Relation between DC PDIV and DC BDV of Mass Impregnated Polypropylene Laminated Paper Considering the Thermal Aging Characteristics

Thermal aging of HVDC Mass Impregnated Polypropylene Laminated Paper (MI-PPLP) cable could reduce the dielectric strength. And degradation of the physical and chemical properties of MI-PPLP could be caused by partial discharge in voids created by cavitation phenomenon. If void discharge is maintained, electrical aging is accelerated at the interface between air void and MI-PPLP, and ultimately dielectric breakdown occurs. There are several reports on the dielectric breakdown and partial discharge characteristics for insulation diagnosis of HVDC MI-PPLP cable. However, studies on the dielectric breakdown and partial discharge characteristics of HVDC MI-PPLP cables considering the thermal aging are insufficient. Therefore, in this paper, breakdown voltage (BDV) and partial discharge inception voltage (PDIV) characteristics are analyzed under the influence of the thermal aging of void defects. since it takes a lot of time to evaluate the insulation performance of MI-PPLP due to thermal aging under normal operating conditions, the thermal aging process was shortened through accelerated aging at 120°C. For reliable experiments, the equivalent lifetime between accelerated aging and normal operating conditions was suggested using the Arrhenius model. Since the Arrhenius model shows the reaction rate according to the activation energy of the specimen, the equivalent lifetime must be derived from the activation energy. The activation energy can be derived by applying the Kissinger method to thermos gravimetric analysis (TGA). From the experimental results, As the thermal aging of MI-PPLP proceeded, decrease in BDV is more severe than PDIV due to the increased Permittivity. Consequently, it is considered that relation between BDV and PDIV characteristics due to thermal aging can be estimated based on the equivalent lifetime obtained through the Arrhenius model.