Effect of Magnetic Field on Electrical Treeing Behavior of Silicone Rubber at Low Temperature

The development of high temperature superconducting (HTS) materials promotes the development of HTS cable. With the development of HTS cable technology, superconducting insulating materials under magnetic field have been taken seriously. This paper presents the study of the relationship between magnetic field and growth characteristics of the electrical tree in silicone rubber. The test was done under -30 °C, -60 °C, and liquid nitrogen temperature. Needle-plate electrode was employed in this paper to generate electrical tree, and silver needle was employed to avoid stress generated by the magnetic field. Samples were applied pulse voltage of +12 kV and +15 kV. 0, 200, and 400 mT magnetic field density (MFD) was applied, respectively. The direction of the magnetic field and the electric field was vertical. Using a digital microscope captured the morphology of the tree. The fractal dimension and the accumulated damage were measured. It is observed that the magnetic field promotes the increase of accumulated damage and tree width increase rapidly with the increase of MFD. The magnetic field will increase the probability of the electrical tree in liquid nitrogen. This shows that the partial discharge activity in the tree channel is influenced by the Lorentz force, the treeing behavior will be different as a result.