Three-dimensional morphology and spherical growth mechanisms of electrical trees in silicone rubber

•Fluorescence microscopy observation method was used in insulation defect diagnosis.•Fluorescence three-dimensional (3D) electrical tree images were obtained.•Electrical tree channels are hollow channels which consist of spherical cavity.•Spherical growth pattern in SIR were explained.•3D schematic electrical tree and the growth process were given.

Electrical tree is an important reason of insulation failure in silicone rubber (SIR) which affects the SIR insulated electrical equipment reliability seriously. We used a confocal laser scanning microscope (CLSM) and fluorescence microscopy for the first time to obtain fluorescence three-dimensional (3D) electrical tree images. Meanwhile, other observation methods were also used to validate its microstructure. Based on the results and partial discharge (PD) theory, spherical growth pattern of electrical trees in SIR is found, which not only corresponds to the observation results, but also explains growing procedure under the PD.

Graphical abstractBy invented fluorescence microscopy observation method, 3D fluorescence electrical tree images of high quantity were derived. It was discovered that electrical tree channels in SIR are hollow channels which consist of spherical cavity by spherical cavity and look like spherical chains which has not been reported yet. Figure optionsDownload full-size imageDownload as PowerPoint slide