Diagnostics of transformer insulation based on dielectric response measurements

Dielectric response measurements on oil-impregnated pressboard samples of different density and moisture content at different ageing times are analysed in this paper. In order to understand the impact of moisture, ageing condition of the insulation and other ageing products on dielectric response measurements, samples are prepared under different conditions and contribution of various parameters are determined. To understand the impact of vibration on mechanical strength of solid insulation a vibration experiment is designed and results are analysed in this paper. Then, analysis of measurements on two field transformers are also carried out based on the findings from the laboratory experiments on oil-impregnated pressboard samples.