New standard IEC61439-2 for low-voltage switchgear and controlgear assemblies

Last week I met Jean-Paul Lionet, a member of IEC technical committee who participates to the evolution of Low Voltage Switchgear & Control Gear Assemblies standards. Below is the summary he prepared for me. Don’t hesitate to add your comments or questions !


The IEC 60439-X standards cover all Low Voltage switchgear and controlgear assemblies, i.e. all kind of switchboards and busbar trunking systems. Intended to ensure safety and power availability, they have a long track record of well proven and widely recognized tools, both for design and verification rules and as a reference for certification.

They are now evolving towards a new IEC 61439-X series, aiming to better cover all Assemblies and ensure that the specified performances are achieved.

The main changes may be summarized as follows :

1 – Recognition is made of the evolution of the organization of the industry, between Original Manufacturer and Assembly Manufacturer :

  • The conditions for Assembly Manufacturers to benefit from the design verifications made by the Original Manufacturer are stated.

2 – Rules for comparison of a variant with a tested design have been detailed :

  • The concepts of TTA (type tested Assembly) and PTTA (Partially Type Tested Assembly), which have been frequently abused and misused, have left the floor to a unified verification approach

3 – Many safety or power availability related requirements have been clarified or reinforced :

  • Clarification of the requirements regarding temperature rise, including the rated diversity factor
  • Calculations based on safety margins as a means of exemption from temperature rise tests for low-power switchboards
  • Increased protection against transient overvoltages
    esp. application of higher clearances as a means of exemption from the impulse withstand test
  • Better definition of the representative test samples
  • Recognition of insulation of live parts and integral housing of the devices as means of meeting internal separation
  • Increased mechanical endurance
  • A lifting test
  • Increased protection against environmental conditions (ingress of water, mechanical impact, resistance to corrosion, resistance to UV for outdoor applications).

4 – These changes and merely editorial choices have resulted in a new structure and a new numbering of the series : the IEC 60439-1 has been split into IEC 61439-1 “general rules” for LV switchgear and controlger assemblies and IEC 61439-2 specific to “Power switchgear and controlgear assemblies”. Parts 2 to 5 of the current series will be aligned on the new IEC 61439-1 by 2011-2012.

IEC 61439-1 and -2 have been published in January 2009.

Each country will apply a transitional period according to its own rules.
In Europe, EN 61439-1 and EN 61439-2 will be published as national standards around mid 2009;
EN 60439-1 will remain valid until 2012, to give time to the manufacturers that might need it to modify their design, to carry out extra testing, and to get 3rd party approval.

A revision of this newly published standard has already been opened.
Schneider Electric will take this opportunity to go on pushing towards more user oriented standards, esp. through an improved Annex C intended to make it easier to specify an assembly.

Jean-Paul LIONET
Member of the IEC SC 17D (Maintenance Teams in charge of the IEC 60439 and IEC 61439 standards)

To obtain the new standard, refer to the IEC website


  • Does the new standard , require the panel builder to supply only ,the same branded circuit breakers ,which were used on the type tested assembly in their client panels ?

    Is so , doesn’t it limit the available options for the panel builder as he will be restricted with only one brand of circuit breakers for all his future projects?

    • The use of electrical protections of the same brand is very important when you desing an electrical system because it´s the only way to satisfay the requirements about coordination (selectivity and shortcircuit energy limitation). All the electrical protections are located in electrical swithboards and panelboards then all of them have to belong the same manufacturer. When you use electrical protections from different brands or manufacturers, it´s impossible to achieve it.
      On the other hand, it´s very important to comply with IEC 439-2 standard because you can offer a tested assembly to your clients if you follow all the manufacturer recomemdations about it, for example, the Prisma Plus System from Schneider Electric. The IEC 439-2 states ten tests that you have to do, the manufacturer makes seven of them in the factory and you have only to do three tests at your workshop. It´s true that the type tested assemblies are much more expensive, but you can achieve much more security and reliability and as a result much more reliability in the electrical service continuity.

    • interesting question from Joy : I decided to give my point of view in this dedicated article, for better visibility by others

    • I feel that Type tests need to repeated for FBA’s if devices mounted on them are different from the original test FBA.

      Different makes of devices have diifernt parameters for watt loss which may effect the temprature rise or different terminal sizes / supporting arrangement etc. which may effect the short circuit withstand of busbars supporting system on ACB’s.

  • Dose we need to retest our samples which were tested recently under the old standard?

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