IEC 61439-6 ED2

Low-voltage switchgear and controlgear assemblies - Part 6: Busbar trunking systems (busways) IEC 61439-6 ED2

Scope

IEC 61439-6:2026 specifies the definitions, service conditions, construction requirements, technical characteristics and verification requirements for low-voltage busbar trunking system (BTS) (see 3.101).

NOTE Where reference to IEC 61439-1:2020 is made, the term “assembly” therefore reads as “BTS”.

This document applies to BTS as follows:
– BTS for which the rated voltage does not exceed 1 000 V AC or 1 500 V DC;
– BTS designed for a nominal frequency of the incoming supply or supplies not exceeding 1  000 Hz;
NOTE 1 Frequencies above 1 000 Hz are considered to be high frequencies (see also IEC 60664-1:2020, 4.4.1 to take into account additional constraints to insulation coordination).
– BTS intended for indoor and outdoor applications;
– BTS intended for use as stationary assemblies with or without an enclosure;
– BTS intended for use in connection with the generation, transmission, distribution and conversion of electric energy, and for the control of electric energy consuming equipment;
– BTS designed for use under special service conditions, for example in ships, in railway applications - rolling stock equipment -, or operated by ordinary persons, provided that the relevant specific requirements are complied with.

NOTE 2 Supplementary requirements in ships are covered by IEC 60092 302-2:2025;
NOTE 3 Supplementary requirements in railway applications – rolling stock equipment – are covered by IEC 61373:2026;
NOTE 4 Supplementary requirements for ordinary persons are covered by IEC 60364-4-41 and IEC 60898 series.

This document provides supplementary requirements for BTS intended for use as part of the electrical equipment of machines and can be applied in addition to the requirements given in IEC 60204-1:2016 and IEC 60204-1:2016/AMD1:2021.

This document applies to all BTS whether they are designed, manufactured and verified on a one-off basis or fully standardized and manufactured in quantity.
Either the manufacture or assembly, or both, may be carried out by a manufacturer other than the original manufacturer (see IEC 61439-1:2020, 3.10.1 and 3.10.2).
This document does not apply to individual devices, for example, circuit-breakers, fuse-switches and self-contained components such as, motor starters, power electronic converter systems and equipment (PECS), switch mode power supplies (SMPS), uninterruptable power supplies (UPS), basic drive modules (BDM), complete drive modules (CDM), adjustable speed power drives systems (PDS), stand-alone energy storage systems (battery and capacitor systems), and other electronic equipment which comply with their relevant product standards. This document describes their integration into an BTS.
This document does not apply to the specific types of assemblies covered by other parts of the IEC 61439 series, to supply track systems for luminaires in accordance with IEC 60570, to cable trunking systems and cable ducting systems for electrical installations in accordance with the IEC 61084 series, nor to power track systems in accordance with the IEC 61534 series.
For some applications involving, for example, explosive atmospheres, functional safety, fire conditions, additional requirements can apply. Such applications can be subject to other standards or local legislation in addition to those specified in this document.

Equipment within the scope of this document, which complies with this document, is deemed to meet essential safety requirements. Essential safety requirements can be subject to local legislation. This includes fully verified specifier options, for example user choice of protection against accidental contact with hazardous live parts of IPXXB or IP3XD. Where special requirements are agreed between the user and manufacturer, that are not fully specified within this document, for example, (i) part of the assembly is outside the scope of this document, (ii) exceptional vibration is present at the place of installation, (iii) exceptional voltage variations occur in service, or (iv) possible adverse effects from sonic or ultrasonic sources, a risk assessment or additional or more severe verifications can be required to demonstrate that the essential safety requirements have been fulfilled.

This second edition cancels and replaces the first edition published in 2012. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
– alignment with the structure and technical content of IEC 61439 1:2020, as applicable;
– introduction of three different types of power connection units (PCUs) (see 3.112, 3.113, 3.114);
– introduction of corresponding new verifications:
• new verifications regarding lifting (see 10.2.5), IP codes (see 10.3) and IK codes (see 10.2.6);
• new verification regarding thermal ageing behaviour of joints in a BT run (see 10.2.103);
• cracks-detection test evaluation for BTS with solid insulation and overmolding insulation (see Annex HH);
• new verifications for tap-off power connection units with several outgoing circuits (see 10.10.2.3.7);
• new mechanical and electrical verifications for BTS and tap-off power connection units trolley-type (see 10.2.8).
– modification of verification details:
• opportunity to use calculations for verification by comparison with a reference design(s) regarding short-circuit withstand strength (see IEC 61439 1:2020, 10.5.3.4 and 10.11.4);
• addition of new temperature-rise limits for conductors made of aluminium or aluminium alloys (see 9.2);
• integration of BTS with solid insulation and overmolding insulation;
• consideration of pressure relief flaps in short circuit tests (see 10.11.5.5 and 10.11.5.6.2);
• rework of Annex BB, Annex CC, Annex DD, Annex EE and Annex FF for better understanding.
– design verification regarding resistance to flame-propagation (see 10.101) is considered optional;
– design verification regarding fire resistance in building penetrations (see 10.102) is considered optional;
– all notes concerning certain countries are collected in new Annex II