSTITUTE

Gunshot Damage

BC

697. CORONA RINGS

What You See: Bullet hole(s) in ring.

Possible Cause: Gunshot.

Resulting Failure Mode: Corona activity � AN/RI

Rating Observation Action

B Damaged but no AN/RIcomplaints

Leave in service

C Damaged with AN/RIcomplaints

Replace at next opportunity and checkfor other damage

Gunshot Damage

B

718. END FITTINGS

8. End FittingsEnd Fitting

End Fitting

End Fittings

ELECTRIC POWERRESEARCH INSTITUTE

Flashover Damage

D C

738. END FITTINGS

What You See: End fitting burned by flashover.

Possible Cause: Lightning and/or power arc follow-on currents.

Resulting Failure Mode: Exposure of rod to moisture � Brittle Fracture, Flashunder, Exposure of Rod to DischargeActivity, possible Mechanical Failure due to end fitting pullout

Rating Observation Action

C End fitting damaged byflashover, rod not exposed

Remove polymer insulatorfrom service at next opportunity

D End fitting damaged byflashover, rod exposed

Remove polymer insulatorfrom service

Flashover DamageD

End Fittings

ELECTRIC POWERRESEARCH INSTITUTE

Degraded Seal

C B

758. END FITTINGS

What You See: Degraded sealant and rust surrounding end fitting seal.

Possible Cause: Aging, harsh environment, poor design or manufacture, and/or mishandling during installation.

Resulting Failure Mode: End fitting seal failure � Moisture penetration � Brittle fracture, Flashunder,Destruction of rod by discharge activity

Rating Observation Action

C Degraded endfitting seal

Remove polymer insulator fromservice at next opportunity

B Degraded end fitting seal

Monitor for progression ofdamage

Degraded SealC

End Fittings

ELECTRIC POWERRESEARCH INSTITUTE

Corrosion

B B

778. END FITTINGS

What You See: Corrosion (rust) on polymer insulator metal end fittings.

Possible Cause: Harsh environment and/or poor galvanization.

Resulting Failure Mode: End fitting seal failure � Moisture penetration � Brittle fracture, Flashunder, Destruction of rod by discharge activityEnd fitting failure � Mechanical failure

Rating Observation Action

B Corrosion and rust accumulation of end fitting

Monitor for further damage

Corrosion

B

799. FAILURE MODE GUIDE

9. Failure Mode Guide

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

Failure Mode Distribution: Based on 221 failures recorded in EPRI Failure Database

Although EPRI has endeavored to collect information about as many failures as possible,only a percentage of the failures to date have been recorded. Most failures collected have beenin North America. If you have information about any failures that may not be recorded pleasecontact Dr. Andrew Phillips, [email protected], 704.595.2234.

Failure Mode Distribution

819. FAILURE MODE GUIDE

0.5%

8.1%10.4%

24.9%

51.1%

BrittleFracture

Flashunder MechanicalFailure:

Rod Failure

Destruction of Rod by Discharge

Activity

End Fitting Pullout

Failure Mode

% o

f Fa

ilure

s R

eco

rded

(22

1)

5%

15%

25%

35%

45%

55%

Failure Mode Distribution

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

Brittle Fracture

Broomstick

Fracture Planes

Axial Delamination

839. FAILURE MODE GUIDE

Type: Mechanical.Identifying Features: Flat Fracture Plane (single or multiple), Multiple fracture planes maybe separated by axial

delamination. Broomstick.Possible Cause: Moisture coming in contact with fiberglass rod. Moisture penetration occurs either through

end fitting seal or through rubber weathershed system.51% of 221 Failures Collected

Brittle Fracture

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

Flashunder

Tracking Through Rod Tracking Through/Along Rod/Rubber Interface

859. FAILURE MODE GUIDE

Flashunder

Type: Electrical.Identifying Features: Tracking through the rod or along the rod/rubber interface. Extends significant length of

insulator. Puncture holes and splits along length of polymer insulator due to power arc and internal discharge activity bursting out.

Possible Cause: Moisture coming in contact with fiberglass rod. Moisture penetration occurs either throughend fitting seal or through rubber weathershed system.

25% of 221 Failures Collected

Tracking Through Rod Splits and Puncture Holes

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

Destruction of Rod by Discharge Activity

879. FAILURE MODE GUIDE

Destruction of Rod by Discharge Activity

Type: Mechanical.Identifying Features: Charred / carbonized fiberglass rod. Often frayed ends of fibers exposed.

Possible Cause: Moisture coming in contact with fiberglass rod. Moisture penetration occurs either through end fitting seal or through rubber weathershed system.

8% of 221 Failures Collected

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

Mechanical Failure: Rod Failure

1

899. FAILURE MODE GUIDE

Mechanical Failure: Rod Failure

Type: Mechanical.Identifying Features: Rod Failure - Broken rod and / or frayed fibers.

Possible Cause: Manufacturing issues (QC) or mishandling during storing, transporting and installing.Usually occurs due to mishandling (See image marked 2).Three cases have been observed due to overheating of the rod during manufacturing and severe overload (See images marked 1).

10% of 221 Failures Collected

1 2

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

Mechanical Failure: End Fitting Pullout

919. FAILURE MODE GUIDE

Mechanical Failure: End Fitting Pullout

Type: Mechanical.Identifying Features: Pullout – rod separated from end fitting. Occurs on both crimped and epoxy cone end fittings.

Possible Cause: Manufacturing issues (QC) or mechanical overstress or degradation of epoxy compound(See images marked 3).

1% of 221 Failures Collected

3 3

Failure Mode Guide

ELECTRIC POWERRESEARCH INSTITUTE

If you experience, or have experienced, any failures of polymer insulators, it would be appreciated if you could informEPRI of these failures. By recording failures in a central repository, industrywide issues and concerns can be identified.By making the industry aware of these concerns, unexpected failures may be avoided in the future. Your assistance inthis regard is appreciated.

If you have any questions about the information provided in this Guide, if you want to communicate findings or actions taken in the field, or if you have suggestions for making the Guide more useful to you, please contact Dr. Andrew J. Phillips at EPRI (see contact information below).

93

Contact Information

Dr. Andrew J. PhillipsTransmission and SubstationsEPRIP.O. Box 217097Charlotte, NC 282219625 Research DriveCharlotte, NC 28262

Cell: 704.953.4030Tel: 704.595.2234

Fax: 704.595.2867E-mail: [email protected]

NOTE: If you find any new conditions that are not identified in this guide, please send us a detailed description, along with any photographs.

Thank you.CONTACT

Other EPRI Visual Field Guides

Corona Rings for Polymer Insulators, 1008741Visual Inspection of Steel Structures, 1012311

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