IEC 61439 - The Switchgear Standard 

By on

Switchboard_Front
IEC 61439 -
The New Switchgear Standard
The new standard IEC 61439 replaces the old 60439.  Compared to the old standard, the new 61439 is a more clearly defined and takes into account the assembly of pre-tested designs. . 

Some key differences are that the distinction between type tested assemblies (TTA) and partially type tested (PTTA) is gone, verifying the performance is addressed in new ways and the specification of current ratings is updated.  

For more information on testing to the standard, see:

IEC 61439 Verification Methods

Current Ratings

Within the 61439, current ratings are clarified and more clearly defined.t ratings.

  • The standard defines the overall rated current of the assembly (Ina) as the smaller of the sum of  rated currents of incoming circuits or the total current the main busbar is capable of distributing.
  • The rated current of a circuit (Inc) is the rating of a circuit taking in to account the installed devices, disposition and application (and may be lower than the rated current of the devices used).
  • A rated diversity factor (RDF) is assigned by the manufacturer to groups of outgoing circuits which can be simultaneously loaded and takes into account the mutual thermal influence between the circuits.  This can be applied to the whole assembly or a group of circuits.

This clarification of ratings ties the consideration and specification of a switchboard more closely into the manufactured product.  Personally I think is a good thing.  It does put more emphasis on specifiers to understand how the assembly will perform and what they want out of it. 

Typical RDF

The RDF is a figure to be given by manufacturers.  Some typical values I found on the Schneider website are:

Number of main outgoing circuits

Diversity factor

2 and 3

0.9

4 and 5

0.8

6 to 9 inclusive

0.7

10 and more

0.6

 

Specification of Switchboards

The standard will change how specifiers state their requirements.  Currently specification is often carried out based around devices (i.e. circuit breakers from a particular manufacturer for example), with the device ratings being applied to switchboards.  This is not the case any longer.  There is now a clear need to consider the effect of the enclosure and surrounding components in addition to those of the protective devices and trip units. 

See Also



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus



Windows Live Writer and myElectrical

When making adding a Note to our site we have a great online WYSIWYG editor and things are pretty simple.  However, if you prefer you can write, manage...

Restricted Earth Fault Protection

The windings of many medium and small sized transformers are protected by restricted earth fault (REF) systems. The illustration shows the principal of...

Back to Basics - Ohm’s Law

Electrical engineering has a multitude of laws and theorems. It is fair to say the Ohm's Law is one of the more widely known; it not the most known. Developed...

Cold Fusion (or not?)

Recently I have seen a few interesting articles on viable cold fusion; the combining of atoms at room like temperatures to create boundless energy. Now...

Tips for a better Low Voltage Protection Discrimination Study

Carrying out a protection system discrimination study is critical to ensure the correct functioning of  the electrical system in the event of faults. ...

ABB Technical Guides - Motor Operation

ABB has produced a range of technical guides that offer concise explanations of the major technologies and technical issues in low voltage AC drives. ...

Why a Sine Wave?

I received this question by email a few weeks. First thoughts was that it is a product of the mathematics of rotating a straight conductor in a magnetic...

Capacitor Theory

Capacitors are widely used in electrical engineering for functions such as energy storage, power factor correction, voltage compensation and many others...

Periodic Electrical Installation Inspection – How Often?

How often installations are inspected is up to the owner of the installation, provided such durations do not exceed any regulatory maximums in force. ...

8 Motor parts and common faults

Straight forward list of some common motor faults.  If I have missed any other common faults, please take a bit of time to add them in as a comment below...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note