EMC implementation - Busway

From Electrical Installation Guide

Busways reduce the risk of exposure to electromagnetic fields.

Fig. R15 – Power cables and metallic busways magnetic field radiations

According to the WHO (World Health Organisation), exposure to electromagnetic fields can be a health hazard starting at levels as low as 0.2 micro-Teslas and could represent a long-term risk of cancer. Some countries have created standards that stipulate limits (e.g. 0.2 µT at 1 metre in Sweden).

All electrical conductors generate magnetic fields proportional to the distance between them. The design of busbar trunking with tightly spaced conductors in a metal enclosure helps to considerably reduce radiated electromagnetic fields.

The electromagnetic field characteristics of busbar trunking are well defined and measurements show that they are far below potentially dangerous levels (see Fig. R16).

In specific cases, where particularly low values are required (computer rooms, medical rooms, some offi ces), it is important to minimize the magnetic induction generated by power cables.

Magnetic induction is:

  • proportional to the current
  • proportional to the distance between the conductors
  • inversely proportional to the square of the distance with respect to the busbar.

Busbar with a steel casing provides a good screening effect compared to power cables: magnetic field reduced from 2 to 30 times, depending on the Canalis model.

This is particularly low because of the short distance between the bars and the additional attenuation provided by the steel casing.

Fig. R16 – Canalis busbar trunking system data