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Guidelines to the construction of a low voltage switchgear

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LV switchgear and controlgear switchgear

An electrical assembly is a combination of more protection and switching devices, grouped together in one or more adjacent cases (column).

Guidelines to the construction of a low voltage switchgear
Guidelines to the construction of a low voltage switchgear (photo credit: infrafox.com)

In an assembly the following parts can be distinguished: a case, called enclosure by the Standards, (it has the function of support and mechanical protection of the housed components), and the electrical equipment, formed by the internal connections and by the incoming and outgoing terminals for the connections to the plant.

As all the components of an electrical system, also assemblies shall comply with the relevant product standard. As far as Standards are concerned, an evolution has occurred with the replacement of the former IEC 60439-1 with the Stds. IEC 61439-1 and IEC 61439-2.

These Standards apply to all the low-voltage switchgear and controlgear assemblies (for which the rated voltage does not exceed 1000 V in case of a.c. or 1500 V in case of d.c.).

Single line diagram and switchboard front view with LV components
Single line diagram and switchboard front view with LV components

Throughout this document, the term assembly is used for a low-voltage switchgear and controlgear assembly.


This Technical Application Paper has the purpose of:

  1. Describing the main innovations and changes introduced in the new Standard as regards structure, definitions and contents (e.g.: methods of verification of assemblies and relevant application conditions), paying particular attention to the performance verifications as regards: temperature-rise limits, short-circuit withstand strength and dielectric properties;
  2. Giving a document which includes useful information for the realization and certification of LV assemblies in compliance with the Standards IEC 61439.

This document is divided into 7 main parts

  1. Introduction and description of the new Stds. IEC 61439;
  2. Definition of the rated electrical characteristics, of IP and IK degrees and of the forms of internal separation for an assembly;
  3. Standard prescriptions as regards: temperature-rise, short-circuit withstand strength and dielectric properties (clearance or creepage distances);
  4. Prescriptions for the protection against direct and indirect contact;
  5. Instructions for construction, handling, transport and final installation of assemblies;
  6. Properties and performances (design verifications) of assemblies and a guide for the carrying out of routine verifications (assembly type-approval);
  7. An example of choice of products (circuit-breakers, conductors, distribution system, busbars and structure) for the construction of ArTu assemblies.

In an assembly the following parts can be distinguished: a case, called enclosure by the Standards, (it has the function of support and mechanical protection of the housed components), and the electrical equipment, formed by the internal connections and by the incoming and outgoing terminals for the connections to the plant).

Such system shall be assembled in order to meet the safety requirements and satisfy as much as possible the functions for which it has been designed.

Title:Guidelines to the construction of a low-voltage assembly (complying with the Standards IEC 61439 Part 1 and Part 2) – ABB
Format:PDF
Size:1.75 MB
Pages:84
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Technical Application Paper - Guidelines to the construction of a low-voltage assembly complying with the Standards IEC 61439 Part 1 and Part 2
Technical Application Paper – Guidelines to the construction of a low-voltage assembly complying with the Standards IEC 61439 Part 1 and Part 2

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