An online method for the assessment of moisture in a power transformer is presented in this paper. It is experimentally tested on simple insulating materials as well as on a sample bushing insulation. It is finally tested during the drying of a 110 kV transformer. The results are presented and show that the method is clearly able to distinguish between levels of moisture in the range of interest.

On-line assessment of moisture in a power transformer

Dielectric measurements have been used for long time for assessment of electrical insulation. The insulation system of a power transformer consists of oil and cellulose, whose dielectric properties are strongly influenced by moisture, temperature and ageing. This condition can therefore be evaluated using the response of the dielectric system. In this work we utilize data published to establish a circuit model of power transformer. Analysis techniques are then suggested in order to simplify the testing procedure for moisture in bulk insulation.

S.R. Kannan

Papers

Evaluation of the moisture content in power transformer