Investigation of ion mobility in insulation liquids for transformers.

Sammanfattning: This thesis studies a method of measuring ion mobility in insulation liquids for transformers (transformer oil). This method works by using a square wave voltage to make the charged particles (space charge) inside the oil move between two electrodes. By measuring and analysing the resulting current, the ion mobility of the oil can be calculated with an equation derived from the ion drift diffusion model. In order to study this method, different aspects of the technique were tried. Four different oils were involved, their measured ion mobility is presented at the end. Two different electrode materials were tried and the effects of measuring with different voltages and different frequencies were documented. At the end it was concluded that in order to get a good measurement using this method, it requires the right combination of voltage and frequency. These parameters are dictated mainly by the oils resistivity and the distance between the electrodes.