General assessment concept for power frequency emissions from switchgear installations

The subject of power frequency magnetic fields has become very popular during recent years. This has mainly been 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 side switchgear installations are often very individual ones with the consequent very individual magnetic field distributions. This means basically an individual investigation of each installation - a procedure which has been shown as 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 used to derive and to determine appropriate distances between switchgear and areas under consideration and hence to comply with any limits concerning people or equipment.