Evaluation of low-frequency emissions of switchgear by a type proof

Power frequency magnetic fields of medium voltage switchgear installations might interfere with sensitive equipment such as cathode ray tubes (CRT) or might even conflict with exposure limits concerning people living or working near such installations. In order to prevent possible influences or adverse health effects, the knowledge of the magnetic field levels produced by the switchgear installations is necessary and further these levels have to be assessed with respect to existing immunity and exposure limits. The paper describes a concept which is suitable to derive minimum distances to be observed between switchgear and the areas accessible to people or sensitive equipment. This concept avoids that every individual switchgear installation has to be investigated in detail. It rather enables to derive the field strength distribution from the data of the switchgear type and can therefore be regarded as a type proof.