Experimental Studies on the Partial Discharge of Insulation for High Tc Superconducting Cable

Partial discharge (PD) is the main factor that can cause failure of the cold dielectric insulation system of superconducting cables. Nine insulation model cables with different insulating materials and wrapping styles are prepared. PD experiments under liquid nitrogen and room temperature are carried out on these model cables. Assuming that the lifetime of superconducting cable is 35 years, 40 thermal cycles from 77 –323 K are carried out on three model cables. Experimental results show that the PD is 100 times lower in liquid nitrogen than at room temperature for both polypropylene-laminated paper (PPLP) and polyimide (PI). Compared with model cables that used PI, the ones that used PPLP show much higher inception electric field. And no decay in partial discharge inception electric filed (PDIE) is found during the thermal cycles. The study will be helpful to the insulation system design for superconducting cable.