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



Standard Cable & Wire Sizes

IEC 60228 is the International Electrotechnical Commission's international standard on conductors of insulated cables. Among other things, it defines a...

Low Voltage Switchroom Design Guide

Low voltage (LV) switchrooms are common across all industries and one of the more common spatial requirements which need to be designed into a project...

Switchboard - Forms of Internal Separation

IEC 61439 'Low-voltage switchgear and controlgear assemblies', specifies standard arrangements of switchboard (call forms of internal separation). The...

Introduction to Lighting

When looking at the design of a lighting scheme it is useful to have an understanding on the nature of light itself and some of the basic theory associated...

MIT OpenCourseWare

MIT OpenCourseWare, makes the materials used in teaching all MIT subjects available on the Web, free of charge, to any user in the world.

Motor Starting - Introduction

Motor starting and its associated problems are well-known to many people who have worked on large industrial processes. However, these things are, of course...

IEC Document Designation

Often document control is dictated by project requirements, for example a particular organisation may have an existing numbering system. Existing company...

3 Phase Loads

Three phase systems are derived from three separate windings, either connected in delta or star (wye). Each winding can be treated separately, leading...

Large Hadron Collider

The 27 km, Euro 6 billion  Collider lies on the border between France and Switzerland, took nearly 30 years to complete.  Some of the lofty goals for the...

Electric Motors

Collection of links to various places with useful motor information. I’ll try and return to the page every now and again to update it with any motor notes...

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