Intro To Iec Rules 61439

Improving safety
and performance
in electrical assemblies
A guide to IEC 61439-2

Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
New series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
New approach . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Fundamentalchanges . . . . . . . . . . . . . . . . . . . 14
Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . 17
Design verification . . . . . . . . . . . . . . . . . . . . . . 18
Ambiguities clarified . . . . . . . . . . . . . . . . . . . . 21
Specific issue addressed . . . . . . . . . . . . . . . . . 22
Summary & conclusion . . . . . . . . . . . . . . . . . . 24
Technical specification. . . . . . . . . . . . . . . . . . 26

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Typical schematic diagram
Medium voltage
Power factor
correction

High power
switchboards

Canalis busbar
solutions

Active
harmonic
filters

Medium power
switchboards

Panelboards

Power
factor
correction
Ready to install assemblies

4Introduction
Since it was first published over 35 years ago,
IEC 60439 has provided the basis for specification and
testing of low-voltage electrical assemblies. As was the case
for many early IEC standards, it was a compromise between
different national approaches, some of which were very
stringent, even prescriptive, and others that were more
subjective.
Where consensus could not beachieved, the subject was ignored, or some
vague clause was added that could be interpreted to suit the reader’s point of view.
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 manufacture and reduce costs.Application needs, however, make it impractical to type test every variant that is provided.
Some frequently used design concepts, such as modular systems, are not adequately covered.
Furthermore, many assemblies produced do not fit neatly into the Type Tested Assembly (TTA)
or Partially Type Tested Assembly (PTTA) categories.
Some smaller assemblies may not be covered by either TTA or PTTA andare therefore
effectively outside the scope of IEC 60439. In the case of a PTTA, the standards’
requirements for proving a design are very subjective and entirely dependent on
the knowledge and integrity of the particular manufacturer.

5

Schneider Electric, along with other leading UK assembly
manufacturers, long recognised the limitations of IEC
60349. Some 10 years ago the companyproposed, via
the Manufacturers’ Associations and British Standards,
that the IEC carry out a radical review of the IEC 60349
series of standards.
It also suggested, if practical, that the IEC restructure and improve
the series of standards to reflect the present and future applications
and requirements for assemblies.
A fundamental review has questioned every aspect of IEC 60439
and hasbeen a long and tortuous task. Despite there having been
an International standard for many years and, although major
manufacturers have attempted to promote international designs
of assemblies, views differ markedly around the world about basic
performance and requirements.

6

Achieving consensus has once again been very difficult. However, the first parts of the new series
of standardshave been published. The approach to specifying an assembly, proving its capability,
and the format of the standard itself, have all fundamentally changed.
In due coarse, the two parts of the series that have been published by IEC will be issued as EN
Standards and then subsequently automatically as British Standards. The EN Standards will be
identical to the IEC Standards. The only...