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, and Schneider Electric's Mark Waters believes that specifiers may take some time to adjust. He explains the changes:
Why is IEC 61439 needed?
IEC 61439 has been urgently needed for many years because the 35-year old IEC 60439 series of standards were lacking in a number of areas - being compromises between different national approaches. Some of these were strict, but others were more subjective. Where agreement could not be achieved, the subject was ignored, or vague clauses were added that could be interpreted to suit the reader's point of view.
It has been clear for some time that the foundations of the old standard were fundamentally flawed considering industry today. Designs and market requirements for assemblies have evolved such that IEC 60439-1 no longer encompasses many commonly used arrangements. To take just one example, under the old standard modular systems are not effectively covered with respect to the crucial issue of temperature rise performance.
As is well known, it is not practical to fully type test every conceivable configuration of assembly produced, and so where type testing is not feasible, there needs to be alternative ways of ensuring an assembly meets the minimum required safety and performance criteria.
The old methods for proving the design of a partially type tested assembly (PTTA) in accordance with IEC 60439-1 were weak and relied entirely on the capability and integrity of assembly designers. Previously, there was no standard for assemblies that do not fit within the categories of type tested assembly (TTA) or partially type tested assembly, so for this reason alone, the old standard is no longer suitable for today's industry. These weak foundations have made it difficult to evolve the standard in line with market needs and pressures. Every assembly manufactured should meet minimum performance and safety criteria, in spite of ever increasing demands to optimise manufacturing and reduce costs.
The new approach:
With the growing pressures for higher network utilisation, assembly design optimisation and more stringent safety regulations, the changes included in the assembly standard IEC 61439-2 are important and long overdue. All assemblies that do not have a specific product standard are covered and there is no opportunity to avoid compliance.
In the new standard, the methods of confirming design performance are practical, reflecting the different market needs and ways in which assemblies are produced. Several alternative means of verifying a particular characteristic of an assembly are also included. These are defined and their use restricted. Overall, the standard is performance based, but in some instances where design rules are used, it has to be prescriptive.
Essential changes:
In order to meet its objectives, the review of the IEC 60439 series of standards had to make changes and these have been radical ones. A number of foundations of the old standard have been discarded, in order to have a standard that better meets the LV assembly market's needs and the way it operates.
Under the previous standard, panels can be TTA or PTTA, but since many panels are too small to be covered by TTA or PTTA certifications, they fell outside of any standard. Therefore the categories of TTA and PTTA have been discarded in favour of a design 'verified assembly'. This is a classless term, where demonstration of design capability can be achieved by type test and/or by other equivalent means that include appropriate margins.
The IEC 61439 series of standards uses the same structure as other series within IEC. Part 1 is General Rules, detailing requirements that are common to two or more generic types of assembly. Each type then has a product-specific Part within the series. This then references valid clauses within the General Rules and details any specific requirements belonging to that particular type of assembly. Any clause in the General Rules that is not in the product-specific Part does not apply. Part 2 of IEC 61439 is the only Part that has a dual role, it covers power switchgear and control gear assemblies, as well as any assembly not covered by any other product specific Part.
The structure of IEC 61439 also makes revisions easier, as changes to General Rules will always tend to lag behind their introduction in product-specific Parts. It also means that assemblies cannot be specified or manufactured to IEC 61439-1, since one of the product-specific Parts must be referenced in any assembly specification. Parts (3, 4, 5 and 6) are currently being prepared by the IEC to cover all product specific Parts from the old standard and more could be added at a later date.
As business becomes more global there is the increasing need for portable designs. This is now fully recognised, as the new standard confirms that designs and design verifications are portable. For example, subject to a suitable quality assurance regime being in place, a type test certificate obtained in France, for a design carried out in the UK, is valid for an assembly manufactured in Australia.
For the first time, the new standard recognises that more than one party may be involved between concept and delivery of an assembly. IEC 61439 identifies the original manufacturer as the one responsible for the basic design and its verification and possibly, the supply of a kit of parts. It then designates the manufacturer who completes the assembly and conducts the routine tests, as the assembly manufacturer.
The original and assembly manufacturer can be the same, or, a transition may take place somewhere between concept and delivery. In any event, all parts of the assemblies must be design and routine verified by a manufacturer.
Responsibilities:
The new standard attempts to focus all parties on their respective responsibilities. Purchasers and specifiers are encouraged to view an assembly as a 'black box'. Their prime task is to specify the inputs and outputs to the assembly and to define the interfaces between the assembly and the outside world.
How the assembly is configured internally and the performance, relative to the external parameters (as defined by the purchaser or specifier) is clearly the responsibility of the manufacturer(s). They are legally responsible for the correct configuration of the individual parts and must ensure the design meets the specification, is fully verified and is fit for purpose.
Conclusion:
Compliance with the new standard is compulsory. All assemblies must be shown to meet minimum safety and performance standards by design and routine verification. Once the European equivalent standard, EN 61439-2 (BS EN 61439-2) has been listed in the Official Journal of the European Union, full compliance will become the easiest route to 'presumption of compliance' with the Electromagnetic Compatibility and Low-voltage Directives, both of which are essential before the CE mark can be applied. Partially proven design or only routine testing of some assemblies is forbidden.
Most assembly manufacturers and builders are already competent and diligent, so the new standard will not mean significant changes. IEC 61439 requires a logical approach to the design and verification of an assembly, which is essentially just good practice.
However, where previously PTTAs, or those outside of the scope of IEC 60439-1 have been provided, the panel builder may find it beneficial to purchase a basic design verified assembly in kit form, from a manufacturer such as Schneider Electric. This will enable the panel builder to avoid the time and cost of much of the design verification process.
A guide available:
As the new IEC 61439 standard needs to be fully understood to be followed correctly, Schneider Electric has published a straight forward guide to help explain the implications. This can be obtained in both printed format and as an internet download by visiting the website: www.schneider-electric.co.uk or order your hard copy by calling 0870 608 8 608.
