Partial discharge and dielectric response behaviour of insulation systems for high voltage rotating machines under electrical stress

In order to understand how the partial discharge (PD), dissipation factor and dielectric response measurements can reflect the changes in the groundwall insulation of high voltage rotating machines due to electrical stress, which lead to insulation degradation, an electrical stress has been applied to the insulation systems of high voltage rotating machines and the change of PD pattern, dissipation factor as a function of the applied test voltage and dielectric response in the time and frequency domain were studied. As test objects, actual stator bars were used, which are based on the epoxy VPI technology, according to the manufacturer´s standard.