Ieee Std C37.42-2016 (fuse)

IEEE Standard Specifications for HighVoltage (>1000 V) Fuses and Accessories

IEEE Power and Energy Society

Sponsored by the Switchgear Committee

IEEE 3 Park Avenue New York, NY 10016-5997 USA

IEEE Std C37.42™-2016

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IEEE Std C37.42™-2016

IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories Sponsor

Switchgear Committee of the

IEEE Power and Energy Society Approved 22 September 2016

IEEE-SA Standards Board

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Abstract: Specifications for high voltage (above 1000 V) Class A and Class B expulsion and current-limiting fuses are detailed in this standard. They include: expulsion type Class A [distribution class] fuses, fuse cutouts, fuse disconnecting switches, their associated fuse links or refill units, disconnecting cutouts, and accessories for these devices with rated voltages from 1 kV through 38 kV; expulsion type Class B [power class] fuses, fuse disconnecting switches, their associated fuse links or refill units, disconnecting cutouts, and accessories for these devices with rated voltages from 1 kV through 170 kV; class A and class B current-limiting fuses and accessories for these devices with rated voltages 1 through 38 kV; distribution and power class expulsion, current-limiting, and combination-type external capacitor fuses and accessories, with rated voltages from 1 kV through 38 kV, for protecting shunt capacitors complying with IEEE Std 18 and NEMA CP 1; any of the above devices used in fuse enclosure packages; all of these devices are intended for use on alternating current distribution systems. Keywords: Class A fuses, Class B fuses, current-limiting fuses, distribution and power class current-limiting fuses, distribution class fuses, distribution fuse cutouts, expulsion fuses, fuse, fuse applications, fuse disconnecting switches, fuse enclosure packages, fuses for the protection of shunt capacitors, fuse hooks, fuse links, high-voltage fuses, IEEE C37.42™, power class fuses, supports and mountings, tongs

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ISBN 978-1-5044-2359-5 ISBN 978-1-5044-2360-1

STD21134 STDPD21134

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Participants At the time this standard was completed, the Revision of Fuse Specifications Standards Working Group had the following membership: Mark W. Stavnes, Chair Alan Yerges, Vice Chair Chris Ambrose Glenn R. Borchardt Sam Chang Sterlin Cochran Jonathan H. Deverick Rodolfo Elizondo David L. Frisch

Gary W. Haynes Frank C. Lambert John G. Leach Chris Lettow Bradley B. Lewis James R. Marek Sean W. Moody

R. Neville Parry Timothy E. Royster Jon Spencer Tom Stefanski William Walter James Wenzel Charles Worthington

The following members of the individual balloting committee voted on this standard. Balloters may have voted for approval, disapproval, or abstention. Chris Ambrose Paul Barnhart Craig Befus Robert Behl Jean-Marc Biasse Glenn R. Borchardt Christopher Borck Clarence Bradley Gustavo Brunello William Byrd Paul Cardinal Gary Donner Edgar Dullni Rodolfo Elizondo Marcel Fortin David L. Frisch Mietek Glinkowski Edwin Goodwin Randall Groves

John Harley Gary W. Haynes Richard Jackson John Kay Yuri Khersonsky Boris Kogan Jim Kulchisky Saumen Kundu Frank C. Lambert John G. Leach Bradley B. Lewis William McBride Sean W. Moody Daniel Mulkey Michael Newman T. W. Olsen Lorraine Padden Iulian Profir

Michael Roberts Timothy Robirds Charles Rogers Timothy E. Royster Thomas Rozek Bartien Sayogo Nikunj Shah Jerry Smith Jon Spencer Tom Stefanski James Van De Ligt John Vergis William Walter John Wang James Wenzel Kenneth White Terry Woodyard Charles Worthington Alan Yerges

When the IEEE-SA Standards Board approved this standard on September 22, it had the following membership: Jean-Philippe Faure, Chair Ted Burse, Vice-chair John D. Kulick, Past Chair Konstantinos Karachalios, Secretary Chuck Adams Masayuki Ariyoshi Stephen Dukes Jianbin Fan J. Travis Griffith Gary Hoffman

Ronald W. Hotchkiss Michael Janezic Joseph L. Koepfinger* Hung Ling Kevin Lu Annette D. Reilly Gary Robinson

Mehmet Ulema Yingli Wen Howard Wolfman Don Wright Yu Yuan Daidi Zhong

*Member Emeritus

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Introduction This introduction is not part of IEEE Std C37.42–2016, IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories.

IEEE Std C37.42™-2016 is a new IEEE standard covering specifications for expulsion and current-limiting type fuses. This standard is a consolidation of all previously published IEEE standards covering these devices. These standards include IEEE Std C37.42, IEEE Std C37.43™, IEEE Std C37.46™, and IEEE Std C37.47™. The consolidation was prepared by a working group of the IEEE Subcommittee on High-Voltage Fuses to improve the alignment with the associated testing document, IEEE Std C37.41™, to eliminate redundancy, and to bring the standard more in line with the related International Electrotechnical Commission (IEC) standards IEC-60282-1 and IEC-60282-2. Previous standards had ratings listed for historical purposes to attempt to account for the ratings of all devices manufactured either to prior standards or before standards existed. With this standard, these are eliminated as preferred values, and are included only for historical reference in an informative annex. In addition, previous standards included devices that have restricted application in terms of performance requirements or geographic applicability. With this standard, those devices have been separated from those that have essentially universal applicability, and are included in a normative annex. This is to preserve inclusion in the standard, but clearly indicate that they do not have a relation to IEC standard devices. Liaison was maintained with the IEC during the development of the revisions in order to incorporate the latest thinking up to the time of publication. This standard is one of a series of complementary standards covering the various types of high-voltage fuses and switches, and contains the specifications, while IEEE  Std  C37.41 covers testing requirements. IEEE Std C37.45™ contains all of the specifications and testing requirements for high-voltage distribution class enclosed single-pole air switches. IEEE Std C37.41 and IEEE Std C37.42 together, and IEEE Std C37.45, provide all of the testing requirements for a device. In addition, IEEE Std C37.48™ provides application, operation, and maintenance guidance for all the devices, and is supplemented by and IEEE Std C37.48.1™ [B8] which is an application, operation, and coordination guide for current-limiting fuses. At the time this standard was approved, this series was comprised of the following standards: IEEE Std C37.41, IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses and Accessories. IEEE Std C37.42, IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories. IEEE Std C37.45, IEEE Standard Design Tests and 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. IEEE Std C37.48.1, IEEE Guide for the Application, Operation, and Coordination of High-Voltage (>1000 V) Current-Limiting Fuses.

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Contents 1.  Overview��������������������������������������������������������������������������������������������������������������������������������������������������� 13 1.1  Scope�������������������������������������������������������������������������������������������������������������������������������������������������� 13 1.2  Purpose����������������������������������������������������������������������������������������������������������������������������������������������� 13 1.3  Background���������������������������������������������������������������������������������������������������������������������������������������� 14 2.  Normative references�������������������������������������������������������������������������������������������������������������������������������� 14 3.  Definitions������������������������������������������������������������������������������������������������������������������������������������������������� 15 4.  Normal and special service conditions������������������������������������������������������������������������������������������������������ 15 5.  Classifications and ratings������������������������������������������������������������������������������������������������������������������������� 15 5.1  Classifications������������������������������������������������������������������������������������������������������������������������������������ 15 5.2  Rating validation�������������������������������������������������������������������������������������������������������������������������������� 15 5.3  Preferred ratings��������������������������������������������������������������������������������������������������������������������������������� 17 6.  Design test requirements��������������������������������������������������������������������������������������������������������������������������� 21 6.1  Dielectric tests������������������������������������������������������������������������������������������������������������������������������������ 21 6.2  Interrupting [breaking] tests��������������������������������������������������������������������������������������������������������������� 23 6.3  Load-break tests��������������������������������������������������������������������������������������������������������������������������������� 25 6.4  Radio-influence tests�������������������������������������������������������������������������������������������������������������������������� 25 6.5  Temperature rise tests������������������������������������������������������������������������������������������������������������������������� 26 6.6  Time-current tests������������������������������������������������������������������������������������������������������������������������������� 27 6.7  Manual operation, thermal cycle, and bolt torque tests����������������������������������������������������������������������� 27 6.8  Liquid tightness tests for liquid immersed current-limiting type fuses and FEPs������������������������������� 27 6.9  Static relief pressure tests for fuses with expendable caps������������������������������������������������������������������ 27 6.10  Lightning surge impulse withstand fuse links����������������������������������������������������������������������������������� 27 7.  Time-current characteristic requirements�������������������������������������������������������������������������������������������������� 27 7.1  General����������������������������������������������������������������������������������������������������������������������������������������������� 27 7.2  “K” and “T” type fuses����������������������������������������������������������������������������������������������������������������������� 28 7.3  Fuses not assigned a specific letter designation���������������������������������������������������������������������������������� 30 8.  Conformance tests������������������������������������������������������������������������������������������������������������������������������������� 30 9.  Construction requirements������������������������������������������������������������������������������������������������������������������������ 30 9.1  Cutout and capacitor unit fuses and associated fuse links������������������������������������������������������������������� 30 9.2  Class B [power class] fuses����������������������������������������������������������������������������������������������������������������� 33 10.  Nameplate marking requirements����������������������������������������������������������������������������������������������������������� 34 10.1  Fuse supports and fuse disconnecting switches�������������������������������������������������������������������������������� 34 10.2  Fuse units or refill units�������������������������������������������������������������������������������������������������������������������� 34 10.3  Fuseholders�������������������������������������������������������������������������������������������������������������������������������������� 35 10.4  Fuse links������������������������������������������������������������������������������������������������������������������������������������������ 35 10.5  Disconnecting blades������������������������������������������������������������������������������������������������������������������������ 35 10.6  Capacitor fuses��������������������������������������������������������������������������������������������������������������������������������� 35 10.7  Additional information��������������������������������������������������������������������������������������������������������������������� 36 11.  Application, operation and maintenance guidelines�������������������������������������������������������������������������������� 36 11.1  General��������������������������������������������������������������������������������������������������������������������������������������������� 36 11.2  Capacitor fuses��������������������������������������������������������������������������������������������������������������������������������� 36 11.3  Class B [power class] fuses��������������������������������������������������������������������������������������������������������������� 36 11.4  Paralleling of fuses��������������������������������������������������������������������������������������������������������������������������� 38 11.5  Load-break ability���������������������������������������������������������������������������������������������������������������������������� 38 8

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Annex A (informative) Historical device rating information�������������������������������������������������������������������������� 39 Annex B (normative) Historical IEEE (non-IEC) devices������������������������������������������������������������������������������ 42 Annex C (normative) Mounting brackets������������������������������������������������������������������������������������������������������� 51 Annex D (normative) Switch sticks (switch hooks)��������������������������������������������������������������������������������������� 56 Annex E (informative) Bibliography�������������������������������������������������������������������������������������������������������������� 57

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List of Figures Figure 1—Typical cutout fuse link construction�������������������������������������������������������������������������������������������� 30 Figure 2—Preferred base mounting dimensions�������������������������������������������������������������������������������������������� 33 Figure C.1—Type-A mounting bracket���������������������������������������������������������������������������������������������������������� 52 Figure C.2—Type-B mounting bracket���������������������������������������������������������������������������������������������������������� 53 Figure D.1—Switch sticks for use with distribution class devices����������������������������������������������������������������� 56

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List of Tables Table 1—Preferred rated maximum voltage (V)�������������������������������������������������������������������������������������������� 17 Table 2—Peak recovery voltages for capacitor fuses������������������������������������������������������������������������������������� 18 Table 3—Preferred rated current for fuses, fuses units, fuse links, and refill units����������������������������������������� 18 Table 4—Preferred rated current for fuse supports����������������������������������������������������������������������������������������� 18 Table 5—Preferred rated lightning impulse withstand voltages��������������������������������������������������������������������� 20 Table 6—Minimum dielectric withstand test voltages for Class A outdoor devices��������������������������������������� 21 Table 7—Minimum dielectric withstand test voltages for Class A indoor devices����������������������������������������� 21 Table 8—Minimum dielectric withstand test voltages for Class B outdoor devices��������������������������������������� 22 Table 9—Minimum dielectric withstand test voltages for Class B indoor devices����������������������������������������� 22 Table 10—Maximum permissible overvoltages for current-limiting type fuses�������������������������������������������� 24 Table 11—Radio-influence voltage testing parameters for Class A fuses������������������������������������������������������� 25 Table 12—Radio-influence voltage testing parameters for Class B fuses������������������������������������������������������� 26 Table 13—Melting currents for type-K (fasta) fusesb�������������������������������������������������������������������������������������� 28 Table 14—Melting currents for type-T (slowa) fusesb������������������������������������������������������������������������������������ 29 Table 15—Requirements for button head diameter���������������������������������������������������������������������������������������� 31 Table 16—Flexible conductor (fuse link leader) requirements����������������������������������������������������������������������� 31 Table 17—Dimensional range of conductor sizes to be accommodated by terminals������������������������������������ 32 Table 18—Inside diameter of fuseholder������������������������������������������������������������������������������������������������������� 32 Table 19—Requirements for expendable fuseholder capsa����������������������������������������������������������������������������� 32 Table 20—Preferred base mounting dimensions for power class expulsion and current-limiting type fuse supports and fuse disconnecting switches����������������������������������������������������������������������������������������������� 34 Table 21—Minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor mounted Class B fuses (except expulsion type)a������������������������������������������������������������������������������������������������������������������������ 36 Table 22—Minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor mounted Class B fusesa37 Table 23—Minimum clearance between live parts for indoor mounted Class B fuses����������������������������������� 37 Table B.1—Preferred ratings for maximum voltage, lightning impulse withstand voltage, current, and maximum interrupting current����������������������������������������������������������������������������������������������������������������� 42 Table B.2—Preferred minimum dielectric withstand test voltages���������������������������������������������������������������� 43 Table B.3—Radio-influence voltage testing parameters for open-link cutouts���������������������������������������������� 43 Table B.4—Dimensional range of conductor sizes to be accommodated by terminals����������������������������������� 43 Table B.5—Length of fuse link between contact buttons������������������������������������������������������������������������������� 44

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Table B.6—Flexible conductor thickness requirements��������������������������������������������������������������������������������� 44 Table B.7—Preferred rated maximum voltage and rated maximum interrupting current������������������������������� 44 Table B.8—Preferred minimum dielectric withstand test voltages���������������������������������������������������������������� 45 Table B.9—Dimensional range of conductor sizes to be accommodated by terminals����������������������������������� 45 Table B.10—Identifying color-coding and nomenclature������������������������������������������������������������������������������ 46 Table B.11—Minimum allowable continuous currents for R-rated fuses������������������������������������������������������� 46 Table B.12—Interrupting rating nomenclature���������������������������������������������������������������������������������������������� 48 Table B.13—Preferred rated short-time withstand currents for disconnecting devices���������������������������������� 49 Table B.14—Historical preferred rated lightning impulse withstand voltages and minimum dielectric withstand test voltages����������������������������������������������������������������������������������������������������������������������������������� 50

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IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories 1. Overview 1.1  Scope This standard establishes specifications for high-voltage (above 1000 V) fuses and accessories for use on ac electrical distribution systems. Devices with rated maximum voltages to 170 kV are covered. The devices to which this standard applies are as follows: a)

Expulsion fuses (including fuse cutouts)

b)

Current-limiting fuses

c)

Items a) and b) used in fuse enclosure packages

d)

Fuse supports of the type intended for use with fuses and fuse disconnecting switches

e)

Disconnecting devices (fuse disconnecting switches, disconnecting switches, and disconnecting cutouts) created by the use of a removable fuse unit or switch blade in a fuse support

f)

Expulsion, current-limiting, and combination types of external capacitor fuses used with a capacitor unit, a group of units, or capacitor banks

g)

Backup current-limiting fuses (“motor-starter fuses”) used in conjunction with high-voltage motor starters

h)

Fuse links when used exclusively with expulsion fuses and fuse disconnecting switches

i)

Items a) through f) having integral load-break means

j)

Accessories including mounting brackets and switch sticks (switch hooks)

This standard may also be used for other devices that are similar to the devices listed in the scope.

1.2  Purpose Standard specifications for the devices covered by this document are necessary to assure consistent development and application of these devices by manufacturers and users of these devices.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

1.3  Background 1.3.1  General The specifications for devices in this standard generally follow the requirements found in IEC HV fuse standards. However, significant differences exist between the requirements of this document and those of IEC (see 1.3 of IEEE Std C37.41 for examples of significant differences). Due to the wide variation in fuse types, interchangeability guidelines have little meaning. Standard ratings such as “C,” “E,” or “R” defined in Annex B of this standard provide only a basic level of time-current characteristic conformance, and do not provide enough information to ensure proper application and coordination of fuses. This is particularly true when different fuse types or fuses from different manufacturers are being applied together. Published information, such as current ratings and time-current characteristic curves should be used to select fuses, following manufacturer’s recommendations. If there are specific questions, the manufacturer should be consulted. 1.3.2  Summary As a result of differences between IEC and IEEE standards, the user is advised to exercise 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.

2.  Normative references The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so 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/ASME B1.1, Unified In Screw Threads (UN and UNR Thread Form).1 ANSI/ASME B18.5, Round Head Bolts (In Series). ANSI/ASME B18.2.2, Square and Hex Nuts (In series). ASTM A153/A153M, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware.2 ASTM A575, Standard Specification for Steel Bars, Carbon, Merchant Quality, M-Grades. IEC 60282-1, High Voltage Fuse—Part 1, Current-Limiting Fuses.3

1 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/​). 2 ASTM publications are available from the American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA (http://​www​.astm​.org/​). 3 IEC publications are available from the Sales Department of the International Electrotechnical Commission, Case Postale 131, 3, Rue de Varembé, CH-1211, Genève 20, Switzerland/Suisse (http://​www​.iec​.ch/​). 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/​).

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

IEC 60282-2, High Voltage Fuse—Part 2, Expulsion Fuses. IEEE Std 18™, IEEE Standard for Shunt Power Capacitors.4,5 IEEE Std C37.41™, IEEE Standard Design Tests for High-Voltage (>1000 V) Fuses and Accessories. 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 Application, Operation, and Coordination of High-Voltage (>1000 V) Current-Limiting Fuses. NEMA CP 1, Shunt Capacitors.6

3.  Definitions For the purposes of this document, the terms and definitions in IEEE Std C37.41 apply. The IEEE Standards Dictionary Online should be consulted for terms not defined in IEEE Std C37.41.7

4.  Normal and special service conditions The normal and special services conditions that apply are as listed in IEEE Std C37.41.

5.  Classifications and ratings 5.1  Classifications Specifications are listed for two classes of expulsion and current-limiting fuses. The class is defined according to the ability of the fuse to comply with transient recovery voltage (TRV), X/R (power factor), and certain interrupting test requirements. They are termed Class A [distribution class] and Class B [power class]. In some cases, the two classes have separate tables (e.g., Table 6 gives preferred values for Class A fuses while Table 8 gives preferred values for Class B fuses) and in other cases a single table contains separate requirements for each class (e.g., Table 5 gives preferred values for all fuses).

5.2  Rating validation 5.2.1  Devices rated for use at a maximum application temperature of 40 °C or less The tests required for the devices covered by this standard are summarized in Table 3 of IEEE Std C37.41. The ratings in this standard are validated as follows: a)

Rated maximum voltage(s), validated by the dielectric and current interrupting [breaking] design tests specified in 6.1 and 6.2, respectively. 1) For fuses that use a replaceable fuse link, fuse unit, or fuse refill, the rated maximum voltage of the device is validated by interrupting tests using the replaceable item.

4 IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854, USA (http://​standards​.ieee​.org/​). 5 The IEEE standards or products referred to in this clause are trademarks of the Institute of Electrical and Electronics Engineers, Inc. 6 NEMA publications are available from Global Engineering Documents, 15 Inverness Way East, Englewood, CO 80112, USA (http://​ global​.ihs​.com/​). 7 IEEE Standards Dictionary Online is available at: http://​dictionary​.ieee​.org.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

2) The replaceable item and the fuse shall be from the same manufacturer or as recommended by the manufacturer of the fuse. The rated maximum voltage is the highest voltage rating of the fuse where the specified replaceable item is capable of properly interrupting the circuit or aiding in the interruption process. b)

Rated current, validated by the temperature-rise design tests at the rated current specified in 6.5.

c)

Rated maximum and minimum interrupting [breaking] currents, validated by the current interrupting design tests specified in 6.2. Minimum interrupting ratings apply only to backup current-limiting fuses. For certain fuse devices, the following ratings apply: 1) For capacitor fuses, the rated capacitive interrupting current specified in 5.3.4.3 is validated by the current interrupting design tests at rated maximum voltage as specified in 6.2.4. 2) For backup current-limiting fuses the rated minimum interrupting current specified in 5.3.6.2, is validated by the current interrupting design tests specified in 6.2. For capacitor fuses of this type, rated minimum capacitive interrupting currents are also specified and validated. 3) While general-purpose current-limiting fuses may have a current below which they have not demonstrated an interruption capability, this potential application limitation is expressed in terms of a melting time limitation rather than a current limitation (i.e., general-purpose fuses have a demonstrated interrupting capability from their rated maximum interrupting current down to a current that causes melting in one hour).

d)

Rated lightning impulse withstand voltage [basic impulse insulation level (BIL)], validated by the impulse withstand tests specified in 6.1. These ratings apply only to devices that have a fuse support.

e)

Rated power frequency, as specified in 5.3.3 and validated by the design tests specified in IEEE Std C37.41.

f)

Rated load-break current (for devices equipped with load breaking provisions), validated by the design tests specified in 6.3.

Current-limiting fuses (Class A and B) have three different subclasses that depend on the low current interrupting capability of the fuse. The three subclasses are backup current-limiting fuses, general-purpose current-limiting fuses, and full-range current-limiting fuses. Only backup current-limiting fuses have a rated minimum interrupting current. The other two types have low current capabilities as described in their definitions. Refer to IEEE Std C37.41 for the definitions of these devices. 5.2.2  Devices rated for use at a maximum application temperature greater than 40 °C For these devices with service conditions with a maximum application temperature above 40 °C, additional testing to validate the ratings of the device may be required and are subject to agreement between the user and manufacturer. 5.2.3  Devices rated for other service conditions For devices and application with service conditions other than those specified in Clause 4, additional testing to validate the ratings of the device may be required and are subject to agreement between the user and manufacturer. 5.2.4  Fuse link ratings Requirements specified in this standard cover the testing of a specific combination of a fuse link together with other components including a fuseholder, fuse support, and fuse disconnecting switch. The performance of other combinations cannot be implied from these tests.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

5.3  Preferred ratings 5.3.1  Rated maximum voltage (V) 5.3.1.1  Fuse links Fuse links do not have a voltage rating independent of a specific device. The fuse link may be voltage sensitive, however, it is the combination of the fuse holder and fuse link that is required to operate properly from the lowest current that melts its element to the maximum interrupting rating of the combination device. Fuse links are tested with a specific voltage rated device and the combination is given a maximum voltage rating by the manufacturer. When applying a fuse link in a device from a different manufacturer than was tested or different rating, proper operation cannot be assumed. 5.3.1.2  Class A and Class B fuses The preferred rated maximum voltage shall be as specified in Table 1. Table 1—Preferred rated maximum voltage (V) Rated maximum voltage (V) (kV) Class A and B fuses

Class B fuses

2.8

17.2

48.3

5.5

23.0

72.5

8.3

27.0

121.0

15.5

38.0

145.0

 —

— 

169.0

5.3.1.3  Capacitor fuses The preferred rated maximum voltages for capacitor fuses shall be as in Table 1. These ratings apply primarily to line fuses, because unit fuses are often designed specifically for a particular capacitor bank. Additional information regarding rated maximum voltage for all capacitor fuses is specified as follows: a)

The rated voltage (V) of a fuse is its rated maximum voltage. That is, the maximum power frequency voltage to which it may be subjected.

b)

When a fuse is subjected to power-frequency capacitive currents, it shall be capable of operating continuously at a voltage of V and then withstand this voltage plus any dc voltage component that results from any capacitive charge trapped on the capacitor or capacitor bank after the fuse melts and subsequently clears the circuit.

c)

The fuse rated maximum voltage is based on proper fuse operation at the maximum continuous system operating voltage. It does not include provision for operation during transient or short-time overvoltage conditions associated with restriking circuit breakers, system faults, etc.

d)

A fuse shall be capable of disconnecting a faulty capacitor unit at the maximum peak voltages specified in Table 2.

e)

A fuse shall be capable of withstanding a peak recovery voltage, which is the fundamental frequency voltage appearing across the blown fuse during the first cycle after interrupting, including any dc component. This fuse peak recovery voltage capability shall be as specified in Table 2.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 2—Peak recovery voltages for capacitor fuses Type of fuse

Maximum peak voltage (V) a

Peak recovery voltage (V)

Non-current limiting

1.0V 2

2.0V 2

Current limiting

2.0V 2

2.0V 2

a The values in column 2 are based on the voltages that normally can occur across the capacitor unit terminals. These values are transients of short duration, with a steady-state value of V.

5.3.2  Rated current 5.3.2.1  Fuses, fuse units, fuse links, and refill units The preferred values of rated current for distribution and power class fuses, fuse units, fuse links, and refill units shall be as shown in Table 3. Table 3—Preferred rated current for fuses, fuses units, fuse links, and refill units Rated current (A) 0.5

3

7

12

20

40

80

140

250

1

5

8

15

25

50

100

150

300

2

6

10

18

30

65

125

200

400

5.3.2.2  Fuse supports The preferred values of rated current for distribution and power class fuse supports shall be as shown in Table 4. Table 4—Preferred rated current for fuse supports Rated current (A) 10

200

600

25

300

700

50

400

720

100

450

 —

5.3.3  Rated frequency The preferred rated frequencies for devices covered by this standard are 50 Hz, 60 Hz, or both. It should be noted that current-limiting fuses are normally tested at either 50 Hz or 60 Hz. However, experience has shown that, while the same fuse design tested at both frequencies at a current that produces a current-limiting action generally exhibits slightly higher peak currents at 60 Hz and slightly higher operating I2t values at 50 Hz, fuses successfully passing all testing at one frequency are suitable for use at the other frequency. NOTE—The equivalence of interrupting capability at 50 Hz and 60 Hz should not be assumed for expulsion fuses.8

5.3.4  Rated maximum interrupting [breaking] current 5.3.4.1  General Rated maximum interrupting currents are designated by the manufacturer and the preferred values shall be selected from the R10 series of preferred numbers. The R10 series is comprised of the numbers 1, 1.25, 1.60, 2.00, 2.50, 3.15, 4.00, 5.00, 6.30, 8.00, and their multiples of 10. 8

Notes to text, tables, and figures are for information only and do not contain requirements needed to implement the standard.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

5.3.4.2  Fuse links Fuse links do not have a rated interrupting current because it is a characteristic of the combination of the fuse link and the device that was tested. 5.3.4.3  Capacitor fuses Capacitor fuses have both an inductive and capacitive maximum interrupting current. The preferred rated maximum inductive interrupting currents of capacitor fuses are as listed in 5.3.4.1. The preferred rated maximum capacitive interrupting currents for capacitor fuses are 1 kA rms, 2.5 kA rms, 3.15 kA rms, 4 kA rms, and 5 kA rms. Other values shall be the subject of an agreement between manufacturer and user. 5.3.5  Rated capacitor discharge energy (joules) for the capacitor discharge interrupting tests A rated capacitor discharge energy (joule rating) is assigned to a fuse based on the energy stored in a capacitor test bank prior to the time it is discharged through the fuse in the capacitor discharge interrupting [breaking] tests (see 9.5.5 of IEEE Std C37.41). Values should be selected from the R10 series with a minimum of 10 kJ. The preferred value for current-limiting fuses is 40 kJ. To assign an “unlimited” rated capacitor discharge energy see 9.5.5.2 of IEEE Std C37.41. The preferred frequency for the capacitor discharge interrupting tests is as follows:

f = 0.8V where

f is in hertz V is the rated voltage of the fuse, in volts 5.3.6  Rated minimum interrupting [breaking] current 5.3.6.1  Capacitor fuses The rated minimum capacitive interrupting current for all types of capacitor fuses and the rated minimum inductive interrupting current for current-limiting backup capacitor fuses shall be designated by the manufacturer. 5.3.6.2  Backup current-limiting fuses The rated minimum interrupting current for backup current-limiting fuses shall be designated by the manufacturer. 5.3.7  Rated maximum application temperature (RMAT) The rated maximum application temperature (RMAT) is the maximum ambient temperature at which the device is suitable for use as designated by the manufacturer. The device shall be capable of withstanding this temperature without any deterioration that would inhibit its ability to properly interrupt the circuit. The minimum rating allowable is 40 °C. The rated maximum application temperature of the device in °C should be selected from the R20 series of preferred numbers. The R20 series is comprised of the numbers 1, 1.12, 1.25, 1.40, 1.60, 1.80, 2.00, 2.24, 2.50, 2.80, 3.15, 3.55, 4.00, 4.50, 5.00, 5.60, 6.3, 7.10, 8.00, 9.00, and their multiples of 10. Preferred values are 40 °C, 71 °C, 112 °C, and 140 °C.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

5.3.8  Rated lightning impulse withstand voltage [basic impulse insulation level (BIL)] The preferred values of rated lightning impulse withstand voltage are a function of the class of the device, the rated maximum voltage, and whether the device is intended for application in an outdoor or indoor environment. Preferred values are given in Table 5. Table 5—Preferred rated lightning impulse withstand voltages Rated maximum voltage (V) (kV)a 2.8 5.5 8.3 15.5 17.2 23.0 27

Rated lightning impulse withstand voltage (kV) Class A devices

Class B outdoor devices

Class B indoor devices

—

45

—

60

95

75

95

110

110

125 150

150

150

45 60 60 75 75 95

38

150 200

150

150

200

200

48.3

—

250

—

72.5

—

350

—

121.0

—

550

—

145.0

—

650

—

170.0

—

750

—

See 5.3.1.

a

5.3.9  Rated maximum load-break current Devices covered by this standard are not inherently load-breaking devices unless fitted with a load-breaking means. The rated load-break current for devices equipped with a load-break means shall be a minimum of the rated current as specified for these devices in 5.3.2. Certain fuses equipped with a load-break means are capable of operating in excess of the rated current during periods of overloading. In this case, the load-break rating shall be the maximum current the specific device can carry without melting the fusible element of the maximum fuse link that can be used in the device. For these devices, the manufacturer should be consulted to assure the proper load-break rating is assigned. In addition to being assigned a rated maximum load-break current (for an inductive current) a device may be assigned a rated maximum capacitive load-break current. 5.3.10  Ratings other than preferred Special circuit or environmental conditions may require devices with ratings that are different from the preferred values specified in 5.3.1 through 5.3.9. For these devices the ratings shall be agreed upon by the user and the manufacturer and additional testing may be required to validate that the device is suitable for the intended application.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

6.  Design test requirements 6.1  Dielectric tests 6.1.1  Class A [distribution class] outdoor devices Outdoor devices shall be capable of withstanding the test voltages specified in Table 6 when tested as specified in Clause 8 of IEEE Std C37.41. Table 6—Minimum dielectric withstand test voltages for Class A outdoor devices Minimum dielectric test voltages Rated lightning impulse withstand voltage (kV) a 45

Terminal-to-ground for all devices and pole-topole (phase-to-phase) for multi-pole devices

Terminal-to-terminal

Power-frequency dry-withstand voltage test (kV, rms)

Power-frequency wet-withstand voltage test (kV, rms)b

Lightning impulse withstand voltage test (kV, peak)

Powerfrequency dry-withstand voltage test (kV, rms)

Lightning impulse withstand voltage test (kV, peak)

15

13

45

15

45

60

21

20

60

21

60

75

27

24

75

27

75

95

35

30

95

35

95

125

42

36

125

42

125

150

70

60

150

70

150

200

95

80

200

95

200

See 5.3.8. Power-frequency wet withstand test voltages on the insulators that meet these values is satisfactory in lieu of this test, provided the design of the complete device does not decrease the power-frequency withstand test voltages of the insulators.

a

b

6.1.2  Class A [distribution class] indoor devices Indoor devices used in fuse enclosure packages (FEPs) shall be capable of withstanding the test voltages specified in Table 7 when tested as specified in Clause 8 of IEEE Std C37.41. Table 7—Minimum dielectric withstand test voltages for Class A indoor devices Minimum dielectric test voltages Rated lightning impulse withstand voltage (kV) a

45

Terminal-to-ground for all devices and pole-topole (phase-to-phase) for multi-pole devices

Terminal-to-terminal

Powerfrequency dry-withstand voltage test (kV, rms)

Power-frequency dew-withstand voltage test (kV, rms)b,c,d

Lightning impulse withstand voltage test (kV, peak)

Powerfrequency dry-withstand voltage test (kV, rms)

Lightning impulsewithstand voltage test (kV, peak)

15

10

45

15

45

60

19

15

60

19

60

75

26

24

75

26

75

95

35

26

95

35

95

125

42

28

125

42

125

150

60

40

150

60

150

200

95

80

200

95

200

See 5.3.8.

a

Table continues

21

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 7—Minimum dielectric withstand test voltages for Class A indoor devices (continued)

Power-frequency dew withstand voltages on the insulators that meet these values is satisfactory in lieu of this test, provided the design of the complete device does not decrease the power-frequency withstand test voltages of the insulators. c When fuse enclosure packages use a liquid or a gas other than air for its dielectric medium, the dew test is not required. d When fuse enclosure packages use air for the dielectric medium, multi-pole devices require dew tests pole-to-pole only when there is a solid type insulation between the poles. b

6.1.3  Class B [power class] outdoor devices Outdoor devices shall be capable of withstanding the test voltages specified in Table 8 when tested as specified in Clause 8 of IEEE Std C37.41. Table 8—Minimum dielectric withstand test voltages for Class B outdoor devices Minimum dielectric test voltages Rated lightning impulse withstand voltage (kV) a

Terminal-to-ground for all devices and pole-topole (phase-to-phase) for multi-pole devices

Terminal-to-terminal

Powerfrequency dry-withstand voltage test (kV, rms)

Power-frequency wet-withstand voltage test (kV, rms)b

Lightning impulse withstand voltage test (kV, peak)

Powerfrequency dry-withstand voltage test (kV, rms)

Lightning impulse withstand voltage test (kV, peak) c

95

35

30

95

39

105

110

50

45

110

55

121

150

70

60

150

77

165

200

95

80

200

105

220

250

120

100

250

132

275

350

175

145

350

193

385

550

280

230

550

308

605

650

335

275

650

368

715

750

385

315

750

424

825

See 5.3.8. Power-frequency wet withstand test voltages on the insulators that meet these values is satisfactory in lieu of this test, provided the design of the complete device does not decrease the power-frequency withstand test voltages of the insulators. c See 9.2.1. a

b

6.1.4  Class B [power class] indoor devices Indoor devices used in fuse enclosure packages shall be capable of withstanding the test voltages specified in Table 9 when tested as specified in Clause 8 of IEEE Std C37.41. Table 9—Minimum dielectric withstand test voltages for Class B indoor devices Minimum dielectric test voltages Rated lightning impulse withstand voltage (kV) a

Terminal-to-ground for all devices and pole-topole (phase-to-phase) for multi-pole devices Powerfrequency dry-withstand voltage test (kV, rms)

Power-frequency dew-withstand voltage test (kV, rms)b,c,d

45

15

60

19

75

26

110

50

Terminal-to-terminal

Lightning impulse withstand voltage test (kV, peak)

Powerfrequency dry-withstand voltage test (kV, rms)

10

45

17

50

15

60

21

66

24

75

29

83

30

110

55

121

Lightning impulse withstand voltage test (kV, peak)

Table continues

22

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Table 9—Minimum dielectric withstand test voltages for Class B indoor devices (continued) Minimum dielectric test voltages Rated lightning impulse withstand voltage (kV) a

150e

Terminal-to-ground for all devices and pole-topole (phase-to-phase) for multi-pole devices

Terminal-to-terminal

Powerfrequency dry-withstand voltage test (kV, rms)

Power-frequency dew-withstand voltage test (kV, rms)b,c,d

Lightning impulse withstand voltage test (kV, peak)

Powerfrequency dry-withstand voltage test (kV, rms)

Lightning impulse withstand voltage test (kV, peak)

60

40

150

66

165

f

150

70

40

150

77

165

200

95

80

200

105

220

See 5.3.8. Power-frequency dew withstand test voltages on the insulators that meet these values is satisfactory in lieu of this test, provided the design of the complete device does not decrease the power-frequency withstand test voltages of the insulators. c When fuse enclosure packages use a liquid or a gas other than air for its dielectric medium, the dew test is not required. d When fuse enclosure packages use air for the dielectric medium, multi-pole devices require dew tests pole-to-pole only when there is a solid type insulation between the poles. e These test voltages apply for fuses rated 23.0 kV to 27 kV. f These test voltages apply for fuses rated 38 kV. a

b

6.1.5  Capacitor fuses 6.1.5.1  Line-type fuses Line-type capacitor fuses shall be capable of withstanding the test voltages of the appropriate Class A or B fuse device as specified in 6.1.1, 6.1.2, 6.1.3, or 6.1.4 when tested as specified in Clause 8 of IEEE Std C37.41. 6.1.5.2  Unit-type fuses Dielectric tests for unit-type fuses are dependent on the capacitor bank configuration and design and cannot be assigned to the fuse itself. 6.1.5.3  Capacitor fuses used in containers or FEPs Line-type capacitor fuses used in containers or enclosures shall be capable of withstanding the test voltages specified for the line-type fuse in 6.1.5.1.

6.2  Interrupting [breaking] tests 6.2.1  General test requirements and test circuit parameters The tests required for devices covered by this standard are as listed in Table 3 of IEEE Std C37.41. 6.2.2  Expulsion-type fuses and fuse disconnecting switches Expulsion-type fuses when tested as specified in Clause 9 of IEEE Std C37.41 shall be capable of interrupting all currents from “low current” up to and including the rated maximum interrupting current of the device, with any degree of asymmetry associated with the specified X/R ratio. For expulsion fuses the “low current” is the current that melts the element in the long time range (300 s minimum). For fuses that use replaceable fuse links, including cutout fuse links used mainly with Class A [distribution class] open cutouts, the fuse shall be capable of interrupting these currents with any type and size of link recommended by the manufacturer and as specified below:

23

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

a)

For all fuses with a rated current of 100 A and below, any link size with a current rating of 1 A through 100 A.

b)

For all fuses with a rated current greater than 100 A, any link size from greater than 100 A up through the rated current of the device.

Interrupting requirements specified in this standard cover a specific combination of these components and other combinations cannot be implied from these tests. 6.2.3  Current-limiting type fuses and fuse disconnecting switches 6.2.3.1  General Current-limiting type fuses when tested as specified in Clause 9 of IEEE Std C37.41 shall be capable of interrupting all currents from “low current” up to and including the rated maximum interrupting current of the device, with any degree of asymmetry associated with the specified X/R ratio. For current-limiting general-purpose fuses, the “low current” is the current that causes the fuse to melt in not less than one hour. For full-range current-limiting fuses it is the minimum test current determined for the series 3 tests, and for backup fuses it is the rated minimum interrupting current [rated minimum breaking current] assigned by the manufacturer. 6.2.3.2  Peak overvoltage Peak overvoltages for current-limiting type fuses, as determined in accordance with Clause  9 of IEEE Std C37.41, shall not exceed the values specified in Table 10. Table 10—Maximum permissible overvoltages for current-limiting type fuses Maximum peak overvoltages (kV, peak)

Rated maximum voltage (V) (kV)a

0.5 A to 12 A

Over 12 A

2.8

13

9

5.5

25

18

8.3

38

26

70

49

23.0

105

72

27.0

123

84

38.0

173

119

15.5 17.2

See 5.3.1

a

6.2.3.3  Peak let-through [cut-off] current Peak let-through [cut-off] current for current-limiting type fuses shall be determined as specified in Clause 9 of IEEE Std C37.41. 6.2.4  Capacitor fuses Capacitor fuses shall be tested for inductive current, capacitive current, and, where applicable, discharge current. These interrupting tests are specified in 9.5 of IEEE Std C37.41. 6.2.4.1  Inductive and capacitive interrupting currents All capacitor fuses shall be capable of interrupting all capacitive currents from the rated minimum capacitive interrupting current up to and including the rated maximum capacitive interrupting current assigned by the manufacturer. Where capacitor fuses may be required to interrupt inductive currents, they shall be capable

24

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

of interrupting such currents up to the rated maximum inductive interrupting current of the device. Refer to IEEE Std C37.41 for testing details. All capacitor fuses shall be capable of interrupting these power frequency currents with all degrees of fault initiation making angle as related to voltage zero. Capacitor fuses that use replaceable fuse links shall be capable of interrupting these currents with any type and size of link recommended by the manufacturer. 6.2.4.2  Capacitor discharge current For capacitor discharge current interrupting tests, the capacitor fuse shall be capable of interrupting all capacitor discharge energy up to the maximum joule rating assigned. Capacitor fuses that use replaceable fuse links shall be capable of interrupting these currents with any size and type of link as recommended by the manufacturer. 6.2.4.3  Peak overvoltages for distribution and power class current-limiting fuses Peak overvoltages for current-limiting or combination capacitor fuses, as determined in accordance with Clause 9 of IEEE Std C37.41 shall not exceed those specified in Table 10. 6.2.4.4  Peak let-through [cutoff] current Peak let-through [cutoff] current for current-limiting or combination capacitor fuses shall be determined as specified in Clause 9 of IEEE Std C37.41.

6.3  Load-break tests Load-break tests (for devices equipped with load-break provisions), when tested as specified in A.5 of IEEE Std C37.41, shall be capable of interrupting all load currents up to the specific device’s assigned rated maximum load-break current. Devices that have a rating for breaking capacitive load current shall be capable of interrupting all capacitive load currents up to its assigned rated maximum capacitive load-break current. If the load breaking means involves breaking of the fuse link, the device shall be capable of interrupting all currents that the fuse link can carry without melting and with any size or type of fuse link recommended by the manufacturer of the load-breaking device.

6.4  Radio-influence tests 6.4.1  Class A [distribution class] fuses Class A fuses, when new, clean, and tested as specified in Clause 10 of IEEE Std C37.41 shall be capable of meeting the limits of radio-influence voltage at the test voltage specified in Table 11. Table 11—Radio-influence voltage testing parameters for Class A fuses Rated maximum voltage (V) (kV)a

Minimum test voltage (kV, rms)b

Maximum allowable radio influence voltage (µV at 1 MHz)

2.8

3.0

250

5.5

5.8

250

8.3

8.7

250

15.5 17.2

16.3

250 Table continues

25

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 11—Radio-influence voltage testing parameters for Class A fuses (continued) Rated maximum voltage (V) (kV)a

Minimum test voltage (kV, rms)b

Maximum allowable radio influence voltage (µV at 1 MHz)

23.0

24.2

250

27.0

23.0

250

38.0

23.0

250

See 5.3.1. For rated maximum voltages of 2.8 kV through 23.0 kV, the test voltages are based on the possibility of line to ground application at the device’s rated maximum voltage. For rated maximum voltages of 27.0 kV through 38.0 kV, the test voltages are based on line-to-line applications with voltages equal to or less than the device’s rated maximum voltage. If these devices are applied line-to-ground, the system voltage should be less than 23.0 kV. If the device is designed to be applied in line-to-ground applications at its rated maximum voltage, the test voltage shall be 1.05 times the rated maximum voltage.

a

b

6.4.2  Class B [power class] fuses Class B fuses, when new, clean, and tested as specified in Clause 10 of IEEE Std C37.41 shall be capable of meeting the limits of radio-influence voltage at the test voltage specified in Table 12. Table 12—Radio-influence voltage testing parameters for Class B fuses Rated maximum voltage (V) (kV)a

Minimum test voltage (kV, rms)b

Maximum allowable radioinfluence voltage (µV at 1 MHz)

2.8

1.7

500

5.5

3.34

500

8.3

5.0

500

15.5

9.4

500

17.2

9.9

500

23.0

14.0

500

27.0

16.4

650

38.0

23.0

650

48.3

29.3

1250

72.5

44.0

1250

121.0

73.4

2500

145.0

88.0

2500

170.0

102.5

2500

See 5.3.1. For power class fuses the minimum test voltage is based on line-to-line applications with voltages equal to or less than the device’s rated maximum voltage. If the device is designed to be applied in line-to-ground applications at its rated maximum voltage, the test voltage shall be 1.05 times the rated maximum voltage.

a

b

6.4.3  Capacitor fuses Line-type capacitor fuses, when tested as specified in Clause 10 of IEEE Std C37.41, shall be capable of meeting the limits of RIV at the test voltages specified in Table 1. RIV for unit fuses is dependent on the capacitor bank configuration and cannot be assigned to the fuse itself.

6.5  Temperature rise tests All devices covered by this standard when tested as specified in Clause 11 of IEEE Std C37.41 shall not exceed the temperature rise and total temperature values specified in Table 2 of IEEE Std C37.41 when the device is carrying rated current and the ambient temperature of the test is within the allowable range specified. Fuse devices being tested shall be fused with the maximum rated fuse unit, refill unit, or fuse link that is used in the

26

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

device being tested. Disconnecting devices equipped with a switch blade shall be tested with a disconnecting blade designed for the device or a blade recommended by the manufacturer. Fuse links, fuse units, or refill units, after carrying their rated current in the devices they are designed to be used in, when tested as specified in Clause 12 of IEEE Std C37.41, shall not cause the temperature rise of the device to exceed the limits specified above. Clause 11 of IEEE Std C37.41 covers testing of devices used at ambient temperatures of 40 °C and below. If the fuse application involves containers, enclosures, or an ambient temperature of greater than 40 °C, the fuse manufacturer should be consulted.

6.6  Time-current tests The minimum melting and total clearing time-current curves for fuse units, refill units, and fuse links covered by this standard shall be determined by the tests specified in Clause 12 of IEEE Std C37.41. A sufficient number of tests shall be made to demonstrate that all devices meet the requirements as follows: a)

“K” and “T” type fuse link test results shall meet the requirements specified in 7.2.2.

b)

Other fuses not specifically assigned a letter designation test results shall meet the requirements specified in 7.3.2.

c)

Capacitor fuse units, refill units, and fuse links melting current shall not exceed the minimum melting current by more than 20% for any given melting time.

6.7  Manual operation, thermal cycle, and bolt torque tests Devices covered by this standard shall be capable of withstanding the appropriate manual operation, thermal cycle, and bolt torque tests specified in Clause 13 of IEEE Std C37.41.

6.8  Liquid tightness tests for liquid immersed current-limiting type fuses and FEPs Current-limiting fuses and FEPs immersed in a liquid in an enclosure shall be capable of withstanding the liquid tightness tests specified in Clause 14 of IEEE Std C37.41.

6.9  Static relief pressure tests for fuses with expendable caps Fuses with expendable caps, tested as specified in Clause 15 of IEEE Std C37.41, shall be capable of withstanding an internal pressure without expelling the pressure-responsive section up to the minimum value of static relief pressure specified in 9.1.3.3. The pressure-responsive section shall be expelled prior to the maximum static relief pressure specified in 9.1.3.3.

6.10  Lightning surge impulse withstand fuse links Fuse links that meet the requirements of Clause 16 of IEEE Std C37.41, shall be classified as surge-resistant fuse links.

7.  Time-current characteristic requirements 7.1  General To comply with this standard, fuse links, fuse units, or refill units are not required to meet any particular time-current characteristic. Some fuse links, fuse units, or refill units have been designed to comply with the specific melting characteristics that are designated as “K” or “T” by this standard in 7.2. These designations

27

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

signify that a fuse will melt, at prescribed times, when carrying current that falls within specific ranges. The assignment of rating of this type to a fuse does not necessarily make any particular fuse interchangeable with any other particular fuse having this rating because the shape of the curves may still be significantly different. The slope and shape of the melting curve is determined by the design of the current responsive element and is a distinctive feature of each manufacturer.

7.2  “K” and “T” type fuses 7.2.1  Minimum melting and total clearing time-current characteristics The melting-time-current characteristics for “K” and “T” type fuses shall meet the minimum and maximum current values required to melt the fuse at the three time points designated in Table 13, Table 14, and as follows: a)

300 s for fuses rated at 100 A and below, and 600 s for fuses rated above 100 A

b)

10 s

c)

0.1 s

Other than with respect to the above time-current characteristics, the assignment of a “K” or “T” rating to a fuse does not make any particular “K” or “T” fuse interchangeable with any other particular fuse having this rating, because its ability to aid in the interrupting process may or may not vary between various designs. 7.2.2  Tolerance The minimum melting-current characteristics for any “K” or “T” fuse shall be not less than the minimum values specified in Table 13 and Table 14. The minimum melting-current characteristics plus manufacturing tolerances for any “K” or “T” fuse shall not be greater than the maximum values specified in Table 13 and Table 14. Table 13—Melting currents for type-K (fasta) fusesb Rated current

10 s melting current

300 s or 600 s melting currentc Minimum

Maximum

Minimum

0.1 s melting current

Maximum

Minimum

Maximum

Speed ratio

Preferred ratings e

6

12.0

14.4

13.5

20.5

72

86

6.0

10

19.5

23.4

22.5

34

128

154

6.6

15

31.0

37.2

37.0

55

215

258

6.9

25

50

60

60

90

350

420

7.0

40

80

96

96

146

565

680

7.1

65

e

128

153

159

237

918

1100

7.2

100

200

240

258

388

1520

1820

7.6

140

e

310

372

430

650

2470

2970

8.0

200

480

576

760

1150

3880

4650

8.1

8

15

18

18

27

97

116

6.5

25

30

29.5

44

166

199

6.6

e

Intermediate ratings 12

e

20

39

47

48.0

71

273

328

7.0

30 e

63

76

77.5

115

447

546

7.1

50

101

121

126

188

719

862

7.1

80

160

192

205

307

1180

1420

7.4 Table continues

28

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 13—Melting currents for type-K (fasta) fusesb (continued) Rated current

10 s melting current

300 s or 600 s melting currentc Minimum

Maximum

Minimum

1

2

2.4

―d

2

4

4.8

d

3

6

7.2

0.1 s melting current

Maximum

Speed ratio

Minimum

Maximum

10

―d

58

―

―

10

―

d

58

―

―d

10

―d

58

―

Ratings below 6 A

The terms “fast” and “slow” are used only to indicate the relative speeds for the type-K and type-T fuses. All current values are in A. c 300 s for fuses rated 100 A and less; 600 s for fuses rated over 100 A. d No minimum value is indicated because the requirement is that 1 A, 2 A, and 3 A ratings shall coordinate with the 6 A rating but not necessarily with each other. e IEC 60282-2 has assigned a rated current for these type K fuses as 6.3, 16, 63, 160, 12.5, and 31.5 respectively. The melting currents for these ratings are the same as those listed in this table. a

b

Table 14—Melting currents for type-T (slowa) fusesb Rated current

10 s melting current

300 s or 600 s melting currentc Minimum

Maximum

Minimum

0.1 s melting current

Maximum

Minimum

Maximum

Speed ratio

Preferred ratings e

6

12.0

14.4

15.3

23.0

120

144

10.0

10

19.5

23.4

26.5

40

224

269

11.5

15

31.0

37.2

44.5

67

388

466

12.5

25

50

60

73.5

109

635

762

12.7

40

80

96

120

178

1040

1240

13.0

65

e

128

153

195

291

1650

1975

12.9

100

200

240

319

475

2620

3150

13.1

140

e

310

372

520

775

4000

4800

12.9

200

480

576

850

1275

6250

7470

13.0

8

15

18

20.5

31

166

199

11.1

25

30

34.5

52

296

355

11.8

e

Intermediate ratings 12

e

20

39

47

57.0

85

496

595

12.7

30 e

63

76

93.0

138

812

975

12.9

50

101

121

152

226

1310

1570

13.0

80

160

192

248

370

2080

2500

13.0

1

2

2.4

―d

11

―d

100

―

2

4

4.8

―

d

11

―

d

100

―

3

6

7.2

―d

11

―d

100

―

Ratings below 6 A

The terms “fast” and “slow” are used only to indicate the relative speeds for the type-K and type-T fuses. All current values are in A. c 300 s for fuses rated 100 A and less; 600 s for fuses rated over 100A. d No minimum value is indicated, because the requirement is that 1 A, 2 A, and 3 A ratings shall coordinate with the 6 A rating but not necessarily with each other. e IEC 60282-2 has assigned a rated current for these type T fuses as 6.3, 16, 63, 160, 12.5, and 31.5 respectively. The melting currents for these ratings are the same as those listed in this table. a

b

29

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

7.3  Fuses not assigned a specific letter designation 7.3.1  Minimum melting and total clearing time-current characteristics Fuse links, fuse units, and refill units are available that meet and comply with this standard except that the melting time-current-characteristics differ from the specific letter designation requirements listed in 7.2 or the rated current differs from that specified in Table 3 or both. The ratings and/or the time-current-characteristics for these devices provide desirable properties for many applications. Because the current responsive element is a distinctive feature of each manufacturer, the minimum melting times and the total clearing times for these fuses shall be shown on each manufacturer’s published time-current-characteristic curves. 7.3.2  Tolerance For all other types of fuse units, refill units, or fuse links the maximum melting current should not exceed the minimum melting current by more than 20% for any given melting time.

8.  Conformance tests For all devices covered by this standard, except for unit-type capacitor fuses, the conformance tests, as defined in IEEE Std C37.41, shall consist of a power-frequency dry-withstand voltage test on the fuse support. The test shall be conducted as specified in Clause 8 of IEEE Std C37.41. Unit-type capacitor fuses do not have conformance test requirements.

9.  Construction requirements 9.1  Cutout and capacitor unit fuses and associated fuse links These construction requirements provide a basic level of dimensional standardization for cutout fuse links having an inner arc-quenching tube, the associated fuse holders, and fuse supports for the fuse cutouts, and capacitor unit fuses with which they are used. Only some dimensions deemed critical are listed. Complete mechanical interchangeability cannot be assured and would need to be determined by agreement between the manufacturer and user. The typical construction of a cutout fuse link specified by this clause is shown in Figure 1. Links rated 50 A and below shall have a removable part of the button head to achieve the requirements of Table 15.

Figure 1—Typical cutout fuse link construction

30

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

9.1.1  Cutout fuse link requirements 9.1.1.1  Length dimensions The minimum overall length of cutout fuse links rated from 1 A to 200 A shall be 510 mm (20 in) for use in devices rated 15.5 kV and less. The length of cutout fuse links for devices rated 27.0 kV and 38.0 kV has not been standardized. 9.1.1.2  Button head dimensions The diameter of the button head on cutout fuse links shall be as in Table 15. Table 15—Requirements for button head diameter Rated current of cutout fuse link (A)

mm

Diameter of button head

1–50

12.7–19.1

51–100b

19.1

0.75

101–200

25.4

1

in a

0.5–0.75a

Either 12.7 mm or 19.1 mm (0.5 in or 0.75 in) shall be readily obtainable. Some special types of cutout fuse links, such as coordinating types, have ratings that are higher than the 100 A value listed above that conform to the dimensional values for the 51 to 100 A cutout fuse links because they are designed to be used in 100 A rated fuses or fuse cutouts. When these links are used in 100 A rated fuses or fuse cutouts, they may not increase the 100 A rated current of these fuses or fuse cutouts.

a

b

9.1.1.3  Flexible conductor dimensions The cutout fuse link flexible conductor should bend readily for installation but not interfere with the proper functioning of the device. The maximum thickness of the flexible conductor shall not exceed the values in Table 16. Table 16—Flexible conductor (fuse link leader) requirements Rated current of cutout fuse link (A)

Flexible conductor thicknessa mm

in

1–50

4.0

0.156

51–100b

6.4

0.250

101–200

9.5

0.375

A flexible conductor that can be flattened easily to these dimensions complies with this standard. Some special types of cutout fuse links, such as coordinating types, have ratings that are higher than the 100 A value listed above that conform to the dimensional values for the 51 A to 100 A cutout fuse links since they are designed to be used in 100 A rated fuses or fuse cutouts. When these links are used in 100 A rated fuses or fuse cutouts they may not increase the 100 A rated current of these fuses or fuse cutouts.

a

b

9.1.1.4  Arc-quenching tube dimensions The cutout fuse link arc-quenching tube and any other terminal or cable dimension intended by the manufacturer to be normally inserted into the fuse holder (i.e., excluding the button head) shall be able to freely pass through a fuse holder meeting the requirements of 9.1.3.1. 9.1.1.5  Mechanical requirements Cutout fuse links shall be capable of withstanding a tension pull of 44.5 N (10 lbf) when tested cold (20 °C to 25 °C) without mechanical or electrical damage to any part of the fuse link.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

9.1.2  Fuse support requirements 9.1.2.1  Terminal requirements The fuse support terminals shall be capable of accommodating the conductor sizes specified in Table 17. Table 17—Dimensional range of conductor sizes to be accommodated by terminals Rated current (A)

Minimum–maximum diameter of conductor mm (in)

100

4.11–11.35 (0.162–0.447)

200

6.53–14.61 (0.289–0.575)

9.1.3  Fuseholder requirements 9.1.3.1  Fuseholder dimensions The size and shape of the fuseholder shall be as shown in Table 18. Table 18—Inside diameter of fuseholder Rated current (Ir) of fuse holder (A)

Inside diameter of fuseholder mm

in

≤ 50

7.9

0.313

≤ 100a

11.1

0.438

100 < Ir ≤ 200

17.5

0.688

Some special types of cutout fuse links, such as coordinating types, have ratings that are higher than the 100 A value listed above that conform to the dimensional values for the 100 A cutout fuse links because they are designed to be used in 100 A rated fuses or fuse cutouts. When these links are used in 100 A rated fuses or fuse cutouts they may not increase the 100 A rated current of these fuses or fuse cutouts. a

9.1.3.2  Fuseholder cap dimensions The size and shape of the fuseholder cap shall be such that it can be properly fastened per the manufacturer’s instructions for cutout fuse links constructed as listed in 9.1.1.2. 9.1.3.3  Expendable fuseholder cap requirements For devices that require expendable fuseholder caps, in addition to the requirements of 9.1.3.2, the requirements in Table 19 shall be met. Table 19—Requirements for expendable fuseholder capsa Characteristic

100 A rated current

200 A rated current

30.16 (1.188)

38.1 (1.5)

12.7-14.3 (0.5–0.563)

12.7–14.3 (0.5–0.563)

7/8–14 UNF-2B

1-1/8–12 UNF-2B

11 721–15 858 kPa (1700–2300 psi)

5516–8274 kPa (800–1200 psi)

Maximum inside diameter of pressure-responsive sectionb

19.1 (0.75)

25.4 (1)

Depth of threadc

3.18 (0.125)

3.18 (0.125)

Minimum identification heightd

4.78 (0.188)

4.78 (0.188)

Maximum outside diameter of cap Depth of bore Thread size Static relief pressure

a Dimensions are shown in mm with inches shown in parentheses, except for fasteners where only the in units are shown since there is no direct metric equivalent available. Table continues

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 19—Requirements for expendable fuseholder caps (continued)

The pressure-responsive section shall have a diameter that allows free passage of a cutout fuse link button head having this diameter. c The bore shall be full threaded to within this depth of the bottom. d Expendable caps shall be identified by the letters “E,” “EC” of height specified, or by the words “expendable cap.” b

9.1.3.4  Fuseholder to cutout fuse link electrical connection requirements To enable proper clamping of the cutout fuse link conductor, the fuseholder shall be designed to accommodate the conductor sizes specified in 9.1.1.3 while meeting the rated current requirements of 5.3.2. 9.1.3.5  Fuseholder to cutout fuse link mechanical connection requirements The fuseholder shall be designed to control the mechanical stress put on the cutout fuse link during normal mechanical (open/close) operation, limiting the tension on the fuse link to less than required in 9.1.1.5.

9.2  Class B [power class] fuses 9.2.1  Break distance The break distance of outdoor and indoor power class fuse supports or fuse disconnecting switches, when measured terminal-to-terminal in the full open position or with the fuse holder or fuse unit removed, shall be at least 10% in excess of the flashover distance over the insulators (terminal-to-ground) and also shall be such that the device in the full open position or with the fuse holder or fuse unit removed shall withstand the terminal-to-terminal test voltages specified in 6.1.3. 9.2.2  Base mounting dimensions Preferred dimensions for the base mounting holes for outdoor power class fuses are shown in Figure 2 for the values in Table 20. Base mounting holes shall not be less than 1.43 cm (9/16 in) in diameter.

Figure 2—Preferred base mounting dimensions

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Table 20—Preferred base mounting dimensions for power class expulsion and currentlimiting type fuse supports and fuse disconnecting switches Rated maximum voltage (V) (kV)a

Dimensions A

B

cm

in

cm

in

8.3

45.7

18

5 or 18

2 or 7

15.5 17.2

53.3

21

5 or 18

2 or 7

23.0 27.0

61 or 69

24 or 27

5 or 18

2 or 7

38.0

76 or 84

30 or 33

5, 8 or 18

2, 3 or 7

48.3

99

39

7.6 or 21

3 or 8 1/4

72.5

130

51

7.6 or 21

3 or 8 1/4

121.0

168

66

21

8 1/4

145.0

198

78

21

8 1/4

169.0

229

90

21

8 1/4

See 5.3.1.

a

10.  Nameplate marking requirements 10.1  Fuse supports and fuse disconnecting switches The following minimum information shall be placed on the fuse supports or fuse disconnecting switches: a)

Manufacturer’s name or identifying mark

b)

Manufacturer’s type or other product identification

c)

Rated current (maximum sizes of fuse units, refill units, or fuse links to be used)

d)

Rated maximum voltage

e)

Rated lightning impulse withstand voltage [basic impulse insulation level (BIL)]

f)

Identifying date code (month and year)

10.2  Fuse units or refill units The following minimum information shall be supplied with the product. All listed items shall be placed on the shipping containers. Items marked with an asterisk (*) shall be the minimum information placed on the fuse units or refill units: a)

Manufacturer’s name or identifying mark (*).

b)

Manufacturer’s type or other product identification of the fuses, fuse supports, or disconnecting switches for which the fuse units or refill units are designed.

c)

Rated current (*).

d)

Manufacturer’s type or identification letter for the fuse unit or refill unit. This identification shall follow the rated current marking (“200E,” “6R,” “12K,” “50E,” or other identifications where applicable) (*).

e)

Rated maximum voltage (*).

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

f)

Rated maximum interrupting current (*).

g)

Rated minimum interrupting current (for backup current-limiting type fuses only).

h)

Rated frequency.

i)

Identifying date code (month and year) (*).

10.3  Fuseholders The following minimum information shall be placed on the fuseholders: a)

Manufacturer’s name or identifying mark

b)

Manufacturer’s type or other product identification of the fuses, fuse supports, or disconnecting switches for which the fuse holders are designed

c)

Rated maximum current

d)

Rated maximum voltage

e)

Rated frequency

f)

Identifying date code (month and year)

10.4  Fuse links The following minimum information shall be placed on fuse links and their shipping containers: a)

Manufacturer’s name or identifying mark.

b)

Rated current.

c)

Manufacturer’s type or identification letter for the fuse link. This identification shall follow the rated current marking (K, T, or other identifications where applicable).

d)

Rated maximum voltage is not typically marked on fuse links. If voltage restrictions do exist, this information shall be published in the fuse link manufacturer’s literature and it is recommended that it be included on the fuse link and shipping container if possible.

10.5  Disconnecting blades The following minimum information shall be placed on all disconnecting cutout blades: a)

Manufacturer’s name or identifying mark

b)

Rated current

c)

Identifying date code (month and year)

10.6  Capacitor fuses The following minimum information shall be placed on all fuses, fuse units, and fuseholders: a)

Manufacturer’s name or identifying mark

b)

Rated current

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

c)

Manufacturer’s type or other product identification. For current-limiting fuses and fuse units, the applicable identification letters may follow the current rating (e.g., 25 C, 50 C, 80 C, etc.)

d)

Rated maximum voltage

e)

Rated maximum inductive interrupting current in rms symmetrical A

f)

Rated maximum capacitive interrupting current in rms symmetrical A

g)

For backup current-limiting-type capacitor fuses only, the minimum capacitive interrupting current and/or, where applicable, rated minimum interrupting current rms symmetrical A

10.7  Additional information Fuses may be designed for use at 50 Hz, 60 Hz, or both frequencies. Information on the suitability of fuses for a particular frequency is typically contained in the manufacturer’s literature. If there is a difference in rated performance between a system frequency of 50 Hz and 60 Hz, the rating information at each frequency, or the only permissible frequency, shall be published in the manufacturer’s literature. It is recommended that any packaging that may be used by the consumer for storage purposes be labeled so the contents can be easily and properly identified.

11.  Application, operation and maintenance guidelines 11.1  General See IEEE Std C37.48 and IEEE Std C37.48.1 for general application guidelines.

11.2  Capacitor fuses The rated capacitor discharge energy for unit fuses shall be presented as the kilojoules of parallel energy the fuse is capable of interrupting. If the tests are made at a frequency and/or voltage different than that specified in IEEE Std C37.41, this data shall also be presented.

11.3  Class B [power class] fuses 11.3.1  Outdoor mounted Class B fuses, except expulsion type The minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor mounted Class B fuses, except those of the expulsion type, should be in accordance with Table 21 in the absence of specific manufacturer’s recommendations. Table 21—Minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor mounted Class B fuses (except expulsion type)a Rated maximum voltage (V) (kV)b

Minimum pole-to-pole (phase-to-phase) centerline spacing cm

in

8.3

46

18

15.5 17.2

61

24

23.0 27.0

76

30

38.0

91

36

48.3

122

48 Table continues

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 21—Minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor mounted Class B fuses (except expulsion type)a (continued) Rated maximum voltage (V) (kV)b 72.5

Minimum pole-to-pole (phase-to-phase) centerline spacing cm

in

152

60

121.0

213

84

145.0

244

96

169.0

274

108

To be used in the absence of specific manufacturer’s recommendations. See 5.3.1.

a

b

11.3.2  Outdoor mounted Class B [power class] expulsion fuses The minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor Class B fuses of the expulsion type should be as specified in Table 22 in the absence of specific manufacturer’s recommendations. Table 22—Minimum pole-to-pole [phase-to-phase] centerline spacing for outdoor mounted Class B fusesa Rated maximum voltage (V) (kV)b

Minimum pole-to-pole (phase-to-phase) centerline spacing cm

in

8.3

91

36

15.5 17.2

91

36

23.0 27.0

122

48

38.0

152

60

48.3

183

72

72.5

213

84

121.0

305

120

145.0

366

144

169.0

427

168

To be used in the absence of specific manufacturer’s recommendations. See 5.3.1.

a

b

11.3.3  Indoor mounted Class B [power class] fuses The minimum clearance between live parts pole-to-pole [phase-to-phase] for indoor mounted power class fuses shall be as specified in Table 23 in the absence of specific manufacturer’s recommendations. Table 23—Minimum clearance between live parts for indoor mounted Class B fuses Rated maximum voltage (V) (kV)a

Minimum clearance between live parts pole-to-pole (phase-to-phase)b,c,d,e cm

in

2.8

9

3.5

5.5

11

4.5

8.3

15

6.0

15.0

19

7.5 Table continues

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table 23—Minimum clearance between live parts for indoor mounted Class B fuses (continued) Rated maximum voltage (V) (kV)a

Minimum clearance between live parts pole-to-pole (phase-to-phase)b,c,d,e cm

in

15.5 17.2

23

9.0

23.0 27.0

33

13.0

38.0

46

18.0

See 5.3.1. Fuses that eject expulsion products may require greater clearances. c Barriers may be used to facilitate insertion or removal of fuse units. Provision of adequate insulating barriers may result in modification of these clearances. d When fuses are mounted in equipment covered by other standards, minimum electrical clearances may be modified in accordance with those standards. e To be used in the absence of specific manufacturer’s recommendations. a

b

11.4  Paralleling of fuses Fuses should not be paralleled unless they have been tested in parallel. Parallel fuses should be considered a separate design and tested accordingly. Consult the fuse manufacturer for this application. See Clause 9 of IEEE Std C37.41 and the subclause concerning parallel fuses in IEEE Std C37.48 for more information.

11.5  Load-break ability Devices covered by this standard, unless incorporating load-breaking means, have no load-break rating and are not intended to be used to interrupt load current.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Annex A (informative)

Historical device rating information Previously, many of the devices covered by this standard were covered by product specific requirements in the now superseded standards IEEE Std C37.42-2009 [B4], IEEE Std C37.42-2008 [B5], IEEE Std C37.46-2000 [B7], and IEEE Std C37.47-2011 [B2]. In order to preserve the historical context of these products, this informative annex is included. Electrical distribution systems started out with voltages that were only in the range of a few thousands of volts. At that time high-voltage fuses as we know them today did not exist. The first attempt at isolating a faulted part of the system was with a couple of nails driven into the wooden crossarm with a small fusible wire wrapped around the nails. This performed satisfactorily at that time because the voltages were very low and the wood of the pole produced a gas similar to the gas produced in modern day fuse tubes that then provides a clean environment at a voltage zero. It did not take long before this became insufficient and a true high-voltage fuse was invented. It consisted of a tube with a metal cap on the top end and a metal fitting on the bottom. These metal parts could be inserted into clips. These clips were mounted on small insulators that were mounted inside a wooden box that had a wooden door on the front of it. A fusible wire of proper size was assembled into the tube and attached to the cap and the lower metal fitting. Thus the beginning of modern day enclosed type fuse cutouts. As time progressed the open type fuses cutouts and the open link fuse cutouts were developed for specific applications. Cutout was the name given to the types of fuses that were mainly used in distribution systems. As these distribution devices were being developed, power class fuses were also developed for application in substations, or other locations that required higher interrupting current capacities and the ability to be used in locations with higher X/R ratios and transient voltage characteristics. Because there were no standards at the time, the voltages of these early systems and the device ratings ranged in values depending on the user’s requirements and the manufacturer of the device. These voltages were 2.6 kV or lower. As electrical distribution systems grew and there were multiple system voltages up to 2.6 kV, the users contacted the National Electrical Manufacturers Association (NEMA) and requested that a standard voltage be developed for devices used on these systems. The standard voltage NEMA agreed upon was 2.6 kV. Interrupting capability for these various devices was 3000 A asymmetrical (approximately 2500 A symmetrical) or lower, so at that time the standard interrupting rating was set at 3000 A asymmetrical. As system voltages and interrupting capacity requirements became higher, the users requested devices with these ever higher ratings and these devices eventually became standard devices. As use of these devices became more widespread it became obvious that if you used a large enough fuse link that would not melt, or essentially a solid link, the fuse device could also be used as a switching device. This then led to the development of solid material switch blades that would fit into the fuse support and serve as the switching device. These devices became known as disconnecting cutouts. Prior to the 1970s, fuses and fuse cutouts were tested and rated for their interrupting ability in rms asymmetrical A. This was logical at that time since small links tested at full offset provided a first loop of current that was a maximum and the I2t of this loop provided the heat that ablated the lining of the fuse tube to produce a gas. This asymmetrical loop of current produced maximum gas production and this produced maximum mechanical stress on the fuse support structure and the fuseholder parts. As such, this was then and still is of interest to the fuse designer. In the latest standards, however, the asymmetrical ratings have been removed because they are of interest only to fuse designers and they were rounded approximations for information only. In the 1980s fuse interrupting ratings were changed again to be expressed in rms symmetrical A because most other distribution devices used that rating terminology. It was not really a big change because when testing

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

for the maximum asymmetrical first loop in the prior days, the circuit was set up for a particular symmetrical current and with a circuit X/R high enough to achieve the required asymmetrical loop. If the tables in the older standards are examined, it can be noted that the asymmetrical values are all round numbers because most of these devices were designed for their asymmetrical interrupting capability. The symmetrical rating was derived by using Figure D.1 in IEEE Std C37.41 Annex D. At that time most fuse engineers had an 8.5 × 11 in copy of this curve with additional lines so that a reasonably accurate factor could be obtained. Using the factor associated with a particular X/R, the symmetrical rating was obtained. To keep the symmetrical ratings somewhat uniform, the results were typically rounded out. As an example in the IEEE Std C37.42-1996 Table 2, the first line device whose asymmetrical rating was 5 kA and the X/R was 8, the resulting calculated symmetrical rating came out to be 3.57, which was rounded to 3.55 for the table. In all cases the number was rounded to a smaller number that gave the user a value that could be used for applying the device on their system, and the manufacturer the knowledge that it would function properly at that rating because it was tested at a slightly higher value than that given in the table. If you look at IEEE Std C37.42-1996, Table 1b, you will note a number of things associated with the momentary ratings (now termed rated peak short-time withstand current) of the disconnecting cutouts. The first is that the rated momentary is in rms asymmetrical A and it is the same as the rating for the cutouts interrupting ability in many cases. Rating them in asymmetrical A was the way of communicating to users that wherever particular fuse was used on a system, that the fuse cutouts support with a switchblade (i.e., disconnecting cutout) could also be used in the same section of the system. As fuses with higher interrupting ratings were developed, the associated disconnecting cutout was tested to see if it could be rated at this higher asymmetrical rating. If it did pass, the lower rated device was given the same rating. As such, the first two lines in this table show a number 10 for the first two devices. It is possible that a new blade could have been developed that met only the rating of the fuseholder, however, at that time it did not appear to be economically advantageous. When another fuseholder was designed for this support structure there were times that the device with a blade could not pass the higher momentary value and as such changes to the blades shape and/or material had to be made. In the case of the third device in this table the blade material had to be changed from a copper alloy to another alloy that had more copper content to obtain the new rating. Because the new alloy or pure copper blade was considerably more expensive, both devices were kept to provide users with economical devices that could be used on their system. As higher voltage ratings were developed, because the contact structure for the new device was the same as the lower voltage unit, these disconnects could be given the same rating as the lower voltage unit. Here again, a design may have been possible that would only have a 15-cycle rating equal to the fuses symmetrical interrupting rating, however, it did not seem economically advantageous at that time. The 8.3 kV units in the old Table 1a is an example of the above. The momentary rating has now been changed from an rms asymmetrical value to the peak value of the first major loop of current. The words and the numbers may be different but in reality the test has not changed. If you look at all the old standards it gave the option of doing the 15-cycle symmetrical current test and the momentary test using the same circuit, or done as a combined test by using a circuit that provided the current for the 15-cycle test and using the X/R for the momentary and initiating the circuit for maximum offset. The test and the current loop obtained is basically the same, except in one case we measured the rms asymmetrical current of the current loop and now we measure the peak current of the loop and use that as the device’s rating. With modern computers, users of these devices have the ability to determine what symmetrical current is available, the system X/R values, and the peak current at particular points on their system, so changing to using peak ratings was a logical step in rating these devices. Simply stated, for disconnecting cutouts if the symmetrical current available and the X/R of the system is equal to or less than the 15 cycle current and the X/R specified for short time currents in the specifications table, the device is usable at that point on the system. The new standard is a consolidation of all previously published IEEE standards covering these devices. These standards include IEEE Std C37.42, IEEE Std C37.43, IEEE Std C37.46, and IEEE Std C37.47. The consolidation was prepared by the IEEE Subcommittee on High-Voltage Fuses in order to improve the alignment with the associated testing document, IEEE Std C37.41, eliminate redundancy, and bring the standard more in line with the related IEC standards IEC-60282-1 and IEC-60282-2. Previous standards were product oriented and had numerous ratings listed for historical purposes to attempt to account for the ratings of all devices manufac-

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

tured either to prior standards or before standards existed. With this new standard, references to these products are eliminated and only the preferred values for devices are listed. In addition, previous standards included ratings for devices currently being produced that are not related to devices in the IEC standards. Table 1a and Table 1b from ANSI C37.42-1996 and Table 1 and Table 2 from IEEE Std C37.42-2009 both show the products that were specified and how the standards changed over time. As stated above, the new standard is not product oriented. These old standards specified the rated current, the required interrupting ratings, a nomenclature, the X/R ratio, the short time currents, terminal properties, and the BIL ratings for the particular devices. While the main body of this standard has been re-organized, the historical non-IEC products and preferred ratings are included in Annex B of this standard.

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Annex B (normative)

Historical IEEE (non-IEC) devices B.1  Background Previously, many of the devices covered by this annex were North American specific devices. While these devices are still acceptable for use when adhering to the appropriate parts of IEEE Std C37.41 and IEEE Std C37.42, in some manner they are more limited in application than devices specified in the main body of this document, and the associated IEEE and IEC standards. They have been moved to an annex to retain the requirements for existing products, but no further advancement of standards for these products is intended by the Committee. This normative annex preserves the historical ratings of these products. The clauses in this annex indicate the exceptions for these devices compared to standard Class A fuses and if not listed here the requirements for Class A fuses have historically applied and continue to apply.

B.2  Open-link cutouts and associated fuse links B.2.1  Preferred ratings The preferred interrupting current ratings for open-link cutouts are a function of the rated maximum voltage of the device as defined in Table B.1. Table B.1—Preferred ratings for maximum voltage, lightning impulse withstand voltage, current, and maximum interrupting current Rated maximum voltage (V) (kV) a

Rated lightning impulse withstand voltage (kV)

Rated current (A)

Rated maximum interrupting currents (kA rms symmetrical)b

Col 1

Col 1a

Col 2

Col 3

Col 4

8.3

7.8

75

50

1.2

15.5

15.0

95

50

1.2

23.0

18.0

125

50

0.75

a The preferred ratings are in column 1. Values in column 1a were the preferred ratings prior to the 1996 revision of this standard. b IEEE Std C37.41 defines the X/R for the tests that determine whether a particular device can be rated per this standard. For all ratings of open-link type fuse cutouts, the specified X/R ratio is 1.3.

B.2.2  Design tests B.2.2.1  Dielectric tests Open-link cutouts shall be capable of withstanding the test voltages specified in Table B.2 when tested as specified in Clause 8 of IEEE Std C37.41. The tests shall be made on three devices equipped with any size fuse link or refill unit.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table B.2—Preferred minimum dielectric withstand test voltages Withstand voltage Terminal-to-ground Rated maximum voltage (V) (kV)a

Terminal-to-terminal

Powerfrequency dry-withstand voltage test (kV, rms)

Powerfrequency wet-withstand voltage test (kV, rms)

Lightning impulse withstand voltage test (kV, peak)

Power-frequency Lightning dry-withstand impulse voltage test withstand voltage (kV, rms) test (kV, peak)

Col 1

Col 1a

Col 3

Col 4

Col 5

Col 6

Col 7

8.3

7.8

27

24

75

27

75

15.5

15.0

35

30

95

35

95

23.0

18.0

42

36

125

42

125

a The preferred ratings are in column 1. Values in column 1a were the preferred ratings prior to the 1996 revision of this standard. See B.2.1.

B.2.3  Radio-influence tests Open-link cutouts, when new, clean, and when tested as specified in Clause 10 of IEEE Std C37.41 shall be capable of meeting the limits of radio-influence voltage at the test voltage specified in Table B.3. Table B.3—Radio-influence voltage testing parameters for open-link cutouts Rated maximum voltage (V) (kV)a Col 1

Minimum test voltage (kV, rms)b

Maximum allowable radio influence voltage (µV at 1 MHz)

Col 3

Col 4

Col 1a

8.3

8.3

8.7

250

15.5

15.5

16.3

250

23.0

23.0

18.9

250

See B.2.1. The test voltages are based on the possibility of line to ground application at the device’s rated maximum voltage.

a

b

Construction requirements B.2.3.1  Open-link cutouts B.2.3.1.1  Terminal requirements The device terminals shall be capable of accommodating the conductor sizes specified in Table B.4. Table B.4—Dimensional range of conductor sizes to be accommodated by terminals Rated current (A)

Minimum–maximum diameter of conductor—mm (in)

50

3.25–6.38 (0.128–0.251)

B.2.3.2  Open-link fuse links B.2.3.2.1  General For open-link fuse links the construction requirements in previous documents were referred to as mechanical interchangeability requirements. The sections below describe the construction requirements that are necessary for mechanical interchangeability of the open-link fuse links covered by this standard. These fuse links are

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

intended to be used outdoors, without any further protection from degradation caused by the weather, and need to be designed accordingly. The fuse link shall be provided with flexible conductors at each end, each conductor terminating in contact buttons that are at least 12.7 mm (0.5 in) in diameter and adapted with rings for installing the fuse link and removing it from the fuse support. B.2.3.2.2  Length The length of the open-link fuse link between contact buttons shall be as specified in Table B.5. Table B.5—Length of fuse link between contact buttons Length between contact buttons

Rated maximum voltage (V) of open-link cutout (kV)

mm

in

8.3

7.8

178–216

7–8.5

15.5

15.0

178–216

7–8.5

23.0

18.0

330–356

13–14

B.2.3.2.3  Maximum thickness of flexible conductors The maximum thickness of the flexible conductors shall be as shown in Table B.6. Table B.6—Flexible conductor thickness requirements Maximum flexible conductor thickness

Rated current of fuse link (A)

mm

in

1–50

4.4

0.172

51–100

6.8

0.266

B.2.3.2.4  Tensile withstand strength Open-link fuse links shall be capable of withstanding a tension pull of 44.5 N (10 lbf) when tested cold (20 °C to 25 °C) without mechanical or electrical damage to any part of the fuse link.

B.3  Enclosed fuse cutouts and disconnecting switches B.3.1  Preferred ratings The preferred interrupting current ratings for enclosed types of fuse cutouts and fuse disconnecting switches are a function of the rated maximum voltage of the device as defined in Table B.7. Table B.7—Preferred rated maximum voltage and rated maximum interrupting current Rated maximum voltage (V) (kV) a

Rated maximum interrupting current (kA rms symmetrical)b

Col 1

Col 1a

5.5

c

5.2

— 

1.6 (2.5 b)

2.5 (4.0 b)

— 

4.0 (6.3 b)

— 

8.0 (11.2 b)

12.5 (16.0 b)

8.3 c

7.8

1.4

 —

 —

2.8

 —

5.6

— 

— 

a The preferred ratings are in column 1. Values in column 1a were the preferred ratings prior to the 1996 revision of this standard. b At 5.5 kV, the preferred interrupting current ratings are defined by two values, the rated interrupting current at maximum voltage and a higher value at 50% of maximum voltage Table continues

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table B.7—Preferred rated maximum voltage and rated maximum interrupting current (continued)

IEEE Std C37.41 defines the X/R for the tests that determine whether a particular device can be rated per this standard. For 5.5 kV rated devices the X/R is 5, and for 8.3 kV rated devices the X/R is 8.

c

B.3.2  Design tests B.3.2.1  Dielectric tests These devices shall be capable of withstanding the test voltages specified in Table B.8 when tested as specified in Clause 8 of IEEE Std C37.41. The number of tests required is as follows: a)

The tests shall be made on three devices equipped with any size fuse link or refill unit.

b)

For disconnecting cutouts the tests shall be made on three devices with the disconnecting blade recommended for the device. Table B.8—Preferred minimum dielectric withstand test voltages Withstand voltage

Rated maximum voltage (V) (kV)a

Single-voltage rated Col 1

Terminal-to-ground Power-frequency Power-frequency dry-withstand wet-withstand voltage test voltage test (kV, rms) (kV, rms)

Col 1a

Col 3

Col 4

Terminal-to-terminal Lightning impulse withstand voltage test (kV, peak)

Power-frequency dry-withstand voltage test (kV, rms)

Lightning impulse withstand voltage test (kV, peak)

Col 5

Col 6

Col 7

5.5

5.2

21

20

60

21

60

8.3

7.8

27

24

75

27

75

a The preferred ratings are in column 1. Values in column 1a were the preferred ratings prior to the 1996 revision of this standard. See 5.3.1.

B.3.3  Construction requirements B.3.3.1  Terminal requirements The device terminals shall be capable of accommodating the conductor sizes specified in Table B.9. Table B.9—Dimensional range of conductor sizes to be accommodated by terminals Rated current (A)

Minimum–maximum diameter of conductor mm (in)

50

3.25–8.03 (0.128–0.316)

100

4.11–11.35 (0.162–0.447)

200

7.34–14.61 (0.289–0.575)

B.3.3.2  Color-coding and interrupting-rating nomenclature for enclosed fuse cutouts Color-coding is not a requirement for compliance to this standard, however, when color-coding is applied to distribution enclosed cutouts, the following shall apply: a)

The colors shall be as specified in Table B.10.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

b)

The color-coding shall be a minimum of 1.61 cm2 (0.5 square in) in area, located so as to be readily visible from the ground when in front of the enclosed cutout. Table B.10—Identifying color-coding and nomenclature

Interrupting rating nomenclature

Identifying color

Rated maximum voltage (V) (kV) 5.5

ND (normal duty)

— 8.3

Rated current (A)

Rated maximum interrupting current at 50% of rated maximum voltage (kA, rms sym)

Rated maximum interrupting current at rated maximum voltage (kA rms sym)

50

2.5

1.6

100

4.0

2.5

50

—

1.4

100

—

2.8

6.3

4.0

200

11.2

8.0

50

—

2.8

50 HD (heavy duty)

Yellow

5.5 8.3

EHD (extra heavy duty)

White

5.5

White (silver)

8.3

100

100

11.2

8.0

200

16.0

12.5

100

—

5.6

B.3.3.3  Color-coding for enclosed disconnecting switches Color-coding is not a requirement for compliance to this standard, however, when color-coding is applied to distribution enclosed disconnecting cutouts, the identifying color shall be red.

B.4  R-rated fuses B.4.1  Rated short-time currents R-rated fuses are designated by the use of an “R” number and are not assigned a rated current. These fuses have a minimum allowable continuous current each fuse shall be capable of carrying. These are specified for two different ambient temperature conditions as shown in Table B.11, and the device shall carry this current continuously without exceeding the specified total temperatures in Table 2 of IEEE Std C37.41. The maximum current each R-rated fuse is capable of carrying may be somewhat higher than this minimum value. Table B.11—Minimum allowable continuous currents for R-rated fuses Fuse designationsa 1.5R

Minimum allowable continuous current (A) At 55 °C ambient

At 40 °C ambient

36

40

2R

63

70

3R

90

100

4R

115

130

5R

135

150

6R

150

170

9R

180

200

12R

210

230

18R

350

390 Table continues

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Table B.11—Minimum allowable continuous currents for R-rated fuses (continued) Fuse designationsa 24R

Minimum allowable continuous current (A) At 55 °C ambient

At 40 °C ambient

400

450

26R

430

480

30R

490

550

32R

540

600

36R

580

650

38R

630

700

Fuses above 38R are available. Because these are special designs, consult the manufacturer for continuous current values.

a

B.4.2  Time-current characteristic requirements The melting-time-current characteristics of fuse units, refill units, and fuse links for power fuses designated as R-rated shall be as follows: a)

The fuse shall melt in a range of 15 s to 35 s at a value of current equal to 100 times the “R” number.

b)

The minimum melting-time-current characteristics of an R-rated fuse at any current higher than the value of 100 times the “R” number (in A) specified in a) above shall be shown by each manufacturer’s published time-current curves, because the current-responsive element is a distinctive feature of each manufacturer.

c)

Power class R-rated current-limiting type fuses are backup type current-limiting fuses that are used with high-voltage motor starters to increase the maximum interrupting rating of the combined package. Time current curves shall be shown in the time range of 0.01 s to 100 s for power class, R-rated, current-limiting fuses.

B.5  C-rated fuses B.5.1  Time-current characteristic requirements The melting-time-current-characteristics of fuse units and refill units for distribution fuses designated as C-rated shall be as follows: a)

The current-responsive element shall melt in 1000 s at an rms current within the range of 170% to 240% of the rated current of the device.

b)

The minimum melting-time-current characteristics of a C-rated current limiting distribution fuse at any current higher than the current specified in a) above shall be shown by each manufacturer’s published time-current curves, since the current-responsive element is a distinctive feature of each manufacturer.

B.6  E-rated fuses B.6.1  Time-current characteristic requirements The melting-time-current-characteristics of fuse units, refill units, and fuse links for power fuses designated as E-rated shall be as follows:

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a)

The current-responsive element for fuses with a rated current of 100 A or below shall melt in 300 s at an rms current within the range of 200% to 240% of the rated current of the device.

b)

The current-responsive element for fuses with a rated current above 100 A shall melt in 600 s at an rms current within the range of 220% to 264% of the rated current of the device.

c)

The minimum melting-time-current characteristics of a power fuse at any current higher than the current specified in a) or b) above shall be shown by each manufacturer’s published time-current curves, because the current-responsive element is a distinctive feature of each manufacturer.

B.7  Open cutouts B.7.1  Interrupting-rating nomenclature Interrupting-rating nomenclature is not a requirement for compliance to this standard, however, when it is applied to open cutouts, the requirements in Table B.12 shall apply. Table B.12—Interrupting rating nomenclature Rated current (A)

Rated interrupting current (kA, rms sym)

200

2.8

100

1.3

100

3.55

200

8.6

100

2.8

200

7.1

27.0

100

2.5

38.0

100

5.0

Interrupting rating nomenclature

Rated maximum voltage (V) (kV)

ND (normal duty)

15.5

8.3 38.0 8.3

HD (heavy duty)

15.5

8.3 EHD (extra heavy duty)

15.5 27.0 8.3

UHD (ultra heavy duty)

15.5 27.0

100

7.1

200

13.2

100

5.6

200

10.6

100

4.0

100

13.2

200

15.0

100

10.3

200

13.2

100

8.0

200

7.1

B.8  Disconnecting devices B.8.1  General Disconnecting devices are created by the use of a removable switch blade or solid fuse link in a fuse support. In addition to the requirements of this standard for the fuse support, additional requirements are included in this annex section.

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B.8.2  Preferred ratings B.8.2.1  General The disconnecting devices covered by this standard have preferred values for rated maximum voltages, rated current, rated frequency, rated maximum application temperature, rated lightning impulse withstand voltage, and rated load-break current as defined by the fuse support that is used as specified in this standard. B.8.2.2  Rated short-time current The preferred rated short-time withstand currents of disconnecting devices shall be as specified in Table B.13. If a value for the peak and 15-cycle withstand currents of a disconnecting device to be tested does not appear in the preferred values given in Table B.13, the 15-cycle withstand current, and the X/R value for the peak short-time withstand current may be determined by the circuit parameters used to establish the rated maximum interrupting current for the expulsion fuse device from which the disconnecting switch was created by the substitution of a solid blade for the fuseholder or fuse unit. Table B.13—Preferred rated short-time withstand currents for disconnecting devices Rated current of switch blade or solid link (A)

Rated short-time withstand current Rated peak shorttime withstand current (kA)

Rated 15 cycle short-time withstand current (kA rms)

Minimum X/R to obtain rated peak short-time withstand current

Rated 3 s shorttime withstand current (kA rms)

13.7

6.3

5

1.6

9.46

4.0

8

1.6

100

9.97

4.0

12

1.6

12.74

5.0

15

1.6

16.7

7.1

8

1.6

21.4

8

12

1.6

200

300

24.4

11.2

5

3.2

26.4

10.6

12

1.6

32.8

13.2

12

1.6

21.4

8

12

1.6

20.3

8.6

8

3.2

32.8

13.2

12

3.2

34.8

16.0

5

5.0

37.3

15.0

12

3.2

B.8.3  Rating validation The rated short-time withstand currents (peak, 15-cycle, and 3 s) are validated by the design tests specified in B.8.4.1. These ratings apply only to devices where the fuse support is fitted with a removable switch blade or fuse holder with a solid link installed. The specified currents each provide validation of a different requirement for the device as follows: a)

The rated peak short-time withstand current is the peak value of current that occurs in the first maximum offset current loop of the specified design tests. This rating provides an index of the ability of the device to withstand the electromagnetic forces that occur under maximum short-circuit conditions.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

b)

The rated 15-cycle short-time withstand current provides an index of the device's ability to withstand the electromagnetic forces and the heat that may be generated under these short-circuit conditions.

c)

The rated 3 s short-time withstand current provides an index of the device’s ability to withstand the heat that may be generated under long-time short-circuit conditions.

B.8.4  Design test requirements B.8.4.1  Short-time withstand current tests Disconnecting devices equipped with a blade designed for the disconnecting device or a blade recommended by the manufacturer shall carry the rated short-time withstand currents as specified in Table B.13, when tested as specified in IEEE Std C37.41, Annex A.4. Other devices that can accept a blade designed for it, a blade recommended by the manufacturer, or a switch link designed for it or recommended by the manufacturer shall also be tested per this requirement.

B.9  Class B indoor devices B.9.1  Historical ratings and minimum dielectric withstand test voltages Historical values that while no longer preferred but that have been applicable to devices that have been in use for more than 40 years are shown in Table B.14. Table B.14—Historical preferred rated lightning impulse withstand voltages and minimum dielectric withstand test voltages Minimum dielectric test voltages Rated maximum voltage (V) (kV)a

Rated lightning impulse withstand voltage (kV)

15.5 23 and 27

Terminal-to-ground for all devices and pole-topole (phase-to-phase) for multi-pole devices

Terminal-to-terminal

Powerfrequency dry-withstand voltage test (kV, rms)

Powerfrequency dewwithstand voltage test (kV, rms)b,c,d

Lightning impulse withstand voltage test (kV, peak)

Powerfrequency drywithstand voltage test (kV, rms)

Lightning impulse withstand voltage test (kV, peak)

95

36

26

95

40

105

125

42

28

125

47

138

See 5.3.1. Power-frequency dew withstand test voltages on the insulators that meet these values is satisfactory in lieu of this test, provided the design of the complete device does not decrease the power-frequency withstand test voltages of the insulators. c When fuse enclosure packages use a liquid or a gas other than air for its dielectric medium, the dew test is not required. d When fuse enclosure packages use air for the dielectric medium, multi-pole devices require dew tests pole-to-pole only when there is a solid type insulation between the poles. a

b

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Annex C (normative)

Mounting brackets C.1  General information Requirements for dimensions, materials, finish, testing, and application of mounting brackets for use with cutouts were developed by NEMA in the 1970s. In time, these brackets began to be used for numerous products covered by this standard as well as other standard products such as distribution enclosed switches and distribution surge arrestors. The requirements for these brackets are presented here.

C.2  Construction requirements The arrangements and dimensions of brackets for crossarm, pole, or wall mounting shall be as follows: —— Type-A brackets shall be in accordance with Figure C.1. —— Type-B brackets shall be in accordance with Figure C.2.

C.3  Material requirements The material requirements for the brackets shall be as follows: a)

Part 1 and part 2—Part 1 and part 2 in Figure C.1 and Figure C.2 shall be made from steel bar with physical characteristics at least equal to those of grade 1020, specified in ASTM A575.

b)

The strength of the part 1 member of the mounting bracket shall be determined by clamping the long leg of the member to a rigid support by 3/8-in carriage bolts with the short leg at the top. A downward force shall be applied along the axis of the 1/2 × 1–1/2 in carriage bolt parallel to the longer leg and in the direction of the longer leg of the member under test. A load of 0.45 kN (100 lbs) shall be applied and then removed to take up any slack in the mounting arrangement before the measurement of position is taken. The permanent set measured at the axis of the 1/2 × 1–1/2 in carriage bolt shall not exceed 1.6 mm (1/16 in) when the following load is applied and removed: type-A bracket, 2.34 kN (525 lbs); type-B bracket, 4.18 kN (940 lbs).

c)

Bolts—Bolts shall be made from open-hearth carbon steel of a quality to meet the requirements herein listed. If hot-headed, bolts shall be made from hot-rolled carbon steel bars in accordance with grades 1020 to 1025, inclusive, of ASTM A575. Bolts, if cold-headed, shall be made from carbon steel cold-heading wire, AISI (American Iron and Steel Institute) grade 1010 to 1020, inclusive.

d)

Nuts—Nuts shall be made from hot-rolled, open-hearth carbon steel bars, AISI grades 1108 to 1120, inclusive, of a quality suitable to meet the requirements herein listed.

e)

Strength of bolts and nuts—The heads, threads, and nuts shall develop the body strength of the bolts. The strength of the 3/8-in bolts shall in no case be less than 18.68 kN (4200 lbs), and the strength of the 1/2-in bolts no less than 3.43 kN (7700 lbs). The unthreaded portion shall be capable of being bent cold at any point through an angle of 180° about a diameter equal to the diameter of the bolt without cracking the steel on the outside of the bent portion.

f)

Round washers—Round washers shall be made of a commercial grade of open-hearth steel or wrought iron.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

g)

External-tooth lockwashers—External-tooth lockwashers shall be made of steel lockwasher stock.

h)

Split lockwashers—Split lockwashers shall be made of steel or silicon bronze.

NOTE 1—Dimensions do not cover galvanizing, but parts should fit together after galvanizing. NOTE 2—Dimensions are shown in mm with inches shown in parentheses, except for fasteners where only the inch units are shown since there is no direct metric equivalent available. NOTE 3—Dimensions are shown in mm with inches shown in parentheses, except for fasteners where only the in units are shown because there is no direct metric equivalent available.

Figure C.1—Type-A mounting bracket

C.4  Dimensional requirements The dimensional requirements for the brackets shall be as follows:

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

NOTE 1—Dimensions do not cover galvanizing, but parts should fit together after galvanizing. NOTE 2—Dimensions are shown in mm with inches shown in parentheses, except for fasteners where only the inch units are shown since there is no direct metric equivalent available. NOTE 3—Dimensions are shown in mm with inches shown in parentheses, except for fasteners where only the in units are shown because there is no direct metric equivalent available.

Figure C.2—Type-B mounting bracket a)

Part 1 and part 2—Part 1 and part 2 of the type-A bracket shall be in accordance with Figure C.1. Part 1 and part 2 for the type-B bracket shall be in accordance with Figure C.2. Dimensions do not cover galvanizing, but parts shall fit together after galvanizing.

b)

Bolts—The bolt length shall be measured from the underside of the head to the end of the bolt.

c)

For part 3 on Figure C.1 and Figure C.2, the bolts shall be 3/8 × 5-in carriage bolts. The minimum diameter of the unthreaded portion before galvanizing shall be 8.2 mm (0.322 in). The head shall be in accordance with Table 1 of ANSI/ASME B18.5. The threaded portion shall be 44.5 mm (1-3/4 in) long

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

and shall be machine rolled or cut. Threads, before galvanizing, shall be in accordance with class 2A, external and class 2B, internal, threads of ANSI/ASME B1.1. d)

For part 4 on Figure C.1 and Figure C.2, the carriage bolt to be held captive in part 1 shall be 1/2 × 1-1/2 in and have at least a 28.6 mm (1-1/8 in) full thread with 13 threads per in. Other specifications for threads and the head shall be the same as in the preceding paragraph.

e)

Nuts—Nuts for the two 3/8 × 5 in carriage bolts shall be square, and for the 1/2 × 1-1/2 in captive bolts, hexagon. They shall be in accordance with the tables for regular square nuts and regular hexagon and hexagon-jam nuts of ANSI/ASME B18.2.2.

f)

Nuts shall be tapped oversize to a proper fit for the bolt so that after galvanizing the nut can be run the entire length of the thread with the fingers, without undue forcing. There shall be no unnecessary looseness between the nut and bolt.

g)

Round washers—Round washers for 3/8-in carriage bolts shall have the following minimum dimension: 25.4 mm (1 in) outside diameters, 10.3 mm (13/32 in) hole diameter, 1.6 mm (1/16 in) thickness.

h)

External-tooth lockwashers—External-tooth lockwashers, part 5, shall have the following dimensions: commercial thickness, 16 gauge [minimum 1.4 mm (0.055 in)]; nominal inside diameter, 13.5 mm (17/32 in); nominal outside diameter, 34.9 mm (1-3/8 in).

C.5  Finishing requirements The finishing requirements for the brackets shall be as follows: a)

Part 1 and part 2—Bolts, nuts, and washers of part 3 and part 4, and the external-tooth lockwasher of part 5 shall be hot galvanized in accordance with ASTM A153/A153M.

b)

Part 1 and part 2—Part 1 and part 2 shall be correctly formed and not cracked or otherwise defective.

c)

Bolts and nuts—Bolts of part 3 and part 4 shall be free from badly formed, mitred, cracked, or otherwise defective heads. The threaded end shall preferably be chamfered or rounded. Nuts shall be symmetrically formed with the holes centrally located and the bearing surface at right angles (tolerance, 3°) to the axis of the hole.

C.6  Test requirements The test requirements for the brackets shall be as follows: a)

Design tests—The manufacturer shall make such design tests on mounting brackets that demonstrates conformity with the specifications for strength and ability to meet the requirement relative to permanent set of part 1.

b)

Routine tests—The manufacturer shall make such routine tests on mounting brackets as deemed necessary to demonstrate uniformity of the product.

c)

Conformance tests—Conformance tests on mounting brackets shall be the manufacturer’s routine tests on mounting brackets unless otherwise specified and arranged for between the manufacturer and the purchaser. When conformance tests are to be made in the presence of a purchaser’s representative, they shall be arranged for between the manufacturer and the purchaser.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

C.7  Application requirements The application requirements for the brackets shall be as follows: a)

Type-A brackets—Type-A brackets shall be used with 5.2 kV to 5.5 kV and 7.8 kV to 8.3 kV open and enclosed distribution class fuses and fuse cutouts, open and enclosed disconnecting cutouts and open and enclosed disconnecting switches for crossarm and pole mounting. They should also be used with 7.8 kV to 8.3 kV, 15.0 kV to 15.5 kV, and 18.0 kV to 23.0 kV open-link distribution class fuses and cutouts for crossarm and pole applications.

b)

Type-B brackets—Type-B brackets shall be used with 15.0 kV to 15.5 kV, 27.0 kV, and 38.0 kV open distribution class fuses and cutouts for crossarm and pole application.

c)

Other distribution devices also use these brackets. Their use will be covered by other standards or by the manufacturer’s literature.

C.8  Mounting strap dimensions and configuration The mounting strap for the devices listed in a) and b) below shall be of dimensions suitable to provide for mounting the device on the mounting bracket. The strap shall be configured so that the centerline through the top and bottom of the insulator will be as follows: a)

For open and enclosed fuses and fuse cutouts, open and enclosed disconnecting cutouts, and open and enclosed fuse disconnecting switches at an angle of 15° to 20° from the vertical.

b)

For open-link fuses and cutouts, vertical or at an angle of 15° to 20°, or both.

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Annex D (normative)

Switch sticks (switch hooks) D.1  Construction requirements Switch sticks for use with distribution class devices covered by this standard shall be constructed to meet the dimensions of the head or hook shown in Figure D.1. The stick shall be 1.22, 1.83, 2.44, 3.05, or 3.66 m (4, 6, 8, 10, or 12 feet) in length. The material used in the head or hook shall provide a minimum yield strength of 138 MPa (20 000 psi). This device can also be used for equipment other than the devices covered by this standard.

NOTE—Dimensions are shown in mm with inches shown in parentheses, except for fasteners where only the in units are shown because there is no direct metric equivalent available.

Figure D.1—Switch sticks for use with distribution class devices

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IEEE Std C37.42-2016 IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories

Annex E (informative)

Bibliography [B1] IEEE C37.42-1996, American National Standard Specifications for High Voltage Expulsion Type Distribution Class Fuses, Cutouts, Fuse Disconnecting Switches, and Fuse Links.9 [B2] ANSI C37.47-2011, American National Standard Specifications for High Voltage Current-Limiting Type Distribution Class Fuses and Fuse Disconnecting Switches. [B3] IEEE Std C37.100.1™, IEEE Standard of Common Requirements for High Voltage Power Switchgear Rated Above 1000 V.10 [B4] IEEE  Std  C37.42™-2009, IEEE Standard for Specifications for High-Voltage (>1000 Volts) Expulsion-Type Distribution-Class Fuses, Fuse and Disconnecting Cutouts, Fuse Disconnecting Switches, and Fuse Links, and Accessories Used with These Devices. [B5] IEEE Std C37.43™-2008, IEEE Standard Specifications for High-Voltage Expulsion, Current-Limiting and Combination Type Distribution and Power Class External Fuses, With Rated Voltages from 1 through 38Kv, Used for the Protection of Shunt Capacitors. [B6] IEEE Std C37.45™-2007, IEEE Standard Specifications for High-Voltage Distribution Class Enclosed Single-Pole Air Switches with Rated Voltages from 1 kV through 8.3 kV. [B7] IEEE C37.46™-2010, IEEE Standard Specifications for High Voltage (>1000 V) Expulsion and Current-Limiting Power Class Fuses and Fuse Disconnecting Switches. [B8] 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.

9 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/​). 10 IEEE publications are available from The Institute of Electrical and Electronics Engineers, Inc., 445 Hoes Lane, Piscataway, NJ 08854, USA (http://​standards​.ieee​.org/​).

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