IEC/TS 61641 Ed. 1.0 en:2026

IEC TS 61641:2026 identifies methods used to verify the ability of the assembly:

• to limit the risk of injury to personnel during an internal arc-fault;
• to limit the damage to an acceptable level as a result of an internal arc-fault;
• to improve the power availability following an internal arc-fault.

This document takes into consideration:

• the effects of the internal overpressure acting on covers, doors, etc.;
• the thermal effects of the internal arc-fault or its roots on the enclosures and of ejected hot gases and glowing particles;
• the correct function of the IAMS within the assembly;
• the prevention of unintended operation of the IAMS within the assembly, for example caused by switching arcs;
• the functioning behaviour of the IAMS immediately after the assembly is energized.

This document describes different methods to assess the performance of an assembly or zones of an assembly in respect of arcing in air due to an internal failure:

• with "passive" arc-fault protection (provided by mechanical construction, e.g. suitable door locks, hinges, pressure relief devices, barriers);
  NOTE 1 This approach corresponds to the method according to IEC TR 61641:2014.
• with "active" arc-fault protection (with the integration of IAMS);
  NOTE 2 This approach corresponds to the method according to IEC TS 63107:2020.
• with the use of an arc ignition protected zone (to make the ignition of an arc-fault an extremely remote possibility).
  NOTE 3 This approach corresponds to the method according to IEC TR 61641:2014.

IAMS consist of internal arc-fault control devices (IACD), e.g. optical-based IACD's in accordance with IEC 60947-9-2 and internal arc-fault reduction devices (IARD), e.g. arc quenching devices (AQDs) in accordance with IEC 60947-9-1 and short-circuit protection devices (SCPD's) in accordance with IEC 60947-2 (see Figure EE.1). IAMS can be provided by a combined-type device according to IEC 60947-9-2.

IEC 60364-4-42:2024 (Clause 427) provides guidance on the need for internal arc-fault protection.

This document does not supersede any individual product standard. Individual devices are required to comply with their relevant standard.

This document does not apply to integration of arc fault detection devices (AFDD) according to IEC 62606.

Informative Annex AA gives guidance for the user (see IEC 61439-1:2020, 3.11) on internal arc-fault mitigation.

Informative Annex BB gives guidance for the user (see IEC 61439-1:2020, 3.11) of assemblies with "active" arc-fault protection (with the integration of IAMS).

Informative Annex CC gives guidance for the original manufacturer of an assembly when incorporating an integrated IAMS.

This document does not consider other effects which can constitute a risk, such as emission of toxic gases, loud noises and/or intense light. Furthermore, this document does not consider conditions during maintenance work and the personal protective equipment used.

This edition cancels and replaces IEC TR 61641:2014 and IEC TS 63107:2020. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous edition:

• a) Introduction of the term "arcing class zone", using the term "arcing classes" from the previous document IEC TR 61641:2014.
• b) Structured using of the terms "zone" and "area". "Area" is used to describe the place of installation and the accessibility of the assembly (macro-environment). "Zone" is used in this document to describe a defined space within the assembly (micro-environment).
• c) Assembly protection is classified into two levels.