Key Standards for Medium Voltage Fuses (IEEE, IEC, UL)

About this list

Each standard below was checked on the publisher's own catalog page (IEEE SA, the IEC Webstore, UL Standards and Engagement's store, NETA) on 22 September 2026. We give the exact designation and title, and we say when a document has been superseded. Editions change, so confirm the edition named in your specification before relying on it.

This page explains what the standards cover in general terms. DENCO makes no claim here about which standards any DENCO product is certified, listed or tested to. For a specific part, ask DENCO engineering what test documentation is available.

1. IEEE C37.41: design tests (and now specifications) for high-voltage fuses

In short: Knowing how a high-voltage fuse design is proven in the laboratory

The active edition is IEEE C37.41-2024, IEEE Standard for Design Tests and Specifications for High-Voltage (> 1000 V) Fuses and Accessories, approved by the IEEE SA Standards Board in December 2024 and published in July 2025. It sets the procedures for design tests on high-voltage fuses and fuse disconnecting switches, including dielectric, interrupting, radio-influence, temperature-rise, time-current, manual-operation, liquid-tightness, thermal-cycle, bolt-torque, motor-circuit withstand, load-break and short-time current tests, for devices rated up to 170 kV.

The previous edition, C37.41-2016, also superseded IEEE C37.40-2003, the long-standing standard for service conditions and definitions. Many catalogs still cite "ANSI C37.40" for the definitions of expulsion and current-limiting fuses and of the full-range, general-purpose and back-up classes.

IEEE C37.41 website

2. IEEE C37.42-2016: the consolidated fuse specification

In short: Finding where the E and R rating definitions now sit

IEEE C37.42-2016, IEEE Standard Specifications for High-Voltage (>1000 V) Fuses and Accessories, brought several older specifications into one document. It superseded IEEE C37.43-2008, IEEE C37.46-2010 (power class fuses) and IEEE C37.47-2011 (distribution class current-limiting fuses). It covers Class A and Class B expulsion and current-limiting fuses, fuse cutouts and fuse disconnecting switches from 1 kV to 170 kV, and external capacitor fuses.

IEEE SA's catalog now lists the 2016 edition as superseded without naming the successor on that page. Because C37.41-2024 adds "Specifications" to its title, check with IEEE which document holds the clause your specification relies on.

IEEE C37.42 website

3. Legacy citations: ANSI/IEEE C37.46 and C37.47 and the E and R ratings

In short: Reading older drawings, purchase specs and catalog pages

Most installed-base documentation cites ANSI/IEEE C37.46 for E and R ratings. Its last edition was IEEE C37.46-2010, Standard Specifications for High-Voltage (>1000 V) Expulsion and Current-Limiting Power Class Fuses and Fuse Disconnecting Switches, now superseded by C37.42-2016. Mersen's 2024 catalog cites C37.42-2016 for the same definitions.

The definitions themselves didn't change meaning. An E-rated fuse of 100E or less melts in 300 seconds at 200 to 240 percent of its E rating; above 100E the test point moves to 600 seconds. An R-rated fuse melts in 15 to 35 seconds at 100 times its R number. The E rating fixes only the melting characteristic, not voltage, interrupting rating, dimensions or mounting.

Legacy C37.46 and C37.47 citations website

4. IEEE C37.48-2020: the application guide and tutorial

In short: Engineers who need the reasoning behind fuse application, not just the test limits

IEEE C37.48-2020, IEEE Guide and Tutorial for the Application of High-Voltage (> 1000 V) Fuses and Accessories, is active. It explains the construction, operation and application of current-limiting, expulsion, electronic and other non-current-limiting fuses, and covers North American, European and other application practices. It replaced C37.48-2005, whose title included operation and maintenance.

As a guide, it contains recommendations rather than product requirements, which makes it the natural companion to the C37.41 and C37.42 specifications.

IEEE C37.48 website

5. IEC 60282-1:2020: current-limiting fuses

In short: The international baseline for current-limiting medium voltage fuses

IEC 60282-1:2020, High-voltage fuses - Part 1: Current-limiting fuses (edition 8.0, April 2020), applies to all types of high-voltage current-limiting fuses for indoor or outdoor use on 50 Hz and 60 Hz systems above 1000 V. It divides current-limiting fuses into back-up, general-purpose and full-range classes, which is how IEC-style datasheets express the same idea as the C37 classes.

The 2020 edition adjusted its Series II voltages and tests to match present North American system voltages and clarified requirements for fuse-links used in surrounding temperatures above 40 °C.

IEC 60282-1 website

6. IEC 60282-2:2008: expulsion fuses

In short: Cutout and expulsion fuse-link applications outside North American C37 practice

IEC 60282-2:2008, High-voltage fuses - Part 2: Expulsion fuses (edition 3.0), covers expulsion fuses for indoor or outdoor use on 50 Hz and 60 Hz systems above 1000 V. The 2008 edition eliminated Class C, revised transient recovery voltage values, added tests for non-ceramic insulators and a lightning impulse withstand test for fuse-links.

If you are replacing cutout expulsion links with current-limiting dropout fuses, the replacement fuse falls under the current-limiting standards instead.

IEC 60282-2 website

7. IEC 60644: fuse-links for motor circuits

In short: Motor protection fuse-links specified to IEC practice

IEC 60644:2009+AMD1:2019, Specification for high-voltage fuse-links for motor circuit applications (consolidated edition 2.1), applies to fuse-links that comply with IEC 60282-1 and are used with motors on 50 Hz and 60 Hz systems. It standardizes time-current characteristics and sets pulse withstand requirements, because a motor fuse has to survive repeated starting currents without damage.

It addresses the same application that North American practice handles with R-rated back-up fuses coordinated with a starter's overload relay.

IEC 60644 website

8. IEC 60549:2013: external fuses for shunt capacitors

In short: Capacitor unit fuses and capacitor bank line fuses

IEC 60549:2013, High-voltage fuses for the external protection of shunt capacitors (edition 2.0), applies to external fuses used with high-voltage capacitors built to IEC 60871-1. It recognizes two jobs: unit fuses that clear a fault inside one capacitor unit so the rest of the bank keeps running, and line fuses that isolate the whole bank from the system.

In North American practice, external capacitor fuses are within the scope of IEEE C37.42-2016.

IEC 60549 website

9. IEC TR 62655:2013 and IEC 62271-105:2021: the tutorial and the switch-fuse standard

In short: Transformer fuse selection and fused switchgear to IEC practice

IEC TR 62655:2013, Tutorial and application guide for high-voltage fuses, is an informative technical report with no requirements. It covers current-limiting, expulsion, electronic and other fuses above 1 kV and replaced IEC TR 60787, the old transformer fuse-link selection guide.

IEC 62271-105:2021, High-voltage switchgear and controlgear - Part 105: Alternating current switch-fuse combinations for rated voltages above 1 kV up to and including 52 kV (edition 3.0), covers three-pole assemblies of a switch or switch-disconnector with current-limiting fuses, where a fuse striker trips the switch.

IEC TR 62655 and IEC 62271-105 website

10. UL 248 series and UL 2579: context, not medium voltage

In short: Understanding why UL appears in fuse specifications at all

UL 248-1, Low-Voltage Fuses - Part 1: General Requirements, applies to low-voltage fuses rated 1000 V or less, ac and/or dc, with interrupting ratings up to 300 kA, used under the NEC and the Canadian Electrical Code. The other parts of UL 248 cover the individual low-voltage fuse classes. Medium voltage fuses fall outside that scope.

UL 2579, Fuses for Photovoltaic Systems, is a product standard written for fuses protecting PV strings and arrays, for dc systems up to 1500 V. Mersen's technical note explains that UL 2579 adds tests beyond UL 248, such as checks for thermally induced drift, operation at temperature extremes and current cycling. It matters for PV string and array fuses on the dc side of a solar plant, not for the medium voltage collection system.

UL 248 and UL 2579 website

Standards for the work, not the fuse

Three more documents appear in almost every fuse-related job, but none of them is a fuse product standard:

• NFPA 70E, Standard for Electrical Safety in the Workplace: work practices, risk assessment, lockout/tagout and PPE when working on or near electrical equipment, including fuse replacement and testing.
• NFPA 70B, Standard for Electrical Equipment Maintenance: converted from a recommended practice to a standard with the 2023 edition.
• ANSI/NETA ATS-2025 (Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems) and ANSI/NETA MTS-2023 (Standard for Maintenance Testing Specifications for Electrical Power Equipment and Systems): field inspection and test procedures for switches, starters and fuses, including fuse resistance measurement.

How to use this list in a specification

Name the standard and the edition. "ANSI C37.46" on an old drawing still tells you what the E or R rating means, but a new purchase specification should reference the current IEEE document and edition. For IEC projects, name IEC 60282-1 for current-limiting fuses and add IEC 60644 or IEC 60549 where the application is a motor or a capacitor bank.

Then ask each supplier for the evidence behind the claim: which standard, which edition, and which laboratory ran the design tests. DENCO tests its fuses in-house at its factory lab, and third-party testing at IPH Berlin (Germany) is available on client request. DENCO does not state on this page which standards any of its products are certified or listed to. Ask DENCO engineering about a specific part.

Frequently asked questions