oSIST prEN IEC 61439-6:2025

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

Niederspannungs-Schaltgerätekombinationen - Teil 6: Schienenverteilersysteme (busways)

Ensembles d'appareillage à basse tension - Partie 6: Systèmes de canalisation préfabriquée

Sestavi nizkonapetostnih stikalnih in krmilnih naprav - 6. del: Zbiralčni povezovalni sistemi (zbiralčna vodila)

General Information

• Status: Not Published
• Public Enquiry End Date: 31-Dec-2025
• ICS: 29.130.20 - Low voltage switchgear and controlgear
• Technical Committee: SKA - Switchgear and control gear
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 28-Oct-2025
• Due Date: 17-Mar-2026
• Directive: 2014/30/EU - Directive 2014/30/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to electromagnetic compatibility (recast)
• Directive: 2014/35/EU - Directive 2014/35/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of electrical equipment designed for use within certain voltage limits
• Mandate: M/511 - Mandate to CEN, CENELEC and ETSI relating to harmonised standards in the field of the Low Voltage Directive
• Mandate: M/552 - [C(2016) 7641 final] Standardisation request as regards harmonised standards in support of Directive 2014/30/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to electromagnetic compatibility
• Ref Project: prEN IEC 61439-6:2025 - Low-voltage switchgear and controlgear assemblies - Part 6: Busbar trunking systems (busways)

Relations

• Revises: SIST EN 61439-6:2012 - Low-voltage switchgear and controlgear assemblies - Part 6: Busbar trunking systems (busways) (IEC 61439-6:2012)
• Effective Date: 13-Dec-2022

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2025
Sestavi nizkonapetostnih stikalnih in krmilnih naprav - 6. del: Zbiralčni
povezovalni sistemi (zbiralčna vodila)
Low-voltage switchgear and controlgear assemblies - Part 6: Busbar trunking systems
(busways)
Niederspannungs-Schaltgerätekombinationen - Teil 6: Schienenverteilersysteme
(busways)
Ensembles d'appareillage à basse tension - Partie 6: Systèmes de canalisation
préfabriquée
Ta slovenski standard je istoveten z: prEN IEC 61439-6:2025
ICS:
29.130.20 Nizkonapetostne stikalne in Low voltage switchgear and
krmilne naprave controlgear
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

121B/223/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61439-6 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2025-10-24 2026-01-16
SUPERSEDES DOCUMENTS:
121B/205/CD, 121B/220/CC
IEC SC 121B : LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR ASSEMBLIES
SECRETARIAT: SECRETARY:
Germany Mr Jörg Hußmann
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 121, SC 121A
ASPECTS CONCERNED:
Electromagnetic Compatibility, Safety
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of CENELEC,
is drawn to the fact that this Committee Draft for Vote (CDV) is
submitted for parallel voting.
The CENELEC members are invited to vote through the CENELEC
online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are aware
and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some Countries” clau ses to be
included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for submitting ISC c lauses. (SEE
AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking systems (busways)

PROPOSED STABILITY DATE: 2029
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

IEC CDV 61439-6 © IEC 2025
CONTENTS
FOREWORD . 4
1 Scope . 7
2 Normative references . 9
3 Terms and definitions . 11
4 Symbols and abbreviations . 15
5 Interface characteristics . 15
5.1 General . 15
5.2.4 Rated impulse withstand voltage (𝑈 ) (of the assembly) . 16
imp
5.3.1 Rated current of an assembly (𝐼 ) . 16
nA
5.3.2 Rated current of a main outgoing circuit (𝐼 ) . 16
nc
5.3.3 Group rated current of a main circuit (𝐼 ) . 18
ng
5.4 Rated diversity factor (RDF) . 18
5.5 Rated frequency (𝑓 ) . 19
n
5.6 Other characteristics . 19
5.101 Phase conductor and fault-loop characteristics . 19
5.102 Electromagnetic flux density . 22
6 Information . 22
6.1 Assembly designation marking . 22
6.2.2 Instructions for handling, installation, operation and maintenance . 22
7 Service conditions . 22
7.1.2 Pollution degree . 22
7.2 Special service conditions . 22
8 Constructional requirements . 23
8.1.1 General . 23
8.1.5 Mechanical strength . 23
8.1.101 Ability to withstand mechanical loads . 23
8.1.102 Ability of plug-in power connection units to withstand thermal variations . 24
8.2.1 Protection against mechanical impact (IK code) . 24
8.2.2 Protection against contact with live parts, ingress of solid foreign bodies
and water (IP code) . 24
8.3.2 Clearances . 25
8.3.3 Creepage distances. 25
8.4.3 Fault Protection . 25
8.5.2 Removable parts . 25
8.5.5 Accessibility . 25
8.6.101 Correct connection between busbar trunking units (BTUs) . 25
8.6.102  Correct connection between busbar trunking runs . 25
9 Performance requirements . 26
9.2 Temperature-rise limits . 26
9.101 Optional: Resistance to flame-propagation . 26
9.102 Optional: Fire resistance in building penetration . 26
IEC CDV 61439-6 © IEC 2025
10 Design verification . 27
10.1 General . 27
10.2.5 Lifting . 27
10.2.6 Verification of protection against mechanical impact (IK code) . 28
10.2.8 Mechanical operation . 28
10.2.101 Ability to withstand mechanical loads . 29
10.2.102 Thermal cycling test of joints in a BT run . 31
10.2.103 Thermal cycling test of plug-in power connection units . 32
10.3 Degree of protection of BTS (IP Code) . 34
10.5.3 Short-circuit withstand strength of the protective circuit . 35
10.10  Temperature-rise . 35
10.10.1 General . 35
10.10.2 Verification by testing . 36
10.10.3 Verification by comparison . 42
10.10.4 Verification assessment. 43
10.11 Short-circuit withstand strength . 44
10.11.1 General . 44
10.11.3 Verification by comparison with a reference design – Using a checklist . 44
10.11.5 Verification by test . 44
10.101 Optional design verification: Resistance to flame-propagation . 47
10.102 Optional design verification: Fire resistance in building penetrations . 48
11 Routine verifications . 49
11.1 General . 49

Annexes . 50
Annex AA (informative) Items subject to agreement between the BTS manufacturer
and the user . 51
Annex BB (informative) Design verification . 55
Annex CC (informative) Calculation of voltage drop of the system . 57
Annex DD (informative) Phase conductor characteristics . 58
Annex EE (informative) Fault-loop zero-sequence impedances . 61
Annex FF (informative) Fault-loop resistances and reactances . 64
Annex GG (informative) Determination of the magnetic flux density in the vicinity of
the BTS . 67
Annex HH (informative) cracks-detection-test evaluation to BTS with solid insulation
or over moulding insulation . 69
Annex II  (informative) List of notes concerning certain countries . 71

Bibliography . 72

Figures 101, 102, 103 Examples of phase transposition BTU . 13
Figure 104 Example of conductor sequence changer BTU . 13
Figure 105 Orientation horizontal edgewise . 17
Figure 106 Orientation horizontal flatwise . 17
IEC CDV 61439-6 © IEC 2025
Figure 107 Positions of a PCU on a horizontal BTU with tap-off facilities . 18
Figure 108 Mechanical load test of a straight unit . 29
Figure 109 Mechanical load test of a joint . 30
Figure 110a Test arrangement for verification of a fire-barrier BTU in a floor . 49
Figure 110b Test arrangement for verification of a fire-barrier BTU in a wall . 49
Figure DD.1 Phase conductors characteristics determination . 58
Figure EE.1 Fault loop (phases – Neutral) zero-sequence impedances determination . 61
Figure EE.2 Fault loop (phases – PE) zero-sequence impedances determination . 61
Figure FF.1 Fault loop (here: L1 – N) resistances and reactances determination . 64
Figure FF.2 Fault loop (here: L1 – PE) resistances and reactances determination . 64
Figure GG.1 Magnetic flux density measurement arrangement . 67
Figure HH.1 Example of BTS with an over moulded insulation . 69
Figure HH.2 Example of test setup . 70

Table 101 Assumed loading factors for a tap-off power connection unit . 19
Table 102 Phase conductor characteristics . 20
Table 103 Fault-loop characteristics . 21
Table 104 Characteristics to be used for fault currents calculations . 21
Table 105 Conditioning for the thermal cycling test . 33
Table AA.1 Items subject to agreement between the BTS manufacturer and the user . 51
Table BB.1 List of design verifications to be performed .
...