Electrical insulation property of liquid nitrogen/synthetic paper composite electrical insulation layer for high temperature superconducting cable

To determine the electrical insulation thickness of the high temperature superconducting cable with cold dielectric, we have investigated PD inception stress of the cold dielectric type electrical insulation layer using coaxial cylindrical insulating specimens with effective lengths of 120 mm and 1000 mm. Experimental results showed that the PD inception stress had little dependency on the effective specimen length, increased with the increase of liquid nitrogen pressure. Moreover, PD inception stress was higher than 15 kV/mm at the liquid nitrogen pressure of 0.3 MPa which is considered to be running pressure of S22-2 the HTS cable.