Calculation and Reduction of Low-Frequency Magnetic Fields Caused by Power Supply Systems

The use of sensitive measuring devices in big buildings can be restricted by disturbing mag­ netic fields caused by components of the power supply system. To avoid such impairments it is advantageous to calculate the magnetic field distribution while the building is planned. The paper contains the derivation of simple far field models for bus bars, transformers, power cables and distributors. These models, numeri­ cal evaluated by a system of computer programs, were used to reorganize the power network of Germany's biggest hospital located in Aachen. The software enables the user to modify the components of the power system by simulation and thus to eliminate the magnetic disturbance in certain areas of the building. For this the distribution of magnetic induction for inter­ esting cross-sections of the building is dis­ played in form of maps, where the cross-sec­ tions are divided into grid squares which show the maximum of magnetic induction calculated for the center of each square. By application of this method disturbing magnetic fields in­ side specific rooms can be eliminated at low costs.