General description and assessment of magnetic field distributions caused by switchgear installations

The subject of power frequency magnetic fields has become very popular during recent years. This is mainly due to two facts: the increasing usage of display units which represent a very sensitive interference victim and the increasing public concern with respect to adverse health effects caused by such fields. Switchgear installations act as one of the prominent sources of power frequency magnetic fields and therefore knowledge of their magnetic field amplitudes is required in order to assess potential effects. On the other hand switchgear installations are often very individual ones with consequently very individual magnetic field distributions. This basically requires an individual investigation of each installation - a procedure which has been shown as a very involved and cost consuming one in practice. The paper describes a basic assessment method which can be used to evaluate magnetic field distributions around switchgear installations from a general point of view. The resulting field distributions can be utilized to derive and to determine appropriate distances between switchgear and areas under consideration needed to comply with any limits concerning people or equipment.