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Berlin Environmental Atlas

08.05 Electromagnetic fields

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Map 08.05.3: Undisturbed electric field strength beneath high-voltage overhead lines (50 Hz)

This map shows the electric field without any kind of environmental influence (except pylon influence). The surface area is the same as in Map 08.05.2. The maximum values calculated, in line with DIN VDE 0848 Part 1 (VDE 0848 1995), for the electric field strengths of the high overhead voltage lines at 1 m above ground and for the assumed parameters are:

overhead line electric field strength E
110 kV 2.0 kV/m
220 kV 4.8 kV/m
380 kV 7.6 kV/m

The validity of these calculations was again confirmed by selected measurements. As a rule, the electric field strength is independent of the current flow. In the case of low load, however, the electric field strength decreases slightly because the temperature of the conductor cable drops, so that the cable is tauter and rises further from the ground.

The electric field strength exceeds 5 kV/m over certain small areas, but all of these are on land, such as forest or meadow, where people are not usually intended to remain for long periods. To assess the maximum electric field strength of 7 kV/m under the 380 kV overhead transmission line, it is important to consider the special circumstances in which it was planned. The line was built in 1979 to the standard TGL 200-0614, which applied in the former GDR. The field strengths should not be considered critical as they occur exclusively outside built-up areas and in reality there is some reduction due to vegetation. In addition, we must regard the calculated electric field as idealised, especially at greater distances from the overhead lines, because once again vegetation and buildings significantly reduce the strength under authentic conditions.

Above the underground line, electric field strength is zero (see Methodology).

Maps 08.05.4 and 08.05.5: Magnetic flux density and undisturbed electric field strength by high-voltage overhead lines (50 Hz) in vertical profile

The position of the profiles is marked on maps 08.05.2 and 08.05.3. The illustrations reveal that field strengths vary vertically as well as horizontally. In this format it is clear that the sources of the field strengths are the conducting cables. Field strengths decrease with distance from the cables at a rate of 1/r (r = radial distance to the cable). The limit values for magnetic flux density imposed by the 26th BImSchV are exceeded only very close to the cables, an area deep inside the safety zone. Anybody approaching the cables would be hit by spark-over before reaching the area where values exceed the limit. With the undisturbed propagation displayed here, the electric fields only just touch these admissible limits around the deepest cable sag.

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