General Description and Assessment Concept for Magnetic Field Distributions Caused by Switchgear Installations

The subject of power frequency magnetic fields has become very popular in 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 those fields. Switchgear installations act as one of the prominent sources of power frequency magnetic fields and, therefore, knowledge of the fields produced by them is required in order to assess any 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, in practice, has been shown as a very involved and cost consuming one. This paper describes a basic assessment method which can be used to evaluate magnetic-field distributions around switchgear installations from a general point of view, where the emphasis is on systems with a medium voltage level. The resulting field distributions can be utilized to derive and to determine appropriate distances required between switchgear and areas under consideration in order to comply with any limits concerning people or equipment