IEC TS 61641:2026 – Low-voltage switchgear and controlgear assemblies

IEC TS 61641:2026 is a technical specification covering internal arc-fault protection of low-voltage switchgear and controlgear assemblies within the IEC 61439 series. It consolidates verification methods for limiting personnel injury, restricting damage, and improving power availability after an internal arc, and it introduces a structured classification of protection approaches and arcing zones.

Standard Information

IEC TS 61641:2026 defines verification methods for the ability of a low-voltage assembly to protect personnel and equipment during an internal arc-fault. Published as a technical specification, it consolidates the earlier passive and active protection approaches into one document and adds a two-level classification of assembly protection. The record details are as follows. - Designation: IEC TS 61641:2026
- Full title: Low-voltage switchgear and controlgear assemblies - Internal arc-fault protection of low-voltage switchgear and controlgear assemblies in accordance with the IEC 61439 series
- Status: Current
- Publication date: 2026-08-19
- ICS classification: 29, 29.130, 29.130.20
- Technical committee: TC 121/SC 121B

Scope and Application

The specification identifies methods used to verify that an assembly can limit the risk of injury to personnel during an internal arc-fault, limit damage to an acceptable level, and improve power availability after such an event. It takes into consideration the internal overpressure acting on covers and doors, the thermal effects of the arc or its roots on enclosures, and the effects of ejected hot gases and glowing particles. A distinctive feature of this document is its treatment of internal arc-fault mitigation systems (IAMS). It addresses the correct function of the IAMS within the assembly, the prevention of unintended IAMS operation — for example caused by switching arcs — and the functioning behaviour of the IAMS immediately after the assembly is energized. These systems comprise internal arc-fault control devices such as optical-based detectors, internal arc-fault reduction devices such as arc quenching devices, and short-circuit protection devices. Three assessment approaches are described: passive protection through mechanical construction such as door locks, hinges, pressure relief devices and barriers; active protection through integration of an IAMS; and the use of an arc ignition protected zone, which makes arc ignition an extremely remote possibility. The document does not supersede any individual product standard, does not cover arc fault detection devices, and does not address toxic gas emission, loud noises, intense light, maintenance conditions, or personal protective equipment.

Products and Materials Covered

The scope covers low-voltage switchgear and controlgear assemblies conforming to the IEC 61439 series, including assemblies or defined zones of assemblies evaluated for arcing in air caused by an internal failure. The ICS classifications 29.130 and 29.130.20 place the document within switchgear and controlgear, specifically low-voltage assemblies. Related equipment falling within the assessment chain includes the components of an IAMS: internal arc-fault control devices, arc quenching devices acting as internal arc-fault reduction devices, and short-circuit protection devices. Individual devices must comply with their own relevant standards; this technical specification addresses the integrated assembly, not the devices in isolation. Guidance annexes support users of assemblies, users of actively protected assemblies, and original manufacturers incorporating an integrated IAMS.

Testing and Compliance Considerations

Verification of arc-fault performance is typically performed as a type test on representative assembly configurations. Laboratories arc-initiate a defined test arrangement and evaluate indicators such as the behaviour of covers and doors under overpressure and the thermal effects on enclosure surfaces. For assemblies with active protection, the test programme also examines whether the IAMS operates correctly, does not trip on normal switching arcs, and functions as expected immediately after energization. Documentation is central to compliance. Test reports record the assembly configuration, the assessed zones and areas, the protection level assigned, and the observation criteria applied. Because this document distinguishes between zone — the micro-environment within the assembly — and area — the place of installation and accessibility — reports should state precisely which space was assessed. Retest triggers follow common industry logic: mechanical construction changes affecting pressure relief, barriers, hinges or locks, alterations to the IAMS composition, and changes in rated short-time characteristics may each require renewed verification. Procurement specialists should confirm that a report covers the specific arcing class zone and protection level claimed for the configuration being purchased.

Related Standards and Series Context

The designation reveals the document's position in IEC structure. The number 61641 places it within the IEC 616xx numbering block for electrical installation and equipment topics, while the prefix "TS" marks it as a technical specification — a normative document of a provisional or complementary nature rather than a full international standard. The year suffix 2026 identifies this edition. The full title ties the document to the IEC 61439 series on low-voltage switchgear and controlgear assemblies, under which it applies without superseding any individual product standard. Readers requiring the authoritative text should obtain it through official IEC channels; this page offers an interpretive overview only, prepared for engineering and procurement reference.