Transformer station

Kompaktstation

Transformer stations are often designed as single-storey kiosk substations or housed in small transformer buildings. In densely built-up city centres, transformer stations are also commonly found in residential or commercial buildings. Transformers are usually connected to the medium- and low-voltage grid via underground cables.

In rural areas, transformers are often installed without an enclosure on an electricity pole. These are referred to as pole-mounted transformers.

Trafohäuschen

Low-frequency magnetic fields occur in the vicinity of transformer stations

The total current on the low-voltage side of a transformer station is higher than that on the medium-voltage side. As the strength of the low-frequency magnetic fields increases with increasing current, the relevant field sources from a radiation protection perspective are above all the live wires on the low-voltage side.

When it comes to assessing the degree to which the general public is exposed to low-frequency fields from transformer stations, the key factor is the magnetic flux density occurring outside the station. This varies according to the current at the present time and therefore depends on how much electrical energy is currently being consumed in or supplied to the connected low-voltage circuits.

How strong are the fields?

The actual exposure to low-frequency magnetic fields depends on factors such as the construction of the transformer and the distance between the low-voltage distribution (the totality of live wires on the low-voltage side) and the walls or ceiling of the station.

Magnetic flux densities in the order of some 100 microtesla can occur at the outer walls of kiosk substations (this value corresponds to the limit value in the 26th Ordinance Implementing the Federal Immission Control Act [26th BImSchV]). These values are significantly lower at a distance of just a few metres. Precise data can be obtained from field measurements or calculations adapted to the individual case.

If installations are located in residential or commercial buildings, the low-frequency magnetic fields act directly on adjacent rooms. Elevated values can therefore occur in rooms next to or above a transformer station.

Where are the limit values defined?

Transformer stations are low-frequency installations within the meaning of the 26th Ordinance Implementing the Federal Immission Control Act (26th BImSchV). The operator of a station is responsible for ensuring that the limit values set out in the Ordinance are adhered to at locations intended for the not merely temporary presence of human beings. In addition, the 26th BImSchV sets out required precautionary measures for newly erected or significantly altered stations.