Transmission of electricity and power lines Transmission of electricity and power lines

Transmission of electricity and power lines

Transmission of electricity and power lines

Household electrical equipment and wiring

Household electrical equipment and wiring

Generally, low frequency electric and magnetic fields in Finnish homes are well below the values recommended for the general public. The background level of the electric field is about 0.01 kV/m, which is one fifth of the population’s recommended value for long-term exposure. The background level of the magnetic field in homes is slightly below 0.1 μT, which is one-thousandth of the population’s recommended value for long-term exposure.

The voltages of household electrical equipment and wiring are small and thus do not give rise to significant electric fields. Magnetic fields exceeding the background level of 0.1 μT may exist in the immediate vicinity of household electrical equipment and wiring. Magnetic fields exceeding a few microteslas may exist in apartments directly above a building transformer. A large main electric switchboard, such as a switchboard in a block of flats, may generate such a magnetic field around it. However, that magnetic field weakens rapidly to a typical background level at a distance of about two metres from the electric switchboard. The magnetic field produced by the distribution panel or fuse box in an apartment weakens to the background level at a distance of less than half a metre.

Magnetic fields exceeding the background level may also be found in the vicinity of metal structures in a building, if the building has an old-fashioned electrical system with only four wires: three phase conductors and a neutral conductor. In that case, all the electric current coming to the building will return via the neutral conductor and the metal structures connected to it back to the point of supply in the form of stray currents that cause a magnetic field. A modern electrical installation eliminates these stray currents and magnetic fields.

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