Methodical recommendations for the selection and placement of ABB circuit breakers in 0.4 kV distribution networks and low-voltage complete devices

A series of design engineers. ABB circuit-breakers in low-voltage switchboards.

View ABB guidelines (pdf, 2,2 Mb)

Low-voltage complete distribution and control device (NKU) is a combination of low-voltage switching devices with control, measurement, signaling, protection, regulation, etc. devices, completely assembled by the manufacturer of the NKU (under its responsibility on a single constructive basis) with all internal electrical and Mechanical connections with the corresponding structural elements.

NKU consists of a supporting structure intended for mounting on it the components of the NKU and the shell, as well as distribution and control equipment with all internal electrical and mechanical connections.

This publication provides reference materials on the power losses for the main components of the NKU:

  • Automatic switches;

  • Cable-conductor products that are part of the main and auxiliary purposes of the NKU;

  • Components of prefabricated and distribution buses.

And also on the basis of concrete examples, practical recommendations are given for a reasonable choice of automatic circuit breakers for NKU.

The manual provides an overview of the requirements of the main standards for NKU and equipment for distribution and management.

The analysis of the main problems faced by manufacturers of the NKU in developing its design and meeting the requirements of technical standards is analyzed.

The manual structurally consists of three main parts.

Chapter 1 is devoted to the problems of overheating in the NKU.

Chapter 2 provides recommendations for solving the problems of overheating by reasonably choosing the rated current characteristics of circuit breakers installed in the NKU.

In Chapter 3 emergency modes of operation of the NKU are considered and recommendations for reducing the probability of their occurrence are given.

The contents of the guidelines for the selection and placement of ABB circuit breakers in distribution networks:

1. Problems of overheating in switchboards

1.1. General Provisions

1.2. Rated current

1.3. Checking the temperature rise through a test

1.4. Checking the temperature rise by extrapolation

2. Recommendations for increasing the rated current of circuit breakers in switchboards

2.1. Power loss in switchboards

2.2. Dissipation of generated heat in switchboards

2.3. Dissipation of heat generated at terminals

3. Short circuit problems

3.1. Basic definitions of the parameters characterizing the electrical panel in short-circuit conditions

3.2. Notes on the electrical circuits of the switchboard

3.3. Reduced short-circuit potential and associated impacts

Example A. Example of electrical switchboards with ABB circuit-breakers

Appendix B. Types of internal separation

Appendix C. Degrees of protection ( IP code )