anci c29-11 1989 composito for transmission

ANSI C29.11-1989 (RI 996)

American National Standard

for Composite Suspension Insulators for Overhead Transmission Lines -

Tests

Secretariat:

National Electrical Manufacturers Association 1300 North 17th Street, Suite 1847 Rosslyn, VA 22209

O Copyright 2001 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions.

NOTICE AND DISCLAIMER

The information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document.

The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic 1

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Approval o f an American National Standard requires verification by ANSI that the re- American quirements for due process, consensus, and other criteria for approval have been met by Nationa] the standards developer.

Standard Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Sub- stantial agreement means much more than a simple majority, but not necessarily unanim- ity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution.

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The American National Standards Institute does not develop standards and will in no circumstances give an interpretation o f any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for inter- pretations should be addressed to the secretariat o r sponsor whose name appears on the title page of this standard.

CAUTION NOTICE: This American National Standard may be revised or withdrawn a t any time. The procedures of the American National Standards Institute require that action be taken periodically to reaffirm. revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute.

Published by

American National Standards Institute 1430 Broadway, New York, New York 10018

Copyright O 1989 by American National Standards institute, h c All rights reserved.

No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.

Printed in the United States of America

A5C1189112

Foreword (This Foreword is not part of American National Standard C29.11-1989.)

This standard comprises a manual of procedures to be followed in making tests to determine the characteristics of insulators used on electric power systems. This new American National Standard is not an insulator specification, but rather it sets forth a test method to be used in conjunction with insulator specifications.

American National Standard for Wet-Process Porcelain Insulators - Composite Sus- pension Insulators for Overhead Transmission Lines - Tests, ANSI C29.11-1989, was prepared by Accredited Standards Committee C29, which is in charge of this work.

Suggestions for improvement of this standard will be welcome. They should be sent to the National Electrical Manufacturers Association, 2101 L Street, NW, Washington, DC 20037.

This standard was processed and approved for submittal to ANSI by Accredited Stan- dards Committee on Insulators for Electric Power Lines, C29. Committee approval of the standard does not necessarily imply that all members voted for its approval. At the time it approved this standard, the C29 Committee had the following members:

J. Nicholls, Chairman N. Spaulding, Vice-chairman C. White, Secretary

Organization Represented Name of Representative Association of American Railroads ....................................................... Representation Vacant) Bonneville Power Administration ....................................................... R. Brown Electric Light and Power Group .......................................................... R. Bush

G. Cook A. Jagtiani J. Karcher W. Kosakowski E. Marchbank D. Soffrin (Alt)

Institute of Electrical and Electronics Engineers ................................ K. Labbe T. Pinkham N. Spaulding

National Electrical Manufacturers Association .................................. A. Baker J. Carter R. Harap R. Harmon B. Kingsbury J. Nicholls A. Schwaim H. Van Herk L. Zimmerman

Stone & Webster Engineering Corporation ........................................ G. Davidson U.S. Department of the Army (Liaison, with Vote) ........................... H. Snyder

Individual Members G. Amburgey J. Buchanan

The C29 Working Group on Nonceramic Insulators, which was responsible for the development of this standard, had the following members:

Robert Brown, Chairman A. Akhtar H. Brown E. Chemey C. deTourreil R. Essig G. Gaibrois R. Harap R. Harmon A. Jagtiani

G. Karady B. Kingsbury J. Kise A. Knotos G. Lusk J. Nicholls R. Robarge E. Wheeler

SECTION Contents PAGE

1 .

2 .

3 .

Scope and Application ................................................................................................ 1.1 Scope .................................................................................................................

Referenced and Related Standards ............................................................................. 2.1 Referenced American National Standards ........................................................ 2.2 Other Referenced Standard ............................................................................... 2.3 Related Amencan National Standard ............................................................... Definitions .................................................................................................................. 3.1 Insulators and Parts ........................................................................................... 3.2 Terms Related to Exposure ............................................................................... 3.3 Mechanical Terms .............................................................................................

1.2 Application .......................................................................................................

6 6 6

6 6 6 6

6 6 7 7

4 . Classification of Tests ................................................................................................ 7 4.1 Prototype Tests ................................................................................................. 7 4.2 Design Tests ...................................................................................................... 7 4.3 Sample Tests ..................................................................................................... 7 4.4 Routine Tests .................................................................................................... 7

5 . Dimensions ................................................................................................................. 8

6 . Marking ...................................................................................................................... 8

8 7.1 8 7.2 Core Time-Load Test ........................................................................................ 9 7.3 Housing Tracking and Erosion Test ................................................................. 9

7 . Prototype Tests ........................................................................................................... Tests on Interfaces and Connection of End Fittings .........................................

7.4 Core Material Tests ........................................................................................... 10

8 . Design Tests ............................................................................................................... 10 8.1 Lightning Critical-Impulse Flashover Test ....................................................... 10 8.2 8.3 Switching Critical-Impulse Flashover Test ...................................................... 11

9 . Sample Tests ............................................................................................................... 11 9.1 Sample Selection ............................................................................................... 11 9.2 Verification of Dimensions ............................................................................... 11 9.3 Verification of the Locking System .................................................................. 11 9.4 Mechanical Load Test ....................................................................................... 12 9.5 Galvanizing Test ............................................................................................... 12 9.6 Retest Procedure for Sample Tests ................................................................... 12

10 . Routine Tests ......................................................................................................... 12 10.1 Mechanical Test ................................................................................................ 12 10.2 Visual Examination ........................................................................................... 12

9

Alternating-Voltage Rated Dry Flashover Test ................................................ 11

Figures Figure 1 Thermal Mechanical Test ........................................................................... Figure 2 Electrodes for High-Voltage Test ............................................................... 11

American National Standard

for Composite Suspension Insulators for Overhead Transmission Lines - Tests

1. Scope and Application

1.1 Scope. This standard describes the tests to be prepared on composite insulators for applications above 70kV, and defines the acceptance criteria for such tests. See 3.1.1 for the definition of a composite insulator. All hitherto published American National Standards in the C29 series are for insulators made of wet-process porcelain or toughened glass. , The standard includes definitions pertinent to

composite insulators. It introduces a new category of tests called prototype tests, designed to evaluate the materials and construction of composite insulators. Prototype tests are expected to be be performed on representative samples but may be performed prior to the start of production.

1.2 Application. This standard is applicable to composite insulators used on transmission lines as suspension or tension insulators.

2. Referenced and Related Standards

2.1 Referenced American National Standards. This standard is intended to be used in conjunction with the following American National Standards. When these standards are superseded by a revision approved by the American National Standards, Inc, the revision shall apply.

ANSI C29.1-1988, Electrical Power Insulators, Test Methods for

ANSIDEEE 4- 1978, Techniques for High-Voltage Testing

2.2 Other Referenced Standard. This standard is also intended to be used in conjunction with Tests on Insulators of Ceramic Material or Glass for Overhead

Lines with a Nominal Voltage Greater Than 1000 V,

2.3 Related American National Standard.- The standard listed here is for information only and is not essential for the completion of the requirements of this standard.

ANSIDEEE 100-1984, Dictionary of Electrical and Electronics Terms

IEC 383-1983.'

3. Definitions

NOTE: Definitions as given in this section apply specifi- cally to the subjects treated in this standard. For additional definitions, see ANSIAEEE 100-1984.

3.1 Insulators and Parts

tor is made of at least two insulating parts - a core and a housing. It is equipped with end fittings.

3.1.2 Core. The core is the internal insulating part of a composite insulator. It is intended to carry the mechanical load. It consists mainly of glass fibers positioned in a resin matrix so as to achieve maximum tensile strength.

3.1.3 Housing. The housing is external to the core and protects it from the weather. It may be equipped with weathersheds. Some designs of composite insulators employ a sheath made of insulating material between the weathersheds and the core. This sheath is part of the housing.

3.1.4 Weathersheds. Weathersheds are insulating parts, projecting from the housing or sheath, intended to increase the leakage distance and to pro- vide an interrupted path for water drainage.

3.1.5 End Fittings. End fittings transmit the mechanical load to the core. They are usually made of metal.

3.1.1 Composite Insulator. A composite insula-

'Available from the American National Standards Institute.

6

3.1.6 Coupling Zone. The coupling zone is the part of the end fitting that transmits the load to the line, to the tower, or to another insulator. It does not include the interface between the core and the end fitting.

3.1.7 Interfaces. An interface is the surface between different materials. Examples of interfaces in composite insulators are as follows:

(1) Glass fiber/impregnating resin (2) Filler/polymer (3) Core/housing (4) Weathers hed/weathers hed (5) Weathers hed/s hea th (6) Housinglend fittings (7) Core/end fittings

3.2 Terms Related to Exposure 3.2.1 Tracking. Tracking is the formation of

electrically conducting paths starting and developing on the surface of an insulating material. These paths are conductive even under dry conditions. Tracking can occur on surfaces in contact with air and also on the interfaces between insulating materials.

3.2.2 Treeing. Treeing is the formation of microchannels within the material. The microchannels can be either conducting or nonconducting and can prog- ress through the bulk of the material until electrical failure occurs.

3.2.3 Erosion. Erosion is nonconductive loss of material from the insulating surface. It can be uni- form, localized, or tree-shaped. Shallow surface traces, commonly tree-shaped, can occur on composite insulators, as on ceramic insulators, after arcing. These traces do not affect the operating characteristics of the insulator.

3.2.4 Chalking. Chalking is a surface condition wherein some particles of the filler become apparent during weathering, forming a powdery surface.

3.2.5 Crazing. Crazing is the formation of surface microfractures of depths up to 0.1 mm.

3.2.6 Cracking. Cracking is any surface fracture of a depth greater than 0.1 mm.

3.2.7 Hydrolysis. Hydrolysis is a chemical process involving the reaction of a material with water in liquid or vapor form. It can lead to electrical or mechanical degradation.

3.3 Mechanical Terms 3.3.1 Specified Mechanical Load (S.M.L.). The

S.M.L. is a load specified by the manufacturer that has to be verified during a Mechanical Load Test (see 9.4). It forms the basis for selection of an insulator.

3.3.2 Routine Test Load (R.T.L.). The R.T.L. is a rating equal to 50% of the S.M.L.

4. Classification of Tests

4.1 Prototype Tests. The purpose of these tests is to verify the suitability of the prototype design, materials, and method of manufacture. The prototype tests are described in Section 7. When a composite insulator is submitted to the prototype tests, the results shall be considered valid for the whole class of insulators represented. A class of insulators is defined as those:

materials and method of manufacture

materials, and method of attachment to the core

(1) Having a core and weathersheds of the same

(2) Having the end fittings of the same design,

(3) Having the same or greater housing thickness (4) Having the same or smaller ratio of S.M.L. to

the smallest core radial cross-sectional area between end fittings

(5) Having the same core diameter The prototype test report shall include a drawing

of the insulator tested, with dimensions. These dimensions shall at a minimum include those dimensions that define a class. To allow for subsequent manufacturing or design variations, the term “same” in 4.1(3), 4.1(4), and 4.1(5) may vary up to 15% before the prototype tests must be repeated. See Sec- tion 5 for tolerances on dimensions.

4.2 Design Tests. The purpose of these tests is to verify those characteristics of a composite insulator which depend on its size and shape. The requirements are given in Section 8.

a composite insulator is defined by the following characteris tics:

4.2.1 Electrical Design. The electrical design of

(1) Dry arcing distance (2) Leakage distance (3) Weathershed inclination (4) Weathershed diameter (5) Weathershed spacing The electrical design tests shall be performed only

once on insulators of a specific electrical design. 4.2.2 Mechanical Design. The mechanical de-

sign of a composite insulator is defined by the following characteristics:

(1) Core diameter (2) Method of attachment of the end fittings

4.3 Sample Tests. These tests verify the conformance of composite insulators to the requirement given in Section 9. They are to be made on insulators taken at random from a production lot. 4.4 Routine Tests. These tests are for the purpose of eliminating insulators with manufacturing defects.

7

AMERICAN NATIONAL STANDARD C29.11-1989

They are to be made on every insulator according to the requirements of Section 10.

5. Dimensions

The following tolerances are allowed on all dimensions for which special tolerances do not apply. x is the dimension in millimeters.

? (0.04~ + 1.5) mm, when x S 300 mm ? (0.02% + 6) mm, when x 2 300 mm with a

maximum tolerance of 50 mm

6. Marking

‘Each insulator shall be clearly and indelibly marked with the name or trademark of the manufacturer, the year of manufacture, the specified mechanical load (S.M.L.), and the routine test load (R.T.L.). The routine test load shall be identified by the word “TEST”.

7. Prototype Tests

Prototype testing is done in four parts as described in Sections 7.1.7.2,7.3, and 7.4. Each part may be performed independently on new test specimens. The test specimens shall pass the tests in each part in sequence. Prototype tests are to be performed only once for each class of insulator. The results shall be recorded in a test report. The test report shall constitute the evidence of successful completion of the prototype tests.

7.1 Tests on Interfaces and Connection of End Fittings 7.1.1 Test Specimen. Three insulators shall be

tested. The insulation length (metal-to-metal spacing) shall be at least 800 mm in length to be valid for all lengths. If insulators less than 800 mm in length are tested, the tests are only considered valid for insulators up to the length tested. The end fittings and end weathershed geometry shall be representative of production insulators. The insulators shall be subjected to the mechanical test of 10.1 prior to testing.

7.1.2 Power Frequency Voltage Test. The dry power frequency flashover voltage shall be obtained by averaging five flashover voltages on each of the three test specimens. The flashover voltage shall be corrected to standard conditions in accordance with

ANSIDEEE 4-1978. The flashover voltage shall be reached within 1 minute by increasing the voltage linearly from zero. 7.1.3 Sudden Load Release Test. Each test

specimen shall be subjected to five sudden load re- leases. The load shall be 30% of the S.M.L. The insulator temperature shall be -2O’C to -25°C. 7.1.4 Thermal Mechanical Test. The insulators

shall be loaded at ambient temperature to at least 5% of the S.M.L. for 1 minute. During this time, the length of the insulators shall be measured. The meas- urement accuracy shall be at least 0.5 mm. This will be the reference length.

The insulators shall be submitted to thermal variations from -35’C to +50’C while under a permanent mechanical load of 0.5 S.M.L. as shown in Figure 1. The time at each temperature shall be at least 8 hours per cycle. The tests may be conducted in any suitable medium.

be allowed to reach ambient temperature and the length shall again be measured using the same load as for the reference length. NOTE: The test may be interrupted for maintenance for a total duration of 4 hours.

7.1.5 Water Penetration Test. The test specimens shall be kept immersed in boiling tap water for 42 continuous hours. At the end of boiling, the insulators shall remain in the vessel until the water cools to approximately 50’C. This temperature shall be maintained until the verification tests start. 7.1.6 Verification Tests. The verification tests

consist of the sequence of tests described in 7.1.6.1 through 7.1.6.3, and are used to verify that the insulators have not been damaged by the previous tests. They shall all be completed within 48 hours.

visually. No cracks are permitted.

The test specimens shall be fitted with a sharp-edged electrode. The electrode shall consist of a clip made of a copper strip approximately 20 mm wide and less than 1 mm thick. The electrode shall lie firmly on the housing between the weathersheds forming two approximately equal test sections. If the test specimens have an insulating length equal to or less than 500 mm, no clip is necessary; the voltage may be applied between end fittings.

An impulse voltage with a front steepness of at least 1000 kV/microsecond shall be applied to each test section. Each test section shall be stressed with 25 impulses of positive and 25 impulses of negative polarity. Each impulse shall cause an external flashover of the test section. No puncture shall occur.

At the end of thermal cycling, the insulators shall

7.1.6.1 Visual. The housing shall be inspected

7.1.6.2 Steep Front Impulse Voltage Test.

8

R.T.L. (2 0.5 S.M.L.)

AIR TEMPERATURE 'C

TIME IN HOURS - r

THERMAL TEST CYCLES

''

71 TIME IN HOURS I I L I -

Figure 1 Thermal Mechanical Test

Following the test, the electrode used to form the test sections shall be removed.

7.1.6.3 Power Frequency Voltage Test. The power frequency flashover voltages shall be determined once more for each specimen using the procedure given in 7.1.2. The average flashover voltage for each test specimen shall be at least 90% of the value determined in 7.1.2.

Each test specimen shall be individually subjected to 80% of its average flashover voltage as determined in 7.1.2. The voltage shall be maintained for 30 minutes. No puncture shall occur and the temperature of the shank measured immediately after the test shall not be more than 20'C above ambient.

7.2 Core Time-Load Test 7.2.1 Test Specimen. Six insulators shall be

tested. The insulation length (metal- to-metal spacing) shall not be less than 800 mm or the longest length to be manufactured, whichever is less. The end fittings shall have a grip to the core that is representative of production insulators, but the coupling zone may be modified to avoid failure of the end fittings.

7.2.2 Determination of the Average Failing Load of the Core. Three of the test specimens shall be tested in tension. The tensile load shall be increased rapidly but smoothly from O to 75% of the expected mechanical failing load, and then shall be gradually increased to failure in a time of 30 to 90 seconds. Failure shall be by fracture or complete pull-out of the core. Failure of an end fitting within the coupling zone shall require testing of additional test specimens until three core failures (fracture or complete pull-out) are obtained.

7.2.3 Core Time Load Test. Three test specimens shall be subjected to a tensile load of 60% of the average failing load obtained in 7.2.2. This load shall be maintained for 96 hours without failure.

7.3 Housing Tracking and Erosion Test 7.3.1 Test Specimen. Two insulators or test

specimens shall be tested. The specimen length shall be chosen such that the leakage distance falls between 484 mm and 692 mm. The applied voltage shall be equal to the value obtained by dividing the leakage distance of the test specimen by 34.6, with

9


the result expressed in kV. The test specimen shall be fitted with end fittings representative of those used in production.

7.3.2 Test Chamber. The volume of the test chamber shall not exceed 10 cubic meters. An aper- ture of not more than 80 square centimeters shall be provided for natural exhaust air. A turbo sprayer or room humidifier of constant spraying capacity shall be used as the water atomizer. It shall not spray directly onto the test specimen. The contaminant shall be sodium chloride (NaCl) and deionized water. The maximum voltage drop permitted is 5% when the test circuit is loaded with a resistive current of 250 mA root-mean-square (r.m.s.). A current of 1 ampere r.m.s. shall cause an overcurrent trip-out.

The test specimen shall be cleaned with deionized water before starting the test. One test specimen shall be tested vertically and one test specimen tested horizontally. There shall be a clearance of at least 200 mm between the roof of the chamber and a test specimen and a clearance of at least 100 mm between the walls and a test specimen.

7.3.3 Test Conditions. The following conditions shall.be maintained for a 1000-hour duration of the test:

Water flow rate 0.4 f O . 1 (See Note 1) Size of droplets 5 to 10 pm Temperature 20'C f 5'C NaCl content of water 10 kg/m3 t 0.5 kg/m3

NOTES: 'The water flow rate is.defined in liters per hour per cubic meter volume of the test chamber. The water may not be recirculated. 'Interruptions for inspection purposes shall not be counted in the test duration. Each interruption shall not exceed 15 minutes.

7.3.4 Evaluation. No more than three overcurrent trip-outs are allowed. No tracking is allowed. No weathershed punctures are allowed. Erosion is not allowed to reach the core.

7.4 Core Material Tests 7.4.1 Dye Penetration Test

7.4.1.1 Test Specimen. Ten samples shall be cut from an insulator. The housing material may be removed from the core but removal is not mandatory. The length of the samples shall be 10 mm k 0.5 mm. They shall be cut 90 degrees to the axis of the core with a diamond-coated circular saw blade under cool running water. The cut surfaces shall be smoothed with a 180-grit abrasive cloth. The cut ends shall be clean and parallel.

layer of steel or glass balls in a glass vessel with the 7.4.1.2 Test. The samples shall be placed on a

fibers vertical. The balls shall be of the same diameter and in the range of 1 mm to 2 mm. The dye, com- posed of 1 gram of fuchsin in 100 grams of methanol, is poured into the vessel until its level is 2 mm to 3 mm above the top of the balls.

7.4.1 3 Evaluation. The time for the dye to rise through the samples by capillarity shall be more than 15 minutes.

7.4.2 Water Diffusion Test 7.4.2.1 Test Specimen. Six samples shall be

cut from an insulator. The housing material may be removed from the core, but removal is not mandatory. The length of the specimens shall be 30 mm Ie 0.5 mm. oval is not mandatory. The length of the samples shall be 10 mm 5 0.5 mm. They shall be cut 90 degrees to the axis of the core with a diamond- coated circular saw blade under cool running water. The cut surfaces shall be smoothed with a 180-grit abrasive cloth. The cut ends shall be clean and parallel.

7.4.2.2 Prestressing. The surfaces of the specimens shall be cleaned with isopropyl alcohol and filter paper immediately before boiling. The specimens shall be boiled in deionized water with 0.1% by weight NaCl in a glass container for 100 hours f 0.5 hours. Only one core material may be boiled at one time.

After boiling, the specimens shall be removed from the salt water and placed into tap water in a glass container at room temperature for at least 15 minutes. The following test shall begin within 3 hours of removal of the specimens from the salt water.

Figure 2. Immediately before the test, the specimens shall be removed from the water and their surfaces dried with filter paper. The specimens shall be placed between the electrodes and the voltage increased at a rate of approximately 1 kV per second to a value of 12 kV where it shall remain for 1 minute.

7.4.2.4 Evaluation. No puncture or surface flashover is allowed. The current during the whole test shall not exceed 1 mA r.m.s.

7.4.2.3 Test. The test arrangement is shown in

8. Design Tests

Design tests are performed on full insulators.

8.1 Lightning Critical-Impulse Flashover Test. This test is to be performed on one insulator in accordance with ANSIDEEE 4-1978. The specimen mounting shall be in accordance with 3.1 of ANSI C29.1-1988, except that the upper surface of the

10


H I G H -VOLTAG E 50 mm 64 mm Y

ELECTRODES MADE OUT OF BRASS

30 mm lr 0.5 mm

I

NOTE: For samples with large diameters, the diameters of the electrodes must be increased. The diameter of the elect~od*s must be at least 20 mm greater than that of the samples.

Figure 2 Electrodes for High-Voltage Test

energized electrode shall be 100 to 200 mm from the connection point of the lower end fitting.

8.2 Alternating-Voltage Rated Dry Flashover Test. This test is to be performed on one insulator in accordance with ANSIDEEE 4-1978,2.3.3.2. The specimen mounting shall be in accordance with 3.1 of ANSI C29.1-1988, except that the upper surface of the energized electrode shall be 100 to 200 mm from the connection point of the lower end fitting.

8.3 Switching Critical-Impulse Flashover Test. This test is to be performed only when the intended service voltage is in excess of 300 kV phase-to- phase. It is to be performed on one insulator in accordance with 2.5 of ANSI/IEEE 4-1978. The specimen mounting shall be in accordance with 18.1.3 or 18.2 of IEC 383-1983.

9. Sample Tests

9.1 Sample Selection. The insulators shall be selected from the lot at random. The purchaser has the

right to make the selection. The insulators shall be subjected to the applicable sample tests.

Number of Tests Samples

Verification of dimensions 7 Verification of locking system 3 Mechanical load test 4 Galvanizing test 3

In the event of a failure of the sample to satisfy a test, the retest procedure of 9.6 shall be applied.

9.2 Verification of Dimensions. The insulators in the sample shall be checked for dimensions against the dimensions on the manufacturer’s drawing. If tolerances are not given on the drawing, the tolerances given in Section 5 shall apply.

9.3 Verification of the Locking System. For ball and socket insulators, the specified samples shall be tested for disengagement force of the cotter key. It shall be between 11 1 and 667 newtons force for three locking-to-unlocking operations.

11

AMERICAN NATIONAL STANDARD C29.11-i989

9.4 Mechanical Load Test. The sample insulators shall be subjected to a tensile load that shall be increased rapidly but smoothly from zero to 75% of the S.M.L. and then gradually be increased to the S.M.L. in a time between 30 and 90 seconds. If 100% of the S.M.L. is reached in less than 90 seconds, the load shall be sustained at S.M.L. for the remainder of the 90 seconds. The test is passed if no failure occurs. The load shall then be increased until the insulator fails. The failure load shall be recorded. The histori- cal failure loads shall justify the manufacturer’s choice of S.M.L.

9.5 Galvanizing Test. The specified size of sample shall be tested in accordance with Section 6 of ANSI C29.1-1988. Five to ten measurements shall be uni- formly and randomly distributed over the entire surface. Both the average thickness value for each individual specimen and the average of the entire sample shall equal or exceed the following:

Average of Average of Entire Individual

Sample Specimen (mil) (mil)

Hardware (except nutshlts) 3.4 3.1

Nutshlts 2.1 1.7

9.6 Retest Procedure for Sample Tests. If only one insulator or metal part fails to comply with the requirements of a sample test, a new sample equal to twice the quantity originally submitted to that test shall be subjected to retesting. The retesting shall comprise the test in which failure occurred, preceded

by those tests that may be considered as having influenced the results of the original test.

If two or more insulators or metal parts fail to comply with any of the sample tests or if any failure occurs during the retesting, the complete lot is considered as not complying with the standard and shall be withdrawn for examination by the manufacturer. The number then selected shall be three times the first quantity chosen for tests.

The retesting shall comprise the test in which failure occurred, preceded by those tests that may be considered as having influenced the results of the original test. If any insulator fails during the retesting, the complete lot is considered as not complying with this standard.

10. Routine Tests

Routine tests are to be performed on every insulator produced.

10.1 Mechanical Test. Every insulator shall with- stand for at least 10 seconds a tensile load equal to or greater than the R.T.L. rating.

10.2 Visual Examination. The mounting of the me- tallic parts shall be in conformance with the manufacturer’s drawing. The color of the insulator shall be approximately as specified on the drawing.

The following imperfections shall be acceptable on the insulator surface: Superficial defects of area less than 25 square millimeters (the total defective area not to exceed 2% of the total insulator surface) and depth less than 1 mm.

12

anci c29-11 1989 composito for transmission

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