Condition Monitoring Of Transformer Insulation By Polarisation And Depolarisation Current Measurements

The measurement and evaluation of the 'dielectric response' is one possible way of diagnosing a transformer's insulation condition. Moisture and ageing strongly influence the dielectric properties of oil/cellulose insulation systems. In our recent research project, dielectric measurement was used for assessing the condition of oil/paper insulation. The Polarisation and Depolarisation Current (PDC) analysis is a non-destructive dielectric testing method for determining the conductivity and moisture content of insulation materials in a transformer. On the basis of this analysis one can decide upon further actions. This paper presents a description of the PDC technique with the physical and mathematical background and some results of dielectric response measurements of several transformers. Data analysis and interpretation of the field test results are also presented in this paper