Cryogenic Discharge Characteristics of Solid Insulation Materials for Superconducting Coil Systems

Several types of solid insulation materials can be used as formers and insulators to develop high voltage superconducting coil systems. Solid insulation materials for a cryogenic environment are necessary to obtain excellent dielectric characteristics and robust mechanical characteristics. In this paper, partial discharge inception and the electrical breakdown characteristics of solid insulation materials are studied in LN2 under AC and DC voltages. Each of the experiments on solid insulation materials, such as glass fiber reinforced plastic and Bakelite, is performed for different thicknesses and stackings. The relationship between the discharge characteristics and the intensity of the electric field of the solid insulation materials can be calculated using the finite element method and can also be analyzed. Results show that the discharge characteristics of the solid insulation materials can be affected by the thickness and number of stacking sheets. In addition, the pattern of the partial discharge inception voltage under a DC voltage is not equal to that under an AC voltage.