A.C. breakdown properties of ice-glycerin mixed system at 77K

In recent year, the improvement of efficiency of electric power apparatus is required because the environmental and energy problem is serious. Thus, the development of superconducting power apparatus has been proceeded. Glass Fiber Reinforced Plastics (GFRP) is widely used as electrical insulating material in superconducting power apparatus. However, GFRP gives heavy load to environment when scrapped because it is not recycled, nor naturally decomposed. We pay attention to combination of natural fiber and ice as electrical insulating material at cryogenic temperature. Both natural fiber and ice are environment-friendly material. A.C. breakdown strength of ice is degraded if void or crack exists. Thus, we used bamboo or kenaf fiber to prevent formation of void or crack. We had confirmed A.C. breakdown strength of the composite system of bamboo-ice or kenaf fiber-ice is comparable to GFRP laminated board at 77K. We consider that mixture of water soluble material and water may prevent formation of void or crack, and improve A.C. breakdown strength of the composite system. We examined A.C. breakdown strength of ice-glycerin mixed system at 77K. As a result, it is suggested that mixture of glycerin increases A.C. breakdown strength of ice at 77K.