Purpose/Aim
In the persuit of increased voltage and capacity of HVDC cable, more threatening insulation problems are coming. Thermal aging of HVDC cable insulation layer is a key factor that destroys its insulation performance. Nowadays, nano dielectrics have brought hope for solving the problem of cable insulation at high voltage levels. At present, most of researches mainly focus on the short-term performance of nano dielectrics, while its long-term aging performance and influence mechanism are still lack of systematic research.
Experimental/Modeling methods
Different nano fillers doped silicone rubber (SIR) are prepared, and the thermal aging test of different nanocomposite SIR is carried out at 200℃ of 0-80 days. Electrical properties including space charge transport with varied aged samples are tested and discussed. The changes of cross-linked network of different nanocomposite SIR under thermal aging are analyzed by observing their micro morphology, elemental analysis. Moreover, the influence law of thermal aging on space charge transport of nanocomposite SIR is discussed.
Results/discussion
With the increase of thermal aging time, all kinds of SIR show gradual decrease of heteropolar charge charge and a transition to the accumulation of homopolar charge. At the same time, the charge accumulation of the MgO/SIR composites is the least and has little change with the thermal aging time. After thermal aging, the SIR material undergoes an obvious thermal oxygen reaction, and defects such as unevenness and holes are generated inside. After adding nano fillers, the degree of thermal aging is reduced.
Conclusions
Significant deterioration of SIR material occurs under thermal aging. The space charge is converted to the homopolar charge. The addition of highly electronegative oxides can inhibit the aging characteristics. The research of this paper provides guidance and reference for the improvement of long-term characteristics of insulating materials of cable accessories.
 

space charge,silicone rubber,thermal aging,HVDC,cross-lined network