Influence of corona discharge aging on trap characteristics of high temperature vulcanized silicon rubber material

Taking high temperature vulcanized (HTV) silicone rubbers aged under different corona intensity (voltage and time) as example, we comparatively investigated the changing rules of surface trap characteristics, surface microstructure (SEM), and element characteristics (XPS) of the samples. Then, we investigated the surface trap characteristics of aged insulator samples from different-operated-year sites. Experimental results show that, along with the enhancement of corona discharge intensity via increasing corona voltage or aging time, electron and hole trap density both increase and finally reach their saturation levels. The SEM and XPS analysis results show that the aged material surface appears to have more defects such as holes and flaws, and also have many new chemical radicals of strong polarity, remarkably affecting the surface trap characteristics as physical and chemical defects, respectively; both electron and hole trap density of specimens of field ageing insulators increase with the operation time. Moreover, the hole trap density time-changing rule shows good regularity and repeatability, thus it is expected to be a novel quantitative parameter for effectively evaluating material ageing of composite insulator.