Verification tests and insulation design method of cold dielectric superconducting cable

Abstract

SUMMARYA High-Temperature Superconducting (HTS) cable has a bulk power transmission capacity as a candidate for the replacement of aged cables and/or for the increase of the power transmission capacity, and its diameter is preferred to be smaller than the inner diameter of the duct for the existing cables. To reduce the diameter of HTS cable, the cold dielectric (CD)-type electrical insulation in which a cable core is immersed into liquid nitrogen (LN 2 ) should be adopted, and the thickness of its electrical insulation layer has to be optimized. Since a partial discharge (PD) in the electrical insulation layer of the CD-type HTS cable is considered as a major cause for the aging of the insulation layer, PD-free design must be adopted for the CD-type HTS cable.This paper describes a design method for the electrical insulation layer of the CD-type HTS cable adopting the PD-free design under AC stress, based on the experimental results such as a PD inception stress (PDIE), an impulse breakdown stress, and PD extinction characteristics under AC stress superimposed with an impulse stress. Moreover, the proposed design method was applied to a 500-m HTS cable and was verified by a field test.

HTS dc transmission and distribution: concepts, applications and benefits

“…The main disadvantage of the warm dielectric configuration is that during ac operation, currents are induced in the metallic cryogenic pipes, which themselves act in part as a metallic shield. This introduces losses at low temperature and greatly decreases the overall efficiency of the cable thus making it unsuitable for ac applications [4,22]. However, this main disadvantage is not relevant if dc operation is considered.…”