ANSI/NEMA C29.17-2022
(Revision of ANSI C29.17-2013)
American National Standard
for Composite Insulators—
Transmission Line Post Type
Secretariat:
National Electrical Manufacturers Association
Approved: March 6, 2023
Published:
American National Standards Institute, Inc.
NOTICE AND DISCLAIMER
The information in this publication was considered technically sound by the consensus of persons
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American National Standards Institute (ANSI) standards and guideline publications, of which the
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© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page i
of an American National Standard requires verification by
AMERICAN Approval
ANSI that the requirements for due process, consensus, and other
NATIONAL criteria for approval have been met by the standards developer.
is established when, in the judgment of the ANSI Board of
STANDARD Consensus
Standards Review, substantial agreement has been reached by directly
and materially affected interests. Substantial agreement means much
more than a simple majority, but not necessarily unanimity. Consensus
requires that all views and objections be considered, and that a
concerted effort be made toward their resolution.
The use of American National Standards is completely voluntary; their
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approved the standards or not, from manufacturing, marketing,
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to the standards.
The American National Standards Institute does not develop standards
and will in no circumstances give an interpretation of any American
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to issue an interpretation of an American National Standard in the name
of the American National Standards Institute. Requests for
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name appears on the title page of this standard.
Caution Notice: This American National Standard may be revised or
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Published by
National Electrical Manufacturers Association
1300 North 17th Street, Rosslyn, VA 22209
 2023 National Electrical Manufacturers Association.
All rights reserved including translation into other languages, reserved under the Universal Copyright
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Printed in the United States of America.
ANSI/NEMA C29.17-2022
Page ii
Foreword
(This Foreword is not part of American National Standard C29.17-2022)
Proposals for modification or improvement of this standard are welcome. They should be sent to the
National Electrical Manufacturers Association, 1300 North 17th Street, Suite 900, Arlington, VA 22209 or
sent via the NEMA website (https://www.nema.org).
This standard was processed and approved for submittal to ANSI by Accredited Standards Committee
(ASC) on Insulators for Electric Power Lines, C29. Committee approval of the standard does not
necessarily imply that all committee members voted for approval. At the time it approved this standard,
the ASC C29 Committee had the following members:
Arjan Jagtiani, Chairman
Paul Crampton, Secretary
Name
Organization
Interest Category
Robert Bernstorf
Ivan Boev
Andy Bui
James Cossavella
Nicholas DeSantis
Kevin Edmonds
Michael Garrels
Jean Marie George
Arjan Jagtiani
John Kuffel
Lan Ping Ling
Patrick Maloney
Guberson (Sonny) Mercedat
Brian Reynolds
Stephen Roberts
Andrew Schwalm
Timothy Shaw
Rick Stanley
Ryan Stargel
Timothy Van Remmen
Mike Warntjes
Prasad Yenumula
Hubbell Incorporated
Kinectrics Inc
Bonneville Power Administration
K-Line Insulators USA Inc.
LineWorks Engineering, LLC
NGK-Locke, Inc.
Xcel Energy
Sediver USA, Inc
Sargent & Lundy LLC
EPRI
Preformed Line Products
PPC USA, Inc.
Marmon Utility LLC
National Grid
Southern Company
Victor Insulators, Inc.
EPRI
Newell-PSN, LLC
Tennessee Valley Authority
Lapp Insulators LLC
American Transmission Co.
Duke Energy
Producer
General
User
Producer
General
Producer
User
Producer
General
General
Producer
Producer
Producer
User
User
Producer
General
Producer
User
Producer
User
User
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page iii
Contents
Scope ..................................................................................................................................................... 1
References to the Text ......................................................................................................................... 1
2.1
References to American National Standards ............................................................................ 1
2.2
Other Standards (Latest Revision Applies) ............................................................................... 1
3 Definitions ............................................................................................................................................. 2
4 Dimensions and Characteristics ......................................................................................................... 2
5 Marking .................................................................................................................................................. 2
6 Classification of Tests ......................................................................................................................... 3
6.1
Prototype Tests—General Description ...................................................................................... 3
6.2
Design Tests—General Description .......................................................................................... 4
6.3
Sample Tests—General Description ......................................................................................... 4
6.4
Routine Tests—General Description ......................................................................................... 4
7 Prototype Tests..................................................................................................................................... 4
7.1
Tests on Interfaces and Connection of End Fittings ................................................................. 4
7.1.1 Test Procedure ............................................................................................................. 4
7.1.2 Evaluation ..................................................................................................................... 4
7.2
Assembled Core Load Tests ..................................................................................................... 4
7.2.1 Core Time-Load Test.................................................................................................... 4
7.2.2 Tensile Load Test ......................................................................................................... 5
7.3
Housing Tracking and Erosion Tests ........................................................................................ 5
7.3.1 Procedure ..................................................................................................................... 5
7.3.2 Evaluation ..................................................................................................................... 5
7.4
Aging or Weathering Test .......................................................................................................... 5
7.5
Core Material Tests ................................................................................................................... 6
7.5.1 Dye Penetration Test .................................................................................................... 6
7.5.2 Water Diffusion Test ..................................................................................................... 6
7.6
Flammability Test ...................................................................................................................... 6
8 Design Tests ......................................................................................................................................... 6
8.1
Low-Frequency Dry Flashover Test .......................................................................................... 6
8.2
Low-Frequency Wet Flashover Test ......................................................................................... 6
8.3
Critical Impulse Flashover Tests—Positive and Negative ......................................................... 6
8.4
Radio-Influence Voltage (Optional) ........................................................................................... 7
9 Sample Tests......................................................................................................................................... 7
9.1
Sample Selection ....................................................................................................................... 7
9.2
Verification of Dimensions ......................................................................................................... 7
9.3
Galvanizing Test ........................................................................................................................ 7
9.4
Verification of Cantilever Strength Test ..................................................................................... 8
9.4.1 Test Setup .................................................................................................................... 8
9.4.2 Cantilever Load-Deflection Test ................................................................................... 8
9.4.3 Cantilever Breaking Load (CBL) Test (Optional) .......................................................... 8
9.5
Specified Tensile Load Test ...................................................................................................... 8
9.5.1 Evaluation ..................................................................................................................... 8
9.6
Retest Procedure for Sample Tests .......................................................................................... 8
10 Routine Tests ........................................................................................................................................ 8
10.1
Tensile Load Test ...................................................................................................................... 8
10.2
Visual Examination .................................................................................................................... 9
Appendix A ................................................................................................................................................ 18
1
2
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page iv
Tables
Table 1
Table 2
Table 3
Table 4
Table 5a
Table 5b
Table 5c
Tolerances .......................................................................................................................... 2
Prototype Tests ................................................................................................................... 3
Sample Size ........................................................................................................................ 7
Minimum Average Thickness of Galvanizing ...................................................................... 7
Class 250 Design Parameters for Horizontal Line Posts with Mounting Base and
Drop Eye Fitting ................................................................................................................ 10
Class 300 Design Parameters for Horizontal Line Posts with Mounting Base and
Drop Eye Fitting ................................................................................................................ 11
Class 350 Design Parameters for Horizontal Line Posts with Mounting Base and
Drop Eye Fitting ................................................................................................................ 12
Figures
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Electrodes for the Voltage Test for Cores with a Diameter Greater Than 1.75 Inches .... 13
Example of Horizontal Clamptop End Fitting .................................................................... 14
Example of Blade Style End Fitting and Recommended Minimum Hole Spacing ............ 14
Example of Flange Style End Fitting and Recommended Connections ........................... 15
Examples of Detachable Gain Base and Common Dimensions ...................................... 16
Examples of Detachable Flat Base and Common Dimensions ........................................ 17
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 1
1
Scope
This standard covers composite transmission line post type insulators with section lengths 41 inches
(1041.4 mm) or greater made of a fiberglass-reinforced resin rod core, polymer material weathersheds,
and metal end fittings as defined in this standard and intended for use on overhead lines for electric
power systems. Mechanical and electrical performance levels specified herein are requirements for new
insulators.
2
References to the Text
2.1
References to American National Standards
This standard is intended to be used in conjunction with the following national standards. When these
standards are superseded by a revision approved by the American National Standards Institute, Inc., the
revision shall apply.
ANSI C29.1
American National Standard for Test Methods for Electrical Power Insulators
ANSI C29.7
American National Standard for Wet-Process Porcelain Insulators—High-Voltage
Line-Post Type
ANSI C29.11
American National Standard for Composite Insulators—Test Methods
2.2
Other Standards (Latest Revision Applies)
IEEE 4
IEEE Standard for High-Voltage Testing Techniques
IEEE 100
The Authoritative Dictionary of IEEE Standards Terms
ASTM A153/A153M
Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
ASTM D2240
Standard Test Method for Rubber Property—Durometer Hardness
ASTM D2565
Standard Practice for Xenon-Arc Exposure of Plastics Intended for Outdoor
Applications
ASTM G26
Standard Practice for Operating Light-Exposure Apparatus (Xenon-Arc Type)
With and Without Water for Exposure of Nonmetallic Materials
ASTM G52
Standard Practice for Exposing and Evaluating Metals and Alloys in Surface
Seawater
ASTM G154
Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for
Exposure of Nonmetallic Materials
IEC 60707
Flammability of solid non-metallic materials when exposed to flame sources - List
of test methods
IEC 60695-11-10
Fire hazard testing - Part 11-10: Test flames - 50 W horizontal and vertical flame
test methods
ISO 3452
Crack Detection
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 2
3
Definitions
See Section 3 of ANSI C29.11 American National Standard for Composite Insulators—Test Methods and
Section 2 of ANSI C29.1 American National Standard for Test Methods for Electrical Power Insulators for
definitions of common terms used in this standard.
Maximum Design Cantilever Load (MDCL): An optional manufacturer assigned working load rating.
Routine Test Load (RTL): A load equal to 50% of the Specified Tensile Load (STL).
Abbreviations used in this document include:
a. mA—milliamperes
b. rms—root-mean-square
c. s—second
d. mm—millimeters
e. kV—kilovolts
f. CIFO—Critical Impulse Flashover
g. MDCL—Maximum Design Cantilever Load
h. SCL—Specified Cantilever Load
i. CBL—Cantilever Breaking Load
j. RTL—Routine Test Load
k. STL—Specified Tensile Load
4
Dimensions and Characteristics
General dimensions and characteristics of the insulator classes shall be in accordance with Tables 5a,
5b, and 5c. Additional sizes may be used by agreement between the user and manufacturer. Dimensions
of end fittings shall be in accordance with Figures 2 through 5, or by agreement between the user and the
manufacturer.
Requirements for the shape and spacing of weathersheds are not a part of this standard.
The tolerances listed in Table 1 are allowed on all dimensions for which special tolerances do not apply.
X is the dimension in either mm or inches as noted in the column heading.
Table 1
Tolerances
SI Units
When x is:
< 300 mm
≥ 300 mm
The tolerance shall be
±(0.04x + 1.5) mm
±(0.025x + 6) mm
Maximum 50 mm
Imperial Units
When x is:
The tolerance shall be
< 11.81 in.
±(0.04x + 0.06) in.
≥ 11.81 in.
±(0.025x + 0.24) in.
Maximum 2 in.
Note: Grading for control of RIV and corona (electric field) may be appropriate for composite
insulators.
5
Marking
Each insulator shall be clearly and indelibly marked with symbols identifying the manufacturer, a
manufacturing date code or year of manufacture, and the specified cantilever load (SCL) with appropriate
units.
Note: For convenience in identifying an insulator, marking may also include the manufacturer’s
historical ratings such as reference cantilever load (RCL), maximum design cantilever load
(MDCL), maximum working load (MWL), or working cantilever load (WCL).
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 3
6
Classification of Tests
6.1
Prototype Tests—General Description
The purpose of these procedures is to verify the suitability of the product design, materials, and method of
manufacture. The prototype tests are described in Section 7. Only one series of tests is required for each
class, as defined below.
a. The core and housing are of the same materials composition and method of manufacture as the
tested insulator.
b. The end fittings are of the same design and material, and use the same method of attachment to
the core as the tested insulator.
c. The design sheath thickness is the same as or greater than the insulator(s) tested.
d. The maximum cantilever bending moment stress in the core at SCL is the same as or less than
that for the tested insulator.
e. The depth and design of the connection zone of the ground end fitting (most highly stressed) are
the same as that for the tested insulator.
The prototype test report will include a drawing of the insulator tested, with applicable dimensions. These
dimensions will at a minimum include those defined for the applicable class. The prototype test will be
performed only once for the same class of insulator.
To allow for manufacturing variations, the weathershed overhang (dimension between sheath and tip of
shed) thickness and shape may vary up to 15% before prototype tests must be repeated. In addition, the
housing thickness and covering of the metal end fittings may vary up to 15% before prototype tests must
be repeated. Prototype testing of the insulator is not required for a greater thickness of the weathershed
and housing, or increased rod dimensions that exceed the 15% variation limitation.
When changes in the design occur that exceed the classification limits, prototype testing shall be
repeated in accordance with the schedule, as shown in Table 2.
Table 2
Prototype Tests
Design Change
7.1
7.2
Prototype Test Required
7.3
7.4
Shed Material
√
√
Shed Design
√
√
Housing Material
√
√
Housing Design
√
√
7.5
7.6
√
√
√
√
√
Core Diameter
Core Material
√
√
Attachment Method
√
√
√
√
End Fitting Material
End Fitting Design
√
Manufacturing Location
of Molding
Manufacturing Location
of Crimping
√
√
√
√
Note: Prototype testing is not required for design changes that increase the thickness of the
weathershed and/or housing.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 4
Test descriptions:
7.1
7.2
7.3
7.4
7.5
7.6
6.2
Tests on Interfaces and Connection of End Fittings.
Assembled Core Load Tests.
Housing Tracking and Erosion Tests.
Aging or Weathering Test.
Core Material Tests.
Flammability Test.
Design Tests—General Description
These tests verify those characteristics of a composite insulator that depend on its size and shape. The
design tests will be performed only once for the same class of insulator. Their requirements are given in
Section 8.
6.3
Sample Tests—General Description
These tests verify the conformance of the post insulators to the manufacturing requirements given in
Section 9. The samples are selected from production lots.
6.4
Routine Tests—General Description
These tests are for the purpose of verifying the final quality acceptance of the manufactured insulators.
These tests are performed according to the requirements of Section 10.
7
Prototype Tests
Prototype testing is done in six parts as described in Sections 7.1, 7.2, 7.3, 7.4, 7.5, and 7.6. Each test
section shall be performed in sequence. Prototype tests are to be performed only once for each class of
insulator as defined in Section 6.1. The results will be recorded in a test report. The test report will
constitute the evidence of successful completion of the prototype tests.
7.1
Tests on Interfaces and Connection of End Fittings
7.1.1
Test Procedure
Four line post insulators shall be tested in accordance with Section 7.1, including all subsections, of ANSI
C29.11.
7.1.2
Evaluation
At the conclusion of the low frequency dry flashover voltage test prescribed in ANSI C29.11, Section
7.1.6.3, the temperature rise of the shank section (measured immediately after the test) shall not be more
than 10°C above the ambient temperature.
7.2
Assembled Core Load Tests
Six line post insulators shall be tested.
7.2.1
Core Time-Load Test
Three line post insulators shall be tested in accordance with Section 7.2.2, including all subsections, of
ANSI C29.11.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 5
7.2.1.1
Evaluation
7.2.1.1.1
Visual Examination
After removal of the load, visually inspect the base end fitting for cracks or permanent deformation. All
threaded connections must be intact and usable.
7.2.1.1.2
Dissection and Dye Penetration
After dissection and dye penetration, there shall be no cracks or delamination found on the cut surfaces
of the fiberglass rod. If any are found, this will constitute failure.
7.2.2
7.2.2.1
Tensile Load Test
Test Specimens
Three insulators manufactured on the production line using the standard end fittings shall be selected.
7.2.2.2
Tensile Test
A tensile load shall be applied to each insulator in line with the axis of the core of the insulator. The load
shall be increased rapidly but smoothly from zero to approximately 75% of the STL and shall then be
gradually increased in a time between 30 s and 90 s until the STL is reached. If the STL is reached in less
than 90 s, the load shall be maintained for the remainder of the 90 s. At the conclusion of the 90 s, the
load shall be removed.
7.2.2.3
Evaluation
The test shall be regarded as passed if there is no evidence of:
a. Pull-out of the core from the end fitting.
b. Breakage of the end fitting.
7.3
Housing Tracking and Erosion Tests
7.3.1
Procedure
Two insulators will be tested. The specimen length will be chosen such that the leakage distance falls
between 200 and 800 mm (7.9 to 31.5 inches) and includes at least two weathersheds. With the
exception of sample size, the test shall be performed in accordance with Section 7.3 of ANSI C29.11.
7.3.2
Evaluation
The test specimens of identical design shall be assessed together. The test is regarded as passed if, on
both test specimens:
a. No tracking occurs;
b. Erosion depth is less than 3 mm and does not reach the core;
c. No shed, housing, or interface is punctured.
7.4
Aging or Weathering Test
The manufacturer shall test and provide information on the elastomeric materials of the insulator, as
defined in ASTM D2565, ASTM G52, or ASTM G154, that shows no indication of cracking or crazing after
one thousand hours.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 6
7.5
Core Material Tests
7.5.1
Dye Penetration Test
7.5.1.1
Test Specimens
Ten samples will be prepared and tested in accordance with Section 7.4.1 of ANSI C29.11.
7.5.1.2
Evaluation
The time for the dye to rise through the samples by capillarity shall be more than 15 minutes.
7.5.2
7.5.2.1
Water Diffusion Test
Test Specimens
The test shall be performed in accordance with Section 7.4.2 of ANSI C29.11, except the electrodes
shown in Figure 1 shall be used.
7.5.2.2
Evaluation
No puncture or surface flashover is allowed. The current during the whole test shall not exceed 1 mA rms.
7.6
Flammability Test
Samples of the elastomeric materials of the insulator shall be tested in accordance with Section 7.5 of
ANSI C29.11. The materials shall meet the requirements of FV0 (per IEC 60695-11-10).
8
Design Tests
Design tests are to be performed on full insulators, as determined by the manufacturer, to establish an
accurate representation for the electrical capabilities of each insulator class, as described in Tables 5a,
5b, and 5c.
8.1
Low-Frequency Dry Flashover Test
One composite insulator shall be selected and tested in accordance with Section 8.2.1 of ANSI C29.11.
Failure of the dry flashover value to equal or exceed 95% of the rated dry flashover value, as given on the
manufacturer's drawing, shall constitute failure to meet the requirements of this standard.
8.2
Low-Frequency Wet Flashover Test
One composite insulator shall be selected and tested in accordance with Section 8.2.2 of ANSI C29.11.
Failure of the wet flashover value to equal or exceed 90% of the rated wet flashover value, as given on
the manufacturer's drawing, shall constitute failure to meet the requirements of this standard.
8.3
Critical Impulse Flashover Tests—Positive and Negative
One composite insulator shall be selected for the critical impulse flashover test, positive, and one for the
critical impulse flashover test, negative, and tested in accordance with Section 8.2.6 of ANSI C29.11.
Failure of the critical impulse flashover value to equal or exceed 92% of the rated critical impulse
flashover value, as given on the manufacturer's drawing, shall constitute failure to meet the requirements
of this standard.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 7
8.4
Radio-Influence Voltage (Optional)
Radio interference and corona tests are not specified in this standard since the RIV and corona
performance are not characteristics of the insulator alone. If required, an RIV test may be performed in
accordance with Section 8.2.8 of ANSI C29.11 but should be discussed between the purchaser and the
manufacturer.
9
Sample Tests
9.1
Sample Selection
The insulator(s) shall be selected from the lot at random. The purchaser has the right to make the
selection. The insulator(s) shall be subjected to the applicable sample tests.
For lots smaller than or equal to 200 insulators, the number of samples tested shall be by agreement
between the purchaser and the manufacturer. For lots of more than 200 insulators, the number of
samples listed in Table 3 shall apply unless otherwise agreed to by the purchaser and manufacturer.
Table 3
Sample Size
Tests
Verification of Dimensions
Galvanizing Test
Cantilever Load-Deflection Test
Cantilever Breaking Load Test
(optional)
Specified Tensile Load Test
Number of Samples
3
3
1
1
1
In the event of a failure of the sample to satisfy a test, the retest procedure of Section 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 4 shall
apply.
9.3
Galvanizing Test
For ferrous end fittings and bases, three pieces representative of each type of galvanized hardware shall
be tested in accordance with Section 9.6 of ANSI C29.11. Five to 10 measurements shall be uniformly
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 value given in Table 4.
Table 4
Minimum Average Thickness of Galvanizing
Hardware
(except
nuts/bolts)
Nuts/bolts
Average of
Entire
Sample
(mil)
3.4
Average of
Individual
Specimen
(mil)
3.1
2.1
1.7
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 8
9.4
Verification of Cantilever Strength Test 1
9.4.1
Test Setup
The sample insulator shall be set up in accordance with Section 9.5.1 of ANSI C29.11.
9.4.2
Cantilever Load-Deflection Test
The sample insulator shall be loaded in accordance with Section 9.5.2 of ANSI C29.11. The deflection of
the top cap from the approximate position before loading shall be monitored throughout the test. A
pre-load may be applied to remove hysteresis from the line post assembly, but if a pre-load is applied, the
load shall be reduced to approximately zero and deflections will be calculated from that unloaded
position. During the 1-minute hold, the deflection of the top cap (from the unloaded position) shall be
monitored and shall not change by more than 4% of the initial deflection. At the conclusion of the
1-minute hold, the load shall be removed.
9.4.3
Cantilever Breaking Load (CBL) Test (Optional)
A cantilever breaking load test, if required, shall be performed in accordance with Section 9.5.3 of
ANSI C29.11.
9.4.3.1
Evaluation
The test is passed if the CBL is greater than or equal to the SCL.
9.5
Specified Tensile Load Test
One sample insulator either randomly selected from or representing the lot shall be subjected to a
specified tensile load test in accordance with Section 9.4.3 of ANSI C29.11. The maximum load shall be
recorded.
9.5.1
Evaluation
The test is passed if the maximum load is greater than the STL. If the maximum load fails to meet or
exceed the STL, the retest procedure (Section 9.6) shall be employed.
9.6
Retest Procedure for Sample Tests
Retest procedures shall be in accordance with Section 9.7 of ANSI C29.11.
10
Routine Tests
Routine tests are to be performed on every insulator produced.
10.1
Tensile Load Test
Every assembled insulator shall be tested in accordance with Section 10.1.2 of ANSI C29.11. The load to
be applied shall be equal to or greater than the routine test load (RTL). No partial or complete pull-out of
the core from the end fitting shall occur.
1 Compound loading is an active topic of research in the industry. Consult with the manufacturer regarding
recommendations for compound loading.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 9
10.2
Visual Examination
Every insulator shall be subjected to a visual examination in accordance with Section 10.2 of
ANSI C29.11.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 10
Table 5a
Class 250
Design Parameters for Horizontal Line Posts
with Mounting Base and Drop Eye Fitting
Design
Section Length2
Minimum
Dry Arcing
Minimum CIFO
Values
Type
Minimum
Inches
(mm)
Maximum
Inches
(mm)
Distance,4
Inches
(mm)
Positive
(kV)
Negative
(kV)
250 – 41
250 – 47
250 – 54
250 – 60
250 – 66
250 – 75
250 – 85
250 – 95
250 – 105
41 (1041)
47 (1194)
54 (1372)
60 (1524)
66 (1676)
75 (1905)
85 (2159)
95 (2413)
105 (2667)
47 (1194)
54 (1372)
60 (1524)
66 (1676)
75 (1905)
85 (2159)
95 (2413)
105 (2667)
115 (2921)
28 (711)
32 (813)
38 (965)
44 (1118)
49 (1245)
53 (1346)
63 (1600)
73 (1854)
83 (2108)
480
550
650
760
850
920
1100
1275
1445
495
560
680
780
885
1010
1180
1360
1500
Min. 60 Hz
Flashover
Values
Dry
Wet
(kV)
(kV)
290
340
410
470
525
590
715
795
880
260
310
365
405
465
520
605
675
745
SCL (lb.)
Minimum1
3800
3300
2850
2650
2300
2000
1750
1600
1300
1
The SCL values shown represent manufacturers’ ratings for line posts manufactured with nominal 2.5 inch diameter core.
Metric values in parentheses ().
Leakage distance should be at least 27.8 mm/kV (line-to-ground).
4
Electrical values and minimum dry arcing distance given are without grading rings.
2
3
Note: If a grading ring(s) is required, then it is possible that there will be a reduction in the dry
arcing distance as well as the electrical values. In order to increase electrical values, a longer post
may be needed. Please note that a longer post will reduce the SCL value.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 11
Table 5b
Class 300
Design Parameters for Horizontal Line Posts
with Mounting Base and Drop Eye Fitting
Design
Section Length2
Minimum
Dry Arcing
Minimum CIFO
Values
Min. 60 Hz
Flashover
Values
Dry
Wet
(kV)
(kV)
SCL (lb.)
Type
Minimum
Inches
(mm)
Maximum
Inches
(mm)
Distance4,
Inches
(mm)
Positive
(kV)
Negative
(kV)
300 – 54
54
(1372)
60
(1524)
66
(1676)
75
(1905)
85
(2159)
95
(2413)
105
(2667)
115
(2921)
60 (1524)
40 (1016)
670
765
430
390
5100
66 (1676)
46 (1168)
765
860
490
445
4600
75 (1905)
52 (1321)
860
955
550
500
4150
85 (2159)
59 (1499)
990
1085
635
575
3525
95 (2413)
69 (1753)
1160
1255
730
640
3085
105
(2667)
115
(2921)
125
(3175)
78 (1981)
1310
1410
800
700
2740
88 (2235)
1480
1580
870
760
2465
96 (2438)
1630
1730
930
815
2240
300 – 60
300 – 66
300 – 75
300 – 85
300 – 95
300 – 105
300 – 115
Minimum1
1
The SCL values shown represent manufacturers’ ratings for line posts manufactured with nominal 3.0 inch diameter core.
Metric values in parentheses ().
3
Leakage distance should be at least 27.8 mm/kV (line-to-ground).
4
Electrical values and minimum dry arcing distance given are without grading rings.
2
Note: If a grading ring(s) is required, then it is possible that there will be a reduction in the dry
arcing distance as well as the electrical values. In order to increase electrical values, a longer post
may be needed. Please note that a longer post will reduce the SCL value.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 12
Table 5c
Class 350
Design Parameters for Horizontal Line Posts
with Mounting Base and Drop Eye Fitting
Design
Section Length2
Minimum
Dry Arcing
Minimum CIFO
Values
Type
Minimum
Inches
(mm)
Maximum
Inches
(mm)
Distance4,
Inches
(mm)
Positive
(kV)
Negative
(kV)
350 – 60
350 – 66
350 – 75
350 – 85
350 – 95
350 – 105
350 – 115
60 (1524)
66 (1676)
75 (1905)
85 (2159)
95 (2413)
105 (2667)
115 (2921)
66 (1676)
75 (1905)
85 (2159)
95 (2413)
105 (2667)
115 (2921)
125 (3175)
44 (1118)
48 (1219)
57 (1448)
66 (1676)
75 (1905)
84 (2134)
95 (2413)
705
785
935
1090
1245
1400
1590
800
880
1030
1190
1340
1495
1690
Min. 60 Hz
Flashover
Values
Dry
Wet
(kV)
(kV)
455
505
600
700
780
850
915
410
455
545
640
685
745
800
SCL (lb.)
Minimum1
6760
5820
4950
4420
3990
3560
3270
1
The SCL values shown represent manufacturers’ ratings for line posts manufactured with nominal 3.5 inch diameter core.
Metric values in parentheses ().
3
Leakage distance should be at least 27.8 mm/kV (line-to-ground).
4
Electrical values and minimum dry arcing distance given are without grading rings.
2
Note: If a grading ring(s) is required, then it is possible that there will be a reduction in the dry
arcing distance as well as the electrical values. In order to increase electrical values, a longer
post may be needed. Please note that a longer post will reduce the SCL value.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 13
Figure 1
Electrodes for the Voltage Test for Cores with a Diameter Greater Than 1.75 Inches
Note: Dimensions in inches (millimeters).
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 14
Figure 2
Example of Horizontal Clamptop End Fitting
To be used with a trunnion clamp. Reference ANSI C29.7 for dimensional details.
Note: Dimensions in inches (millimeters).
Class
250
300
350
Minimum Spacing (inches)
1.5
2
2.5
Figure 3
Example of Blade Style End Fitting and Recommended Minimum Hole Spacing
Note: Dimensions in inches (millimeters).
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 15
Class
250
300
350
350
Bolt Circle Diameter
(B.C.D.)
5”
5”
5”
7”
Hole Type
Length of Engagement
11/16” Through Hole
5/8”-11 UNC Tapped1)
5/8”-11 UNC Tapped1)
Through (Hole or Slot)2)
NA
Min. 0.625”
Min. 0.625”
NA
1) Pitch diameter 0.5882”-0.5810” in order to accommodate a galvanized bolt (tap after hot-dip galvanizing).
2) Through hole or through slot varies depending on the manufacturer.
Figure 4
Example of Flange Style End Fitting and Recommended Connections
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 16
A,
bolt
hole
spacing
(inches)
B,
nominal
bolt size
(inches)
D,
nominal
(degrees)
12
12
14
14
14
7/8
3/4
7/8
1
1
12
12
14 to 17
14 to 17
14 to 17
Class
250
250
300
300
350
Figure 5
Examples of Detachable Gain Base and Common Dimensions
Note: While there are variations of these dimensions in use today, it is intended that the
dimensions provided here will become standard with time and use.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 17
Class
250
250
250
250
300
300
300
350
350
350
A, bolt hole
spacing
(inches)
8
8
8
8
9
9
9
10
10
10
B, bolt hole
spacing
(inches)
10
10
10
13
13
13
14
15
15
15
C, nominal
bolt size
(inches)
3/4
7/8
7/8
7/8
1
7/8
7/8
1
7/8
3/4
D, nominal
(degrees)
12
12
12
12
14 to 17
14 to 17
14 to 17
15 to 17
15 to 17
15 to 17
Figure 6
Examples of Detachable Flat Base and Common Dimensions
Note: While there are variations of these dimensions in use today, it is intended that the
dimensions provided here will become standard with time and use.
© 2023 National Electrical Manufacturers Association
ANSI/NEMA C29.17-2022
Page 18
Appendix A
(This Appendix is not part of American National Standard C29.17-2022
but is included for information only.)
Packaging
Packaging of insulator should be such as to afford reasonable and proper protection to the insulators in
shipping and handling.
Each box or container should be marked with the number of insulators contained therein; the catalog
number, class number, or a description of the contents; and the manufacturer’s name.
§
© 2023 National Electrical Manufacturers Association