A very large proportion of the medium voltage cable network’s lenght are oil-paper cables. As these cable lines age several decades, it’s very important to know the status of these cables. Operational safety of electrical equipment the insulation is one of the most critical point. During the operation and storage the material structure changes. These structural changes in the chemical, physical, and electrical properties change in manifest.
My thesis deal with diagnostic of oil-paper insulated cables. After the presentation of oil-paper cables organization structure, I come to the degradation process of insulation materials. The two most important process are wetting and aging.
To determine these qualitative features, I present two measurement methods based on voltage measurement: the VR (Voltage Response) and RVM (Return Voltage Measurement). Then I describe the thermal aging process undergone laboratory samples and measurements. Comparing the reasults of these measurements, I picture the state of evaluation of the cables, and I make suggestions to developments and futher investigations.