Converter stations are necessary for the transformation of alternating current to direct current and vice versa. They consist of a huge converter hall (e.g. 50 x 200 m, 20 m high), outside facilities of even bigger dimensions and power pylons in close proximity (up to 75 m high). Inside of the station and outside along the power lines, static and alternating fields occur, respectively. Their strengths depend on the voltage and the amount of flowing current. As in the case of conventional substations (Substations) electric fields are present in the outside facilities and in close proximity to the power lines. Directly at the converter station they are shielded by the metal cover of the hall. Magnetic fields are generated by almost all components of the converter station. Converter station access is limited to qualified personnel.