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Berlin Environmental Atlas

08.05 Electromagnetic fields

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Map Description

Map 08.05.1: Power stations, electricity grid and lines of distribution

The map shows the high and highest voltage grids operated by Bewag at stages 380 kV, 220 kV and 110 kV. The Bewag grid is linked into Germany's interregional power grid via the 380 kV and 220 kV lines and the transformer stations (TS) at Teufelsbruch in the west, Malchow in the north and Wuhlheide in the south-east of the city.

Currently a 380 kV diagonal link is being constructed underground from TS Teufelsbruch via TS Mitte to TS Friedrichshain, and by the year 2000 this will be extended onwards to the transformer station in the eastern Borough of Marzahn. From TS Marzahn to TS Neuenhagen (to the east of Berlin) a new 380 kV overhead line is being built. Once the 380 kV diagonal link is completed, the 110 kV and 220 kV lines which still bring power from Neuenhagen into the city can be decommissioned.

The 110 kV system links Bewag's inner-city power stations to Berlin's electricity grid. Simultaneously, this stage of voltage is used to supply approx. 80 110/10(6) kV transformer stations which distribute electricity across town. In the western part of the city, the 110 kV lines are predominantly underground, in the east a 110 kV overhead network is the backbone of power provision.

Map 08.05.2: Magnetic flux density beneath high-voltage overhead lines (50 Hz)

The illustration shows the magnetic flux density generated 1 m above ground by the high overhead voltage line in Buch/Karow. We can see that areas of equal flux density merge beneath the lines. It is not possible to distinguish which field is caused by which line. At the bottom, the course of the 110 kV line which is partly constructed under ground is clearly discernible. Even though the field strengths above the course are consistent, they do not spread as far in the vicinity of the underground cable. The reason for this is the compact way the 110 kV cable was laid, leaving only a weak residual field. Directly above the cable, however, this advantage is cancelled out by the proximity of the cable to the surface of the ground compared to the overhead cables. At higher voltages the field strengths above underground supply lines are actually higher than those beneath equivalent overhead lines, because due to the increased transmission wattage the cables need additional cooling, which prevents a compact laying.

In line with DIN VDE 0848 T1 (VDE 0848 1995), the maximum magnetic flux densities calculated for the high overhead voltage lines for a height of 1 m above ground show the following values for the assumed parameters (medium load):

overhead line magnetic flux density B increase at peak load
110 kV 2.0 µT + 53%
220 kV 4.2 µT + 14%
380 kV 2.6 µT + 42%

The validity of the calculation was substantiated by selected measurements. In the case of a greater load the magnetic flux density increases in proportion to wattage. The calculated maximum fields strengths at 1 m above ground for the 110 kV underground line at average transmission loads are:

laying technique of the 110 kV line magnetic flux density B
cable in a pipe * 0.35 µT
free cable 0.24 µT

*This technique is only used beneath roads.

To place this in context, we should indicate the magnetic flux density at 1 m above ground for 1 or 10 kV underground lines in Buch/Karow. The maximum was 0.67 µT, which is higher than the values for the 110 kV line.

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