中文摘要：

电树枝是引起聚合物绝缘材料破坏的重要因素之一，电树枝通道形貌包含了材料绝缘寿命、缺陷形成机理等重要信息。为此，利用共焦显微镜，首次使用荧光显微法对电缆内绝缘用硅橡胶（SIR）材料中电树枝老化通道进行逐层扫描观测，得到荧光显微法三维电树枝形态图和透射光源法电树枝微观形态图。另外，利用扫描电子显微镜（sEM）对电树枝通道横切面进行观测，得到电树枝通道横切面电镜图像并利用暗视野显微成像得到电树枝通道落射光法显微图像。通过上述4种实验观测方法得到的电树枝通道形貌图表明，硅橡胶电树枝通道整体形态为由球状破坏点连成的树枝状中空气隙通道，这种形貌特点首次通过实验方法直接观测得到。进而，基于这一实验结果和电树枝局部放电理论，提出了硅橡胶电树枝球状生长模式，不仅与实验观测相符合，也可为进一步研究硅橡胶中电树枝生长机理提供基础。

英文摘要：

Electrical tree is an important reason that causes insulation failure of polymeric dielectrics. Micromorphology of electrical trees indicates information of insulation condition and formation mechanism of deficiencies. In this paper, using a confocal laser scanning microscope （CLSM） and fluorescence microscopy, we obtained fluorescence three-dimensional （3D） electrical tree images and transmission light microscopy images of electrical trees simultaneously. Additionally, we also used a darkfield microscope and a scanning electron microscope （SEM） to acquire reflection light images and cross section surface images of electrical trees. The images obtained using the four observation methods demonstrate that electrical trees branches in silicone rubber （SIR） are hollow channels which are composed of spherical cavities forming tree-like shapes, which are considered as a new morphology firstly observed in experiments. Furthermore, based on the results and partial discharge （PD） theory, we proposed a spherical growth pattern of electrical trees in SIR, which not only corresponds to the observation, but also offers keys to understand the mechanisms of electrical trees growth in SIR.