Investigations on characteristic parameters to evaluate the condition of the insulation system for high voltage rotating machines

This contribution reports on the investigations of partial discharge (PD) and dissipation factor measurements as function of the applied test voltage to evaluate the actual status of insulation system for high voltage rotating machines due to thermo-mechanical stress. As test object actual stator bars were used, based on the epoxy VPI technology. A defined, well-known accelerated aging procedure was applied on the stator bars model which simulates the aging procedures of the stator insulation system due to service cyclic duty. During the thermo-mechanical aging procedure the changes in the dissipation factor as function of applied voltage and partial discharge activities were studied and possibilities to determine the condition of the insulation system researched.