Methods to measure and limit electromagnetic interference, with reference to power systems and satellite earth stations

M.Ing.This thesis investigates why electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems exist and how EMI is generated, measured and limited. This investigation is done with reference to power systems and satellite earth stations. To understand the full extend of EMI generation from power systems on satellite earth stations, it was necessary to do a study of EMI, in order to understand EMI in its simplest form. This study consists of the following work: •A background study investigates the components of EMI, how EMI are generated and manifest in electric systems, methods to limit conducted EMI, a theoretical model on how to estimate conducted EMI quantities and EMI measurement techniques. •A conducted EMI model with which the parasitic impedances could be controlled was developed. With this model it could then be determined how conducted EMI would manifest in 3-wire circuit designs and how conducted EMI could be reduced in such circuits. •It was investigated how inductive coupling and capacitive coupling can be reduced. Time and frequency domain measurements were used to investigate the effects of these couplings. It was also of great importance to understand how EMI from measurement set-ups could influence measurements to give inaccurate results. This work investigated how high frequency measurements can be done effectively, how high frequency circuit designs can be improved and how parasitic impedances can be limited in high frequency equipment. •The expected EMI problem at the Klipheuwel wind farm was analysed. Simulations of expected EMI levels, worst case scenarios and measurements taken there showed that no significant EMI are generated from the wind generators and that power systems don’t hold a threat to satellite earth stations, if the necessary precautions are taken