IEC Publications

The IEC 60439 series of standards for low-voltage (LV) switchgear and controlgear assemblies is being replaced by the restructured and substantially revised IEC 61439 series. As such, the old standard, the fourth edition of IEC 60439-1:1999 is being replaced by IEC 61439-1 and IEC 61439-2. What does this entail?

The new series is expected to include the following parts (note that others may be added):

• IEC 61439-1 - General rules
• IEC 61439-2 - Power switchgear and controlgear assemblies
• IEC 61439-3 - Distribution boards (to supersede IEC 60439-3)
• IEC 61439-4 - Assemblies for construction sites (to supersede IEC 60439-4)
• IEC 61439-5 - Assemblies for power distribution (to supersede IEC 60439-5)
• IEC 61439-6 - Busbar trunking systems (to supersede IEC 60439-2).

IEC 61439-3, IEC 61439-5 and IEC 61439-6 are being developed and are expected to be published in 2011. IEC 61439-4 is to follow shortly after, with an expected publication date of 2012. Note that until all the parts of the new IEC 61439 series are available, the current product parts of the IEC 60439 series still apply. This implies that the previous part, IEC 60439-1, will remain applicable in the context of the IEC 60439 series until the final product part, IEC 61439-4, has been integrated in the new series.

Why the change?

The standard has been changed because assembly designs and market needs have evolved to the extent that IEC 60439-1no longer relates to many common arrangements today. For example, modular systems are not effectively covered with respect to temperature rise performance.

• It is not practical to fully type test every conceivable configuration of assembly produced. Where type testing is not feasible, there have to be alternative ways of ensuring an assembly meets the minimum required safety and performance criteria.
• The methods for proving the design of a PTTA in accordance with IEC 60439-1 are weak and rely entirely on the capability and integrity of assembly designer.
• There is no standard for assemblies that do not fit within the categories of TTAs or PTTAs.
  

IEC 61439-1 and IEC 61439-2

Regarding LV switchgear and controlgear assemblies, the following information is provided by the IEC:

IEC 61439-1:2009 provides the definitions, service conditions, construction requirements, technical characteristics and verification requirements for LV switchgear and controlgear 'assemblies'. This new standard applies only when required by the relevant 'assembly'standard.

The aim has been to provide restructured and substantially revised International Standards in a new series of publications that should provide users with clearer and more concise reference documents. This restructure means that for each type of LV switchgear and controlgear assembly, there are only two main standards required to determine requirements with the corresponding methods of verification. These are:

• The basic general rules part, IEC 61439-1, referred to in the specific standards that cover the various types of low-voltage switchgear and controlgear assemblies. IEC 61439-1, harmonises all the general rules and requirements applicable to LV switchgear and controlgear assemblies. It contains the definitions and states the service conditions, construction requirements, technical characteristics and verification requirements for low-voltage switchgear and controlgear assemblies.
• The product standard replacing IEC 60439-1 is IEC 61439-2.
• The assembly standard for each specific type of LV switchgear and controlgear assemblies, for example, IEC 61439-3, which deals with distribution boards. This is still being developed.

The technical differences:

There are some significant technical changes compared with IEC 60439-1, which is a pure 'general rules' standard to be referred to by subsidiary product parts of the IEC 61439 series. The product standard replacing IEC 60439-1 is IEC 61439-2; the discrimination between type-tested assemblies (TTA) and partially type-tested assemblies (PTTA) is eliminated by the new verification approach.

Thee different but equivalent types of verification of requirements have been introduced: verification by testing, verification by calculation/measurement, or verification by satisfying design rules; the requirements regarding temperature rise have been clarified; the rated diversity factor (RDF) is covered in more detail; and requirements from the standard for empty enclosures for assemblies (IEC 62208) have been incorporated. In addition, the new standard's whole structure has been aligned with its new function as 'general rules' standard. However, when a dated reference to IEC 60439-1 is made in another Part of the IEC 60439 series of assembly standards not yet transferred into the new IEC 61439 series, the superseded IEC 60439-1 still applies.

More specifically, IEC 61439-1 compares to the previous edition, IEC 60439-1, in that the discrimination between type-tested assemblies (TTA) and partially type-tested assemblies (PTTA) is done away with by the verification approach - as already stated. Also, three different, but equivalent types of verification of requirements have been introduced. These are:

• Verification by testing.
• Verification by calculation/measurement.
• Verification by satisfying design rules.

In addition to proper testing, IEC 61439 specifies how calculations and design rules can be used to prove that the product family complies with the specified short circuit ratings and the temperature rise limits as stated by the standard. This is ideal for testing assemblies made up of several variants.

Compliance with the new standard is compulsory. All assemblies must be shown to meet minimum safety and performance standards by design and routine verification.

What the change means for contactors and panel builders:

Essentially, the change for contractors is to ensure they specify assemblies in accordance with IEC 61439-2. They should also ensure that they provide all the details specified in Annex CC of BS EN 61439-2.

For competent manufacturers and panel builders, there should be little change in approach to the provision of assemblies. This is because the new standard requires a logical approach to the design and verification of an assembly that is really present good practice. Where previously PTTAs, or assemblies outside of the scope of IEC 60439-1 have been provided, the panel builder may find it an advantage to purchase a basic design verified assembly in kit form. This will enable the panel builder to avoid the time and cost of much of the design verification process.

Manufacturers may have to provide more proof that their product families follow the correct design guidelines and rules to comply with IEC 61439.

Summary of differences between 60439-1 and 61439 Parts 1 and 2 - Originally intended for switchboards and motor control centres, IEC 60439-1 has become a general purpose document for specifiers of switchgear, but now lacks the depth of detail for many of the products to which it is now being applied. This is the reason for the new IEC 61439 standard. This brief but concise BEAMA guide outlines the main differences between the two standards.

Out with IEC 60439 and in with IEC 61439 - Following a review of IEC 60439, significant changes have been made and the new IEC 61439, governing the safety and performance of electrical panels, now better meets the low voltage (LV) assembly market's needs. The changes are fundamental.