MT 2 - TC 121/SC 121B/MT 2

IEC 61439-2:2020 defines the specific requirements for the power switchgear and controlgear assembly (abbreviated "PSC-assembly" throughout this document see 3.1.101) as follows:
- assemblies for which the rated voltage does not exceed 1 000 V AC or 1 500 V DC;
- assemblies designed for a nominal frequency of the incoming supply or supplies not exceeding 1 000 Hz;
NOTE 1 Frequencies above 1 kHz are considered as high frequencies, see also IEC 60664-1:2007, 5.3.3.2.5 to take into account additional constraints to insulation coordination.
- assemblies intended for indoor and outdoor applications;
- stationary or movable assemblies with or without enclosures;
- assemblies intended for use in connection with the generation, transmission, distribution and conversion of electrical energy, and for the control of equipment consuming electrical energy and for associated data processing;
- assemblies designed for use under special service conditions, for example in ships and in rail vehicles, provided that the other relevant specific requirements are complied with;
NOTE 2 Supplementary requirements for assemblies in ships are covered by IEC 60092-302-2.
This third edition cancels and replaces the second edition published in 2011. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) addition of Annexes DD, EE and FF for assemblies for use in photovoltaic installation;
b) clarification of the requirements for forms of internal separation and the addition of the requirement, when the form of separation is higher than 1, all parts within the functional unit compartment that remain live when the functional unit is switched off shall be protected to at least IPXXB;
c) alignment with the structure of IEC 61439-1:2020;
d) addition of temperature-rise verification for; (i) temperature-rise verification of assemblies with natural cooling and circuits rated above 1 600 A by a combination of comparison with a reference design and calculation, and; (ii) temperature-rise verification of assemblies with active cooling and rated currents up to 1 600 A;
e) consideration of IP with active cooling.

IEC 61439-1:2020 is available as IEC 61439-1:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 61439-1:2020 lays down the general definitions and service conditions, construction requirements, technical characteristics and verification requirements for low-voltage switchgear and controlgear assemblies. NOTE Throughout this document, the term assembly(s) (see 3.1.1) is used for a low-voltage switchgear and controlgear assembly(s). For the purpose of determining assembly conformity, the requirements of the relevant part of the IEC 61439 series, Part 2 onwards, apply together with the cited requirements of this document. For assemblies not covered by Part 3 onward, Part 2 applies. This third edition cancels and replaces the second edition published in 2011. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) clarification that power electric converter systems, switch mode power supplies, uninterruptable power supplies and adjustable speed power drive systems are tested to their particular products standard, but when they are incorporated in assemblies the incorporation is in accordance with the IEC 61439 series of standards;
b) introduction of a group rated current for circuits within a loaded assembly and the refocusing of temperature-rise verification on this new characteristic;
c) addition of requirements in respect of DC;
d) introduction of the concept of class I and class II assemblies regarding protection against electric shock.
The contents of the corrigendum of December 2021 have been included in this copy.

IEC TR 61641:2014 gives guidance on the method of testing of ASSEMBLIES under conditions of arcing in air due to an internal fault. The purpose of this test is to assess the ability of the ASSEMBLY to limit the risk of personal injury, damage of ASSEMBLIES and its suitability for further service as a result of an internal arcing fault. This third edition cancels and replaces the second edition published in 2008. It constitutes a technical revision. This third edition includes the following significant technical changes with respect to the previous edition:
- arcing classes to define the different forms of protection provided against arcing faults; (i) personnel protection, (ii) damage restricted to part of the ASSEMBLY, and (iii) ASSEMBLY suitable for limited further service.;
- two levels of personnel protection afforded by ASSEMBLIES under arcing fault conditions; (i) for ASSEMBLIES installed in areas where access to the ASSEMBLY is restricted to skilled persons, and (ii) for ASSEMBLIES installed in areas where the area is accessible to ordinary persons;
- option of individually insulating all live conductors to make the complete ASSEMBLY an arc ignition protected zone (referred to as an 'arc free zone' in previous editions of the Technical report);
- arc fault protection front, back and sides of an ASSEMBLY as the normal requirement;
- minimum performance requirements for arc ignition protected zone.

IEC/TR 61439-0:2013(E), which is a technical report identifies, from the user's perspective, those functions and characteristics that should be defined when specifying ASSEMBLIES. It provides:
- an explanation of the ASSEMBLY characteristics and options within the IEC 61439 series;
- a guidance on how to select the appropriate option and to define characteristics so as to meet specific application needs, using a functional approach; and
- an assistance in the specification of ASSEMBLIES. This second edition cancels and replaces the first edition published in 2010. It constitutes a technical revision. This second edition includes the following significant technical changes with respect to the previous edition:
- alignment with IEC 61439-1:2011;
- alignment of Annex B with Annex AA of IEC 61439-2:2011;
- alignment of Table C.1 with Table BB.1 of IEC 61439-2:2011;
- addition of a new Annex D regarding IEC 61439-3;
- addition of a new Annex E regarding IEC 61439-4;
- addition of a new Annex G regarding IEC 61439-6;
- general editorial review. Within the IEC 61439 series of standards for low-voltage switchgear and controlgear assemblies (ASSEMBLIES), there are system and application details that are specified by the user to enable the manufacturer to produce an ASSEMBLY that meets the needs and expectations of the user.

IEC 61439-1:2011 lays down the definitions and states the service conditions, construction requirements, technical characteristics and verification requirements for low-voltage switchgear and controlgear assemblies. This standard cannot be used alone to specify an ASSEMBLY or used for a purpose of determining conformity. ASSEMBLIES shall comply with the relevant part of the IEC 61439 series; Parts 2 onwards. This standard applies to low-voltage switchgear and controlgear assemblies (ASSEMBLIES) only when required by the relevant ASSEMBLY standard as follows:
- ASSEMBLIES for which the rated voltage does not exceed 1 000 V in case of a.c. or 1 500 V in case of d.c.;
- stationary or movable ASSEMBLIES with or without enclosure;
- ASSEMBLIES intended for use in connection with the generation, transmission, distribution and conversion of electric energy, and for the control of electric energy consuming equipment;
- ASSEMBLIES designed for use under special service conditions, for example in ships and in rail vehicles provided that the other relevant specific requirements are complied with;
- ASSEMBLIES designed for electrical equipment of machines provided that the other relevant specific requirements are complied with. This second edition cancels and replaces the first edition published in 2009. It constitutes a technical revision. This second edition includes the following significant technical changes with respect to the last edition of IEC 61439-1:
- revision of service conditions in Clause 7;
- numerous changes regarding verification methods in Clause 10;
- modification of routine verification in respect of clearances and creepage distances (see 11.3);
- adaption of the tables in Annex C and Annex D to the revised requirements and verification methods;
- revision of the EMC requirements in Annex J;
- shifting of tables from Annex H to new Annex N;
- new Annex O with guidance on temperature rise verification;
- new Annex P with a verification method for short-circuit withstand strength (integration of the content of IEC/TR 61117);
- update of normative references;
- general editorial review.

IEC 61439-2:2011 defines the specific requirements of power switchgear and controlgear assemblies (PSC-ASSEMBLIES) as follows:
- ASSEMBLIES for which the rated voltage does not exceed 1 000 V in case of a.c. or 1 500 V in case of d.c.;
- stationary or movable ASSEMBLIES with or without enclosure;
- ASSEMBLIES intended for use in connection with the generation, transmission, distribution and conversion of electric energy, and for the control of electric energy consuming equipment;
- ASSEMBLIES designed for use under special service conditions, for example in ships and in rail vehicles provided that the other relevant specific requirements are complied with;
- ASSEMBLIES designed for electrical equipment of machines.
Supplementary requirements for ASSEMBLIES forming part of a machine are covered by the IEC 60204 series. This second edition cancels and replaces the first edition published in 2009. It constitutes a technical revision. This second edition includes the following significant technical changes with respect to the last edition of IEC 61439-2:
- clarification of the scope;
- revision of requirements for withdrawable and removable parts;
- revision of mechanical impact test (10.2.6);
- extension of Table 101;
- review of Table BB.1 to reflect modified requirements and verifications;
- general editorial review.
This publication is to be read in conjunction with IEC 61439-1:2009.