Analysis of electric quality

Sammanfattning: In todays society it’s usual with non linear loads in the electric power system. These loads contribute to the problems in the distriubution net. This student thesis will describe the different types of problems that can evolve with specific focus on a problem at Billerud AB Skärblacka. The purpose with the work was to see what causes a heat problem in one of their transformers. The report begins with a theoretic part that describes diffrent power quality concepts and informations areas necessary for the work. After the theoretical part the system is described and also the harmonics- and asymmetry measurments done with purpose to analyze the heat problem. The measurments were logged for a couple of days to be able to get information about different loads, to see if that had any effect on the amount of the harmonics. There is also a simulation of the system done, which indicates that the problem doesn’t have to depend on the frequency converter in the system. The investigation indicates that it can be the transformer that isn’t correctly dimensioned to handle the amount of harmonics from the frequency converter and that’s why it gets overheated. The result indicates that the amount of harmonics from the converter is as the supplier issued. A difficultiy during the work was to be able to measure on all connections, since the voltage and current are too high for the measurement equipment and also hard to reach in all areas of the system. Further measurments would lead to more specific analysis. The final part of the report gives different proposals for an upcoming work.