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Berlin Environmental Atlas

08.05 Electromagnetic fields

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Berlin S-Bahn (Rapid Transit Railtrack)

The procedure for the S-Bahn track was the same as the one described above. Unlike the main line, however, the field was a direct one, as the Berlin S-Bahn is powered by direct current (operating voltage 700 V).

Measurements of the magnetic flux density along S-Bahn routes indicate a time variance different from that of the railroad service (see Fig. 10) due to the greater frequency of trains. It is easy to recognise how fluctuations in the direct magnetic field fade with the reduction in service once normal operations close for the night around 1 a.m.

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Fig. 10: Constant Magnetic Field beneath the S-Bahn Bridge over Knesebeckstrasse by Savignyplatz during Night-time Measurement which Shows Rail Traffic Waning
The level at the end of the measurement is accounted for by the Earth's magnetic field, but with the measuring probe positioned vertically and not towards the Earth's magnetic field of 42 µT.

Again, in the longitudinal values measured for the S-Bahn, maximum values tallied with those calculated by numerical simulation on the basis of a traction current of 1,300 A and a reverse current component of 100 % (see Fig. 11). Due to the relatively short distances between the feeder points a very high reverse current component can be assumed.

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Fig. 11: Measured and Calculated Development of the Magnetic Field under the Bridge over Knesebeckstrasse in Berlin-Charlottenburg
The Earth's magnetic field of up to 42 µT has already been subtracted. Position 0 is half-way between two S-Bahn tracks.

It should be borne in mind that the natural (constant) electromagnetic field is 42 µT and both EMT thresholds and human health recommendations are several magnitudes larger.

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