Noninvasive ageing assessment by means of polarization and depolarization currents analysis and its correlation with moisture content for power transformer life management

This paper presents the Brazilian experience on the application of a noninvasive technique based on the dielectric response using the polarization and depolarization currents analysis and its correlation with moisture contents to have an assessment of ageing processes in power transformers. The theory, the procedure, the basis of analysis, the interpretation of measurements and field measurement results are given. The dielectric response analysis and its derived none-invasive moisture and ageing assessment procedures using the PDC-analysis (PDC=polarization, depolarization current-analysis) are discussed in detail.