Partial discharge activities under AC/impulse superimposed voltage in LN2/polypropylene laminated paper insulation system for HTS cables

This paper discusses electrical insulation characteristics of high temperature superconducting (HTS) cables for their reliable and rational insulation design. We focused on a severe and practical operational condition of HTS cables, i.e. under commercial ac / lightning impulse superimposed voltage. Experimental results for a HTS cable insulation model composed of liquid nitrogen (LN2) and polypropylene (PP) laminated paper revealed that ac / impulse superimposed voltage could trigger partial discharge (PD) by the impulse voltage invasion and cause consecutive PD under the subsequent ac voltage. The PD generation characteristics were summarized for different ac / impulse superimposed voltages, and a criterion for consecutive PD generation was identified.