Mohsen Farahani - University of Hannover, Institute of Electric Power System (Schering-institute) Germany
Hossein Borsi - University of Hannover, Institute of Electric Power System (Schering-institute) Germany
Ernst Gockenbach - University of Hannover, Institute of Electric Power System (Schering-institute) Germany

A significant method to characterize the electrical properties of materials and to evaluate the condition of the insulating systems is the dielectric response study which can be done in the time or frequency domain. The dielectric response measuring results can be affected by different arameters like measuring voltage, temperature, water content and aging condition of insulating system. In this work numerous measurements re presented, thus to understand, how the dielectric response measurement results can be affected by the water content and aging condition of insulating system of high voltage rotating machines in the time and frequency domain. Because of the importance of the dielectric response application as a nondestructive diagnostic method the possibilities and limitations of this method to reflect the deterioration processes due to thermal and electrical stress were investigated. As test object, actual stator bars were used, that were manufactured with Epoxy VPI technology.

Rotating machine Insulation, Dielectric response measurement, Polarization, Diagnostics, Aging, Moisture