C37.41
TM
IEEE Standard Design Tests for High-Voltage
(>1000 V) Fuses, Fuse and Disconnecting
Cutouts, Distribution Enclosed Single-Pole Air
Switches, Fuse Disconnecting Switches, and Fuse
Links and Accessories Used with These Devices
IEEE Power & Energy Society
Sponsored by the
Switchgear Committee
IEEE
3 Park Avenue
New York, NY 10016-5997, USA
13 March 2009
IEEE Std C37.41™-2008
(Revision of
IEEE Std C37.41-2000)
IEEE Std C37.41TM-2008
(Revision of
IEEE Std C37.41-2000)
IEEE Standard Design Tests for High-Voltage
(>1000 V) Fuses, Fuse and Disconnecting
Cutouts, Distribution Enclosed Single-Pole Air
Switches, Fuse Disconnecting Switches, and Fuse
Links and Accessories Used with These Devices
Sponsor
Switchgear Committee
of the
IEEE Power & Energy Society
Approved 10 November 2008
IEEE-SA Standards Board
Abstract: Required procedures for performing design tests for high-voltage distribution class and
power class fuses, as well as for fuse disconnecting switches and enclosed single-pole air
switches, are specified. These design tests, as appropriate to a particular device, include the
following test types: dielectric, interrupting, load-break, radio-influence, short-time current,
temperature-rise, time-current, manual-operation, thermal-cycle, bolt-torque, and liquid-tightness.
Keywords: distribution enclosed single-pole air switches, fuse accessories, fuse design tests,
fuse disconnecting switches, fuse enclosure package, high-voltage fuses
____________________________
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Copyright © 2009 by the Institute of Electrical and Electronics Engineers, Inc.
All rights reserved. Published 13 March 2009. Printed in the United States of America.
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PDF:
Print:
ISBN 978-0-7381-5844-0
ISBN 978-0-7381-5845-7
STD95852
STDPD95852
Second printing 22 May 2009. Changes made to Table 7 and Table 8.
To obtain errata information, please go to http://standards.ieee.org/reading/ieee/updates/errata/index.html.
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Introduction
This introduction is not part of IEEE Std C37.41-2008, IEEE Standard Design Tests for High-Voltage (>1000 V)
Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches,
and Fuse Links and Accessories Used with These Devices.
IEEE Std C37.41-2008 is a revision of IEEE Std C37.41-2000, done in order to bring it up to date and into
agreement with current requirements for high-voltage fuses and switches. Distribution class oil cutouts
were devices formerly covered by IEEE/ANSI standards. However, ANSI C37.44-1981, which covered
specifications for such devices, has been withdrawn. Since these devices are now considered obsolete,
testing for oil cutouts has been removed from this standard. The rules covering homogeneous series testing
of expulsion fuses have been greatly expanded, and homogeneous series testing for parallel current-limiting
fuses has been introduced. Certain information, previously in ANSI C37.53.1, concerning the testing of
motor-starter fuses has been incorporated. Several changes to current-limiting fuse testing have been made
to align more closely with the latest IEC test requirements. At the request of testing authorities, several
clarifications concerning test methods and interpretation of results have been added. The Revision of Fuse
Standards Working Group of the IEEE Subcommittee on High-Voltage Fuses prepared the standard.
Liaison was maintained with the International Electrotechnical Commission (IEC) during the development
of the revisions in order to incorporate the latest activities at the time of publication.
The Switchgear Committee of the IEEE Power and Energy Society has recently approved and published
IEEE Std C37.100.1™-2007 [B4]. a Although IEEE Std C37.100.1-2007 is not specifically referenced in this
document, any information that may apply to fuse devices has been incorporated.
This standard is one of a series of complementary standards covering various types of high-voltage fuses
and switches, arranged so that certain standards apply to all devices while other standards provide
additional specifications for a particular device. For any device, IEEE Std C37.40™, this IEEE Std
C37.41™, plus any additional standards covering that device, constitute a complete standard for the device.
In addition, IEEE Std C37.48™ provides application, operation, and maintenance guidance for all the
devices, and it is supplemented by IEEE Std C37.48.1™-2002 [B3], which is an operation, classification,
application, and coordination guide for current-limiting fuses.
At the time this standard was approved, this series was comprised of the following standards:
ANSI C37.42, American National Standard Specifications for High Voltage Expulsion Type Distribution
Class Fuses, Cutouts, Fuse Disconnecting Switches and Fuse Links.
ANSI C37.46, American National Standard for High Voltage Expulsion and Current-Limiting Type Power
Class Fuses and Fuse Disconnecting Switches.
ANSI C37.47, American National Standard for High-Voltage Current-Limiting Type Distribution Class
Fuses and Fuse Disconnecting Switches.
IEEE Std C37.40™, IEEE Standard Service Conditions and Definitions for High-Voltage Fuses,
Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories.
IEEE Std C37.41™, IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and
Disconnecting Cutouts, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and
Fuse Links and Accessories Used with These Devices.
a
The numbers in brackets correspond to those of the bibliography in Annex F .
iv
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IEEE Std C37.43™, IEEE Standard for Specifications for High-Voltage Expulsion, Current-Limiting and
Combination Type Distribution and Power Class External Fuses, With Rated Voltages from 1kV through
38kV, Used for the Protection of Shunt Capacitors.
IEEE Std C37.45™, IEEE Standard Specifications for High-Voltage Distribution Class Enclosed SinglePole Air Switches with Rated Voltages from 1 kV through 8.3 kV.
IEEE Std C37.48™, IEEE Guide for Application, Operation, and Maintenance of High-Voltage Fuses,
Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories.
IEEE Std C37.48.1™, IEEE Guide for the Operation, Classification, Application, and Coordination of
Current-Limiting Fuses with Rated Voltages 1−38 kV.
Notice to users
Laws and regulations
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v
Copyright © 2009 IEEE. All rights reserved.
Patents
Attention is called to the possibility that implementation of this draft standard may require use of subject
matter covered by patent rights. By publication of this draft standard, no position is taken with respect to
the existence or validity of any patent rights in connection therewith. The IEEE is not responsible for
identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the
legal validity or scope of Patents Claims or determining whether any licensing terms or conditions provided
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the validity of any patent rights, and the risk of infringement of such rights, is entirely their own
responsibility. Further information may be obtained from the IEEE Standards Association.
Participants
At the time this standard was submitted to the IEEE-SA Standards Board, the Revision of fuse Standards
Working Group had the following membership:
John G. Leach, Chair
Glenn R. Borchardt, Secretary
Chris Ambrose
John G. Angelis
L. Ronald Beard
Sheila Brown
Fernando Calderon
H. Edward Foelker
Dan Gardner
Stephen P. Hassler
Gary Haynes
Frank G. Ladonne
James R. Marek
Frank J. Muench
Donald M. Parker
R. Neville Parry
Philip Rosen
Tim E. Royster
John S. Schaffer
Mark W. Stavnes
Frank M. Stepniak
John G. St.Clair
Janusz Zawadzki
This document was sponsored by the Switchgear Committee of the IEEE Power and Energy Society. When
this document was approved, the members of the Switchgear Committee had the following membership:
Ted A. Burse, Chair
Bill Long, Vice Chair
Ken Edwards, Secretary
Michael Wactor, Standards Coordinator
Roy Alexander
Chris Ambrose
John G. Angelis
Charles J. Ball
Paul D. Barnhart
Robert Behl
W. J. (Bill) Bergman
Anne Bosma
John Brunke
Ray Capra
Patrick DiLillo
Alexander Dixon
Randall Dotson
Denis Dufournet
Peter W. Dwyer
Douglas Edwards
Marcel Fortin
Mietek Glinkowski
S. S. (Dave) Gohil
Keith I. Gray
Carlos Isaac
Richard Jackson
Frank G. Ladonne
Stephen Lambert
John G. Leach
Dave Lemmerman
James R. Marek
Neil McCord
Nigel P. McQuin
Steven Meiners
Alec Monroe
Georges Montillet
Anne F. Morgan
Frank J. Muench
vi
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Yasin Musa
Jeffrey Nelson
T. W. Olsen
Michael Orosz
Robert J. Puckett
Carl Reigart
Timothy Royster
Roderick Sauls
Devki Sharma
Michael D. Sigmon
R. Kirkland Smith
H. M. Smith
David Stone
Alan D. Storms
Thomas Tobin
Rich York
Janusz Zawadzki
The following members of the balloting committee voted on this standard. Balloters may have voted for
approval, disapproval, or abstention.
William J. Ackerman
Steven Alexanderson
Michael Baldwin
Steven Bezner
William Bloethe
Glenn Borchardt
James Bouford
Harvey Bowles
Chris Brooks
Robert Brown
Eldridge Byron
Thomas Callsen
Yunxiang Chen
Tommy Cooper
F. A. Denbrock
Carlo Donati
Gary Engmann
Marcel Fortin
Daniel Gardner
Manuel Gonzalez
Edwin Goodwin
Randall Groves
Ajit Gwal
John Harder
Ronald Hartzel
Gary Heuston
William Hurst
Richard Jackson
Joseph L. Koepfinger
David W. Krause
Jim Kulchisky
Saumen Kundu
Frank G. Ladonne
Chung-Yiu Lam
Stephen Lambert
John G. Leach
R. Long
Federico Lopez
G. Luri
Frank Mayle
Gary Michel
Georges Montillet
Frank J. Muench
Jerry Murphy
Jeffrey Nelson
Michael S. Newman
Joe Nims
T. W. Olsen
Miklos Orosz
Donald Parker
R. Neville Parry
Iulian Profir
Michael Roberts
Timothy Robirds
Charles Rogers
Timothy Royster
Thomas Rozek
Bartien Sayogo
James E. Smith
James Smith
Francois Soulard
James Swank
Michael Swearingen
John Vergis
Janusz Zawadzki
When the IEEE-SA Standards Board approved this standard on 10 November 2008, it had the following membership:
Robert M. Grow, Chair
Tom A. Prevost, Vice Chair
Steve M. Mills, Past Chair
Judith Gorman, Secretary
Victor Berman
Richard DeBlasio
Andrew Drozd
Mark Epstein
Alexander Gelman
William R. Goldbach
Arnold M. Greenspan
Kenneth S. Hanus
James Hughes
Richard H. Hulett
Young Kyun Kim
Joseph L. Koepfinger*
John Kulick
David J. Law
Glenn Parsons
Ronald C. Petersen
Chuck Powers
Narayanan Ramachandran
Jon Walter Rosdahl
Anne-Marie Sahazizian
Malcolm V. Thaden
Howard L. Wolfman
Don Wright
*Member Emeritus
Also included are the following nonvoting IEEE-SA Standards Board liaisons:
Satish K. Aggarwal, NRC Representative
Michael Janezic, NIST Representative
Jennie M. Steinhagen
IEEE Standards Program Manager, Document Development
Matthew J. Ceglia
IEEE Standards Program Manager, Technical Program Development
vii
Copyright © 2009 IEEE. All rights reserved.
Contents
1. Overview .................................................................................................................................................... 1
1.1 Scope ................................................................................................................................................... 1
1.2 Purpose ................................................................................................................................................ 2
1.3 Background.......................................................................................................................................... 2
1.4 Description of fuse-enclosure packages (FEPs) using expulsion type indoor power class fuses......... 2
1.5 Description of FEPs using current-limiting type indoor distribution and power class fuses ............... 3
2. Normative references.................................................................................................................................. 3
3. Required tests ............................................................................................................................................. 4
3.1 General ................................................................................................................................................ 4
3.2 Device tests .......................................................................................................................................... 5
3.3 FEP tests .............................................................................................................................................. 6
3.4 Test values ........................................................................................................................................... 6
3.5 Testing responsibility .......................................................................................................................... 6
3.6 Test report ............................................................................................................................................ 6
4. Common test requirements ......................................................................................................................... 6
4.1 General ................................................................................................................................................ 6
4.2 Test site conditions .............................................................................................................................. 7
4.3 Frequency and wave shape of test voltage ........................................................................................... 7
4.4 Devices to be tested ............................................................................................................................. 7
4.5 Acceptance criteria .............................................................................................................................. 7
4.6 Test-conductor dimensions .................................................................................................................. 8
4.7 Mounting and grounding of the device for tests .................................................................................. 9
5. Dielectric tests ...........................................................................................................................................11
5.1 General ...............................................................................................................................................11
5.2 Measurement of test voltages .............................................................................................................11
5.3 Description of power-frequency dry-withstand voltage tests .............................................................11
5.4 Description of power-frequency wet-withstand voltage tests on outdoor devices ..............................12
5.5 Description of power-frequency dew-withstand voltage tests on indoor devices ...............................12
5.6 Description of impulse withstand voltage tests ..................................................................................12
5.7 Distribution class expulsion type fuses, cutouts, and fuse disconnecting switch test connections and
test values .................................................................................................................................................13
5.8 Distribution class enclosed single-pole air switch test connections and test values ...........................14
5.9 Power class expulsion fuses, power class current-limiting fuses, and power class fuse disconnecting
switch test connections and test values .....................................................................................................14
5.10 Distribution class current-limiting fuse and fuse disconnecting switch test connections and test
values ........................................................................................................................................................15
5.11 Distribution class, power class expulsion and current-limiting type fuses, and fuse disconnecting
switches used in FEPs...............................................................................................................................16
5.12 Distribution and power class external fuses for shunt capacitors .....................................................18
6. Interrupting tests ........................................................................................................................................18
6.1 Procedures common to all interrupting tests .......................................................................................18
6.2 Interrupting tests on a homogeneous series of expulsion type fuses...................................................20
6.3 Description of interrupting tests on distribution class open-link cutouts ............................................26
6.4 Description of interrupting tests on distribution class fuse cutouts (open and enclosed) (except
current-limiting fuses) ..............................................................................................................................26
viii
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6.5 Description of interrupting tests on power class fuses and fuse disconnecting switches (except
current-limiting fuses and liquid-submerged expulsion fuses) .................................................................32
6.6 Description of interrupting tests on current-limiting power and distribution fuses ............................35
6.7 Description of interrupting tests for FEPs using current-limiting-type indoor distribution and power
class fuses .................................................................................................................................................48
6.8 Description of interrupting tests for FEPs using liquid-submerged, expulsion type indoor power class
fuses ..........................................................................................................................................................50
6.9 Description of interrupting tests for air-insulated FEPs using expulsion type indoor power class fuses
..................................................................................................................................................................52
6.10 Description of interrupting tests for external fuses for shunt capacitors ...........................................54
7. Load-break tests.........................................................................................................................................62
7.1 Procedures common to all load-break tests ........................................................................................62
7.2 Description of load-break tests for all fused devices ..........................................................................64
8. Radio-influence tests .................................................................................................................................64
8.1 Procedures common to all radio-influence tests .................................................................................64
8.2 Description of radio-influence tests on a single device ......................................................................66
8.3 Description of radio-influence tests on multiple devices ....................................................................67
8.4 Description of radio-influence tests for assembled apparatus.............................................................67
9. Short-time current tests..............................................................................................................................67
9.1 General ...............................................................................................................................................67
9.2 Mounting and grounding of device for the momentary test................................................................67
9.3 Test connections .................................................................................................................................67
9.4 Test circuit ..........................................................................................................................................67
9.5 Description of 15-cycle current tests ..................................................................................................69
9.6 Description of 3-second current tests..................................................................................................69
9.7 Description of momentary current tests ..............................................................................................69
9.8 Acceptance criteria .............................................................................................................................70
10. Temperature-rise tests .............................................................................................................................70
10.1 Procedures common to all temperature-rise tests .............................................................................70
10.2 Description of temperature-rise tests ................................................................................................71
10.3 Description of temperature-rise tests for air-insulated FEPs using expulsion type indoor power class
fuses ..........................................................................................................................................................71
11. Time-current tests ....................................................................................................................................72
11.1 Procedures common to all time-current tests ....................................................................................72
11.2 Description of melting time-current tests .........................................................................................73
11.3 Description of total-clearing time-current tests ................................................................................74
12. Manual-operation, thermal-cycle, and bolt-torque tests (distribution cutouts) ........................................74
12.1 Description of manual-operation tests ..............................................................................................74
12.2 Description of thermal cycle tests .....................................................................................................75
12.3 Description of torque tests ................................................................................................................76
13. Liquid-tightness tests ...............................................................................................................................76
13.1 Description of liquid-tightness tests .................................................................................................76
13.2 Test series .........................................................................................................................................77
13.3 Acceptance criteria ...........................................................................................................................77
14. Description of expendable-cap static-relief pressure tests .......................................................................77
Annex A (informative) Recommended methods for determining the value of a sinusoidal current wave and
a power-frequency recovery voltage .............................................................................................................78
ix
Copyright © 2009 IEEE. All rights reserved.
A.1 Current waves ....................................................................................................................................78
A.2 Power-frequency recovery voltage ....................................................................................................79
Annex B (informative) Recommended method of determining the equivalent steady-state rms current for
plotting time-current curves...........................................................................................................................81
Annex C (informative) Simplified fault-current calculation .........................................................................82
C.1 Interrupting duty and rated short-time withstand current ...................................................................82
Annex D (informative) TRV parameters .......................................................................................................83
D.1 Measurement of peak factor...............................................................................................................84
Annex E (informative) Criteria for determining It testing validity ................................................................86
E.1 Introduction ........................................................................................................................................86
E.2 Interrupting processes ........................................................................................................................86
Annex F (informative) Bibliography .............................................................................................................88
x
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IEEE Standard Design Tests for High-Voltage
(>1000 V) Fuses, Fuse and Disconnecting Cutouts,
Distribution Enclosed Single-Pole Air Switches,
Fuse Disconnecting Switches, and Fuse Links and
Accessories Used with These Devices
IMPORTANT NOTICE: This standard is not intended to ensure safety, security, health, or environmental
protection in all circumstances. Implementers of the standard are responsible for determining appropriate
safety, security, environmental, and health practices or regulatory requirements.
This IEEE document is made available for use subject to important notices and legal disclaimers. These
notices and disclaimers appear in all publications containing this document and may be found under the
heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They
can also be obtained on request from IEEE or viewed at http://standards.ieee.org/IPR/disclaimers.html.
1. Overview
1.1 Scope
This standard specifies design test requirements for high-voltage (above 1000 V) fuses, distribution enclosed
single-pole air switches, disconnecting cutouts, fuse disconnecting switches, and accessories for use on ac
power and distribution systems. Devices with rated maximum voltages to 170 kV are covered. The devices to
which this standard applies are as follows:
a)
Distribution and power class expulsion type fuses
b) Distribution and power class current-limiting type fuses
c)
Distribution and power class fuse disconnecting switches
d) Item a) through item c) used in fuse enclosure packages
e)
Fuse supports of the type intended for use with distribution and power class fuses, and fuse
disconnecting switches
f)
Fuse and disconnecting cutouts
g) Disconnecting devices created by the use of a removable switch blade in a distribution or power
class fuse support
h) Distribution class enclosed single-pole air switches
1
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
i)
Distribution class and power class expulsion, current-limiting, and combination types of external
capacitor fuses used with a capacitor unit, groups of units, or capacitor banks
j)
Backup current-limiting fuses (“motor-starter fuses”) used in conjunction with high-voltage Class
E2 motor starters (see ANSI/UL 347-2000 [B1]) 1
k) Fuse links when used exclusively with distribution class and power class fuses, and distribution
class and power class fuse disconnecting switches
l)
Item a) through item d) and item f) through item i) having integral load-break means
1.2 Purpose
This standard specifies the minimum testing requirements for fuses and related devices. Such standardization
is needed to ensure uniform minimum product testing for devices within the document scope. Test areas
covered are based on historical experience.
1.3 Background
The distribution and power class expulsion type fuses listed in 1.1 are similar to those now covered in
IEC 60282-2. 2 The distribution class expulsion type fuses are similar to the class “A” fuses covered in the
document, and the power class fuses are similar to their class “B” fuses. Some of the current-limiting type
fuses listed in 1.1 are similar to those now covered in IEC 60282-1. However, significant differences exist in
the testing requirements of IEC and IEEE/ANSI. IEEE fuse standards primarily reflect applications common in
North America and in countries that use electrical systems designed using similar principles. IEC standards
tend to rely heavily on practices common in Europe. Since IEC testing differences include testing at different
voltages for the same fuse rated voltage, and different or no testing for fuses intended for use in a surrounding
temperature above 40 °C, the user is advised to exercise extreme caution if devices specified and tested per
IEC standards are compared with those specified and tested per IEEE/ANSI standards. The differences in test
requirements may result in devices tested to IEC not being suitable for applications where devices tested to
IEEE/ANSI standards are required, or vice versa.
In the headings and the text of this document, there are some areas where information is included in brackets [
]. The information in the brackets is a term used in IEC standards that may be similar to the term used in this
document, a term that is common in some parts of the world, or a term that has been used previously in IEEE
or ANSI standards. Caution is again advised when making comparisons.
1.4 Description of fuse-enclosure packages (FEPs) using expulsion type indoor
power class fuses
 Type 1E: A fuse mounted in an enclosure with relatively free air circulation within the enclosure
(e.g., an expulsion fuse mounted in an enclosure or vault).
 Type 2E: A fuse mounted in a container with restricted air flow surrounding the fuse, but with
relatively free air circulation within the enclosure on the outside of the container (e.g., an expulsion
fuse in an enclosure with insulating barriers that form a container that restricts the air flow).
 Type 3E: A fuse directly immersed in liquid and mounted in an enclosure with relatively free liquid
circulating around the fuse (e.g., an expulsion fuse in a liquid-filled switchgear enclosure).
1
2
The numbers in brackets correspond to those of the bibliography in Annex F.
Information on references can be found in Clause 2.
2
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
1.5 Description of FEPs using current-limiting type indoor distribution and power
class fuses
 Type 1CL: A fuse mounted in a large enclosure with relatively free air circulation within the
enclosure (e.g., a fuse mounted in a live-front pad-mounted transformer or in a vault). The relevant
fuse rated maximum application temperature (RMAT) is based on that of the air that is cooling the
fuse. It may be noted that if a fuse were mounted outdoors but in an ambient temperature above 40
ºC, conditions on the fuse would be the same.
 Type 2CL: A fuse mounted in a fuse container. This is a relatively small enclosure, defined as one
supporting the fuse and restricting the air, gas, or liquid flow surrounding the fuse (e.g., a fuse
inside a canister in a transformer or a vault). However, the fluid flow (gas, liquid, or a combination
of the two) that cools the outside surface of the container has relatively free circulation. The
relevant fuse RMAT is based on that of the fluid that is cooling the container. Fuses tested in
accordance with 6.6 (i.e., tested for use in air no hotter than 40 ºC), which are encapsulated with
solid insulation (e.g., rubber or epoxy), can be considered to be this type of FEP when so
encapsulated. In this case, the relevant fuse RMAT is based on that of the fluid that is cooling the
encapsulated fuse.
 Type 3CL: A fuse directly immersed in liquid and mounted in an enclosure with relatively free
liquid circulation around the fuse (e.g., an oil-immersed fuse in a transformer or switchgear
enclosure). The relevant RMAT is based on that of the liquid that is cooling the fuse.
NOTE—In IEEE Std C37.41TM-2000 and the versions of ANSI C37.46, ANSI C37.47, and IEEE Std C37.48TM approved
before this standard, FEPs using current-limiting fuses are designated as being of types 1C through 5C. In order to simplify
FEP types, include additional types, and align with IEC practice, these types have been rationalized into three categories.
Type 2CL includes the former types 2C, 3C, and 4C, whereas type 3CL is the same as type 5C. The new classifications
will be introduced into the other standards when they are revised. 3
2. Normative references
The following referenced documents are indispensable for the application of this document (i.e., they must be
understood and used, so that each referenced document is cited in text and its relationship to this document is
explained). For dated references, only the edition cited applies. For undated references, the latest edition of the
referenced document (including any amendments or corrigenda) applies.
ANSI C37.42, American National Standard Specifications for High Voltage Expulsion Type Distribution Class
Fuses, Cutouts, Fuse Disconnecting Switches and Fuse Links. 4
ANSI C37.46, American National Standard for High Voltage Expulsion and Current-Limiting Type
Distribution Class Fuses and Fuse Disconnecting Switches.
ANSI C37.47, American National Standard for High Voltage Current-Limiting Type Distribution Class Fuses
and Fuse Disconnecting Switches.
ANSI C63.2-1987, American National Standard for Electromagnetic Noise and Field Strength Instrumentation,
10 kHz to 1 GHz—Specifications.
IEC 60282-1, High Voltage Fuses—Part 1, Current-Limiting Fuses. 5
3
Notes in text, tables, and figures are given for information only and do not contain requirements needed to implement the standard.
ANSI publications are available from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New
York, NY 10036, USA (http://www.ansi.org/).
5
IEC publications are available from IEC Sales Department, Case Postale 131, 3, rue de Varembé, CH-1211, Genève 20, Switzerland/
Suisse. IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 25
West 43rd Street, 4th Floor, New York, NY 10036, USA (http://www.ansi.org/).
4
3
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
IEC 60282-2, High Voltage Fuses—Part 2, Expulsion Fuses.
IEEE Std 4™-1995, IEEE Standard Techniques for High-Voltage Testing. 6, 7
IEEE Std C37.20.3™, IEEE Standard for Metal-Enclosed Interrupter Switchgear.
IEEE Std C37.40™, IEEE Standard Service Conditions and Definitions for High-Voltage Fuses, Distribution
Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories.
IEEE Std C37.43™, IEEE Standard for Specifications for High-Voltage Expulsion, Current-Limiting and
Combination Type Distribution and Power Class External Fuses, With Rated Voltages from 1kV through
38kV, Used for the Protection of Shunt Capacitors.
IEEE Std C37.45™, IEEE Standard Specifications for High-Voltage Distribution Class Enclosed Single-Pole
Air Switches with Rated Voltages from 1 kV through 8.3 kV.
IEEE Std C37.48™, IEEE Guide for Application, Operation, and Maintenance of High-Voltage Fuses,
Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories.
NOTE—Fuse standards listed as “ANSI C37.xx,” were formerly developed by NEMA. The responsibility for maintaining
them has passed to the IEEE and will, at their next revision, carry the designation “IEEE Std C37.xx.”
3. Required tests
3.1 General
The tests to be conducted upon completion of a design or following a design change that affects performance
are summarized in Table 1 and are completely specified in the appropriate standards listed below:
 ANSI C37.42
 IEEE Std C37.43
 IEEE Std C37.45
 ANSI C37.46
 ANSI C37.47
6
IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854, USA
(http://standards.ieee.org/).
7
The IEEE standards or products referred to in this clause are trademarks of the Institute of Electrical and Electronics Engineers, Inc.
4
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 1 —Design tests required
ANSI C37.42
IEEE Std C37.43
Specifications for
high-voltage
Design test Specifications for high-voltage
distribution and
given in
expulsion type distribution power class expulsion,
following
class fuses, cutouts, fuse
current-limiting, and
sections of
disconnecting switches, and combination types of
this standard
fuse links
external capacitor
fuses for shunt
capacitors
Fuse Disconnecting Fuse Capacitor Capacitor
cutouts
cutouts
links line fuses unit fuses
5. Dielectrica
X
X
—
X
—
6. Interrupting
X
—
Xc
X
X
7. Load-break
Xd
Xd
—
Xd
—
8. RadioX
X
—
X
X
influencea
9. Short-time
—
X
—
—
—
current
10.
TemperatureX
X
X
X
X
rise
11. Time—
—
X
X
X
current
12. Manualoperation,
X
X
—
—
—
thermal-cycle,
and bolt-torque
13. Liquid—
—
—
—
—
tightness
14. Expendablecap static-relief
Xf
—
—
Xf
—
pressure
IEEE Std
C37.45
ANSI
C37.46
ANSI
C37.47
Specifications
for highvoltage
distribution
class enclosed
single-pole air
switches
Specifications
for highvoltage
expulsion and
currentlimiting type
power class
fuses and fuse
disconnecting
switches
Specifications
for highvoltage
currentlimiting type
distribution
class fuses,
and fuse
disconnecting
switches
X
—
—
Xb
Xb
—
Xb
Xb
—
X
Xb
Xb
X
—
—
X
Xb
Xb
—
X
X
—
—
—
—
Xe
Xe
—
—
—
a
Required only on fuses and fuse units when they are mounted in a particular fuse support (see 5.1 and 8.1.1).
When these types of fuses are used in enclosures, additional tests may be required. See the appropriate IEEE/ANSI standard listed
above for complete requirements.
c
Required only on open-link fuses.
d
Required only on load-break cutouts having means provided for breaking load current.
e
Required only on liquid-submersible fuses used in FEP.
f
Required only on expendable caps for expendable-cap cutouts.
b
3.2 Device tests
For devices covered by this standard, all applicable tests need not be performed on each design modification of
a previously qualified design. To assure that overall performance has not been adversely affected as a result of
the design modification, sufficient tests shall be performed to ensure that the modified design will have a
performance that meets or exceeds the ratings and performance requirements of the standards specified in
Clause 3. For devices that have been assigned ratings or performance requirements that are different from the
standards specified in Clause 3, the modified design shall have ratings and performance requirements that meet
or exceed the values assigned to the original device.
Fuses connected in parallel shall be considered a separate design and be tested accordingly. Note that this
includes fuses mounted in parallel by the fuse manufacturer and those intended by the manufacturer to be
paralleled by another party. When single current-limiting fuses have been tested in accordance with
IEEE Std C37.41, the testing of these fuses in parallel is subject to the homogeneous testing rules in 6.6.4.
5
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
3.3 FEP tests
The design tests for FEPs are performed to determine the adequacy of a particular type of design, style, or
model of equipment to meet its assigned ratings and for satisfactory operation. In general, a fuse need not be
tested if it has already been tested in an equivalent enclosure.
3.4 Test values
3.4.1 Allowable tolerances
Testing parameters in this document and the specification documents for each device are listed as a value with
an allowable plus tolerance (e.g., +5% –0%), a value with an allowable minus tolerance (e.g., +0% −10%), a
minimum value, a maximum value, or a range. When a range is specified, the test may be performed anywhere
within that range. When a minimum value or a value with a plus tolerance is specified, the manufacturer may
perform the test at any value that equals or exceeds the minimum value (e.g., voltage). When a maximum
value or a value with a minus tolerance is specified, the manufacturer may perform the test at any value that is
equal to or less than the maximum value allowed. When a minimum value, maximum value, or a tolerance is
specified, testing by persons other than the manufacturer shall be at the specified value, or permission to test at
a different level shall be obtained from the manufacturer. The general principle to be followed is that a
manufacturer, for testing convenience, may choose to test with values more severe than prescribed for the
tests, whereas other persons performing tests shall obtain approval from the manufacturer before more severe
testing is performed.
3.4.2 Preferred values
In this standard and the specification standards referred to herein, the ratings and performance requirements
represent preferred values and requirements. Special circuit or environmental conditions may require devices
with ratings and performance that are different from the preferred values and requirements specified in these
documents. For these devices, the user and the manufacturer shall agree upon the ratings and performance
requirements.
3.5 Testing responsibility
A fuse or switch manufacturer shall test their device and supply the appropriate application data. An FEP
manufacturer is responsible for ensuring that appropriate testing has been performed and for supplying the
appropriate application data.
3.6 Test report
The results of all tests shall be recorded in a test report containing the data necessary to prove compliance with
the applicable standards. The test report shall include the manufacturers name and completely describe the
device tested. Photographs of devices as tested, type numbers, production drawings, product bulletins, or other
descriptive literature for the device may be included.
4. Common test requirements
4.1 General
The requirements of Clause 4 are common to all tests. Where the conditions for a specific test deviate from
these common test requirements, they are identified in the specific subclause for the test.
6
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
4.2 Test site conditions
4.2.1 Ambient temperature during test
The ambient temperature prevailing at the test site shall conform to the usual service conditions in accordance
with IEEE Std C37.40.
4.2.2 Atmospheric conditions during test
Tests shall be conducted under atmospheric conditions prevailing at the time and place of the test. It is
recommended that the barometric pressure and dry and wet bulb thermometer readings be recorded so that
applicable correction factors can be applied to the measurements.
4.3 Frequency and wave shape of test voltage
4.3.1 Frequency of test voltage
The frequency for all power-frequency tests shall be (50 ± 2) Hz or (60 ± 2) Hz, except as otherwise specified.
4.3.2 Wave shape of test voltage
A sine wave of acceptable commercial standards shall be applied to the device. For the definition of the wave
shape, see IEEE Std 4-1995.
4.4 Devices to be tested
4.4.1 Condition of device to be tested
The device shall be new and in good condition, and tests shall be applied before the device is put into
commercial service, unless otherwise specified.
4.4.2 Compatibility of components
Unless otherwise specified, tests performed according to this standard shall utilize components made by the
same manufacturer or as recommended for use by the manufacturer.
4.5 Acceptance criteria
The successful completion of tests listed in this standard requires that various criteria be met, including the
following:
a)
A device shall perform all of its intended functions. While it is not feasible to list all possible
device functions, typical examples are that devices intended to drop down, drop open, or initiate
operation of other devices after current interruption shall perform these functions in their intended
manner on all interrupting test series (see NOTE 2).
b) A filled current-limiting fuse shall not emit filler material or flame during interrupting tests,
although a minor emission of flame from a striker or indicating device is permissible, provided this
does not cause breakdown or significant leakage to ground.
7
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
c)
Fuses that operate an indicating device need not comply with any specific requirements but shall
visually and fully operate. If a current-limiting fuse includes a device, the only function of which is
to provide indication of a fuse operation, and that indicator does not operate, then although the fuse
has failed to pass the test as a fuse with an indicator, the test may be used as part of a series to
demonstrate that an otherwise identical nonindicating fuse has met the requirements of the
standard.
d) After an interruption test, all parts of the device shall be in proper position, and the fuse shall be
removable from its support in one piece as intended.
In addition, after replacing parts that are normally field replaceable (see NOTE 1), excluding a fuse holder, the
condition of the device shall be as follows:
e)
Mechanical requirements: In substantially the same condition as at the beginning of the test.
Depending on the current interrupted during interrupting tests, it is acceptable for the bore of
expulsion devices to have some amount of erosion.
f)
Electrical requirements: Capable of carrying rated current continuously at the rated maximum
voltage. If there is evidence to suggest the device may not be able to carry rated current
continuously because of contact deterioration, a temperature-rise test shall be performed using the
maximum size fuse link, fuse unit, or refill unit. This temperature-rise test shall be performed on
the device at rated current for the time it takes for the temperature to stabilize. Temperatures
reached by the device may be higher than those achieved by a new device. The criterion for
acceptability is long-term temperature stabilization.
g) Dielectric requirements: If there is evidence of insulator contamination from the test, a powerfrequency dry-withstand test shall be performed at 75% of the normal test value for the device.
After certain groups of tests, as specified in Table 7, Table 8, Table 11, and Table 19, the fuse holder may be
changed. The acceptance criteria e) through g) are to be met with the fuseholder that has just been tested, even
though it may not be suitable for any additional testing.
NOTE 1—Examples of parts that are normally field replaceable include replaceable fuse links, fuse units, refill units,
expendable caps, and exhaust-control devices. Requirements of individual tests may limit the replacement of some parts
until certain tests, or groups of tests, have been completed.
NOTE 2—The location of the lower test conductor relative to the fuseholder of a fuse or fuse cutout may, on some tests,
influence its dropout characteristics by interfering with the movement of the fuse link leader (the flexible conductor used to
complete the electrical circuit between the fusible element and the lower fuseholder contact). The manufacturer’s
recommendations for conductor placement relative to the tested device should therefore be followed.
4.6 Test-conductor dimensions
4.6.1 Interrupting, load-break, and short-time test conductors
Electrical connections shall be made by a bare conductor connected to each terminal of the device being tested.
These conductors shall be of sufficient size to carry the test current adequately for the anticipated time. The
source side lead shall be connected to the upper terminal of the device and the return or load side lead to the
lower terminal, unless normal service conditions, manufacturer’s recommendations, or other IEEE Std C37.41
clauses require that the connections be reversed or that the device be mounted horizontally. For generalpurpose and full-range current-limiting fuses, test series 3 tests (long-time melting tests) shall use conductor
sizes as specified in Table 2, unless the manufacturer specifies a different conductor size due to the typical
application.
8
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
4.6.2 Dielectric and radio-influence test conductors
Electrical connections shall be made by a bare conductor connected to each terminal of the device being tested.
These conductors shall be the smallest size the device terminal is designed to accept. Use of other wire sizes is
acceptable if it can be demonstrated that this size does not affect the test results.
4.6.3 Temperature-rise and time-current test conductors
Electrical connections shall be made by a bare conductor connected to each terminal of the device being tested.
These conductors shall be of the size and length specified in Table 2. For fuses connected in parallel, the
current rating to be considered is the total current assigned by the manufacturer.
4.7 Mounting and grounding of the device for tests
4.7.1 General
Devices shall be mounted in the normal service position(s) recommended by the manufacturer. Where more
than one service position exists, the orientation that results in the most onerous duty shall be used. When
grounding of a particular part of the device is required during the test, the ground lead(s) shall be of a
sufficient size so that it can adequately carry any anticipated current for the expected duration of current flow.
If detection of the ground current is desired, then current-metering devices may be used. Specific mounting
and grounding information for the various devices to be tested is described in 4.7.2 through 4.7.7.2.
Table 2 —Size and length of bare conductor for specified tests
Rated continuous cur r ent of fuse cutout, switch, or fuse suppor t (A)
Distr ibution enclosed, open, and open-link
cutouts when tested as a:
Distr ibution
enclosed air
switch
Power fuse
and
distr ibution
cur r entlimiting fuse
Fuse cutout
Disconnecting cutout
50
—
—
Up to 50
—
100
—
—
100
—
—
100
—
200
—
—
200
—
200
200
—
—
—
300
—
—
300
400
600
300
400
—
Size of leads
No. 6 AWG
Solid
No. 2 AWG
Stranded
No. 1 AWG
Stranded
No. 2/0 AWG
Stranded
No. 4/0 AWG
Stranded
250 kcmil
400 kcmil
600 kcmil
Size and length of bar e
copper leads
Minimum length
m
(in)
1.2
(48)
1.2
(48)
1.2
(48)
1.2
(48)
1.2
(48)
1.2
1.2
1.2
(48)
(48)
(48)
4.7.2 Distribution class expulsion type fuses, cutouts, and distribution class expulsion type
fuse disconnecting switches
Crossarm-mounted, distribution class, expulsion type fuses, cutouts, and fuse disconnecting switches shall be
mounted on a wood crossarm that measures 9 cm × 11 cm (3½ in × 4½ in) in cross section. The device
mounting bracket shall be grounded by a lead attached to the mounting bracket on the side of the crossarm
opposite the device. Devices designed for other types of mounting arrangements shall be mounted in their
normal service positions, and the mounting structures shall be grounded.
9
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
4.7.3 Distribution class enclosed single-pole air switches
Distribution class enclosed single-pole air switches shall be mounted on a wood crossarm that measures
9 cm × 11 cm (3½ in × 4½ in) in cross section. The mounting bracket shall be grounded by a lead attached to it
on the side of the crossarm opposite the switch.
4.7.4 Power class expulsion fuses, power class current-limiting fuses, and power class fuse
disconnecting switches
Power class expulsion fuses, power class current-limiting fuses, and power class fuse disconnecting switches,
shall be mounted on a rigid structure. The base shall be grounded.
4.7.5 Distribution class current-limiting fuses and fuse disconnecting switches
Distribution class current-limiting fuses and fuse disconnecting switches shall be mounted on a rigid structure.
The base shall be grounded.
4.7.6 Distribution and power class fuses and fuse disconnecting switches used in FEPs
Distribution fuses, power class fuses, and fuse disconnecting switches used in FEPs shall be mounted in
accordance with the fuse manufacturer’s specifications. The enclosure and base of the device, as applicable,
shall be grounded.
4.7.7 Distribution and power class external fuses for shunt capacitors
4.7.7.1 Capacitor line fuses
Depending on the class and type of line capacitor fuse, it shall be mounted as specified in 4.7.2, 4.7.4, 4.7.5, or
4.7.6.
4.7.7.2 Capacitor unit fuses
For interrupting tests on expulsion and current-limiting capacitor unit fuses that automatically provide an
isolating gap after operation, the fuses shall be mounted in the same manner as they would be used in a
capacitor bank. An energized fuse shall be placed on each side of the fuse under test, in the normal service
position, to determine that any expulsion gas or part movement does not reduce clearances or dielectric
properties that might cause flashovers and, as such, cause operation of these adjacent fuses.
Current-limiting fuses not having a disconnect or isolating feature may be mounted in any convenient manner.
For temperature-rise tests, the mounting configuration shall simulate the capacitor bank configuration where
the fuse is to be used and shall be such that it does not restrict or promote heat transfer in a manner different
from service conditions.
10
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
5. Dielectric tests
5.1 General
Dielectric test procedures shall be as specified in Clause 4 and as described in Clause 5.
Dielectric tests are performed to determine the power-frequency dry and wet dielectric withstand voltages, and
withstand voltages, from an energized part to adjacent energized or grounded parts. They are performed to test
a device’s dielectric properties from terminal to terminal (open gap) or from terminals to parts that may be
grounded in service. This standard does not cover dielectric testing across a blown (or unblown) fuse of any
type, or across a fuseholder without a fuse link installed, since no meaningful or useful data can be obtained
with such tests.
Any test of this type must be performed on the fuse in its mounting. The test should be configured so that the
electrical stress on the fuse and mounting, which is created by mechanical structures of the mount, the spatial
relationship between other phases, and sources of voltage and grounds, match the electrical stress that the
device under test will experience in use. The manufacturer of the device under test should detail any
restrictions on the location of any adjacent structures or ground. Any test summary or report should detail the
locations of these associated parts.
Dielectric tests for unit type capacitor fuses are dependent on the capacitor bank configuration and design and
cannot be assigned to the fuse itself.
5.2 Measurement of test voltages
The voltage for dielectric tests shall be measured and corrected for standard conditions in accordance with
IEEE Std 4-1995.
5.3 Description of power-frequency dry-withstand voltage tests
5.3.1 Application of test voltage
The test voltage specified, with appropriate atmospheric corrections, shall be applied to the device for
1 min.
Seventy-five percent of the rated dry-withstand voltage may be applied in one step and then gradually raised to
the required value in not less than 5 s and not more than 30 s.
5.3.2 Acceptance criteria
There shall be no flashover or damage to the insulating material.
NOTE—The terminal-to-terminal (open gap) required dielectric withstand values for some devices are 10% higher than
those from terminal to ground. However, successful completion of these gap tests does not ensure that a device, when
open, will flashover to ground instead of across the open gap.
11
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
5.4 Description of power-frequency wet-withstand voltage tests on outdoor devices
5.4.1 Application of test voltage
The test voltage specified, with appropriate atmospheric corrections, shall be applied to the device per IEEE
Std 4-1995. Corrections for relative humidity shall not be made on wet-withstand tests. Seventy-five percent of
the rated wet-withstand voltage may be applied in one step and then gradually raised to the required value in
not less than 5 s and not more than 30 s.
5.4.2 Application of test precipitation
Precipitation shall be applied per IEEE Std 4-1995. Due to long field experience, the conventional procedure,
practice in the United States for precipitation conditions, is acceptable for devices tested according to this
standard. If testing per this procedure, the water shall be projected downward toward the front of the device
and at an angle of 45º from the vertical, so that the spray strikes equally on the front and on one sidewall of the
device. The standard test procedure defined by IEEE Std 4-1995 is also fully acceptable for the purposes of
meeting this standard, at the manufacturer’s option.
5.4.3 Acceptance criteria
There shall be no flashover or damage to the insulating material.
5.5 Description of power-frequency dew-withstand voltage tests on indoor devices
5.5.1 Dew test procedure
The insulation of the device shall be thoroughly cleaned. The cleaned device shall be placed in a cold chamber
(refrigerator) having a temperature of –10 ºC to –15 ºC until it is thoroughly cooled (may take
10 h to 12 h). The device shall then be mounted in a test chamber having a normal temperature of 22 ºC to
25 ºC and a humidity of approximately 100%. When the device is completely covered with dew, the test
voltage as specified in 5.5.2 shall be immediately applied.
5.5.2 Application of test voltage
The test voltage specified, with appropriate atmospheric corrections, shall be applied to the device for 10 s.
Corrections for relative humidity shall not be made on dew-withstand tests. Seventy-five percent of the rated
dew-withstand voltage may be applied in one step and then gradually raised to the required value in not less
than 5 s and not more than 30 s.
5.5.3 Acceptance criteria
There shall be no flashover or damage to the insulating material.
5.6 Description of impulse withstand voltage tests
5.6.1 Impulse test voltage wave shape
The wave shape and application of the 1.2/50 μs full-wave test voltage is described in IEEE Std 4-1995 and
shall have the following limits for design tests.
12
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
The impulse test wave shall have a virtual front time less than or equal to 1.2 μs, a crest voltage greater than or
equal to the rated full-wave impulse withstand voltage, and a time, from initiation, of at least 50 μs for the
voltage to fall to 50% of the crest value.
It may be noted that in the event that laboratory limitations are encountered due to the capacitance of the test
device, the maximum rise achievable may be used if it is mutually acceptable to the user and the manufacturer.
5.6.2 Polarity of voltage for impulse withstand tests
The device being tested shall be capable of passing this test with voltages of both positive and negative
polarity. Where there is evidence that one polarity (usually the positive) will consistently produce lower
withstand voltages on this or similar equipment, it is acceptable to test using only that polarity.
5.6.3 Application of test voltage
Three consecutive impulses of the test voltage specified, with appropriate atmospheric corrections, shall be
applied to the device.
5.6.4 Acceptance criteria
If no disruptive discharge occurs during any of the three consecutive impulses, then the device has passed the
test. If more than one disruptive discharge occurs, then the device has failed the test. If one disruptive
discharge occurs, then nine additional impulses of the test voltage specified are applied, and if no disruptive
discharge occurs, then the device has passed the test. If failure occurs in a non-self-restoring part of the
insulation, then the device has failed the test.
NOTE—The terminal-to-terminal (open gap) required dielectric withstand values for some devices are 10% higher than
those from terminal to ground. However, successful completion of these gap tests does not ensure that a device, when
open, will flashover to ground instead of across the open gap.
5.7 Distribution class expulsion type fuses, cutouts, and fuse disconnecting switch
test connections and test values
5.7.1 Test conductor arrangement
The bare wires shall project horizontally, at least 30 cm (12 in) from the terminals in a straight line
approximately parallel to the face of the crossarm or steel structure, and in such a manner as to not decrease
the withstand value. Any necessary bends may be made at the terminals. For enclosed cutouts, the bare wires
shall be located approximately in the center of the entrance holes.
5.7.2 Terminal-to-ground tests
For terminal-to-ground tests, the fuse holder, including the conducting element (fuse link or equivalent), shall
be in the closed position. The test lead connection shall be made to one of the wires projecting from the
terminals. The fuse mounting bracket shall be grounded.
5.7.3 Terminal-to-terminal tests
For terminal-to-terminal tests, the fuse holder, including the conducting element (fuse link or equivalent), shall
be in the open position. The test lead connection shall be made to the wire projecting from the upper terminal.
The ground test lead connection shall be made to the wire projecting from the lower terminal. The mounting
bracket shall not be grounded.
5.7.4 Dielectric test values
13
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
The preferred dielectric test values for distribution open, enclosed, and open-link cutouts and fuses are listed in
ANSI C37.42.
5.8 Distribution class enclosed single-pole air switch test connections and test
values
5.8.1 Test conductor arrangement
The bare wires shall project horizontally at least 30 cm (12 in) from the terminals in a straight line
approximately parallel to the face of the crossarm or steel structure, and in such a manner as to not decrease
the withstand value. Any necessary bends may be made at the terminals.
5.8.2 Terminal-to-ground tests
For terminal-to-ground tests, the switch blade shall be in the closed position. The test lead connection shall be
made to one of the wires projecting from the terminals. The frame of the switch shall be grounded.
5.8.3 Terminal-to-terminal tests
For terminal-to-terminal tests, the switch blade shall be in the open position. The test lead connection shall be
made to the wire projecting from the upper terminal. The ground test lead connection shall be made to the wire
projecting from the lower terminal. The frame of the switch shall not be grounded.
5.8.4 Dielectric test values
The preferred dielectric test values for distribution enclosed single-pole air switches are listed in
IEEE Std C37.45.
5.9 Power class expulsion fuses, power class current-limiting fuses, and power class
fuse disconnecting switch test connections and test values
5.9.1 Test conductor arrangement
The conductors shall project from the terminals of the fuse in (substantially) a straight line parallel to the fuse
unit or fuse holder for an unsupported distance of at least the break distance of the fuse.
5.9.2 Terminal-to-ground tests
For terminal-to-ground tests, the fuse unit or fuse holder, including the conducting element (fuse link or
equivalent), or the disconnecting switch blade, shall be in the closed position. The test lead connection shall be
made to one of the wires projecting from the terminals. The base shall be grounded.
5.9.3 Terminal-to-terminal tests
For terminal-to-terminal tests, the fuse unit, fuse holder, or switch blade shall be in one of the following
positions:
a)
For fuse disconnecting switches, the fuse unit, fuse holder, or switch blade in the fully open
position
b) For dropout power fuses, with the fuse holder or fuse unit in the dropout position
c)
For non-dropout power fuses, with the fuse holder or fuse unit removed from the support
14
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
The high-voltage test lead shall be connected to the wire protruding from the upper terminal, and the ground
lead shall be attached to the wire projecting from the lower terminal. The base shall not be grounded.
A power fuse or fuse disconnecting switch rated 72.5 kV and above shall be equipped with standard strength
insulator units; one or more insulator units identical to those supporting the current-carrying parts shall be
added to each of the insulator supports or columns (only for the test).
A power fuse or fuse disconnecting switch rated 48.3 kV or below shall be mounted with its base insulated
from a grounded metal structure by means of insulator units identical to those assembled on the fuse. In the
case of a rear-connected indoor power fuse bus, support insulators of equivalent electrical characteristics shall
be used to support the base (only for the test).
5.9.4 Dielectric test values
The preferred dielectric test values for all types of indoor and outdoor power fuses are listed in
ANSI C37.46.
5.10 Distribution class current-limiting fuse and fuse disconnecting switch test
connections and test values
5.10.1 Test conductor arrangement
The conductors shall project from the terminals of the fuse in substantially a straight line parallel to the fuse
unit or fuse holder for an unsupported distance of at least the break distance of the fuse.
5.10.2 Terminal-to-ground tests
For terminal-to-ground tests, the fuse unit or fuse holder, including the conducting element (fuse link or
equivalent), or the disconnecting switch blade, shall be in the closed position. The test lead connection shall be
made to one of the wires projecting from the terminals. The base shall be grounded.
5.10.3 Terminal-to-terminal tests
For terminal-to-terminal tests, the fuse unit, fuse holder, or switch blade shall be in one of the following
positions:
a)
For fuse disconnecting switches, the fuse unit, fuse holder, or switch blade in the fully open
position
b) For dropout current-limiting fuses, with the fuse holder or fuse unit in the dropout position
c)
For non-dropout current-limiting fuses, with the fuse holder or the fuse unit removed from the
support
The high-voltage test lead shall be connected to the wire protruding from the upper terminal, and the ground
lead shall be attached to the wire projecting from the lower terminal. The base shall not be grounded.
5.10.4 Dielectric test values
The preferred dielectric test values for distribution current-limiting fuses are listed in ANSI C37.47.
15
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
5.11 Distribution class, power class expulsion and current-limiting type fuses, and
fuse disconnecting switches used in FEPs
5.11.1 General
When distribution class and power class expulsion or current-limiting type fuses are used in FEPs, dielectric
testing of the complete FEP is required.
5.11.2 Arrangement
All fuses and other apparatus in the enclosure shall be mounted in their normal locations; the conductors shall
be in their normal positions and of the size normally used in that enclosure. If the enclosure uses liquid or a gas
other than air for the insulating medium, then it should be filled in accordance with the manufacturer’s
specifications.
5.11.3 Terminal-to-ground tests
a)
For terminal-to-ground tests, the fuse unit(s), fuse holder(s), or the disconnecting blade(s) shall be
in the closed position.
b) Where a fuse link, fuse unit, or refill unit is required to complete the electrical circuit, it may be of
any convenient size.
c)
The base and the enclosure, if applicable, shall be grounded.
d) For multipole devices, all poles shall be tested. They may be energized simultaneously or
separately (one at a time).
e)
For devices that can be opened with a part left inserted and hanging in the opened position, an
additional test shall be performed. For this test, energize the appropriate terminal(s) that will
energize the part(s) that is (are) hanging in the open position. Condition b) through condition d) are
applicable for this test.
5.11.4 Terminal-to-terminal tests
a)
For terminal-to-terminal tests, the fuse unit, fuse holder, or disconnecting blade shall be in one of
the following positions:
1) For fuse disconnecting switches, the fuse unit, fuse holder, or disconnecting blade in the
fully open position
2) For dropout-type fuses, with the fuse unit or fuse holder in the dropout position
3) For non-dropout-type fuses, with the fuse unit or fuse holder removed from the support
b) Where a fuse link, fuse unit, or refill unit is required to complete the electrical circuit, it may be of
any convenient size.
c)
The base or the enclosure, if applicable, shall not be grounded. It may be necessary to insulate the
enclosure from ground when the open gap dielectric value exceeds the terminal-to-ground value.
d) For multipole devices, all poles may be energized simultaneously.
16
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
e)
The terminal(s) to be energized are as follows:
1) Incoming terminal(s) with outgoing terminal(s) grounded
2) Outgoing terminal(s) with incoming terminal(s) grounded
If the device is completely symmetrical, only test 1) is required.
5.11.5 Closed-position, pole-to-pole (phase-to-phase) tests for multipole devices
a)
For pole-to-pole closed-position tests, the fuse unit(s), fuse holder(s), or disconnecting blade(s)
shall be in the closed position.
b) Where a fuse link, fuse unit, or refill unit is required to complete the electrical circuit, it may be of
any convenient size.
c)
The base and the enclosure, if applicable, shall not be grounded. It may be necessary to insulate the
enclosure from ground when the pole-to-pole dielectric value exceeds the terminal-to-ground value.
d) One pole at a time shall be energized with all other poles grounded. For three-pole devices, if the
outer poles are symmetrical with respect to the center pole, then testing of only one outer pole and
the center pole is required.
5.11.6 Open-position, pole-to-pole (phase-to-phase) tests for multipole devices
a)
For pole-to-pole open-position tests, the fuse unit, fuse holder, or disconnecting blade shall be in
one of the following positions:
1) For fuse disconnecting switches, in the fully open position
2) For dropout-type fuses, with the fuse unit or fuse holder in the dropout position
3) For non-dropout-type fuses, with the fuse unit or fuse holder removed from the support
b) Where a fuse link, fuse unit, or refill unit is required to complete the electrical circuit, it may be of
any convenient size.
c)
The base and the enclosure, if applicable, shall not be grounded. It may be necessary to insulate the
enclosure from ground when the pole-to-pole dielectric value exceeds the terminal-to-ground value.
d) Taking one pole at a time, each end shall be energized separately, with all other poles on that end
grounded. For three-pole devices, if the outer poles are symmetrical with respect to the center pole,
then testing each end of only one outer pole and each end of the center pole is required.
5.11.7 Dielectric test values
The preferred terminal-to-ground, terminal-to-terminal, and pole-to-pole test values for all types of power class
fuses are specified in ANSI C37.46.
The preferred terminal-to-ground, terminal-to-terminal, and pole-to-pole test values for all types of distribution
class current-limiting fuses are specified in ANSI C37.47. For all distribution class expulsion type fuses, the
values are specified in ANSI C37.42.
17
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
5.12 Distribution and power class external fuses for shunt capacitors
5.12.1 Capacitor line fuses
Capacitor line fuses shall be tested per the requirements for the appropriate equipment, as specified in 5.7, 5.9,
5.10, or 5.11.
5.12.2 Capacitor unit fuses
Capacitor unit fuses are normally mounted on the bus of the capacitor bank, or sometimes on one of the
bushings of the capacitor. The dielectric strength of the system is determined by the insulation level of the bus
of the capacitor bank, the capacitor bushing, and/or the way the fuse is positioned in the system. The dielectric
strength of a capacitor unit fuse cannot be evaluated without consideration of the mounting arrangement.
6. Interrupting tests
6.1 Procedures common to all interrupting tests
6.1.1 General
Interrupting test procedures shall be as specified in Clause 4 and as described in Clause 6.
6.1.2 Test circuit
6.1.2.1 Test circuit configuration
The interrupting tests shall be made using a single-phase, alternating-current circuit. The circuit elements used
to control the current and X/R ratio shall be in series with each other and the fuse. The testing circuit frequency
shall be the rated frequency ±2 Hz. If 60 Hz test facilities are not available, then tests at
50 Hz ± 2 Hz
are acceptable for verifying 60 Hz ratings. Note that 50 Hz tests may produce lower peak let-through currents
but may let through more I2t than 60 Hz tests.
The parameters of the test circuits and other testing information are specified in Table 6 through Table 20 and
the associated clauses. The current applied to a tested device is specified as a prospective or test current. These
current parameters given in Table 6, Table 7, Table 8, Table 11, Table 14, Table 17,
Table 19, and Table 20 are expressed in symmetrical amperes. However, the test circuit will provide a
symmetrical or associated asymmetrical short-circuit current, depending on the making angle, as required by
the appropriate table. Where an asymmetrical current is produced, it shall be equal to or greater than the
asymmetrical current associated with the symmetrical current and X/R ratio specified in the appropriate table
(see Figure C.1). If tests are made at an X/R ratio higher than is specified in the appropriate table, then the test
duty may be more severe, because the prospective asymmetrical current will be equal to or greater than the
asymmetrical current associated with the symmetrical current and specified X/R ratio. However, it is not
permissible to decrease the prospective symmetrical current to achieve the proper asymmetrical current value.
Typical test circuits are shown in Figure D.1. Methods of determining transient recovery voltage (TRV)
parameters are also shown in Annex D. Overvoltage protective equipment used for protecting test circuit
apparatus shall not significantly affect the current through the fuse or the recovery voltage across the fuse.
18
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.1.2.2 Determination of the X/R ratio and the prospective or test current of the test circuit
6.1.2.2.1 X/R and prospective current for short-duration tests
To determine the X/R ratio and prospective short-circuit current of the test circuit, the device to be tested shall
be replaced or bypassed in the test circuit with a connection having negligible impedance, thereby creating a
“bolted fault” condition.
Where the interrupting tests involve short melting times (i.e., less than or equal to 1.5 cycles), both the X/R
ratio and the prospective symmetrical short-circuit current may be determined as follows.
To determine the symmetrical short-circuit current, power shall be applied at the point on the voltage wave that
minimizes the offset in the first loop (i.e., power should be applied at an angle approximately equal to the
value of the arctan [X/R] with respect to voltage zero, where X/R is the estimated X/R ratio of the test circuit).
The symmetrical current may be calculated in accordance with Figure A.1. The root-mean-square (rms) current
should be measured during the first cycle of current.
To determine the X/R of the circuit, an asymmetrical prospective current is required. X/R can then be obtained
from the ratio of the peak asymmetrical current (of a fully asymmetrical current) to the rms symmetrical
current, using Figure C.1, or by appropriate equivalent digital analysis.
6.1.2.2.2 X/R and test current for long-duration tests
Where the interrupting tests involve long melting times (i.e., greater than 1.5 cycles), it may be appropriate to
use alternate methods to determine the circuit X/R ratio and test current.
For these tests, the test current may be taken as the prospective current (measured per 6.1.2.2.1) if the melting
time is still quite short or the rms value of the current measured immediately prior to the initiation of arcing.
The reason for measuring the actual circuit current during the test rather than the prospective current (i.e., with
the test device replaced by a link of negligible impedance) is that heating of circuit components or other factors
may result in a lower actual current at device melting than the current measured during a practical-duration
bolted fault current test.
It should be noted that when the alternate test method for test series 3 tests on current-limiting fuses is used
(6.6.2), the “melting time” for determining the X/R and test current is from the time when the high-voltage
current starts to flow to the time when the fuse melts. If the fuse begins to arc immediately (i.e., the elements
have melted before changeover occurs), then the current shall be taken as the prospective current (see
6.1.2.2.1).
6.1.2.3 Application of test power
The device shall be tested in the circuit described in 6.1.2.1 and 6.1.2.2, with the negligible impedance
connection removed. Power shall be applied at a point on the voltage wave that produces the conditions
specified in the appropriate table covering the particular device being tested.
6.1.2.4 Recovery voltage
After current interruption, the power-frequency recovery voltage shall be maintained across an open device for
the duration specified in Table 6, Table 7, Table 8, Table 11, Table 14, Table 17, and Table 19. Where test
station limitations make it difficult for the full value of recovery voltage to be maintained for specified
durations longer than 10 s, the test circuit may be switched to an auxiliary source. Such changeover shall not
be made until a time of at least 10 s has elapsed from current interruption. Any necessary circuit interruption to
19
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
effect this changeover shall not exceed 0.2 s duration. The auxiliary source shall be capable of supplying a
current of at least 1 A, while maintaining the specified recovery voltage, for the remainder of the specified
duration. Any breakdown of the fuse during this voltage-holding period (i.e., an increase in leakage current
through the fuse to 1 A or more) shall be considered an unsuccessful fuse interruption. Current monitoring may
be by any convenient method. One acceptable method is to set the tripping level of a circuit breaker, used to
protect the auxiliary source, to approximately 1 A.
If additional resistance and/or reactance is switched into the test circuit after device interruption to monitor
leakage current and/or reduce the severity of effects resulting from a device failure during the voltage
maintenance period, such switching may occur at any convenient time after current interruption, providing
there is no interruption in the recovery voltage. If there is an interruption, switching shall not occur before 10 s
has elapsed from current interruption, and any necessary circuit interruption to effect this changeover shall not
exceed 0.2 s duration. If impedance is added to the circuit after current interruption, the voltage across the
tested device must be monitored and must remain above the device’s rated maximum voltage for the recovery
voltage period.
6.1.3 Acceptance criteria
The condition of the device after interrupting tests shall be as specified in 4.5.
6.2 Interrupting tests on a homogeneous series of expulsion type fuses
6.2.1 Information common to all devices
6.2.1.1 General information
The types of devices that are covered by 6.2 are devices that use replaceable components such as fuse links,
fuse units, or fuse refill units. The devices that use replaceable fuse links are distribution class fuses, fuse
cutouts, liquid immersed fuses, some types of power class fuses, and some types of expulsion type capacitor
fuses. The devices that use replaceable refill units or replaceable fuse units are some types of power class fuses
and some types of capacitor fuses. All of these devices are fuses, so for brevity, if the text covers all of these
devices in a particular category(s), the term “fuse” will be used except when the information relates to a
specific device.
The performance of the whole device is a function of the interaction of reusable and replaceable components,
and the performance tests specified in this standard cover the specific combinations of components tested.
Successful performance of other combinations cannot necessarily be implied from these tests, so it is important
that the specific components tested be noted (for example in test reports).
When a group of fuse current ratings meet the requirements of a homogeneous series, as defined in this
standard, homogeneous series testing requires that only certain ratings be tested to qualify all other ratings in
the series. This is particularly significant in the case of expulsion fuses that use replaceable links, since the
variety of links that can be used in a particular fuse can be very large. Although protective performance of
certain specific combinations of a fuse and fuse link can only be assured by the testing performed on this
combination, use of the homogeneous rules as specified in the text, tables, and table notes of this standard can
significantly reduce the necessity for performing, what could be, a prohibitively large number of tests. It
should be noted that, while some fuse links may have mechanical interchangeability as defined in ANSI
C37.42, only by a knowledge of the homogeneous requirements and the testing that has been performed can a
manufacturer determine whether a particular fuse link is suitable for use in a particular device.
Distribution class fuses or power fuses that differ in design from those previously tested only in their insulators
(to increase or decrease their dielectric properties) may require testing but only at the high current levels
(above the 400 A to 500 A test) specified in the table.
20
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
It should be noted that interrupting tests alone do not qualify that a device is suitable for field service. Other
tests specified in this standard, plus other tests deemed necessary by a manufacturer to ensure proper field
performance, may be required.
6.2.1.2 Devices that use replaceable fuse links
For devices that use replaceable fuse links, testing as specified in this standard is normally performed by the
manufacturer of the fuse, using their own replaceable fuse link or other fuse links that they accept as being
satisfactory for use in their device. Additionally, when a fuse consists of a fuse support and a fuseholder that
uses replaceable fuse links, the same manufacturer usually makes both. However there are some cases where
the manufacturer of replaceable fuse links will wish to demonstrate the suitability of such links for use in
another manufacturer’s fuse. Such testing is done solely by the link manufacturer, who has total responsibility
for the performance of that fuse link and fuse combination. Changes to the fuse or the replaceable fuse link
may require retesting, as specified in 3.1. If changes to a fuse are made that could affect the performance of a
link, the user, when informed of these changes, shall inform the link manufacturer of such changes. It is then
the responsibility of the fuse link manufacturer to assess the impact of the changes on the overall performance
of the combination, and to perform such additional testing as is necessary to demonstrate that the new
combination is satisfactory.
Again, these performance tests cover the specific combinations used, and successful performance of other
combinations cannot be implied from the tests. However, after the specified testing and with certain other
limited testing and/or examination of the relevant fuse links, the manufacturer of a fuse may be able to
determine:
 Whether other types of fuse links made by them, or a different manufacturer, are acceptable for use
in their device (i.e., fuse links not type “K” and “T”)
 Whether another manufacturer’s fuse links are acceptable for use in their device (of the same type
e.g., ”K” or “T”)
 Whether the tested fuse links are acceptable for use in other devices they manufacture
The manufacturer of a fuse listed in 6.2.1 may use the following characteristics for qualifying fuse links for
these situations:
a)
They use the same materials and construction techniques as the tested K and T fuse links.
b) The element mass is equal to or greater than the minimum fuse link of the homogeneous series
tested and equal to or less than the maximum fuse link of the homogeneous series tested.
c)
The number of conductors used to complete the electrical circuit between the fusible element and
the remaining parts of the device shall be the same as used in the tested fuse links. In addition, the
cross section shall be the same as the tested links.
d) The distance between the element’s attachment points is equal to or more than 0.75 times the
shortest element attachment spacing of the K and T link series tested and is equal to or less than
1.33 times the longest element attachment points spacing tested.
e)
The speed ratio of the other type of link(s) falls somewhere within the K and T boundaries
specified in ANSI C37.42.
If these conditions are not met, the fuse links need to be tested in the particular fuse.
Fuses that use replaceable fuse links work as a system in which the main bore of the fuseholder interrupts the
higher currents and the fuse link’s tube interrupts the lower currents. The specified test series may need to be
augmented by additional tests to prove correct operation in the region(s) of current where the interrupting duty
is transferred from one interrupting mechanism to another. Because fuse designs differ widely, specifying test
requirements applicable to all designs is not possible. However, the general criterion to be observed is to test in
the region where the low current interrupter sees a maximum interrupting current, and the high current
21
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
interrupter sees a minimum interrupting current. The interrupting mechanisms shall be shown to operate
correctly to effect proper interruption within this transitional current region. For many fuse links 50 A and less,
the maximum current for the fuse link may be the 400 A to 500 A test specified. For other link sizes and fuse
links designed for special applications, the maximum current may be considerably higher.
Devices that use replaceable fuse links shall be capable of operating with the lowest current rated fuse link that
is recommended for use in the fuseholder. Frequently, laboratory limitations do not allow very small fuse links
to be tested to the requirements of this standard, and a 6 K fuse link will normally prove to be adequate to
demonstrate the satisfactory performance of fuses with fuse links having lower current ratings. Other testing
and checks of the fuse links construction may be used to verify the ability of these small fuse links to operate
properly and interrupt the circuit.
6.2.1.3 Devices that use replaceable fuse units or refill units
For devices that use replaceable components such as fuse units or refill units, testing as specified in this
standard is normally performed by the manufacturer of the fuse, using their own replaceable components or
other replaceable components that they accept as being satisfactory for use in their device. Additionally, when
a fuse consists of a fuse support and a fuseholder that uses replaceable components, the same manufacturer
usually makes both. However, there are some cases where the manufacturer of replaceable components will
wish to demonstrate the suitability of such components for use in another manufacturer’s fuse. Such testing is
done solely by the component manufacturer, who has total responsibility for the performance of that
component and fuse combination. Changes to the fuse or the replaceable component may require retesting. If
changes to a fuse are made that could affect the performance of a component, then the user, when informed of
these changes, shall inform the component manufacturer of such changes. It is the responsibility of the
component manufacturer to assess the impact of the changes on the overall performance of the combination
and to perform such additional testing as is necessary to demonstrate that the new combination is satisfactory.
Again, these performance tests cover the specific combinations used, and the successful performance of other
combinations cannot be implied from the tests. However, after the specified testing and with certain other
limited testing and/or examination of the relevant fuse components, the manufacturer of a fuse may be able to
determine:
 Whether other types of components made by them or a different manufacturer are acceptable for
use in their device (i.e., other types of fuse units or refill units)
 Whether another manufacturer’s components are acceptable for use in their device
 Whether the tested components are acceptable for use in other devices they manufacture
The manufacturer of the fuse devices listed in 6.2.1 may use the following characteristics for qualifying fuse
units and refill units for these situations:
a)
They use the same materials and construction techniques as the tested fuse units or refill units.
b) The element mass is equal to or greater than the smallest fuse of the homogeneous series tested and
equal to or less than the maximum fuse of the homogeneous series tested.
c)
The number of conductors used to complete the electrical circuit between the fusible element and
the remaining parts of the device shall be the same as used in the tested components. In addition,
the cross section shall be the same as the tested components.
d) The distance between the element’s attachment points is equal to or more than 0.75 times the
shortest element attachment spacing of the smallest component tested and is equal to or less than
1.33 times the longest element attachment points spacing tested.
If these conditions are not met, then the fuse units or refill units need to be tested in the particular fuse.
22
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.2.2 Testing requirements
Testing performed in accordance with 6.4, 6.5, and 6.8, if appropriate, shall be made in accordance with the
rules for a homogeneous series as specified in 6.2.3 and 6.2.4 and the appropriate table notes. Table 3 covers
devices that use replaceable fuse links originally intended for use in fuse cutouts but that are now also used in
other types of fuses. In a homogeneous series of expulsion type fuses, interrupting tests on a fuse that uses
these fuse links need only to be made in accordance with Table 3. Tests for liquid-submerged expulsion fuses
need only to be made in accordance with Table 4, and tests for power fuses that use replaceable refill units or
replaceable fuse units need only to be made in accordance with Table 5.
6.2.3 Rules for determining a homogeneous series for devices that use replaceable fuse links
6.2.3.1 Homogeneous series compliance
These devices are considered as forming a homogeneous series when their characteristics comply with the
following:
a)
Fuse links shall be made by the same manufacturer.
b) Rated voltage, rated interrupting current, and frequency shall be the same.
c)
All materials used in the devices shall be the same, except that different sized fuses or fuse links
may use different element diameters and lengths for the fusible element, and the leader or leaders
may be different (a leader is a flexible conductor used to complete the electrical circuit between the
fusible element section and the conductor’s termination on the fuse, or fuseholder). However, the
winding techniques for this(these) leader(s) shall be the same.
d) The bore diameter and length of the areas that facilitate the high current-interrupting process for the
fuse or fuseholder shall be the same. All other dimensions of the fuse, or fuseholder, shall be the
same.
e)
All materials used in the fusible element designs shall be of the same type. Fuse links with different
element designs or construction techniques require additional testing.
f)
Any mechanical means that aids in the arc interruption process must be the same.
When determining compliance with the properties of a device for homogeneous series, any strain wire that is
connected in parallel with the fuse element in order to relieve it of tensile strain can be ignored if the strain
wire is sized, and of a material, such that it carries a negligible amount of current at the fuse’s rated current.
6.2.3.2 Fuse link sizes to be used for testing these devices
Experience has shown that for distribution fuses, fuse cutouts, and power class fuses, which use replaceable
links as specified in Table 3, testing using a homogeneous series defined as follows will demonstrate the
suitability of all K and T ratings smaller than the maximums listed:
a)
The minimum current rating of fuse links for 50 A and 100 A rated fuses, fuse cutouts, and power
fuses is a 6 K fuse link, and for 200 A rated devices, it is a 140 K fuse link.
b) The maximum current rating of fuse links for 50 A rated devices is a 50 T fuse link, for 100 A rated
devices it is a 100 T fuse link, and for 200 A rated it is a 200 T fuse link.
The manufacturers of distribution class fuses or power fuses that do not produce K and T links may qualify
their device with another manufacturer’s K and T links or by using other types of fuse links they do
manufacture and testing the smallest fastest link they make and the largest slowest link they make that use the
same construction techniques as typical of most K and T fuse links. If the link sizes used do not correspond to
the current ratings specified (e.g., 6 A and 100 A links for a 100 A fuse), then the fuse sizes used shall be noted
in the test report and the manufacturer’s literature.
23
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Other types of links, having significantly different designs and ratings than the specified K and T links, may
require additional testing, as agreed upon between the user and the manufacturer.
6.2.3.3 Fuse sizes to be used for testing liquid-submerged expulsion fuses
Experience has shown that for the liquid-submerged expulsion fuses specified in Table 4, testing using a
homogeneous series defined as follows will demonstrate the suitability of all ratings smaller than the
maximum tested. Furthermore, for liquid-submerged expulsion fuses that use replaceable fuse links, the testing
will show that other types of links than those tested are suitable for use, providing they are produced by the
same manufacturer, and the only difference between the tested links and the other types is the diameter and
length of the element. Only the fuse manufacturer can determine whether another manufacturer’s fuse link is
suitable for their device (see 6.2.1):
a)
The minimum current rating of fuse, or fuse and fuse link, for testing at test series 1 and 2 is the
smallest fuse link produced by the manufacturer.
b) The maximum current rating of fuse, or fuse and fuse link, for testing at test series 1 is the largest
fuse link produced by the manufacturer.
Table 3 —Homogeneous series test requirements for expulsion fuses that use replaceable fuse
links
Type of fuse
Single-voltage rated
distribution class fuses
and fuse cutouts
Slant-voltage rated
distribution class fuses
and fuse cutouts
a
C37.41
Test table
number
Table 7
Table 8
Power class fuses
Table 11
Capacitor line fuses—
a
inductive currents
Table 7
Table 8
Table 11
Capacitor line fuses—
capacitive currents
Capacitor unit fuses—
a
inductive currents
Capacitor unit fuses—
capacitive currents
Table 19
Table 7
Table 11
Table 19
Test series
1,2,3
Fuse units to be tested
Minimum current
Maximum current
rating
rating
X
X
4,5
X
1,2,3,6
X
4,5
X
1,2,3,4
X
5,6
X
1 ,2 ,3
1,2,3,6
1,2,3,4
X
X
X
X
X
X
X
X
3,
4
1,2,3
1,2,3,4
1,
2
See 6.10.2 for devices requiring this test.
24
Copyright © 2009 IEEE. All rights reserved.
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X
X
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 4 —Homogeneous series test requirements for liquid-submerged expulsion fuses
Type of fuse
C37.41
Test table number
Liquid-submerged expulsion
fuses
Table 17
Test
series
Fuse units to be tested
Minimum current
Maximum current
rating
rating
1
X
2
X
X
6.2.4 Rules for determining a homogeneous series for devices that use a replaceable refill
unit or a replaceable fuse unit
6.2.4.1 Homogeneous series compliance
These types of devices normally have the higher current-interrupting areas and the lower current-interrupting
areas contained within the fuse, fuseholder, or the refill unit. For these tests, power fuses are considered as
forming a homogeneous series when their characteristics comply with the following:
a)
All components shall be made by the same manufacturer.
b) Rated voltage, rated interrupting current, and frequency shall be the same. All materials used in the
devices shall be the same, except that different current rated devices may use different diameters
and lengths for the fusible element.
c)
The conductors used to complete the electrical circuit between the fusible element and the
remaining parts of the device shall be the same number as the device tested. In addition, the cross
section shall be the same as the device tested.
d) All materials and dimensions of components involved in the interrupting process shall be the same.
e)
Any mechanical means that aids in the arc interruption process must be the same.
6.2.4.2 Fuse sizes to be used for devices that have a replaceable refill unit or a replaceable
fuse unit
These devices have either an integral element within the fuse unit or have a replaceable fuse refill unit within
the fuseholder. Experience has shown that for the types of power fuses that use replaceable fuse units or
replaceable refill units as specified in Table 5, testing using a homogeneous series defined as follows will
demonstrate the suitability of all ratings smaller than the maximum:
a)
The minimum current rating of fuse, or fuse with a refill unit, for testing at test series 1 through 6 is
the smallest fuse or fuse refill unit produced by the manufacturer.
b) The maximum current rating of fuse, or fuse with refill unit, for testing at test series 1 through 4 is
the largest fuse or refill unit produced by the manufacturer.
When a group of fuses have been tested using the homogeneous series rules, additional units that vary in only
certain aspects from the tested design (for example, in a fuse employing separate high current and low current
mechanisms, where one is different but the other is not) may not require a full series of tests. In this case, for
example, a fuse may be part of one homogeneous series for test series 1 through 4, and a different
homogeneous series for tests 5 and 6.
25
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 5 —Homogeneous series test requirements for power class expulsion fuses that use
replaceable fuse units or replaceable refill units
Type of fuse
Power class fuses
a
Capacitor line fuses—
a
inductive currents
Capacitor line fuses—
capacitive currents
C37.41
test table
number
Test series
Fuse units to be tested
Minimum current
Maximum current
rating
rating
1, 2, 3, 4
X
5, 6
X
Table 11
1, 2, 3, 4
X
X
Table 19
3, 4
X
X
Table 11
X
See 6.10.3 for devices requiring this test.
6.3 Description of interrupting tests on distribution class open-link cutouts
Tests shall be made at the rated maximum voltage in accordance with Table 6. A description of the required
test series is as follows:
 Test series 1: Verification of fuse operation with prospective currents equal to its rated interrupting
current.
 Test series 2: Verification of fuse operation with small overload currents.
6.4 Description of interrupting tests on distribution class fuse cutouts (open and
enclosed) (except current-limiting fuses)
6.4.1 Test series for single-voltage-rated fuse cutouts
Tests shall be made at the rated maximum voltage in accordance with Table 7. Fuses that form a part of a
homogeneous series require only the interrupting tests as specified in 6.2 and associated Table 3. A description
of the required test series is as follows:
 Test series 1: Verification of fuse operation with prospective currents equal to its rated interrupting
current.
 Test series 2: Verification of fuse operation with the prospective currents ranging from 70% to 80%
of its rated interrupting current.
 Test series 3: Verification of fuse operation with prospective currents ranging from 20% to 30% of
its rated interrupting current.
 Test series 4: Verification of fuse operation with prospective currents in the range of 400 A to
500 A.
 Test series 5: Verification of fuse operation with small overload currents.
26
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 6 —Interrupting performance tests and test circuit parameters for distribution class openlink cutouts
Parameters
1a
Test series
2a
Power-frequency recovery voltage
Rated maximum voltage: +5%, −0%
TRV
—
See Footnote b
Prospective (available) current—
c
From 2.7 to 3.3 times fuse link rating
Rated interrupting current +5%, −0%
rms symmetrical
X/R ratio (power factor)
Not less than 1.33 (not more than 0.60)
From 0.75 to 1.33 (from 0.80 to 0.60)
Making angle related to voltage
Random timing
zero—degrees
A lumped capacitance not exceeding
Allowable shunt capacitance
—
0.65 µF may be shunted across the fuse.
Current rating of fuse link
Maxd
Mind
Mind
Number of tests
3
3
2
e
3
3
2
Number of tests on each cutout
Duration of power-frequency
Not less than 0.5 s
recovery voltage after interruption
a
Prior to 1999, a sufficient number of tests were to be made at maximum rated voltage to satisfy the interrupting requirements, using
the X/R ratio and allowable shunt capacitance values that are given in the table for test series 1. Based on current understanding, the
additional tests represent the minimum requirements for adequate testing of a new device that does not have the benefit of extensive
field experience.
b
The TRV for this test circuit shall be critically damped. Shunting the load reactance with a resistance having a value equal to
approximately 40 times the value of the reactance is usually adequate to critically damp the circuit. However, if this value does not
result in critical damping, the resistance may be reduced to achieve critical damping. For testing convenience, an oscillatory TRV
may be acceptable with the agreement of the manufacturer. Critical damping is obtained when
R=
where
c
fo
X
2 fn
fo is the natural frequency of the test circuit without damping
fn is the power frequency
X is the reactance of the circuit at power frequency
If the test involves a melting time appreciably higher than 2 s, then the current may be increased to obtain a melting time of
approximately 2 s.
d
The minimum fuse link rating is 6 K, and the maximum fuse link rating is 50 T; if not available, any available 6 A and 50 A fuse link
is acceptable.
e
After each test, only the parts that are normally field replaceable shall be replaced.
27
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 7 —Interrupting performance tests and test circuit parameters for single-voltage-rated
distribution class fuse cutouts (except current-limiting fuses and open-link cutouts)
Parameters
Power-frequency recovery
voltage
TRV
Prospective or test
current—rms symmetrical
X/R ratio (power factor)
Making angle related to
voltage zero—degrees
e
Fuse link rating
Number of tests required
with above fuse link ratingf
Number of tests required on
each fuseholder and fuse
supportf
Number of fuseholders to
be testedf
Number of fuse supports to
be testedf
Duration of
Dropout
power
fuses
frequency
recovery
Nondropout
voltage after
fuses
interruption
a
2
4
5
Rated maximum voltage: +5%, −0%
See Footnote a
See Table 9, column 1
See Table 9,
column 3
Rated interrupting From 70% to 80% From 20% to 30% From 400 A to
c
current +5%,
rated interrupting rated interrupting
500 A
b
current
current
−0%:
From 2.7 to 3.3
times fuse link
d
rating
From 1.3 to 0.75
(from 0.6 to 0.8)
See Table 10
1st test: from −5 to +15
2nd test: from 85 to 105
3rd test: from 130 to 150
Min
Max
Min
Max
From 85 to 105
Random timing
Min
Max
Min
Min
1
1
2
2
3
3
3
3
3
3
3
3
2
4
1
1
1
1
1
1
1
1
1
1
1
1
Not less than 0.5 s
Not less than 0.5 s
The TRV for this test circuit shall be critically damped. Shunting the load reactance with a resistance having a value equal to approximately
40 times the value of the reactance is usually adequate to damp the circuit critically. However, if this value does not result in critical damping,
then the resistance may be reduced to achieve critical damping. For testing convenience, an oscillatory TRV may be acceptable with the
agreement of the manufacturer. Critical damping is obtained when
R=
where
b
1
Test series
3
fo
X
2 fn
fo is the natural frequency of the test circuit without damping
fn is the power frequency
X is the reactance of the circuit at power frequency
For cutouts with an interrupting rating of 2.8 kA or less, test series 3 need not be made.
For cutouts rated at 200 A, test series 4 need not be made.
d
If the test involves a melting time appreciably higher than 2 s, the current may be increased to obtain a melting time of approximately 2 s.
e
“Min” and “max” represent the minimum and maximum rated currents of a homogeneous series; see 6.2.
f
A fuse cutout support [fuse base] shall be capable, at a minimum, of the number of tests listed as “Number of tests required on each
fuseholder and its fuse support.” For test series 1, this represents three tests with the minimum fuse link rating using one fuseholder and
support, and three tests with the maximum fuse link rating using another fuseholder and support. The same quantities would be used for test
series 2, whereas for test series 3, one fuse holder and its support would be used for the two required tests. For test series 4 and 5, the same
fuseholder and support is used for the four required tests. Only the manufacturer has the discretion to permit a fuseholder, or cutout support to
be used for more than the specified number of individual tests.
After each test on a fuseholder that uses replaceable links, only the fuse link and the expendable cap, if used, may be replaced. Only the
manufacturer has the discretion to use an expendable cap for more than one test if it is determined that the cap was not damaged during a
previous test.
If the fuse element is an integral part of the fuseholder, then the number of fuseholders to be tested is the number listed for “Number of tests
required on each fuseholder and fuse support.”
The mounting brackets used for the cutout testing should be as specified in ANSI C37.42. Any deviation from this specification shall be noted
in the test report for the device.
c
28
Copyright © 2009 IEEE. All rights reserved.
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.4.2 Test series for slant-voltage-rated (multiple-voltage-rated) fuse cutouts (example: 15/27
kV)
Tests shall be made at the rated maximum voltages specified and in accordance with Table 8. Fuses that form a
part of a homogeneous series require only the interrupting tests as specified in 6.2 and associated Table 3. A
description of the required test series is as follows:
 Test series 1: Verification of fuse operation with prospective currents equal to its rated interrupting
current and conducted at its maximum voltage to the left of the slant.
 Test series 2: Verification of fuse operation with prospective currents ranging from 70% to 80% of
its rated interrupting current and conducted at its maximum voltage to the left of the slant.
 Test series 3: Verification of fuse operation with prospective currents ranging from 20% to 30% of
its rated interrupting current and conducted at its maximum voltage to the right of the slant.
 Test series 4: Verification of fuse operation with prospective currents in the range of 400 A to 500
A and conducted at its maximum voltage to the right of the slant.
 Test series 5: Verification of fuse operation with small overload currents and conducted at its
maximum voltage to the right of the slant.
 Test series 6: Verification of fuse operation of two fuse cutouts in electrical series connection with
prospective currents equal to the rated interrupting current of both series devices and conducted at
its maximum rated voltage to the right of the slant.
29
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 8 —Interrupting performance tests and test circuit parameters for slant-voltage-rated
(multiple-voltage-rated) distribution class fuse cutouts
Parameters
1
2
3
Test series
4
5
6
a
Power-frequency recovery Rated maximum voltage to the
Rated maximum voltage to the right of the slant +5%, −0%
voltage
left of the slant +5%, −0%
Transient recovery voltage
See Table 9, See Table 9,
See Table 9,
b
See Table 9, column 1
See Note
(TRV)
column 2
column 4
column 2
Prospective or test
Rated
From 70% to From 20% to
From 2.7 to
current— rms symmetrical interrupting
30% rated
From 400 A
Rated interrupting
80% rated
d 3.3 times fuse
interrupting
current +5%, −0%
current +5%,
interrupting
to 500 A
e
link rating
c
−0%
current
current
X/R ratio (power factor)
From 1.3 to
See Table 10
0.75 (from
See Table 10
0.6 to 0.8)
Making angle related to
1st test: from −5 to +15
1st test: from −5 to +15
voltage zero—degrees
2nd test: from 85 to 105
2nd test: from 85 to 105
Random timing
From 85 to 105
3rd test: from 130 to 150
3rd test: from 130 to 150
f
g
g
Min
Max
Fuse link rating
Max,
Min
Max
Min
Max
Min
Min
Min,
Number of tests required
3
3
3
3
1
1
2
2
3
3
h
with above fuselink rating
Number of tests required
on each fuseholder and
3
3
3
3
2
4
3
3
h
fuse support
Number of fuseholders to
1
1
1
1
1
1
1
1
h
be tested
Number of fuse supports to
1
1
1
1
1
1
1
1
h
be tested
Duration of
Dropout
Not less than 0.5 s
powerfuses
frequency
recovery
Non-dropout
Not less than 0.5 s
voltage after
fuses
interruption
a
b
Test series 6 uses two identically rated cutouts in electrical series connection. Test-circuit ground must not be between the cutouts.
The TRV for this test circuit shall be critically damped. Shunting the load reactance with a resistance having a value equal to approximately 40times the value of the reactance is usually adequate to critically damp the circuit. However, if this value does not result in critical damping, the
resistance may be reduced to achieve critical damping. For testing convenience, an oscillatory TRV may be acceptable with the agreement of the
manufacturer. Critical damping is obtained when:
R=
where
c
fo
X
2 fn
fo is the natural frequency of the test circuit without damping
fn is the power frequency
X is the reactance of the circuit at power frequency
For cutouts with an interrupting rating of 2.8 kA or less, Test Series 3 need not be made.
For cutouts rated 200 A, Test Series 4 need not be made.
e
If the test involves a melting time appreciably higher than 2 s, the current may be increased to obtain a melting time of approximately 2 s.
f
“Min” and “max” represent the minimum and maximum rated currents of a homogeneous series, see 6.2.
g
Use same fuse link rating in both cutouts.
d
30
Copyright © 2009 IEEE. All rights reserved.
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
h
A fuse cutout support [fuse base] shall be capable, at a minimum, of the number of tests listed as “Number of tests required on each fuseholder and
its fuse support”. For test series 1, this represents three tests with the minimum fuse link rating using one fuseholder and support, and three tests with
the maximum fuse link rating using another fuseholder and support. The same quantities would be used for test series 2, while for test series 3, one
fuse holder and its support would be used for the two required tests. For test series 4 and 5, the same fuseholder and support is used for the four
required tests. Only the manufacturer has the discretion to permit a fuseholder, or cutout support, to be used for more than the specified number of
individual tests.
After each test on a fuseholder that uses replaceable links, only the fuse link and the expendable cap, if used, may be replaced. Only the
manufacturer has the discretion to use an expendable cap for more than one test, if it is determined that the cap was not damaged during a previous
test.
If the fuse element is an integral part of the fuseholder, the number of fuseholders to be tested is the number listed for “Number of tests required
on each fuseholder and fuse support.”
The mounting brackets used for the cutout testing should be as specified in Std. C37.42. Any deviation from this specification shall be noted in the
test report for the device.
Table 9 —Inherent TRV test circuit parameters for distribution class fuse cutouts, liquidsubmerged expulsion fuses, and distribution class capacitor line fuses
Rated maximum
voltage (kV)
Column 1
Column 2
Column 3
Column 4
Applicable test tables and test series
Table 7, test series 1, Table 8, test series 3 Table 7, test series 4 Table 8, test series 4
2, and 3
and test series 6
Table 8, test series 1
and 2
SingleSlantvoltagevoltage- Table 17, test series 1
Table 19, test series 3
rated
rated
and 4
devices
devices
Frequency Peak Frequency Peak Frequency Peak Frequency Peak
a
(f) (kHz) factora (f) (kHz) factora (f) (kHz) factora (f) (kHz)
factor
+10%,
+10%,
+10%,
+10%,
+10%,
+10%,
+10%,
+10%,
–0%
–0%
–0%
–0%
–0%
–0%
–0%
–0%
2.6–2.8
—
6.1
1.3
—
—
37.0
1.45
—
—
5.2–5.5
—
4.3
1.3
—
—
37.0
1.45
—
—
7.8–8.3
7.8/15.0–
3.3
1.3
2.3
1.3
31.0
1.55
24.0
1.60
8.3/15.5
15.0–15.5 15.0/ 27.0–
2.3
1.3
1.7
1.3
24.0
1.60
15.0
1.60
15.5/27.0
22.0–27.0 27.0/38.0
1.7
1.3
1.5
1.3
15.0
1.60
10.0
1.60
38.0
—
1.5
1.3
—
—
10.0
1.60
—
—
a
Peak factor =
(
first TRV peak in kV
)
(
2 × power frequency recovery voltage in kV × sin arctan X/R
)
X/R is the value from Table 7, Table 8, Table 17, or Table 19.
Peak factor should be determined based on symmetrical current.
TRV envelope is a (1– cos) shape, with time-to-peak (in microseconds) =
1000
2 f in kHz
RRRV = Average rate of rise of the (transient) recovery voltage (in volts/microseconds)
=
first TRV peak
time to peak
= 2 2 (power-frequency recovery voltage in kV) × [sin (arctan X/R)] × (peak factor) × (f in kHz)
31
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 10 —Minimum X/R ratios for distribution class fuse cutout interrupting tests (except
current-limiting fuses and open-link cutouts)
Rated maximum voltage (kV)
Single-voltage-rated
cutouts
Slant-voltage-rated
cutouts
2.6–2.8
—
5.2–5.5
—
7.8–8.3
—
15.0–15.5
7.8/15.0–8.3/15.5
22.0–27.0
15.0/27.0–15.5/27
38.0
27.0/38.0
Table 7, test series 1, 2, and 3
Table 8, test series 1, 2, 3, and 6
Rated interrupting
current—
Minimum X/R
symmetrical rms
amperes
5
≤ 16000
≤ 12500
5
≤ 10000
> 10000
≤ 7100
> 7100
≤ 2500
> 2500
≤ 10000
8
12
8
12
8
12
15
Table 7 and Table 8,
test series 4
Minimum X/R
1.5
1.5
1.8
2.4
3.7
5.1
6.5 Description of interrupting tests on power class fuses and fuse disconnecting
switches (except current-limiting fuses and liquid-submerged expulsion fuses)
6.5.1 General
Tests shall be made at the voltages specified and in accordance with Table 11. Power fuses that form a part of
a homogeneous series are tested as specified in 6.2 and associated Table 3 or Table 5. A description of the
required test series is as follows:
 Test series 1: Verification of fuse operation with prospective currents equal to its rated interrupting
current and conducted at 87% of its rated maximum voltage.
 Test series 2: Verification of fuse operation with prospective currents ranging from 87% to 91% of
its rated interrupting current and conducted at its rated maximum voltage.
 Test series 3: Verification of fuse operation with prospective currents ranging from 60% to 70% of
its rated interrupting current and conducted at its rated maximum voltage.
 Test series 4: Verification of fuse operation with prospective currents ranging from 20% to 30% of
its rated interrupting current and conducted at its rated maximum voltage.
 Test series 5: Verification of fuse operation with prospective currents in the 400 A to 500 A range
and conducted at its rated maximum voltage.
 Test series 6: Verification of fuse operation with small overload currents and conducted at its rated
maximum voltage.
6.5.2 Test requirements for expulsion fuses with exhaust-control devices
Expulsion fuses can be used in an enclosure if fitted with an exhaust-control device. The exhaust-control
device must contain the gaseous by-products of the fault-interrupting event to an extent that is sufficient to
maintain dielectric integrity of the enclosure during and immediately after the fuse clears. Since fuses can be
applied in various enclosure designs, fuses with exhaust-control devices can be tested in a manner to verify the
exhaust-control device provides this required function independent of the enclosure. Expulsion fuses shall be
tested with a ground plane below the fuse when the bottom terminal of the fuse is connected to the source side
32
Copyright © 2009 IEEE. All rights reserved.
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
of the circuit. In other words, a conductive plane perpendicular to the orientation of the fuse shall be in place
below the fuse such that the potential across the fuse during the test is also applied from the bottom of the
exhaust-control device to this plane. As shown in Figure 1, this plane shall be located no further than the
minimum electrical clearance distance “R” as recommended by the fuse manufacturer.
Figure 1 —Location of ground plane for fuse fitted with exhaust-control device
33
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 11 —Interrupting performance tests and test circuit parameters for power class fuses
(except current-limiting fuses)
Test series
Parameters
Power-frequency recovery
voltage
3
87% of rated
maximum
voltage +5%,
0%
4
5
6
Rated maximum voltage +5%, 0%
See Table 12, column 1
TRV
Prospective or test
current—rms symmetrical
X/R ratio (power factor)
Making angle related to
voltage zero—degrees
Current rating of fuse link
or fuse unit
Number of tests
Number of tests on each
fuse employing refill units
or fuse linkse
Number of tests on each
nonrenewable fuse
Number of tests on each
exhaust-control device, if
applicable
Duration of
powerDropout fuses
frequency
recovery
voltage after Non-dropout
interruption fuses
a
2a
1
See Table 12, See Footnote b
column 3
Rated
From 87% to From 60% to From 20% to From 400 A to From 2.7 to 3.3
interrupting 91% rated
70% rated
30% rated
500 Ac,d
times link or
current +5%, interrupting interrupting
interrupting
fuse unit ratingd
0%
current
current
current
From 1.3 to
Not less than 15 (not greater than 0.067)
See Table 13 0.75 (from 0.6
to 0.8)
1st test: from –5 to +15
From 85 to
Random timing
2nd test: from 85 to 105
105
3rd test: from 130 to 150
Min
Max
Min
Max
Min
Max
Min
Max
Min
Min
3
3
3
3
3
3
1
1
2
2
3
3
3
3
3
3
1
1
1
1
1
1
3
3
3
3
3
3
2
1
4
1
1
2
1
4
Not less than dropout time or 0.5 s, whichever is greater
Not less than 10 minf
Not less than 1 min
If test series 1 tests are made at 100% of rated maximum voltage, then test series 2 tests need not be made.
The TRV for this test circuit shall be critically damped. Shunting the load reactance with a resistance having a value equal to
approximately 40 times the value of the reactance is usually adequate to critically damp the circuit critically. However, if this value
does not result in critical damping, then the resistance may be reduced to achieve critical damping.
For testing convenience, an oscillatory TRV may be acceptable with the agreement of the manufacturer. Critical damping is obtained
when
f
R= o X
2 fn
b
where
c
fo
fn
X
is the natural frequency of test circuit without damping
is the power frequency
is the reactance of the circuit at power frequency
If the values are lower than those of series 6, then series 5 tests need not be made.
d
If the test involves a melting time appreciably higher than 2 s, then the current may be increased to obtain a melting time of
approximately 2 s.
e
f
After each test, the refill unit or fuse link and expendable cap (if used) shall be replaced.
If leakage current through the fuse is monitored following interruption, then the recovery voltage may be removed after leakage current
has been less than 1 mA for a 2 min duration.
34
Copyright © 2009 IEEE. All rights reserved.
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 12 —TRV test circuit parameters for power class expulsion fuses, power and distribution
class current-limiting fuses, and power class capacitor line fuses
Column 1
Column 2
Column 3
Applicable test table and test series
Table 11, test series 1, 2, 3, and 4
Table 14, test series 2
Table 11, test series 5
Rated maximum
Table 14, test series 1
a
voltage (kV)
Table 19, test series 3 and 4
Peak factorb
Peak factorb
Frequency (f)
Frequency (f)
Frequency (f)
Peak factorb
(kHz) +10%, 0% + 10%, 0% (kHz) +10%, 0%
+10%, 0%
(kHz) +10%, 0%
+10%, 0%
2.8
8.5
1.4
3.3
1.5
38.0
1.45
5.1–5.5
6.0
1.4
2.7
1.5
29.0
1.55
8.3
4.7
1.4
2.3
1.5
19.0
1.65
15.0–17.2
3.2
1.4
1.8
1.5
18.0
1.65
22.0–27.0
2.1
1.4
1.3
1.5
12.0
1.65
38.0
1.6
1.4
1.1
1.5
8.0
1.65
a
For rated maximum voltages above 38 kV, the TRV parameters of the test circuit are not specified. Appropriate values may be selected by
agreement between the users and the manufacturer.
b
Peak factor =
(
first TRV peak in kV
)
(
)
2 × power frequency recovery voltage in kV × sin arctan X/R
X/R is the value from Table 11 for test series 1, 2, 3, and 4 and from Table 13 for test series 5 for expulsion type power fuses; Table 14 for
current-limiting fuses; and Table 19 for power class capacitor fuses.
Peak factor should be determined based on symmetrical current.
1000
2 f in kHz
RRRV = Average rate of rise of the (transient) recovery voltage (in volts/microseconds)
TRV envelope is a (1– cos) shape, with time-to-peak (in microseconds) =
=
first TRV peak
time to peak
= 2 2 (power-frequency recovery voltage in kV) × [sin (arctan X/R)] × (peak factor) × (f in kHz)
Table 13 —Minimum X/R ratios for test series 5 for power class fuses
(except current-limiting fuses)
Rated maximum voltage
(kV)
2.8–5.5
8.3
15.0–27
38.0–48.3
72.5–170
Minimum X/R ratio
1.5
1.8
8.0
12.0
15.0
6.6 Description of interrupting tests on current-limiting power and distribution fuses
6.6.1 Test series
Tests shall be made at the voltages specified and in accordance with Table 14. Descriptions of the required test
series are as follows.
It is not necessary to make interrupting tests on fuse units of all current ratings of a homogeneous series; see
6.6.4 for requirements to be met and tests to be performed.
35
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
 Test series 1:
a)
Current-limiting power fuses: Verification of fuse operation with prospective currents
equal to its rated interrupting current I1 and conducted at 87% of its rated maximum
voltage, and with prospective currents equal to 87% of its rated interrupting current I1 and
conducted at its rated maximum voltage. At the manufacturer’s option, these two tests can
be combined in a single test, a prospective current of I1 at rated maximum voltage, as is
done for distribution and motor-starter fuses.
b) Current-limiting distribution and motor-starter fuses: Verification of fuse operation with
prospective currents equal to its rated interrupting current I1 and conducted at its rated
maximum voltage.
 Test series 2:
Verification of fuse operation with prospective current I2 at which current initiation occurs when a
high level of energy is stored in the inductance of the circuit.
 Test series 3:
Verification of fuse operation at low current I3.
a)
For backup fuses, I3 is the rated minimum interrupting current assigned by the
manufacturer.
b) For general-purpose fuses, I3 is the current value that causes melting of the fuse in no less
than 1 h.
c)
For full-range fuses, I3 is the minimum test current. The minimum test current is a current
that is less than the minimum continuous current that causes melting of the fusible
element(s) with the fuse applied at the maximum ambient temperature specified by the
manufacturer. See 6.6.2.3 for the method of determining this current.
36
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 14 —Interrupting performance tests and test circuit parameters for current-limiting power,
distribution class, and motor-starter fuses
Parameters
Power-frequency recovery
voltage
TRV
Prospective or test current
rms symmetrical
X/R ratio (power factor)
Type of fuse
Power
Distribution and
motor starterb
Power and
distribution
Motor starterd
Power
Distribution and
motor starter
Power and motor
starter
Distribution
Power, distribution,
and motor starter
Power, distribution
and motor starter
Power, distribution,
and motor starter
Power, distribution,
and motor starter
Making angle after voltage
zero—degrees
Instantaneous current at
initiation of arcing
Initiation of arcing after
voltage zero—degrees
Duration of
Dropout
powerfuse
frequency
Nonrecovery voltage dropout
after interruption fuse
Current rating of fuse or fuse Power, distribution,
unit
and motor starter
Number of tests (see 6.6.4)
Power
Distribution and
motor starter
1
87% of rated maximum
voltage +5%, −0%
Rated maximum voltage
+5%, –0%
Test series
Rated maximum
voltage +5%, −0%
Not required
3a
See Table 12,
column 2
See Footnote c
Rated maximum voltage +5%, −0%
See Table 12, column 1
I1 +5%, −0%
I1 +5%, −0%
2
See Footnote d
87% of I1 +5%, −0%e
Not required
I2
Not less than 15 (not greater than 0.067)
Not less than 10 (not greater than 0.100)
Not applicable
0 to 20
0.85 I2 to 1.06 I2
Not applicable
I3 +0%, −10%
From 2.3 to 1.3
(From 0.4 to 0.6)
Random timing
Not applicable
For one test: from 40 to 65
Not applicable
Not applicable
For two tests: from 65 to 90f
Not less than dropout time or 1s, whichever is greater
Not less than 60 s, or 10 min h
Not less than 60 s g
See 6.6.4
3
3
3
Not required
3
3
2
2
a
Test series 3 tests verify the operation of the fuse at low currents. For the value of these currents, see 6.6.1. When test station limitations prevent the
maintenance of constant current, the tolerance on the current may be exceeded during not more than 20% of the melting time, provided that the current at
the initiation of arcing is within the tolerance specified, and the minimum time for melting of general-purpose and full-range fuses is maintained. To avoid
testing at the specified voltage for the full test period, an alternative method for test series 3 tests is specified in 6.6.2. The test method for test series 3 tests
for full-range fuses is specified in 6.6.3.
b
See item j) of 1.1.
c
The TRV for this test circuit shall be critically damped. Shunting the load reactance with a resistance having a value equal to approximately 40 times the
value of the reactance is usually adequate to critically damp the circuit. However, if this value does not result in critical damping, then the resistance may be
reduced to achieve critical damping. For testing convenience, an oscillatory TRV may be acceptable with the agreement of the manufacturer. Critical
damping is obtained when:
R=
fo
X
2 fn
where
is the natural frequency of test circuit without damping
fo
is the power frequency
fn
X
is the reactance of the circuit at power frequency
d
Because of the special application conditions for motor-starter fuses, they are tested in critically damped circuits and with a minimum of 1 min duration of
recovery voltage. Motor-starter fuses may be tested with power class TRV and power-frequency recovery voltage durations with the consent of the
manufacturer.
e
Test need not be performed if tests at the I1 level are made at 100% of rated maximum voltage.
f
Since the operating conditions can produce a wide variety of stresses on the fuse, and as the interrupting tests are intended (in principal) to produce the most
severe conditions (mainly as regards the arc energy and the thermal and mechanical stresses for this value of current), it is recognized that these conditions
will be practically obtained at least once when making the three tests indicated.
g
If series 2 tests are not made, then the duration shall be not less than that specified for a test series 2 test (see Footnote h).
h
The duration of recovery voltage shall be 10 min for the following specific cases:
Test series 2: for backup (except motor starter), general-purpose, and full-range types.
Test series 3: for general-purpose and full-range types, and backup (except motor-starter) fuses having a melting time >100 s.
These longer periods of recovery voltage duration only apply to the largest current rating of a homogeneous series.
37
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
 Series It:
Verification of operation for fuses that exhibit crossover current(s) (see 6.6.11).
In the case of fuses that incorporate different arc-quenching mechanisms within the same physical
envelope (for example, current-limiting elements and expulsion elements in series), test series 1, 2,
and 3 shall be augmented by additional tests to prove correct operation in the region(s) of current It
where the interrupting duty is transferred from one interrupting mechanism to another. Since fuse
designs differ widely, specifying precise test requirements that are applicable to all designs is not
possible. However, the general criterion to be observed is to test in the region where the low current
interrupter sees a maximum interrupting current and the high current interrupter sees a minimum
interrupting current. It is the responsibility of the fuse manufacturer to demonstrate by the It
interrupting test that the interrupting mechanisms are operating correctly to effect proper current
interruption within the transitional current region. Typical criteria used in assessing compliance
with this requirement are discussed in Annex E.
The following additional requirements may apply:
 If, when making tests in accordance with series 2, the requirements of series 1 are completely met
for one or more tests (TRV parameters excepted), then these tests need not be repeated as a part of
series 1.
 Traditionally, the I2 test condition has approximated a condition of maximum arc energy in the
tested fuse. If a particular design exhibits maximum arc energy at a significantly different current
than that meeting the I2 criteria, then additional tests should be performed at a current that
approximates the maximum arc energy.
 In very exceptional cases, the current I2 may be higher than the rated maximum interrupting current
I1. Series 1 and 2 shall then be replaced by six tests at rated maximum interrupting current with
making angles as nearly as possible equally distributed with approximately 30° between each.
[Parameters used will be those of series 2 (see Table 14) except making angle and value of
instantaneous current at initiation of arcing.]
 If during series 1 tests, it is impossible to initiate arcing as early as 65° after voltage zero, then the
requirement of one test with the initiation of arcing from 40° to 65° after voltage zero is replaced by
an additional test (making a total of three) with initiation of arcing from 65° to 90° after voltage
zero.
NOTE 1—Values of I1, I2, I3, and It are the rms values of the ac component of the current.
NOTE 2—As a guide, the value of the current I2 to comply with this requirement may be determined by one of the
following methods:
a)
From the following equation, if one test at a current 150 times the current rating or higher has been made
under symmetrical fault initiation in series 1:
I 2 = i1
i1
I1
where
I2
is prospective current for series 2
i1
is instantaneous current at instant of melting in series 1
I1
is prospective current in series 1
b) By taking between three and four times the current that corresponds to a melting time of 0.01 s on the
time/current characteristic.
38
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.6.2 Alternative test methods for series 3 tests on current-limiting fuses
6.6.2.1 General
Test series 3 may be performed using a single high-voltage source throughout the test (as in series 1 or series
2). Where melting times are long, and/or where there are limitations in test-station capability, series 3 may be
conducted as a two-part test. For the first part of the test, the current is supplied from a low-voltage source. For
the second part, which includes the interruption of the current by the fuse, the current shall be supplied from a
high-voltage source. The test circuit for the two-part test is shown in Figure 2.
R
HIGHVOLTAGE
SOURCE
TRANSFER
SWITCH
R1
XL1
FUSE
LOWVOLTAGE
SOURCE
Figure 2 —Alternative test circuit for series 3 test of current-limiting fuses
It is also permissible to perform a two-part test using a single high-voltage source where the power factor for
part of the melting period is of a lower value. In this case, the changeover to the correct power factor must
occur before arcing commences.
6.6.2.2 Circuit requirements and testing procedures for a two-part test
a)
The circuit requires a low-voltage power source that is able to cause the desired current to flow
through the fuse under test and that provides a means for holding the current constant during the
test. The value of the low-voltage current may be higher than I3 for some or all of the melting test
period, as explained in item b) and item c) of 6.6.2.3.
b) The circuit also requires a high-voltage source, as described in 6.1.2. The value of the high-voltage
current is the current I3, as defined in 6.6.1.
c)
Provision shall be made for switching either manually or automatically from the low-voltage source
to the high-voltage source at the desired instant during each test. The time interval during which the
current is interrupted shall not exceed 0.2 s. It should be noted that, at the X/R values specified for
this test, the current should have very little asymmetry when the circuit is randomly switched to the
high-voltage source. A synchronous closing switch is, therefore, not necessary for closing in the
high-voltage circuit. If the fuse manufacturer allows a higher X/R ratio than specified for the test,
then a synchronous closing switch may be necessary for controlling the symmetry of the current.
d) In general, the changeover shall take place while at least one fuse element is still carrying current.
For a multi-element fuse, this would be in the period when elements are melting successively, as
shown by step increases in the voltage developed across the fuse.
e)
With the consent of the manufacturer, it is permissible for the changeover to be delayed until all the
fuse elements (but not an indicator element, where included in the fuse design) have melted. This
procedure is of value in cases where it is difficult to detect the onset of element melting, or where
the value of melting current has to be significantly higher than the chosen value of series 3 current,
as explained in item b) and item c) of 6.6.2.3. The voltage of the LV circuit should be chosen to
minimize any arcing that could occur before the switchover to the HV circuit. In general, this will
require a circuit voltage of less than 100 V, unless the design of the fuse is such that LV arcing will
not significantly affect the HV arcing process
39
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Test method e) is held to be more onerous for the fuse than test method d). Testing to method d) is
closer to actual service conditions; therefore, if a failure occurs when method e) is used, the series 3
tests may be repeated using method d).
6.6.2.3 Value of melting current for series 3 tests
a)
For tests on backup fuses where the melting time is less than 1 h, the low-voltage source shall be
set to the value I3 and maintained at this value throughout the test.
b) For general-purpose fuses where a minimum time to melt of 1 h is required, the current of the lowvoltage source shall be set to I3, but it may be increased after 1 h by up to 1.15 times I3 to induce
melting.
c)
For full-range fuses, I3 shall be determined using 6.6.3.1. The low-voltage source may be set to a
value higher than I3 throughout the test in order to avoid an unnecessarily long testing time,
provided the resulting melting time is not less than 1 h.
After 1 h, the low-voltage current may be increased by up to 1.15 times its original value to induce
melting.
6.6.3 Test method for series 3 tests on full-range current-limiting fuses
6.6.3.1 Method of determining the minimum test current (I3) of the fuse
This procedure may be performed by the manufacturer.
Three samples shall be used for the determination of the I3 value. Each sample is placed in a stable thermal
environment, such as a temperature-controlled oven, that is set to the maximum temperature for which the fuse
is rated by the manufacturer to have an interrupting capability (rated maximum application temperature).
Once the fuse body has reached a stable temperature, any circulating air fans must be switched OFF for the
remainder of the test. Current is then applied to the fuse. When the fuse body temperature has again stabilized,
the value of the current is increased. This process is repeated until the fuse melts open. For the purpose of this
test, temperature is defined as being stable when the temperature rise above ambient increases by less than 2%
per hour.
The increments by which the current is increased are not specified but could typically be in the range of 5% to
10%. It should be recognized that larger increases will reduce the number of steps but may result in a more
onerous test current, whereas smaller increases will yield a more accurate test current but require more testing
steps.
The highest current that each of the three fuses carried without melting is then considered. I3 is defined as 0.9
times the lowest current of these three values. The 0.9 is used to allow for manufacturing tolerances; hence, the
I3 test is then performed with a current slightly less than the lowest current that could melt a fuse when it
operates, surrounded by the maximum temperature for which it is rated by the manufacturer.
6.6.3.2 Method of performing the series 3 tests
Full-range-type fuses shall be capable of interrupting the lowest current that can produce melting when the
fuse is subjected to its rated maximum application temperature. This temperature shall be at least 40 °C. It is
necessary to ensure that the series 3 test simulates this condition to check the ability of the fuse to withstand
any high temperatures generated during operation. Test series 3 shall, therefore, be performed using the
following method.
40
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Each sample shall be placed in a stable thermal environment, such as a temperature-controlled oven, which is
set at the rated maximum application temperature of the fuse.
Once the fuse body has reached a stable temperature, any circulating air fans used shall be switched OFF for the
remainder of the test. Stability is defined as having the fuse within 2% of the oven temperature in degrees
Celsius.
A two-part interrupting test is then carried out as described in 6.6.2. The high-voltage current I3 is determined
from the thermal testing described in 6.6.3.1.
Temperatures higher than the rated maximum application temperature may be used to expedite melting, if
agreed to by the manufacturer. In all cases, the melting time shall be at least 1 h.
Physical changes in fuse components that result from long-term application and that may affect interruption
should be considered when conducting testing.
6.6.4 Interrupting tests on a homogeneous series of fuses
When a group of fuse current ratings meets the requirements of a homogeneous series, as defined in this
standard, homogeneous series testing requires that only certain ratings be tested to qualify all other ratings in
the series. Current-limiting fuses are available as fuses that have only one barrel, as two or more parallel
barrels permanently connected by the fuse manufacturer, and as fuse units (having one or more connected
barrels) that can be connected in parallel by the user in accordance with the manufacturer’s instructions. Table
15 covers single-barrel fuses and may also be used for multiple-barrel fuses permanently connected by the
manufacturer, at the manufacturer’s discretion. Table 16 covers fuses made by connecting fuse units in
parallel, usually when the user makes such a connection. However, this table can also be used for the
homogeneous testing of parallel barrels permanently connected together by the manufacturer, if this results in
less tests being necessary.
41
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 15 —Homogeneous series test requirement for single fuse units
Homogeneous series achieved by
Fuse units to be tested
A
B
C
1
X
—
X
2a
X
—
X
3
X
Xb
X
1
X
—
X
a
X
—
X
3
—
—
X
1
X
—
X
2
—
—
X
3
X
Symbols in Table 15 are defined as follows:
A fuse unit of lowest current rating
B any fuse unit of a current rating between A and C
C fuse unit of highest current rating
X shows the tests that are to be performed
n
the number of parallel fuse elements
s
cross-sectional area of each fuse element
—
X
Progressive monotonic change in n
or s, or both, with respect to rated
current
n(A) ≤ n(B) ≤ n(C)
s(A) ≤ s(B) ≤ s(C)
Constant n,
increasing s
s(A) < s(B) < s(C)
Constant s,
increasing n
n(A) < n(B) < n(C)
a
Test series
2
c
The parameters to be considered are as follows:
s(A), s(B), and s(C), the cross sections of the individual main fuse element in A, B, and C.
n(A), n(B), and n(C), the number of main fuse elements in A, B, and C.
The test current I2 for fuse units A and C will have been chosen according to the current ratings of fuse units A and C,
respectively.
b
Every rating need not be tested; however, with diminishing current ratings, a test is to be made only for the current rating at
which the number of elements is reduced.
c
The fuse unit(s) with the lowest current rating shall contain at least two main fuse elements in addition to the element, if
present, used for operating an indicator or striker.
42
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 16 —Homogeneous series test requirements for fuses using parallel fuse units
Homogeneous
series
achieved by
paralleling
multiple fuse
units
Fuse unit assembly to be tested
Test
series
A'
1
X
b
c
2
X
a
a
B
C
X
—
X
X
—
X
C'
e
f
X
3d
X
X
X
The symbols used in Table 16 are defined as follows:
y the number of parallel fuse units for a given fuse
A' fuse assembly of lowest current rating that uses the smallest number of parallel units, y(A')
C' fuse assembly of the highest current rating using the same number of parallel units as A' [i.e.,
y(C') = y(A')]
B any fuse assembly of a current rating between A' and C that has individual fuse units no larger
than those used in C'
C fuse assembly of the highest current rating, using the maximum number of parallel units, each
the same as the unit used in C'
X shows the tests that are to be performed
n the number of parallel main fuse elements in a single fuse unit
s cross-sectional area of each main fuse element in a single fuse unit
The parameters to be considered are as follows:
s(A'), s(C'), s(B), and s(C), the cross sections of the individual main fuse elements in A', C', B and
C.
n(A') n(C'), n(B), and n(C), the number of main fuse elements in A', C', B, and C'.
a
This is typically a single fuse unit, y = 1. If the smallest number of parallel fuse units have been previously tested or qualified,
as part of a homogeneous series, additional testing is unnecessary.
b
The test current I2 for fuse unit assemblies A', C', and C will have been chosen according to the current ratings of fuse units
A', C', and C, respectively.
c
If s(A') equals s(C') but n(A') < n(C'), then this test is unnecessary (see Table 15, “constant s, increasing n”).
d
e
f
For a constant s and changing n, only A' and C need be tested, provided A' has at least two main fuse elements in addition to
the element, if present, used for operating an indicator or striker.
If n(A') equals n(C') but s(A') < s(C'), then this test is unnecessary (see Table 15, “constant n, increasing s”).
Every intermediate rating need not be tested. In the case of full-range and general-purpose fuses, ratings between C' and A'
shall be tested only when the number of elements is reduced. Ratings between C and C' need not be tested, provided the
individual fuse units that make up the rating have been tested, or are covered, as part of the homogeneous series testing C'
through A'. For backup fuses, ratings between C' and A' shall be tested only when the number of elements is reduced (except
see Footnote d). When one or more fuse units have been tested or are covered as part of the homogeneous testing rules, using
more of the same fuse unit in parallel does not require additional test series 3 testing. However, in this case, the minimum
interrupting rating for the larger number of parallel fuse units cannot be claimed to be lower than the appropriately
proportioned value relative to the actual tested value [see item c) of 6.6.6].
Fuse units are considered as forming a homogeneous series when their characteristics comply with the
following:
a)
Rated voltage, interrupting current, and frequency shall be the same.
b) All materials shall be the same.
c)
All dimensions of the fuse unit shall be the same, except the cross section of the fuse elements and
the number of fuse element(s), as detailed below in item d) through item h).
d) In any fuse unit, the main fuse elements shall be identical.
e)
The laws governing the variations in the cross sections of individual fuse elements along their
length shall be the same.
f)
All variations in thickness, width, and number shall be monotonic (continually varying in the same
direction for a given direction of the same variable) with respect to rated current; thus, balancing an
increase in cross section by reducing the number of fuse elements, and vice versa, is not allowed.
43
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
g) The variation in distance, if any, between individual fuse elements and in distance, if any, between
the fuse element(s) and fuse barrel shall be monotonic with respect to the rated current.
h) A special fuse element used for an indicator or striker is exempt from item e) and item f) above;
however, this element shall be the same for all the fuse units.
i)
A fuse unit that uses more than one barrel permanently connected in parallel contains identical
elements in each barrel, except for an indicator or striker that may be in only one barrel. Individual
barrels meet the requirements a) through h).
j)
Fuses that use parallel assemblies composed of separate fuse units, where the individual fuse units
meet the requirements a) through i).
k) Fuses connected in parallel are from the same manufacturer and have the same design and rating.
l)
All parallel fuse units are mounted in their designated fuse supports or in accordance with the
manufacturer’s specifications.
It should be noted that, when the user connects fuses in parallel, it is particularly important that they be
mounted as specified by their manufacturer. Unless a fuse manufacturer has determined that the mounting
arrangement of a specific design of parallel fuses is not critical, the manufacturer shall make available to the
user instructions as to how such fuses should be connected in parallel (i.e., how they have been tested). In the
absence of specific instructions, the installation should allow for an even sharing of the current between the
fuse units; this requires equal length leads, equal resistance and inductance in the current paths, and the fuse
units should experience equivalent external magnetic fields. If a user connects fuses in parallel without the
manufacturer’s knowledge or consent, after appropriate testing as specified in this and other standards, the
manufacturer should be informed. Changes to a fuse’s design may subsequently render them unsuitable for
paralleling, without additional testing (see 3.2).
6.6.5 Interpretation of homogeneous series interrupting test results (single fuse units)
If the results of tests made according to Table 15 are successful, then any current rating of fuse units within the
homogeneous series shall be deemed to comply with the interrupting requirements of this standard. If a fuse
unit does not perform satisfactorily on one or more test series, that fuse unit shall be rejected from the
homogeneous series; however, such failure does not necessarily cause rejection of the other current ratings. It
should be noted that a particular range of current ratings in one barrel size or configuration may constitute one
homogeneous series for one test duty but two or more homogeneous series for the purpose of another test duty.
General-purpose fuse units not tested because they are within the homogeneous series are considered to have
met the requirements for being able to interrupt currents causing melting in 1 h. If the tested fuse units have
been shown to interrupt lower currents (having a longer melting time than 1 h), the rules of item a) through
item c) in the subsequent list can be used to determine the low current interrupting ability of untested units.
Full-range fuse units not tested because they are within the homogeneous series are considered to have met the
requirements for being able to interrupt any continuous current that causes them to melt at their rated
maximum application temperature.
The values of minimum interrupting current of backup fuse units not tested are determined from test series 3
tests that have been performed as follows:
a)
Constant n, increase of s: It is assumed that the melting time at I3 for fuse unit A and B is not less
than that for fuse unit C. The test in accordance with Table 15, therefore, proves that fuse units A
and B have a minimum interrupting current ascertained by reading from their time/current
characteristics the currents corresponding to the melting time given by the minimum interrupting
current of fuse unit C and its time/current characteristics.
44
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
b) Constant s, increase of n: The minimum interrupting current I3 of fuse units A and C may or may
not be the same. If they are the same, I3 is deemed to apply to fuse unit(s) B. If they are different, a
straight line is drawn through the points corresponding to the respective minimum interrupting
currents on the time/current characteristics and, plotted to a log-log scale, of fuse units A and C.
The intersection of this line and the time/current characteristics of fuse unit(s) B is(are) deemed to
define the minimum interrupting current of fuse unit(s) B.
c)
Values of the minimum interrupting current less than those derived from either item a) or
item b) shall be proved by a separate test.
6.6.6 Interpretation of homogeneous series interrupting test results of parallel fuse units
If the results of tests made according to Table 14 are successful, then any current rating of parallel fuse units
within the homogeneous series shall be deemed to comply with the interrupting requirements of this standard.
If parallel fuse units do not perform satisfactorily on one or more test series, that combination of fuse units
shall be rejected from the homogeneous series; however, such failure does not necessarily cause rejection of
the other current ratings. It should be noted that a particular range of current ratings may constitute one
homogeneous series for one test duty but two or more homogeneous series for the purpose of another test duty.
General-purpose fuse units not tested because they are within the homogeneous series are considered to have
met the requirements for being able to interrupt currents causing melting in 1 h. If the tested fuse units have
been shown to interrupt lower currents (having a longer melting time than 1 h), the rules in item a) through
item c) in the subsequent list can be used to determine the low current-interrupting ability of untested units.
Full-range fuse units not tested because they are within the homogeneous series are considered to have met the
requirements for being able to interrupt any continuous current that causes them to melt at their rated
maximum application temperature.
45
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
The values of minimum interrupting current of backup-type parallel fuse units not tested are determined from
test series 3 tests that have been performed as follows:
a)
Constant n, increase of s: It is assumed that the melting time at I3 for any fuse units having a smaller
s and the same n as fuse B that has been tested is not less than for B. The test in accordance with
Table 16, therefore, proves that such fuses have a minimum interrupting current ascertained by
reading from their time/current characteristics the currents corresponding to the melting time given
by the minimum interrupting current of fuse unit or units B tested, and its time/current
characteristics.
b) Constant s of fuse elements, but with a different number of parallel elements and fuse units: The
minimum interrupting current I3 of fuse units A' and C may or may not be the same. If they are the
same, then I3 is deemed to apply to fuse units B. If they are different, a straight line is drawn
through the points corresponding to the respective minimum interrupting currents on the
time/current characteristics, plotted to a log-log scale, of fuse units A' and C. The intersection of
this line and the time-current characteristic(s) of fuse units B is(are) deemed to define the minimum
interrupting current of fuse units B.
c)
When a minimum interrupting current (M') has been established for a particular rating of single or
multiple fuse units (number of parallel fuse units Y'), the minimum interrupting rating (M) of a
larger number Y of parallel units can be derived from
M = M' × Y/Y'
When the minimum interrupting current has been established in this manner, test series 3 testing of
the larger number of fuse units is unnecessary.
d) Values of the minimum interrupting current less than those derived from item a) through item c)
shall be proved by a separate test.
6.6.7 Overvoltages produced by current-limiting fuses
Overvoltages produced during the series 1 and 2 interrupting tests specified in 6.6.1 shall be recorded by a
cathode ray oscillograph, or other instrument, having a frequency response greater than that of the waveforms
being measured.
6.6.8 Peak let-through [cutoff] current for current-limiting fuses
The values of the peak let-through [cutoff] current obtained from the oscillograms taken during series 1
interrupting tests specified in 6.6.1 shall not exceed those specified by the fuse manufacturer.
The characteristic curve showing the relationship of peak let-through current to prospective current in the
current-limiting range shall be plotted on log-log coordinate paper with peak let-through current on the y-axis
and prospective current (rms symmetrical available) on the x-axis, so that the peak let-through current for each
rating of current-limiting fuse can be obtained.
2
6.6.9 I t characteristics for current-limiting fuses
The manufacturer shall make available values of clearing [operating] I2t and melting [pre-arcing] I2t for those
prospective currents for which the fuse exhibits a current-limiting action.
Values stated for the clearing I2t shall represent the highest values likely to be experienced in service. These
values shall refer to the test conditions of this standard, for example, the values of voltage, frequency, and
power factor.
Values stated for the melting I2t shall represent the lowest values likely to be experienced in service.
46
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
The presentation of I2t values may be in simple tabular or diagrammatic form (for example, histograms) or
may employ graphical presentation with prospective current as abscissa and I2t as ordinate, both scales being
logarithmic with preferred dimensions as in 11.1.5.
The I2t values determined as a part of the interrupting tests specified in 6.6 shall not be greater (for clearing I2t)
or less (for melting I2t) than the values stated by the manufacturer.
6.6.10 Fuses intended for use in liquid-filled enclosures
Test series 1 through 3 and It may be performed in air or in a liquid-filled enclosure. Since testing in air is held
to be more onerous, this may only be done with the agreement of the manufacturer. In the case of failure, the
relevant test series may be repeated with the fuse in a liquid-filled enclosure, using an arrangement of test
conductors suitable for that enclosure.
6.6.11 Test It for fuses that exhibit crossover current(s)
In general, tests shall be performed at a minimum of two values, It1 and It2. At least two tests shall be
performed at each test value.
and
It1 = 1.2 It (±0.05 It)
It2 = 0.8 It (±0.05 It)
where It is the value of crossover current provided by the fuse manufacturer.
If it is known that these values do not represent the most onerous conditions for the given design of fuse, then
the manufacturer may nominate other values of It1 and It2.
The parameters to be used when performing the tests, depending on the values of the crossover current It, are
as follows:
 It in the short-circuit (current-limiting) range: all test conditions as given in Table 14 as appropriate
for the test current
 It in the low overcurrent range, that is, below 12 times rated current: X/R and power-frequency
recovery voltage as specified for test series 3
 It in the intermediate current range:
Power-frequency recovery voltage = rated maximum voltage +5%, –0%
X/R (power factor):
a)
2.3 to 3.2 (0.4 to 0.3 lagging) if the crossover current It is between 12 and 25 times rated
current Ir
b) 3.2 to 4.9 (0.3 to 0.2 lagging) if the crossover current It is between 25 times rated current Ir
and I2
TRV: Specified by the fuse manufacturer, so as to represent typical values found in circuits for which the fuse
is intended as being suitable for use, based on the necessary test currents. Guidance as to appropriate values of
TRV may be obtained from test standards for other switching devices intended for use under similar
circumstances.
The tests should be performed in the current region where there is an abrupt or gradual crossover of
interrupting duty from one interrupting mechanism to another. The test current values are to be provided by the
manufacturer. The typical criteria used in assessing compliance with this requirement are discussed in Annex
E.
47
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.7 Description of interrupting tests for FEPs using current-limiting-type indoor
distribution and power class fuses
6.7.1 Use of current-limiting fuses in enclosures
Many applications require the use of current-limiting fuses in enclosures where the fuse and associated
contacts may be subjected to air temperatures above 40 ºC. Other applications may require the fuse to be
immersed in a liquid such as transformer oil hotter than 40 ºC. Current-limiting fuses intended for such
application shall comply with the applicable design tests specified in this subclause in addition to those
specified in 6.6, unless otherwise specified in 6.7.
When current-limiting fuses are applied in enclosures of any type, the performance characteristics of the total
system shall be evaluated. This evaluation of the total system shall be the responsibility of the supplier of the
FEP. The following tests and test descriptions reflect this basic requirement. (See 1.5 for descriptions of the
FEP types covered by this subclause.)
6.7.2 Fuse ambient temperatures
When a fuse intended for such an application is tested according to this subclause, it is assigned a RMAT. It is
the temperature at which these tests are performed. If the maximum temperature for a particular application is
known, then an appropriately tested fuse may be chosen (that is one having an RMAT equal to or greater than
the maximum temperature anticipated in service). It should be noted that for some applications, the RMAT
might only occur under abnormal conditions, for example, transformer overload or during equipment failure.
In such cases, although a fuse can be assigned an appropriate RMAT, it may not be suitable for continuous
operation at such a temperature without exceeding the maximum temperatures specified in Table 1 in IEEE Std
C37.40. Indeed, some typical RMAT values may be higher than the maximum temperatures specified in Table
1. (See 1.5 for descriptions of the cooling fluid to which the RMAT refers.)
6.7.3 Description of tests to be made
The following tests shall replace the tests specified in 6.6 for certain fuse ratings (generally the maximum
current rating of a homogeneous series), unless otherwise specified in this subclause.
NOTE—Generally, tests performed at a fuse’s RMAT replace the tests specified in 6.6, unless tests at a lower temperature
produce more onerous conditions for the fuse.
a)
Test series 1:
No additional tests are required
NOTE—Series 1 tests are considered unnecessary since elevated temperature test failures are generally related
to elevated component temperatures, and series 2 tests (intended to approximate maximum arc energy) are apt
to produce higher temperatures.
b) Test series 2:
For backup, general-purpose and full-range fuses, three test series 2 tests, in addition to those
specified in Table 14, shall be performed with the fuses at its RMAT. The additional tests apply
only to the largest current rating of a homogeneous series.
48
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Where the RMAT is less than 15% of the melting temperature (in degrees Celsius) of the material
that forms the current-limiting fuse element, experience has shown that more severe series 2 test
conditions will result from tests done at the RMAT for a given fuse, rather than at the ambient
temperature prevailing at the test site (used for the testing specified in 6.6.1 and Table 14). In this
case, the I2 test at the RMAT replaces the test specified in 6.6.1 for the maximum current rating of a
homogeneous series.
NOTE—When a fuse is tested at surrounding temperatures within the normal service conditions (–30 °C to 40
°C), the series 2 tests normally produce the highest fuse component temperatures seen in typical applications
(approximately maximum arc energy). If the test is performed with the fuse starting at its RMAT, I2t and arc
energy will typically be reduced slightly, because the element starts closer to its melting temperature, resulting
in a slightly lower temperature-rise for all of the fuse’s components. However, due to the higher starting
temperature, maximum final temperatures will be higher than with a test performed at normal service
conditions. Elevated temperatures can cause a fuse to fail to interrupt fault current, since the heat can reduce
the strength of cap/tube joints, carbonization of an organic based fuse body (typically an epoxy/fiberglass fuse
tube), or a dielectric breakdown of the fuse element support or the fulgurite created during the interruption
process. Therefore, a test that results in the maximum energy release at a particular starting temperature,
combined with the highest temperature for which the manufacturer rates the fuse as being suitable (RMAT), is
the most severe thermal test of fuse performance. If the melting temperature of the fuse’s element is relatively
low compared with the fuse’s RMAT, a significant reduction in melt I2t, and hence, arc energy, may result in
lower component temperatures or a much easier duty on the fuse. For this reason, testing at normal service
conditions is still required if the RMAT is more than 15% of the element melting temperature.
c)
Test series 3
 Backup fuses: For a backup fuse, if the melting time observed during test series 3 tests
specified in 6.6.1, and performed with a surrounding temperature below 40 ºC, resulted in
a melting time greater than 100 s, then two additional test series 3 tests shall be performed
with the fuse at its RMAT. These additional tests apply only to the largest current rating of
a homogeneous series that has a melting time in excess of 100 s, and the duration of
recovery voltage shall be 10 min.
 General-purpose fuses: The test current for an FEP using a general-purpose fuse shall
cause fuse melting in not less than 1 h. For tests at its RMAT, this current may require
derating. Refer to IEEE Std C37.48 for further information.
 Full-range fuses: The tests specified in 6.6, and Table 14, are performed with the fuse at
its RMAT. No additional testing is required.
6.7.4 Test procedure
Test procedures shall be as specified in 6.1, 6.6.2, 6.6.3, and as follows.
For FEP types 1CL and 3CL, the elevated temperature testing covered in 6.7 can usually be performed with the
test sample placed in a stable thermal environment, such as a temperature-controlled oven, set to the
temperature for which the fuse is rated by the manufacturer (RMAT). Once the fuse body has reached a stable
temperature, any circulating air fans used shall be switched OFF for the remainder of the test. If a fuse only
intended for use in liquid-filled enclosures is being tested, for convenience, in air (see 6.6.10), then a
circulating fan need not be switched OFF during the test.
Generally, when testing is performed according to 6.7, a fuse will not be mounted in actual equipment with
which it will be used in service (for example, when an oven is used to create the RMAT). In this case, although
the fuse should be mounted in a manner that simulates service conditions as closely as possible, it is
recognized that all aspects of its mounting (for example, grounding of components) may not fully comply with
all the requirements of Clause 4.
49
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
If a fuse required to be tested according to this subclause is intended for use in a fuse container (FEP type
2CL), it shall be tested in an appropriate small enclosure (forming an FEP) to simulate service conditions. If
the RMAT assigned to the fuse/FEP is above 40 °C, then the fuse and enclosure combination shall be mounted
in an oven or larger enclosure to permit the surrounding medium that cools the FEP (e.g., air or oil) to have a
temperature equal to or greater than the assigned RMAT. Auxiliary heating, as detailed above, may be used. In
general, an individual FEP need not be tested if the fuse it uses has been tested under equivalent, or more
severe, conditions.
When a fuse produces condensable gases (e.g., water vapor to assist in the arc interruption process), and it is
intended for use with a type 2CL FEP, two series 3 tests shall be performed on the maximum rating of a
homogeneous series, with the fuse in an appropriate fuse container, and with the temperature of the FEP
cooling fluid between 10 ºC and 40 ºC. These tests shall be in addition to any other tests specified in 6.7 and
are intended to show that any gases that could condense inside the fuse canister do not cause an electrical
breakdown during the recovery voltage period. For these tests, any part of the fuse container normally
grounded in service shall be connected to ground.
Any fuse intended for use in an FEP that is not assigned an RMAT higher than 40 ºC may have any tests
specified in 6.7 performed in a surrounding temperature of between 10 ºC and 40 ºC (that is, a fuse effectively
having an RMAT of 40 ºC can generally be tested at the prevailing ambient temperature without the need for a
heated enclosure). In the case of a full-range fuse, however, the series 3 minimum test current (see 6.6.3.1)
shall be established in an ambient temperature of 40 ºC.
6.7.5 Temperature of device after test
The FEP shall be allowed to cool naturally during the voltage withstand period.
6.7.6 Mounting and grounding of device
The tests specified shall be performed with the current-limiting fuse or FEP mounted in a manner that will
simulate the service conditions specified by the supplier of the FEP. Liquid-immersible fuses may be tested in
either air or liquid at the discretion of the manufacturer.
6.7.7 Overvoltages for current-limiting fuses in enclosures
Overvoltages produced during the series 2 interrupting tests specified in 6.6.1 shall be recorded by a cathoderay oscillograph or other instrument having a frequency response greater than that of the waveforms being
measured.
6.8 Description of interrupting tests for FEPs using liquid-submerged, expulsion type
indoor power class fuses
6.8.1 Applicable devices
Subclause 6.8 applies to expulsion fuses that are immersed in liquid and used in switchgear (not directly
associated with transformers). It is intended to provide testing requirements for such fuses in an enclosure. It is
not intended to apply to distribution oil cutouts, which are devices formally covered by this standard that are
now obsolete. (See 1.4, Type 3E, for a description of the FEP covered by this subclause.)
6.8.2 Grounding
The enclosure shall be grounded as specified by the manufacturer.
50
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.8.3 Liquid
The enclosure shall be filled with insulating liquid(s) as specified by the manufacturer. When testing liquidsubmerged fuses to verify their ratings, the liquid shall not be changed or reconditioned during the tests.
6.8.4 Condition of the device
Where parts of a tested assembly are reusable, the manufacturer’s guidelines should be followed regarding the
number and type of tests. All specified cleaning, inspection, and maintenance steps recommended by the
manufacturer shall be followed.
6.8.5 Mounting of device
The tests specified shall be performed with the device mounted in a manner that will simulate the normal
service conditions specified by the manufacturer. Liquid-submerged expulsion fuses are sometimes used in
series with current-limiting fuses. Since the objective of these tests is to determine the performance of only the
expulsion fuses, these tests should be performed without the current-limiting fuse in series. The mounting of
these type devices should simulate their normal mounting position and structure.
6.8.6 Test circuit and test series
Tests for liquid-submerged expulsion fuses used in enclosures shall be made in accordance with Table 17.
Fuses that form a part of a homogeneous series are tested as specified in 6.2 and associated Table 4. A
description of the two series of tests required is as follows:
 Test series 1: Verification of operation with available currents equal to the rated interrupting
current of the expulsion fuse.
 Test series 2: Verification of operation with small overload currents.
51
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 17 —Interrupting performance test and test circuit parameters for liquid-submerged
a
expulsion fuses used in enclosures
Parameters
Power-frequency voltage
TRV
Prospective (available) current—
rms symmetrical
X/R ratio (power factor)
Making angle after voltage zero—
degrees
Current rating of fuse link or fuse
unit
Number of testse
Duration of power-frequency
recovery voltage after interruption
Test series
1
2
Rated maximum voltage: +5%, 0%
See Table 9, column 1
See Footnote b
Rated interrupting current: +5%, 0%
2.7 to 3.3 times link or fuse-unit ratingc
Not less than 8 (not greater than 0.124)
1st test: from +5 to +15d
2nd test: from 85 to 105
3rd test: from 130 to 150
From 1.3 to 0.75 (from 0.6 to 0.8)
Random timing
Min
Max
Min
Max
3
3
2
2
Not less than 1 min
a
In some cases, these devices are designed to be used in series with a current-limiting fuse. For those devices where the currentlimiting fuse is an integral part of the device, the test should be performed without the current-limiting fuse but with a device that
simulates the size and shape of the current-limiting fuse except for its fusible element.
b
The TRV for this test circuit shall be critically damped. Shunting the load reactance with a resistance having a value equal to
approximately 40 times the value of reactance is usually adequate to critically damp the circuit. However, if this value does not result
in critical damping, then the resistance may be reduced to achieve critical damping. For testing convenience, an oscillatory TRV may
be acceptable with the agreement of the switchgear manufacturer. Critical damping is obtained when
R=
where
fo
fn
X
fo
X
2 fn
is the natural frequency of test circuit without damping
is the power frequency
is the reactance of the circuit at power frequency
c
If the test involves a melting time appreciably higher than 2 s, then the current may be increased to obtain a melting time of
approximately 2 s.
d
A phenomenon has been observed in which a wire element expulsion fuse, melting close to zero on the voltage waveform (usually a
low current rating fuse with a relatively high prospective current), produces sufficient arc voltage to cause a significant currentlimiting effect. Since this does not represent typical fuse behavior, such a test shall be repeated. Setting the minimum angle for this
test at 5 degrees is normally sufficient to prevent this phenomenon, but if necessary, a further increase in closing angle, within the
specified limits, should produce a more normal “non–current-limiting” behavior.
e
The number of tests on any one holder for devices with replaceable links should be limited to the number recommended by the
switchgear manufacturer.
6.9 Description of interrupting tests for air-insulated FEPs using expulsion type
indoor power class fuses
6.9.1 Use of expulsion fuses in enclosures
The installation of a fuse or fuse and container combination (F/C) in an enclosure results in a total system that
shall have performance capabilities suitable for the application intended. Expulsion fuses intended for this
application shall comply with the interrupting tests specified in 6.9 and the applicable tests specified in 6.5.
When expulsion fuses are applied in enclosures of any type, the performance characteristics of the total system
shall be evaluated. The following tests reflect this basic requirement. See 1.4, Types 1E and 2E, for
descriptions of the devices covered. The following tests, beyond those specified in 6.5, are conducted to
52
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
a)
Verify that the enclosure containing the fuse or F/C does not adversely affect proper performance
and servicing of the fuse or F/C
b) Verify that the operation of the fuse or F/C in an enclosure does not adversely affect the mechanical
and dielectric integrity of the enclosure
6.9.2 Test site conditions
Normal ambient temperature conditions may prevail when testing a fuse or F/C having a rated maximum
application temperature no higher than 55 °C. However, if the rated maximum application temperature is
higher than 55 °C, testing shall be performed with the fuse or F/C in its rated maximum application
temperature.
In all cases, the device shall be stabilized at the referenced ambient temperature before the test current is
applied to the fuse.
a)
For Type 1E fuses, the rated maximum application temperature is the air temperature inside the
enclosure.
b) For Type 2E fuses, the rated maximum application temperature is that of the air outside the
container.
6.9.3 Mounting and grounding of device for test
The fuse or F/C shall be mounted in the enclosure in its normal service position. The fuse or F/C
manufacturer’s guidelines for installation in an enclosure should be followed. These guidelines should present
information on the minimum required electrical clearances and the minimum construction requirements for the
enclosure. All conducting parts of the enclosure shall be grounded.
6.9.4 Test series
6.9.4.1 Single-phase devices
For fuses or F/Cs that are applied to protect only single-phase circuits, single-phase interrupting tests shall be
performed. A three-phase test is an acceptable alternative. Using a fuse link or fuse unit having a current rating
between 20 A and 50 A, the three tests of Table 11, power fuses, test series 1, shall be performed on a single
fuse or F/C. However, the single-phase circuit voltage shall be equal to the single-phase voltage rating of the
switchgear, and the TRV frequency and peak factor shall be appropriate for rated maximum line-to-line
voltage.
Use of a fuse current rating between 20 A and 50 A will result in a duty-severity representative of, or
exceeding, the result when using current ratings of a larger size.
6.9.4.2 Three-phase devices
For fuses or F/Cs that are applied to protect three-phase circuits, a three-phase interrupting test is required. In a
three-phase circuit with voltage equal to the maximum rated voltage of the fuse or F/C, and with either the
neutral of the source grounded or the three-phase fault point grounded, but not both, a current equal to the
maximum symmetrical interrupting rating of the fuse or F/C shall be applied. Fuse links or fuse units having a
current rating between 20 A and 50 A shall be used. The current-making angle shall be such as to produce a
current of maximum asymmetry in at least one of the phases. The circuit X/R and inherent transient recovery
voltage conditions specified in Table 11, power fuses, test series 1, with peak factor based on 0.87 three-phase
test voltage, shall prevail across the first phase to clear. TRV control elements may be selected by
53
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
a)
Using an ideal interrupting device to interrupt the three-phase circuit
b) Current injecting one open phase while the other two phases are closed
6.9.5 Acceptance criteria
The condition of the device after interrupting tests shall conform to 4.5, and the enclosure shall be as follows.
The enclosure shall be capable of withstanding the forces resulting from the operation of the fuse or F/C. There
shall be no operation-impairing deformation or effect on the enclosure and its doors, latches, and interlocks (if
present), and no internal components shall be affected, except the fuse and exhaust-control device.
6.10 Description of interrupting tests for external fuses for shunt capacitors
6.10.1 General
Depending on the applications intended for the device, the interrupting tests specified in Table 18 shall be
made on the device. These tests shall be performed as specified in 6.10.3, 6.10.4, and 6.10.5, as well as the
referenced tables. For all interrupting tests, records of source voltage, fuse voltage, and current through the
fuse shall be obtained. Instrumentation should be adequate such that the high frequencies involved during the
interrupting process are accurately recorded. The metering instrumentation used should not significantly affect
the recovery voltage. Appropriate metering methods will allow convenient determination, when required, of
performance parameters such as peak overvoltage, arc energy, recovery voltage, peak let-through current, and
I2t.
Table 18 —Types of interrupting performance tests required for capacitor fuses
Fuse type
Tests
Power-frequency inductive currents (see
6.10.3)
Power-frequency capacitive currents (see
6.10.4)
Capacitive-discharge currents (see
6.10.5)
a
Capacitor line fuse
Capacitor unit fuses
used where inductive
faults can occur
X
X
Capacitor unit fuses
used where inductive
faults are unlikely to
occur (see Footnote a)
—
X
X
X
See Footnote b
X
X
Examples of these applications are as follows:
1) Individual fuses in wye-connected banks with ungrounded neutral and ungrounded frames
2) Banks with series capacitors
b
Unusual applications, such as back-to-back banks on the same pole with each bank having its own line fuse could require the fuse
to be capable of interrupting capacitive discharge currents. Since the size of these banks would generally be small, most line fuses
could satisfactorily handle the discharge currents. Consult the fuse manufacturer for these types of applications.
54
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.10.2 Determination of available short-circuit current
Determination of available short-circuit current of the test circuits shall be as specified in 6.1.2.2 and 6.10.4.
6.10.3 Interrupting tests—inductive currents
All capacitor fuses that are rated for interrupting inductive currents shall be tested for inductive fault current
interrupting performance as follows:
Capacitor line fuse
Power fuses (except current limiting)
Table number and test series
Table 11: test series 1, 2, 3, and 4
Single-voltage-rated distribution cutouts
Table 7: test series: 1, 2, and 3
Slant-voltage-rated distribution cutouts
Table 8: test series 1, 2, 3, and 6
Current-limiting power and distribution fuses
Table 14: test series 1 and 2
Capacitor unit fuse
All capacitor unit fuses (except current limiting)
Table 11: test series 1, 2, 3, and 4, or Table 7: test series
1, 2, and 3
Current-limiting capacitor unit fuse
Table 14: test series 1 and 2
For the inductive current interrupting tests for capacitor unit fuses, a capacitor shall be placed in parallel with
the fuse under test. This parallel capacitor shall be sized to draw a current at the test voltage of between 25%
and 75% of the allowable continuous current of the fuse under test. The transient recovery voltage
requirements of Table 7, Table 11, and Table 14 do not apply to the tests on capacitor unit fuses when parallel
capacitors are used in the test circuit.
Capacitor unit fuses that have met the interrupting requirements when tested without parallel capacitors need
not be retested with parallel capacitors in the test circuit.
Examples of applications where inductive currents can flow are as follows:
a)
Capacitor line fuses
b) Capacitor unit fuses in delta-connected banks without capacitor units in series
c)
Capacitor unit fuses in wye-connected banks, without capacitor units in series, and with the neutral
or the frame grounded
d) Capacitor line and capacitor unit fuses, without capacitor units in series, used on single-phase
circuits
55
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.10.4 Interrupting tests—power-frequency capacitive currents
All fuses applied to protect capacitors can be called upon to interrupt power-frequency capacitive currents.
Tests shall be made in accordance with Table 19 and shall consist of the following test series:
Test type
Verification of the operation with available current equal to rated
maximum capacitive interrupting current at rated maximum voltage.
Verification of the operation with available currents equal to rated
minimum capacitive interrupting current at rated maximum voltage.
This duty simulates progressive elements (pack) failure in a capacitor
unit.
For capacitor For capacitor
unit fuses
line fuses
Test series 1
Test series 3
Test series 2
Test series 4
Examples of conditions where capacitive overcurrents can occur are as follows:
a)
Partial capacitor failure for those applications listed in 6.10.3
b) Capacitor unit or capacitor line fuses in wye-connected banks with an ungrounded neutral
c)
Banks with capacitor units in series
The test circuits and equipment arrangement for capacitive current-interrupting tests should be as follows:
 The circuit elements used to control the test circuit’s short-circuit current and X/R ratio, to the
requirements specified in Table 19 and Table 20, shall be in series with each other and the test
specimen.
 The test circuit’s source short-circuit current shall be measured per 6.1.2.2, except all circuit
capacitive loading shall also be short-circuited for this measurement.
 The test circuit’s capacitive current shall be controlled by capacitor units connected in series with
the test specimen and with the test circuit’s short-circuit control loading.
 The waveform of the current to be interrupted should, as nearly as possible, be sinusoidal. This
condition is considered to be complied with if the ratio of the rms value of the current to the rms
value of the fundamental component does not exceed 1.2.
56
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 19 —Capacitive current-interrupting performance tests and test circuit parameters for
all types of capacitor fuses
Capacitor unit fuses
Parameters
Capacitor line fuses
Test series
Test series
1
2
3
4
Rated maximum voltage: +5%, −0%
(see 6.10.6 for crest recovery voltage requirements) (See Footnote a)
Power-frequency recovery
voltage (excluding dc
voltage component)
Rated capacitive interrupting
Prospective or test
current +5%, −0%
current—rms symmetrical
X/R ratio
Source
TRV
parameters
Capacitive
current value
resulting in a
melting time of
10 s minimum
No TRV control required
Rated capacitive interrupting
current +5%, −0%
≥8
Capacitive
current value
resulting in a
melting time of
10 s minimum
Distribution class fuses, except current limiting—
see Table 9, column 1, Power class fuses and
distribution class current limiting—see Table 12,
column 1
See Table 20
Short-circuit 12.5 to 25 times rated capacitive interrupting
current
current
See 6.10.4 and figures listed below
(Where two figures are listed for a test series, the circuit used is optional.)
Test circuit
Figure 3a)
Figure 3b)
Figure 3c)
Figure 3d)
Figure 3e)
Figure 3e)
Switching angle related to From −10 to From +85 to Random timing From −10 to +10 From +85 to
+10
+105
+105
voltage zero of source—
degrees
Max
Min
Max
Min
Max
Current rating of fuse unit Min Max Min Max Min
or fuse link to be tested
(see Footnote b and
Footnote c)
3
3
3
3
2
2
3
3
3
3
Number of tests (see
Footnote d)
Number of tests on each
3
3
3
3
4
3
3
3
3
fuse holder for expulsion
type fuses (see Footnote
d)
Duration of Dropout and
Not less than dropout time or 0.5 s, whichever is greater
powerisolating-gap
frequency fuses
recovery
Non-dropout
Not less than 1 min
voltage
and nonafter
isolating-gap
interruption fuses
a
Random timing
Min
Max
2
2
4
For slant-voltage-rated cutouts, test series 3 and 4 shall be made with a test voltage at the value to the right of the slant. For example,
the test voltage for 15/27 kV rated cutouts shall be 27 kV.
b
For all types of expulsion fuses that use replaceable links, the minimum and maximum fuse links to be used for the tests are related to
the ampere rating of the fuse and the basic construction of the fuse link. For all fuses rated 50 A maximum, the minimum size link
for testing is a 6 A type K and the maximum is a 50 A type T; for fuses rated 100 A maximum, the minimum size link for testing is
a 6 A type K, and the maximum size link for tests is a 100 A type T; for fuses rated above 50 A to 100 A maximum, the minimum
size link is a 65 A type K, and the maximum is a 100 A type T; for fuses rated above l00 A to 200 A maximum, the minimum link
is a l40 A type K and the maximum link is a 200 A type T. If the construction of intermediate fuse links differs from the
construction of the minimum or maximum rated fuse links, and this difference in construction is likely to affect interruption
performance adversely, then additional testing of such ratings is required.
c
“Min” and “Max” represent the minimum and maximum rated currents of a homogeneous series, see 6.2 and 6.6.4.
d
After each test, only the parts normally field replaceable shall be replaced.
57
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
R1
XL1
CB
Ct
CS
G
S
Vs
If
Vf
F
Cp
a)
R1
XL1
CB
CS
G
Vs
Ct
S
If
Vf
F
Cp
b)
R1
XL1
CB
CS
G
Vs
Ct
S
If
Cp
Vf
F
c)
R1
G
XL1
CB
C1
R2
Ct
CS
S (Optional)
Vs
Vf I
f
F
d)
R1
G
XL1
CB
C1
R2
CS
Ct
Vs
If
F Vf
S
e)
Figure 3 —Typical circuit diagrams for capacitive current interrupting tests
58
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
NOTE 1—Definitions for Figure 3 are as follows:
C1
CB
Cp
CS
Ct
F
G
If
is the transient recovery voltage frequency control for the source
is the circuit breaker
are the capacitors corresponding to the capacitors in parallel with the failed unit
is the laboratory closing or isolating switch
are the capacitors for producing the required capacitive test current
is the fuse under test
is the power source
is the fuse current
If = Vs × 2π × (power frequency in Hz) × Ct
is the resistance to control the X/R of the source
is the damping resistance to control the peak factor of the source
is the switch for initiating the fuse operation
is the rated maximum fuse voltage (i.e., the power-frequency component of this voltage, after
the fuse interrupts the current, shall be equal to or greater than the rated maximum voltage of
the fuse)
R1
R2
S
Vf
For a) and b) in Figure 3:
 Ct
V f = ( Vs )×
 C p + Ct





For c), d), and e) in Figure 3: Vf = Vs
Vs
XL1
is the source voltage
is the inductive reactance of the source
NOTE 2—For d) and e) in Figure 3, damping circuits, other than those shown for controlling the inherent TRV parameters
of the test circuit, may be used by mutual agreement between manufacturer and test laboratory. Such use shall be noted and
explained in the test report.
NOTE 3—In circuits a), b), and c) in Figure 3, the effect of capacitance on the recovery voltage appearing across the fuse
is taken into account by Cp. This value represents between 300 kVAR and 400 kVAR. Experience has shown that the value
of Cp is not critical on the capacitive interrupting performance of fuses.
Cp shall be
C p (μF ) ≥
1000
(V f )2 (kV )
NOTE 4—For a) and d) in Figure 3, closing the switch S initiates the fuse operation, and for b), c), and e) in Figure 3,
opening the shunting switch S initiates the fuse operation. Note that closing of the switch CS may also be used to initiate
the fuse operation for the test circuit shown in d) in Figure 3.
The impedance of the shunting switch S, including the connected cable, used for the test circuits as shown in b), c), and e)
in Figure 3, should be minimized to ensure that with the switch closed, the current through the fuse does not exceed 1.5
times the current rating of the fuse, as shown on the nameplate. As an alternative, a small impedance may be connected in
series with the fuse, thereby reducing the current through the fuse and increasing the current through the parallel connected
shunting switch.
59
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Table 20 —Source short-circuit current for capacitor line fuses
a
Continuous current rating of fuse unit or
fuse link as shown on the nameplate (A)
>1 and 50
>50 and 100
>100 and 200
>200 and 300
>300
Short-circuit level of source in rms
symmetrical amperesa,b,c
1250–2500
2500–5000
5000–10 000
7500–15 000
10 000–20 000
The values for the short-circuit level have been selected based on 2% to 4% e. The e chosen is
representative of the percent voltage regulation attributed to capacitor bank installations in the field and is
estimated as follows:
%Δe ≈
I
XL
× 100 ≈ C × 100
XC
I SC
where
XL
XC
IC
ISC
is the inductive reactance of the source
is the capacitive reactance of the load
is the continuous current rating of the fuse unit or fuse link as shown on the nameplate (A)
is the symmetrical rms short-circuit current of the fault
b
Current-limiting fuses conforming to a homogeneous series should use the short-circuit current values listed
above, based on the maximum continuous current rating in the homogeneous series.
c
If the inductive interrupting current rating of the fuse is less than the values shown, use this lower value.
6.10.5 Interrupting tests—capacitor discharge
This test verifies the maximum parallel stored energy where the capacitor unit fuse will operate successfully.
After the circuit-interrupting operation, the components of the fuse (except for those intended for field
replacement) shall be substantially in the same condition as they were prior to the test. Erosion of the bore of
the fuse tubes of expulsion fuses is acceptable. Flashover to ground or adjacent fuses, emission of flame or
filler material from current-limiting fuses, or bursting of any parts is not acceptable. A minor spark or flame
from an indicating device is acceptable.
The test circuit for capacitor discharge current interrupting tests shall be as follows:
a)
The capacitance of the test circuit shall be such that the stored energy (joules) in the capacitor(s)
has the specified value at the test voltages specified below.
The capacitor(s) shall be charged by means of dc to one of the following voltages:
1.00(+10% – 0%) V f 2 for expulsion fuses
2.00(+10% – 0%) V f 2 for current-limiting fuses
where
Vf
is the rated maximum voltage of the fuse in rms volts.
At the manufacturer’s option, if the required energy cannot be achieved with the capacitors
available, then the charge voltage may be increased as necessary above the 10% allowed.
60
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
b) If an unlimited “joule rating” is claimed for the fuse, then the charge voltage may be increased such
that at the instant of interruption, the voltage remaining on the bank shall not be less than
2.0V f
2
where
Vf
c)
is the rated maximum voltage of the fuse in rms volts.
The oscillatory frequency of the test circuit shall not be less than
F = 0.8V f
where
F
Vf
is the frequency (hertz),
is the rated maximum voltage of the fuse (rms volts)
No additional inductance shall be added to the test circuit. If the test circuit conditions do not
permit the required discharge frequency to be obtained, then the actual discharge frequency
recorded during the tests shall be specified along with the maximum stored energy (joules) rating
when it is published or when the rating information is disseminated.
d) The ratio between successive current peaks (reversal) shall be between 0.8 and 0.95. This
requirement shall be determined by replacing the fuse with a shorting link of negligible impedance
compared with that of the test circuit. This calibration test may be made at a reduced voltage.
e)
For fuses that do not provide an automatic isolating gap after operation, the voltage trapped on the
capacitors shall be left on the fuse for a minimum of 10 min after the fuse operates. This may
require that the capacitors used in the test circuit be without discharge resistors.
The test procedures for capacitor discharge current interrupting tests shall be as follows:
 For current-limiting fuses belonging to a homogeneous series per 6.6.4, the fuse with the smallest
current rating in that particular series and the fuse with the largest current rating in that series shall
be tested. Any current rating of fuses within this series shall be deemed to comply with the
interrupting requirements of this standard if these units operate satisfactorily. If a fuse does not
perform satisfactorily, then it may be rejected from the homogeneous series and a new series should
be selected.
 For expulsion type fuses, the tests should be made on all fuse types where the bore of the fuse tube
and/or its length changes, and on any fuses where the materials of the fuse tube are different from
other tested devices. For fuses that use replaceable links, the tests should be made with the smallest
and the largest link that is intended to be used in the particular fuse holder. A
6 A type K link may be used for the minimum size requirement.
 Two tests are to be made on each size fuse. For expulsion type fuses, a complete new fuse shall be
used for the second test.
 The residual voltage across the capacitor(s) shall be measured immediately after discharge to
determine the amount of energy dissipated in the fuse and the circuit resistance. This residual
voltage shall be recorded in the test report.
 The “joule rating” that may be assigned to the fuse being tested is the energy stored in the capacitor
test bank prior to the time it is discharged through the fuse.
61
Copyright © 2009 IEEE. All rights reserved.
IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
6.10.6 Criteria for successful interruption tests
a)
Flashover to ground or adjacent components shall not occur during operation when the fuse is
mounted in accordance with the manufacturer’s recommendations and per 4.7.7.
b) Following the interrupting of the test current, the fuse shall be capable of withstanding the recovery
voltage of the test circuit, which may be as high as
2 × 2 ×V f
where
Vf
c)
is the rated maximum voltage of the fuse (rms volts)
After the fuse has operated, the components of the fuse (apart from those intended to be replaced
after each operation) shall be in substantially the same condition as at the beginning of the test,
except for erosion of the bore of the fuse tube of expulsion fuses. After completion of the
interrupting discharge tests, however, the components of the fuse may be damaged and require
replacement to restore the fuse to its operating condition.
7. Load-break tests
7.1 Procedures common to all load-break tests
7.1.1 General
Devices, unless they incorporate a load-breaking means, have no load-break rating. Load-break test procedures
for devices with load-breaking equipment shall be as specified in Clause 4 and in Clause 7.
7.1.2 Mounting of device
The device shall be mounted in all positions for which it is designed or for which it is recommended for loadbreak operation.
7.1.3 Test circuit
7.1.3.1 Test circuit power factor
The power factor of the test circuit shall be between 70% and 80% for lagging power factor tests and between
0% and 10% for leading power factor tests. If test laboratory limitations or special applications require a more
severe test circuit, the lagging power factor may be reduced to less than 70% upon agreement with the device’s
manufacturer. In special applications, the allowable limits for tests shall be as agreed upon by the manufacturer
and the user.
7.1.3.2 Test circuit impedance
The circuit impedance Z shall consist of two components connected in series. The first component shall not be
less than 10% or more than 20% of the total impedance of the test circuit and shall have an X/R ratio of 2 or
more. This circuit component shall have its inductive and resistive elements in series relationship. The second
component for lagging power factor tests shall consist of inductance and resistance in parallel relationship (see
62
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Figure 4). The second component for leading power factor tests shall consist of capacitance alone. When tests
are made line to ground, at least the second component of impedance shall be on the load side of the device.
XL1
R1
Z1 is > .1Z AND < .2Z
TEST
SPECIMEN
XL1 / R1 > 2
R2
XL2
Z is the total circuit impedance
a)
Typical lagging power factor test circuit
XL1
R1
Z1 is > .1Z AND < .2Z
TEST
SPECIMEN
XL1 / R1 > 2
C2
Z is the total circuit impedance
b) Typical leading power factor test circuit
Figure 4 —Test circuit for load-break tests
7.1.3.3 Test circuit capacitance
The total shunt capacitance of the test circuit (measured across the open switch) when breaking inductive loads
shall not exceed the following.
Test voltage
(kV)
2.6
5.2
7.8
15.0
18.0
27.0
38.0
Maximum capacitance (µF)
0.003
0.066
0.10
0.20
0.20
0.35
0.40
NOTE—These values apply only to devices designed for use on distribution circuits.
63
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
7.1.3.4 Power-frequency recovery voltage
The power-frequency recovery voltage across the terminals of the device shall be the rated maximum voltage
of the device.
7.1.4 Measurement of test values
7.1.4.1 Measurement of test current
The current interrupted shall be the rms symmetrical current measured from the envelope of the wave at the
start of arcing.
7.1.4.2 Calculation of test current and recovery voltage
The rms alternating test current and recovery voltage shall be determined. This may be accomplished by
following the methods described in Annex A.
7.1.5 Acceptance criteria
There shall be no failure to interrupt the circuit for any test condition, fuse link rating, and mounting position.
Tests shall be made under a sufficient number of conditions to ensure meeting the requirements specified for
the device or mechanism undergoing test.
The condition of the device at the conclusion of any series of five load-break operations for distribution
enclosed, open, or open-link cutouts, the device and the load-break mechanism, after renewing the fuse link if
destroyed in the normal load-break operation, shall be as specified in 4.5.
7.2 Description of load-break tests for all fused devices
Load-break tests shall be conducted as follows.
One or more devices with the means for interrupting load currents, or one or more load-break mechanisms
properly assembled on devices of the rating and type recommended by the manufacturer, shall be opened
manually or automatically, at an equivalent speed, when carrying the specified load current. The test shall be
repeated five times with an interval between tests of not less than 3 min.
8. Radio-influence tests
8.1 Procedures common to all radio-influence tests
8.1.1 General
Radio-influence test procedures shall be as specified in Clause 4 and in Clause 8.
Radio-influence voltage is the result of electrical stress from an energized part to adjacent energized or
grounded parts. Radio-influence voltage for a fuse by itself does not have any meaning. Any test of this type
must be performed on the fuse in its mounting. The test should be configured so that the electrical stress on the
fuse and mounting, created by mechanical structures of the mount, the spatial relationship between other
phases, and sources of voltage and grounds, match the electrical stress that the device under test will
experience in use. The manufacturer of the device under test should detail any restrictions on the location of
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
any adjacent structures or ground. Any test summary or report should detail the locations of these associated
parts.
8.1.2 Test site conditions
8.1.2.1 Ambient humidity and air density during test
Tests shall be conducted under atmospheric conditions prevailing at the time and place of the test; it is
recommended, however, that tests be avoided when the vapor pressure of moisture in the atmosphere is below
680 Pa (0.2 in Hg) or exceeds 2030 Pa (0.6 in Hg). Since the effects of humidity and air density on radioinfluence voltage are not definitely known, correction factors are not recommended at the present time. It is
recommended, however, that the barometric pressure as well as dry and wet bulb thermometer readings be
recorded so that, if suitable correction factors should be determined, they can be applied to previous
measurements.
8.1.2.2 Ambient radio-influence noise during test
Tests may be made under the conditions prevailing at the time and place of the test. It is recommended,
however, that tests be avoided when the ambient radio-influence voltage (including the influence voltage of
irrelevant electrical devices with the device under test disconnected from the test equipment) exceeds 25% of
the radio-influence voltage of the device to be tested.
8.1.2.3 Tests on fluid-immersed devices
The tanks of fluid-immersed apparatus shall be filled with the specified amount of fluid.
8.1.3 Proximity of other objects during test
No other grounded or ungrounded object or structure (except a mounting structure when required) shall be in
closer proximity to any part of the device undergoing test than three times the longest overall dimension of the
device, with a minimum permitted spacing of 0.9 m (3 ft). Where space limitations under test conditions do not
permit the above clearance to be maintained, the test will be considered valid if the limits of radio-influence
voltage obtained are equal to or less than those specified for the device. In such cases, it is desirable that a
record be made of the object, structures, and so on, as well as their distances from the device under test. These
data may be useful for future use in determining proximity effect.
These clearance guidelines apply predominately to parts used on overhead systems, where maintaining a
relatively large clearance between energized parts and grounded components controls the location of adjacent
parts. On underground circuits or within fluid-filled devices, the ground or adjacent parts may be closer to
parts of the device under test. In these cases, the manufacturer of the fuse and fuseholder shall specify the
clearances for the part under test.
8.1.4 Test conductor arrangement
The conductors shall be arranged as specified in 4.6.2. The free end of all conductors shall be terminated in a
sphere having a minimum diameter of twice the diameter of the conductor, or the free end shall be shielded in
some other suitable manner to eliminate the effect of the end of the conductor as a source of radio-influence
voltage.
8.1.5 Measurement of test values
8.1.5.1 Measurement equipment for test
The meter used for making radio-influence measurements shall be in accordance with ANSI C63.2-1987.
65
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
8.1.5.2 Measurement of test voltage impulses with low repetition rates
When making measurements on radio-influence voltage impulses with repetition rates so low that meter
fluctuation makes reading of either the minimum or the maximum pointer deflection doubtful, the slow-speed
indicating output meter listed in 16.2 of ANSI C63.2-1987 shall be used. The highest pointer deflection of the
meter during a 15 s interval of observation shall be recorded as the radio-influence voltage, so that differences
between various operators in recorded results for noise sources with low repetition rates may be minimized.
8.1.5.3 Test instrument calibration
Calibrations and adjustments of the radio noise meter shall be made as specified in the instruction manual for
the radio noise meter.
8.1.5.4 Test instrument settings
The detector function selector switch shall be set to the quasi-peak position on the radio noise meter.
8.1.5.5 Characterization of radio-influence voltage during test
When it is desired to identify the character of the radio-influence voltage, measurements should be monitored
using a headset, loudspeaker, or oscilloscope. Precautions should be taken to determine whether or not these
devices affect the radio-noise meter indications during measurements.
8.1.5.6 Precautions in taking test measurements
The following precautions shall be observed when making radio-influence tests:
a)
The device shall be at approximately the same temperature as the room in which the test is
performed. It shall be dry and clean, and it shall not have been subjected to dielectric tests within 2
h prior to the radio-influence test.
b) In some cases, it may be found that the radio-influence voltage falls off rapidly after the ratedfrequency voltage has been applied for a short time. In such cases, it is permissible to re-excite the
test piece at normal operating voltage for a period not to exceed 5 min before proceeding with the
tests.
8.1.6 Acceptance criteria
The radio-influence voltage measured in the test is the total ionization voltage at the terminals of the device.
Since this is conducted radio-influence voltage, the permissible maximum values specified for the device in the
appropriate standard (see Clause 3) will add a negligible amount to the radio-influence radiated from an
otherwise normal line to which the device is connected, even at short distances from the device.
8.2 Description of radio-influence tests on a single device
Tests at 1 MHz shall be made on the device with the fuse unit or fuse holder, including the conducting element
(fuse link) or disconnecting switch blade, in the closed and open positions. When a test is made in the open
position, the pole or group of poles not connected to the influence-measuring equipment shall be grounded and
ungrounded, and the radio-influence voltage shall be determined for each condition.
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
8.3 Description of radio-influence tests on multiple devices
In the case of multiple devices, one pole or terminal (or groups of the same) may be tested at a time following
the procedures specified in 8.2.
8.4 Description of radio-influence tests for assembled apparatus
In the case of assembled apparatus, the test shall be made without removing any component part, and the test
voltage shall be based on the lowest rated voltage of any component part. The limiting radio-influence voltage
shall be identical to the highest value specified for any of the component parts that determine the test voltage.
9. Short-time current tests
9.1 General
Short-time current test procedures shall be as specified in Clause 4 and in Clause 9. Tests consist of
momentary, 15-cycle, and 3 s tests for disconnecting cutouts, and momentary and 3 s tests for distribution class
enclosed single-pole air switches (called “air switches” in this clause for convenience).
9.2 Mounting and grounding of device for the momentary test
For distribution disconnecting cutouts only one mounting position (vertical or angle) is required for attaching
the support to the devices mounting bracket. If some of these devices do not use a mounting bracket and are
designed for other mounting arrangements that have various mounting positions only one position is required
for this test. If air switches have various mounting positions provided, only one position is required for this
test. Grounding of the mounting bracket or mounting structure of distribution class enclosed or open
disconnecting cutouts and air switches is not necessary.
9.3 Test connections
The device shall have a bare conductor connected to each terminal that has the size and minimum length
specified in Table 2. The conductors shall leave the terminals in substantially a straight line, parallel to the
blade of the device. The minimum unsupported length of these conductors shall be the open-gap distance of
the device.
9.4 Test circuit
9.4.1 Test circuit configuration
Short-time tests shall be made using a single-phase alternating current circuit. The circuit elements used to
control the current and X/R ratio shall be in series with each other and with the device being tested. The test
circuit frequency shall be the rated frequency of the device ± 2 Hz. If 60 Hz test facilities are not available,
tests at (50 ± 2) Hz are acceptable for verifying 60 Hz ratings.
The circuit for 15-cycle and/or 3 s tests shall be capable of providing the symmetrical current as specified for a
particular device in its specification standard. The X/R for these tests may be any convenient value, except as
specified in 9.4.4.
67
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
For disconnecting cutouts, the circuit for the momentary tests shall be capable of providing the symmetrical
current specified for the device’s rated 15-cycle withstand current, as listed in the appropriate table in the
device’s specification standard. The circuit X/R shall be equal to the value specified in this same table for the
device being tested (if this is not listed for the disconnecting cutout, the value for the equivalent fuse cutout
shall be used).
For air switches, the circuit for the momentary tests shall be capable of providing the symmetrical current
specified for the device’s 3 s rating and the X/R shall be as specified for that particular device.
9.4.2 Test circuit tolerances
For the manufacturer, tolerances shall be +5%, –0% for current, and where a specific X/R is required, it is a
minimum value. See 3.4.1 for test parameters for testing performed by other than the device manufacturer.
9.4.3 Test circuit voltage
The test circuit voltage may be any convenient voltage that is capable of supplying the required test currents.
9.4.4 Test circuit X/R ratio for combined tests
For convenience, the momentary test may be combined with the rated 15-cycle disconnecting cutout test, or
the rated 3 s air switch test. In this case, the momentary and the 15-cycle or 3 s requirements will be met if the
X/R ratio is a value that will provide the rated momentary current specified in 9.7, and the rated
15-cycle
or 3 s currents specified in 9.5 or 9.6.
Table 21 —Momentary (first peak) current for a specified 15-cycle or 3 s current and circuit X/R
15-cycle current
(disconnecting cutouts) or 3 s
current (air switches)
(kA rms symmetrical)
4
4
5
6.25
6.3
7.1
8
8.6
10.6
11.2
12.5
13.2
15
16
X/R
Momentary current
(peak kA)
8
12
15
25
5
8
12
8
12
5
25
12
12
5
9.46
9.97
12.7
16.5
13.7
16.7
19.9
20.3
26.4
24.4
33.0
32.8
37.3
34.8
9.4.5 Making angle
When conducting the 15-cycle and 3 s tests separately from the momentary test, the power is applied at the
point on the voltage wave that minimizes offset in the first loop of current.
For the momentary test, and for the 15-cycle or 3 s test when combined with the momentary test, the power
shall be applied at the point on the voltage wave that produces the required preferred momentary current (first
peak asymmetrical current), listed in Table 21. A making angle, related to voltage zero, from 0° to +10° and
the proper X/R will provide the asymmetrical current that has a first peak value equal to, or greater than, that
specified in Table 21.
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
9.4.6 Determination of short-time current
During testing of the circuit or the device, the currents involved shall be measured as follows.
For momentary tests, the current peak of the first major current loop shall be determined.
For 15-cycle and 3 s tests, the symmetrical current shall be determined. This may be accomplished by
following the method shown in Figure A.1.
For 3 s tests, the current value may be determined with an ammeter if the circuit characteristics are such that
there is no decay in the current values after any initial transient. If current decay does occur, an oscillograph or
equivalent metering methods should be used to determine the true rms current.
9.4.7 Determination of the circuit current
Prior to testing of the device, the circuit may be checked (if desired) for correctness and capability by using a
reduced voltage check test or, in some cases, a reduced time check test. Normal ratio methods and engineering
judgment are used to determine the voltage required for the device test. If the device has negligible impedance,
another check method is to replace the properly connected device in the test circuit with a connection having a
negligible impedance. If an alternative connection was used to check the circuit, remove it before testing the
device.
9.5 Description of 15-cycle current tests
One sample of the device shall be tested in the circuit described in 9.4. The test rms symmetrical current shall
be at least the rated 15-cycle current value during the test, with the final measurement taken at the end of the
15 cycles. The preferred values of the rated 15-cycle currents are specified in the specification standard for the
device.
9.6 Description of 3-second current tests
One sample of the device shall be tested in the circuit described in 9.4. If the integrated heating equivalent of
the 3-second rating has been obtained, the device shall be considered to have been properly tested. The tests
may also be conducted at a reduced current if the integrated heating equivalent of the 3-second rating is
obtained in a time period not exceeding 8 s. However, for momentary current tests on air switches, the full
value of the 3-second current shall be used. The preferred values of the rated 3-second currents are specified in
the specification standard for the device being tested.
9.7 Description of momentary current tests
One sample of the device shall be tested in the circuit described in 9.4. The current shall be maintained for a
minimum of three cycles.
The preferred rated momentary current is achieved when the first major current peak (peak asymmetrical
current) meets or exceeds the preferred rated momentary current value specified for the device. This is listed in
its specification standard, and in Table 21, based on a device’s preferred 15-cycle or 3-second current and X/R
ratio. Momentary tests may be combined with the 15-cycle test or 3-second test (see 9.4.4) When this is done,
the circuit shall be closed at the point on the voltage wave that will provide the required momentary current.
NOTE—Prior to the publishing of this standard, momentary currents were defined in terms of first loop rms asymmetrical
current. In common with other standards, a change has been made to redefine momentary currents in terms of the value of
the first peak of the asymmetrical waveform. Although the intention has been to change the definition of momentary
currents, it has not been intended to change the actual method of testing or, indeed, the test currents associated with the
69
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
test. It is therefore anticipated that devices tested to earlier versions of the standard will meet the requirements of this
standard.
9.8 Acceptance criteria
After successful completion of the tests, the condition of the device shall be as specified in 4.5, except the tests
may have resulted in some visual evidence of the device having passed current, such as slight contact
markings. If this occurs, ratings shall be considered met when the device will withstand repeated mechanical
operations without cumulative damage and is capable of carrying its rated continuous current as specified in
4.5.
10. Temperature-rise tests
10.1 Procedures common to all temperature-rise tests
10.1.1 General
Temperature-rise tests shall be as specified in Clause 4 and in Clause 10.
10.1.2 Test site conditions
The device shall be mounted in a closed room substantially free from air currents other than those generated by
heat from the device being tested. The ambient temperature shall be taken as that of the surrounding air, which
should not be less than 10 ºC and not more than 40 ºC. Corrections shall not be applied to any ambient
temperature within this range. The ambient temperature shall be determined by taking the average of the
readings of three thermocouples (or thermometers) placed as follows:
a)
One 30 cm (12 in) above the device
b) One 30 cm (12 in) below the device, 30 cm (12 in) above the floor, and 30 cm (12 in) to the side of
the floor-mounted apparatus
c)
One midway between the above two positions and 30 cm (12 in) from the side of the device
NOTE—For small devices, such as distribution cutouts or distribution-enclosed single-pole air switches, one thermocouple
(or thermometer) at location c) is sufficient.
10.1.3 Mounting and grounding of device
Grounding of the mounting bracket or base as specified in 4.7 is not required.
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
10.1.4 Measurement of test values
10.1.4.1 Method of determining temperature during test
The temperature of a device shall be determined by thermocouples or by mercury or alcohol thermometers.
Any of these instruments shall be applied to the hottest parts of the device, excepting the conducting element
of a fuse, while maintaining all parts in normal operating condition.
10.1.4.2 Use of oil cups
To avoid errors due to the time lag between the temperature of large devices or apparatus and the variation of
ambient temperature, all reasonable precautions must be taken to reduce these variations and the errors arising
from them.
Thus, when the ambient temperature is subject to such variations that error in the temperature-rise might result,
the thermocouples (or thermometers) for determining the ambient temperature should be immersed in a
suitable liquid such as oil, in suitably heavy metal cups, or should be attached to suitable masses of metal. A
convenient form for such an oil cup consists of a metal cylinder with a hole drilled partly through it. This hole
is filled with oil, and the thermocouple (or thermometer with its bulb) is placed therein so it is well immersed.
The response of the thermocouple (or thermometer) to various rates of temperature change will depend largely
on the size, kind of material, and mass of the containing cup, and it may be further regulated by adjusting the
amount of oil in the cup. The larger the apparatus under test, the larger should be the metal cylinder used as an
oil cup in determining the ambient temperature. The smallest size of the oil cup employed in any case shall
consist of a metal cylinder with 25 mm (1 in) diameter and 50 mm (2 in) height.
10.1.4.3 Use of thermometers
If thermometers are used for taking temperatures, the bulbs of thermometers shall be covered by felt pads
cemented to the apparatus, by oil putty, or by cotton waste. Dimensions of felt pads for use with large
apparatus shall be 40 × 50 × 3 mm thick (1½ × 2 × ⅛ in thick). The use of smaller pads is permissible on small
devices.
10.2 Description of temperature-rise tests
The test current shall be applied continuously until three consecutive temperature readings taken at 30 min
intervals show a maximum variation of 1 ºC in the temperature-rise above ambient.
10.3 Description of temperature-rise tests for air-insulated FEPs using expulsion
type indoor power class fuses
Additional rated continuous current testing shall be conducted, as specified in the “Ratings” and “Rated
continuous current” discussions in IEEE Std C37.20.3, using fuse links or fuse units of the maximum current
rating permitted by the rating of the mounting. Connecting conductors and temperature limits for buses and
connections shall be the same as specified for switches in IEEE Std C37.20.3. The reference ambient
temperature of the fuse or F/C shall also be measured and related to both the ambient temperature surrounding
the enclosure and the maximum reference ambient temperature specified by the fuse or F/C manufacturer.
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
11. Time-current tests
11.1 Procedures common to all time-current tests
11.1.1 General
Time-current test practices shall be as specified in Clause 4 and in Clause 11.
11.1.2 Mounting and grounding of device
Only one position for mounting all devices is required. Grounding of the mounting bracket or base as specified
in 4.7 is not necessary.
11.1.3 Measurement of test values
11.1.3.1 Measurement of current during tests
The measurement of current through the fuse during a time-current test shall be made as follows:
a)
A current existing for 5 s or more may be measured with a standard indicating ammeter.
b) A current of less than 5 s duration shall be measured with an oscillograph or other suitable
instrument, and the current wave (including the dc component of current and the ac decrement)
shall be corrected to steady-state conditions for plotting both melting and total clearing time curves
(see Annex B for method of correction).
NOTE—A standard ammeter equipped with an adjustable stop to reduce the movement of the needle during test will
improve the accuracy of the measurement.
11.1.3.2 Measurement of time during test
The measurement of the time shall be made as follows:
a)
A time longer than 10 s may be measured with a stopwatch, electric clock, or timer.
b) A time longer than 1 s may be measured with a synchronous timer.
c)
A time shorter than 1 s shall be measured with an oscillograph or suitable instrument.
11.1.4 Description of time-current test parameters
11.1.4.1 Initial conditions
Tests shall be initiated with the fuse at an ambient temperature of 20 °C to 30 °C and without an initial load
passing through the current-responsive element.
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
11.1.4.2 Test samples
The fuse links or fuse units shall be tested in the fuse cutout or fuse support with which they are designed to be
used.
11.1.5 Presentation of time-current test data
The results of time-current tests shall be presented as time-current curves on log-log paper (preferably with
current as abscissa and time as ordinate, and with the dimension of each decade as 5.6 cm). The curves shall
show the following:
a)
The relation between the time in seconds and the rms symmetrical amperes required either to melt
and sever the conducting element or to interrupt the circuit.
b) The basis of time on which the curves are plotted; that is, only the melting time required to melt
and sever the conducting element, or the total clearing time, which combines both melting and
arcing time.
c)
The voltage at which the tests are made when plotted on the basis of total clearing time.
d) The type and rating of distribution or power fuses for which curve data apply.
e)
The time range for the fuses, as indicated in item a) through item e) in 11.1.6.
11.1.6 Time parameters of tests
Tests shall be made so that time-current curves are plotted in the time range of
a)
0.01 s to 300 s for power class fuses (except current-limiting fuses) and distribution fuse links,
rated 100 A and below.
b) 0.01 s to 600 s for power class fuses (except current-limiting fuses) and distribution fuse links,
rated above 100 A.
c)
0.01 s to 3600 s for general-purpose power class and distribution class current-limiting fuses.
d) 0.01 s to 10 000 s for full-range power class and distribution class current-limiting fuses.
e)
0.01 s to 1000 s for minimum-melt time-current characteristics for backup-type power and
distribution current-limiting fuses and the time corresponding to the rated minimum interrupting
current for total-clearing time-current characteristics. For motor-starter fuses, the minimum-melt
time-current characteristics need only be presented for 0.01 s to 100 s.
NOTE—The total-clearing time-current characteristics for power class and distribution class fuse links covered under item
a) and item b) will have minimum clearing times greater than 0.01 s due to the clearing time associated with these types of
fuses.
11.2 Description of melting time-current tests
11.2.1 Application of test parameters
Melting time-current tests shall be made at any voltage, up to the maximum voltage of the unit being tested,
with the test circuit so arranged that current through the fuse is held to essentially a constant value. For lowvoltage tests, when testing fuses that change their resistance during the melting process, by element resistance
change and/or having parallel elements that melt progressively (such as a fusible element and a strain wire),
73
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
the test circuit shall prevent a material change in the current during the melting process, either by having
sufficient impedance, or by being capable of responding sufficiently rapidly to changes in the desired current.
11.2.2 Presentation of melting time-current test data
Melting time-current curves for all fuse links, fuse units, or refill units shall be plotted to minimum values on
the current axis, and the value shall be determined by taking the manufacturer’s average test value, as
determined by the test specified in this clause, and subtracting a value equal to the manufacturer’s allowable
minus variation. The minimum melting time-current curves should be black.
11.3 Description of total-clearing time-current tests
11.3.1 Application of test parameters
Total-clearing time-current tests shall be made at the rated maximum voltage under the test circuit conditions
specified for interrupting tests in Clause 6.
11.3.2 Presentation of total-clearing time-current test data
The total-clearing time-current curves for all fuse links, fuse units, and fuse refill units shall be as follows:
a)
Be plotted to maximum values (using the current during the melting part of the total period), which
shall include the minimum melting time plus the tolerance
b) Add the maximum arcing time as determined by the test specified in this clause
When arcing time factors are used in place of tests at rated voltage, the method used to arrive at the total
clearing time shall be shown. The total-clearing time-current curves should be dark red.
12. Manual-operation, thermal-cycle, and bolt-torque tests (distribution
cutouts)
12.1 Description of manual-operation tests
12.1.1 Test series
Three cutouts shall each be closed and opened 200 times per the manufacturer’s specifications.
12.1.2 Mounting of the device
The cutout shall be mounted and operated per the manufacturer’s specifications.
12.1.3 Acceptance criteria
After testing the cutout shall be in the condition as specified in 4.5. There shall be no cracks in the insulators or
loose hardware. A visual check for cracks may be used.
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
12.2 Description of thermal cycle tests
12.2.1 Mounting of device
During the entire test, the cutouts shall be mounted in the service position(s) that would most likely permit
water to enter any openings in the device.
12.2.2 Test series
The thermal-cycle test shall consist of consecutive water immersion, cold chamber, and hot chamber cycling of
the cutouts. Separate cold and hot chambers may be used.
12.2.3 Number of devices to be tested
Five cutouts in new condition shall be tested. Open cutout fuse holders and disconnecting switch blades may
be omitted from the test device for the convenience of testing.
12.2.4 Number of tests per device
Each cutout shall receive 10 thermal cycles.
12.2.5 Thermal cycle
Each cycle shall consist of the following:
a)
The cutout shall be immersed in water for a minimum of 1 h. Water temperature shall be from
5 °C to 35 °C. The depth of immersion shall provide a minimum water level of 13 mm (½ in) above
any porcelain cavity, filled or open, or any hardware.
b) The cutout shall be removed from the water. The temperature of the air surrounding the device shall
be lowered from ambient room temperature to –40 °C at a rate controlled to prevent thermal shock.
A temperature of –40 °C to –50 °C shall be maintained for a minimum of 2 h.
c)
The temperature of the air surrounding the cutout shall be raised from –40 °C to 60 °C at a rate
controlled to prevent thermal shock. A temperature of 60 °C to 70 °C shall be maintained for a
minimum of 2 h. The device shall be permitted to return to room temperature before reimmersing it
in water for subsequent test cycles.
NOTE—As a guide, thermal shock may be avoided by maintaining the rate of temperature change at less than 2 °C per
minute. The transition time should be 2 h or less.
Separate hot and cold chambers may be used, which may require movement of the cutout. The position of the
cutout shall not change during transfer from the water or movement between chambers.
12.2.6 Acceptance criteria
The condition of the cutout after test shall be as specified in 4.4. There shall be no cracks in the porcelain or
loose hardware. A visual check for cracks may be used.
75
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
12.3 Description of torque tests
12.3.1 Test series
Torque tests shall be performed on cutouts that utilize threaded fasteners to attach the hardware to the
insulator. Five new cutouts shall be tested.
12.3.2 Application of test parameters
A torque of 125% of the nominal values specified by the manufacturer shall be applied to the threaded
fasteners that attach the hardware to the insulator.
12.3.3 Acceptance criteria
The condition of the device after testing shall be as specified in 4.4. There shall be no damage to the insulators,
thread failures, or loose components.
13. Liquid-tightness tests
13.1 Description of liquid-tightness tests
13.1.1 General
Liquid-tightness tests are required on certain types of current-limiting fuses used in FEPs. These tests apply to
any fuse or fuse container that is used in a liquid environment, such as those described in 1.5 for Types 2C and
3C.
13.1.2 Mounting of device
The fuse or fuse container shall be mounted or supported in the liquid as specified by the manufacturer.
13.1.3 Thermal cycle for test in air
The device shall be thermally cycled in air from –30 ºC to the rated maximum application temperature (as
specified by the manufacturer) and back to –30 ºC. The rate of temperature change shall be controlled to
prevent thermal shock. Each thermal cycle from one temperature extreme to the other shall be accomplished in
not more than 8 h, with a holding period at each temperature extreme of sufficient duration for the temperature
of the device to stabilize. Current may be used as a supplemental heat source during the heating cycle.
13.1.4 Thermal cycle for test in liquid
The device shall be thermally cycled in liquid with current passed through the fuse for part of the cycle. The
device shall be immersed in liquid, and the liquid temperature shall be raised from room temperature to the
rated maximum application temperature (specified by the manufacturer) in not more than 6 h. The rate of rise
of liquid temperature should not exceed 0.5 ºC/min. When the liquid temperature reaches the maximum
specified temperature, the fuse rated current (or the maximum permissible continuous current) shall be
maintained through the fuse for a period of 2 h with the liquid temperature held at or above this maximum
temperature. Current may be used as a supplemental heat source during the heating cycle.
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Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
At the conclusion of the 2 h current period, the liquid shall be allowed to cool to the cold-cycle ambient
temperature of (25 ± 5) ºC.
13.1.5 Alternative test
The requirements of 13.1.3 and 13.1.4 may be met by a single test series made according to 13.1.4 with the
following exceptions. The test device shall be cycled from –30 ºC to the rated maximum application
temperature (specified by the manufacturer) in not more than 8 h, with a holding period at –30 ºC of sufficient
duration for the temperature of the fuse or the device to stabilize. In addition, at the conclusion of the 2 h
maximum-temperature period, the liquid shall be cooled to –30 ºC in not more than 8 h.
13.2 Test series
13.2.1 Number of tests
The test series shall consist of 10 thermal cycles over any convenient time period.
13.2.2 Number of samples
A total of five devices with the largest current-rated fuse in each of the physical fuse sizes manufactured shall
be tested.
13.3 Acceptance criteria
All five samples shall pass one of the alternative test criteria methods selected for determining whether or not a
particular design passes the test for liquid-tightness. Alternative, but not necessarily equivalent, test criteria
methods are as follows:
a)
Maintain a minimum of 96 kPa (14 lbf/in2) positive pressure differential while the device is
submerged in the appropriate liquid (or suitable equivalent liquid) over a 5 min period. There shall
be an absence of bubbles.
b) Measure the leak rate using a helium-detecting mass spectrometer. The maximum permissible leak
rate, both before and after exposure to the above specified test cycles, shall be 10–6 cm3 per second
(1 atm pressure differential).
c)
The test device shall be carefully inspected for liquid ingress using ultraviolet light, spectrographic
analysis, or another equivalent, positive liquid-detecting technique. No liquid ingress shall be
detected.
Note that the use of ultraviolet light, or another technique, for detecting the presence of liquid inside the fuse
will require a quantizing of the test to provide a correlation with expected long-time service when submersed
in liquid. The use of a fluorescent dye in the liquid, plus comparison with an unexposed fuse, are possible
techniques that should be considered.
14. Description of expendable-cap static-relief pressure tests
The device shall be tested without a fuse link. It shall be mounted, and a means provided for exerting the
prescribed test pressure through a medium of a liquid against the entire surface of the pressure-responsive area.
(See ANSI C37.42 for test details.)
77
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Annex A
(informative)
Recommended methods for determining the value of a sinusoidal current
wave and a power-frequency recovery voltage
A.1 Current waves
A.1.1 Classification of current waves
The determination of the current interrupted by a circuit-interrupting device involves the measurement of the
rms or effective values of sinusoidal waves. These waves may be divided into two groups: those that are
symmetrical about the zero axis and those that are asymmetrical with respect to the zero axis.
A.1.2 Symmetrical sinusoidal wave
The symmetrical sinusoidal wave has an rms value equal to the peak-to-peak value divided by 2.828. To
determine the rms value at a given instant, draw the envelope of the current wave, determine from it the peakto-peak value at the given instant, and divide by 2.828. See Figure A.1 for an example.
ENVELOPE
t
RMS VALUE
B
ZERO LINE &
AXIS OF WAVE
A
t
ENVELOPE
T
A
B
is the time for which measurement was made
is the peak-to-peak value
A
is the rms value =
2.828
Figure A.1—Symmetrical sinusoidal current wave
A.1.3 Asymmetrical sinusoidal wave
The asymmetrical sinusoidal wave can be considered to be composed of two components—an alternating
component and a direct component.
A.1.3.1 Alternating component
The alternating component has a peak-to-peak value equal to the distance between the envelopes, and it has an
axis midway between the envelopes.
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Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
A.1.3.2 Direct component
The direct component has an amplitude equal to the displacement of the axis of the alternating component. See
Figure A.2 for an example.
ENVELOPE
AXIS OF WAVE
A'
A
D
ZERO LINE
B'
ENVELOPE
A
D
A’
B’
is the peak-to-peak value of alternating component = │A’│ + │B’│
is the direct component = A’ – (A/2)
is the major ordinate (peak asymmetrical current)
is the minor ordinate
A
The rms value of the sinusoidal component =
2.828
Figure A.2—Asymmetrical sinusoidal current wave
A.2 Power-frequency recovery voltage
The power-frequency recovery voltage shall be determined from the envelope of each voltage wave at a point
in time coincident with that peak that occurs more than 0.5 cycle, and not more than 1 cycle, after final arc
extinction in the last phase to clear. The power-frequency recovery voltage for a three-phase short circuit shall
be taken as the average of the three values obtained in this manner for the three voltage waves. See Figure A.3.
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Phase A
OO
G1 G1
G2 G2
1
is the first to open circuit
is the instant of final arc extinction
1
is the interval
from OO
2f
1
is the interval
from OO
f
is equal to 1 period at system frequency
f
E1
2.828
E2
2.828
E3
2.828
is normal frequency recovery voltage, phase A
is normal frequency recovery voltage, phase B
is normal frequency recovery voltage, phase C
Average normal frequency recovery voltage
E2
E3 
 E1
= 
+
+
 ÷3
 2.828 2.828 2.828 
Figure A.3—Determination of power-frequency recovery voltage
NOTE—In phase B, a voltage peak occurs exactly at interval G1 G1. In such event, measurement is made at
the later interval G2 G2.
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Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Annex B
(informative)
Recommended method of determining the equivalent steady-state rms
current for plotting time-current curves
The current that melts a fuse in less than 1 s may contain a number of transients in the wave. The magnitude of
these transients varies with each fuse operation, and the equivalent steady-state rms value of the current wave
can be obtained only by evaluating each case individually. The following methods are recommended for fuse
tests that fall in this class:
a)
When the fuse melts during transient conditions, the area under the melting part of the current wave
is integrated to determine the root-mean-square value of the wave. This value is then multiplied by
the scale of the oscillogram to give the rms current.
b) When the fuse melts after transient conditions subside, the transient part of the wave is integrated
as described in item a), and the crest-to-crest height of the steady-state wave is measured. The two
values obtained are combined as follows:
2
2

 Time of    crest - to - crest of steady - state part 

+
 transient part   
 [Time of steady - state part ]
2
2



 
 rms value of current wave 


 =
to
melting
point
total
time
to
melt


It may be noted that methods
are now more commonly available to obtain equivalent steady-state rms current by electronic integration over
longer periods of time. Combining transient and steady-state periods, using the formula above, is then
unnecessary.
rms value of 
 transient part 


81
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IEEE Std C37.41-2008
IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Annex C
(informative)
Simplified fault-current calculation
C.1 Interrupting duty and rated short-time withstand current
To select the proper rating for a device, it is necessary to calculate the maximum symmetrical fault current on
the load side of the device and compare this value with the interrupting capability of the fuse or the short-time
withstand current capability of disconnecting cutouts and distribution class enclosed single-pole air switches.
Most power fuses, distribution current-limiting fuses, and distribution cutouts are now rated by the
manufacturer in terms of symmetrical current. A direct comparison can be made between the calculated values
of fault current and the fuse rating. However, many power fuses and distribution cutouts of earlier manufacture
(pre-1970) were rated on the basis of asymmetrical current. In addition, momentary currents for disconnecting
cutouts and distribution class enclosed single-pole air switches have been defined in terms of asymmetrical
current until the publishing of this standard. For those devices that used an asymmetrical current rating, the
equivalent rms symmetrical current value can be obtained by dividing the asymmetrical value by an
appropriate factor. Momentary current, now defined as an asymmetrical peak current, can then be obtained
from an rms symmetrical current by multiplying it by another factor.
The factors to be applied depend on the circuit X/R ratio used for the appropriate tests on the device, and they
are shown in Figure C.1. The curve labeled “rms multiplication factor” is used to obtain the equivalent rms
symmetrical current from a quoted rms asymmetrical current. The curve labeled peak multiplication factor
then gives the value of the first peak of a fully asymmetrical waveform (peak asymmetrical current, i.e., the
momentary current), when multiplied by the momentary rms symmetrical current.
Figure C.1— Relation of X/R ratio to multiplication factor
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Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Annex D
(informative)
TRV parameters
Figure D.1 shows typical test circuits.
Typical circuit diagram for:
Table 7—test series 1, 2, and 3
Table 8—test series 1, 2, 3, and 6
Table 11—test series 1, 2, 3 and 4
Table 14—test series 1 and 2
Table 17—test series 1
Table 7—test series 4 and 5a
Table 8—test series 4 and 5a
Table 11—test series 5 and 6a
Table 14—test series 3a
Table 17—test series 2a
a
For these test series, C2 may be required, and its value is under consideration; R3 is not required across XL2. Also, TD may be used as an
alternative to XL2 and R4 and may have impedance connected between secondary terminals.
Typical circuit diagram for:
A
CB
CS
CT
CVD
C1
C2
F
G
I
XL1
XL2
R1
R2
R3
R4
TD
T1, T2
VF
is the removable link used for the calibration test
is the circuit breaker protecting the source
is the closing switch
is the current transformer or noninductive current shunt
is the capacitance voltage divider
is the transient recovery voltage frequency control for source
is the transient recovery voltage frequency control for load (value under consideration)
is the fuse under test
is the generator
is the current measurement
is the reactance for source
is the reactance for load (see TD)
is the resistance to control X/R ratio of source
is the damping resistance to control peak factor of source
is the damping resistance to control peak factor of load
is the resistance to control X/R ratio of load
is the distribution transformer with short-circuited secondary terminals (alternate to XL2 and R4)
is the possible locations of transformers for tests at voltages higher than generator voltage
is the recovery voltage measurement
NOTE—Damping circuits other than shown, for controlling the inherent TRV parameters of the test circuit, may be used by mutual
agreement between manufacturer and test laboratory. Such use shall be noted and explained in the test report.
Figure D.1—Typical test circuits
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
D.1 Measurement of peak factor
The peak factor is the ratio of the first peak of the TRV to the instantaneous value of source voltage at the time
of current zero, which is defined by
Peak factor =
first TRV peak
[
]
2 × (power frequency recovery voltage ) × sin (arctan X / R )
This parameter is used in lieu of the amplitude factor (the ratio of the first peak of the transient recovery
voltage to the peak value of the power-frequency recovery voltage) and is considered superior especially when
testing in circuits with low X/R ratios.
The peak factor may be measured by current injecting the test circuit or, alternatively, by conducting an actual
fault-interrupting test using a low-arc-voltage interrupting device that does not distort the TRV. Either method,
incidentally, can also be used to determine the frequency of the test circuit TRV.
The characteristic and use of current-injecting equipment shall be such as not to alter the inherent TRV
characteristics of the circuit during measurement. For further information on such equipment, see Annex F.
D.1.1 Measurement of peak factor by current injection
The peak factor is graphically determined from the TRV appearing across the open interrupting device when
the circuit is current injected at the point (see Figure D.2).
Peak factor =
57.5
= 1.6
35.9
Figure D.2—Peak factor determination from current-injection test record
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Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
D.1.2 Measurement of peak factor by fault interruption
The peak factor is determined from the TRV record of an actual fault-interrupting test on a circuit employing a
low-arc-voltage device that does not distort the TRV. (The peak factor cannot be determined from the TRV
record of a test that uses a fuse cutout as the interrupting device, since cutouts typically distort the TRV.) (See
Figure D.3.)
Peak Factor =
B+A
−1
Csin(Tan X R) + A
64.2 + 11.5
=
= 1.6
−1
38.2sin(tan 2.8) + 11.5
Figure D.3—Peak factor determination from the fault-interruption test record
For this case, the first peak of the TRV is measured from the extinction peak as its starting point, as is the
measurement of the instantaneous power-frequency recovery voltage at the time of current zero. The following
equation shows the calculation:
peak factor =
{
(first TRV peak ) + (extinction peak )
2 x power frequency recovery voltage x [sin (arctan X R )]}+ (extinction peak )
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Annex E
(informative)
Criteria for determining It testing validity
E.1 Introduction
Fuses that require an It test are those in which, at different current levels, different series parts of the element
perform most of the current interrupting duty. When the high current tests (series 1 and series 2) and low
current tests (series 3) do not cover the transitional region between currents interrupted by the different parts of
the element, the It testing is intended to demonstrate that there are no currents that cannot be interrupted, either
by the different sections individually or in combination. Because of the wide variety of fuse designs, there are
no simple rules for determining the validity of such testing, so it is the intent of this annex to give general
guidance to those attempting to verify that the It testing that has been performed does indeed show what is
intended.
E.2 Interrupting processes
Possibly the simplest illustration of the It phenomenon would be with a fuse having a single element consisting
of a current-limiting section (strip with restrictions) in series with an expulsion section (element in a sleeve).
At high currents, only the strip melts and arcs (with all restrictions melting virtually simultaneously), whereas
at low currents, only the expulsion section melts and arcs. With such a design, the melting time-current
characteristics (TCCs) of the two series sections will cross at some intermediate current where both the low
current section and at least one restriction of the high current section will melt and arc. Such a crossover
current can usually be determined relatively easily, and it is well defined if the TCC curves cross each other
with a relatively large angle. The crossing current is the It current of the fuse. Tests at two current levels, a
little above and below this It current, will therefore demonstrate that the fuse can interrupt the highest current
that the low current section must interrupt (without help from the high current section) and the lowest current
that the high current section must interrupt (without help from the low current section).
It is then a reasonable assumption that the high current section can break all currents higher than It, and the low
current section can break all currents lower than It. Conformance with the standard can be verified if each test
current produces arcing only in the relevant section. This can be determined by techniques such as physical
examination (that is opening the fuse), X-ray examination, or the equivalent.
The above simple illustration shows the basic principle to be followed for all fuses. However, many fuse
designs do not conform to this simple process. The melting TCC of the series sections may cross at such a
shallow angle that there is not one distinct It value but instead a crossover zone that is larger than ±20% of any
one current value. For other designs, the melting TCC may not actually cross at all, so it is possible for one
section to melt for all currents, even when it is another section that is performing most of the interrupting
function. With some designs that have many elements in parallel, the current value at which the high current
sections begin to melt and participate in the interrupting process may be substantially below the apparent
“crossover” value that corresponds to the intersection of the TCC curves for the different sections. This is
caused by the phenomenon whereby, at some currents, parallel elements do not arc simultaneously but
sequentially.
In all of these cases, only the fuse manufacturer is in a position to specify the values of test current that will
demonstrate compliance with the standard, and often, only the manufacturer is in a position to determine
whether a particular test has demonstrated the desired result. This is because simply demonstrating current
interruption is not a sufficient criterion to show that the crossover zone has been adequately explored. For this
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Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
reason, 6.6.11 permits the manufacturer to specify other test currents than 1.2 It and 0.8 It, if these values are
not appropriate.
It should be noted that without the expertise of the fuse manufacturer, it is not possible for a test station or user
to assess the adequacy of testing to demonstrate compliance with the standard in regard to crossover testing.
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IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses, Fuse and Disconnecting Cutouts, Distribution Enclosed Single-Pole
Air Switches, Fuse Disconnecting Switches, and Fuse Links and Accessories Used with These Devices
Annex F
(informative)
Bibliography
[B1] ANSI/UL 347-2000, Standard for High Voltage Industrial Control Equipment. 8
[B2] Hammarlund, P., Transient recovery voltage subsequent to short-circuit interruption with special
reference to Swedish power system. Proceedings, Royal Swedish Academy of Engineering Sciences, no. 189,
1946.
[B3] IEEE Std C37.48.1™-2002 (Reaff 2008), IEEE Guide for the Operation, Classification, Application, and
Coordination of Current-Limiting Fuses with Rated Voltages 1-38 kV.
[B4] IEEE Std C37.100.1™-2007, IEEE Standard of Common Requirements for High Voltage Power
Switchgear Rated Above 1000V. 9, 10
[B5] Jackson, R. L., Low voltage injection equipment for determining the transient response of power system
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[B6] Kotheimer, W. C., A method for studying circuit transient recovery voltage characteristics of electric
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[B7] Sing-Yui-King, Determination of restriking transients on power networks by a half-wave injection
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8
ANSI publications are available from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New
York, NY 10036, USA (http://www.ansi.org/). UL standards are available from Global Engineering Documents, 15 Inverness Way East,
Englewood, CO 80112, USA (http://global.ihs.com/).
9
IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854, USA
(http://standards.ieee.org/).
10
The IEEE standards or products referred to in this clause are trademarks of the Institute of Electrical and Electronics Engineers, Inc.
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