Multiple Data Source Analysis of PPLP/Epoxy Resin Interface Discharge in HTS Cable Joint

Polypropylene laminated paper (PPLP) and epoxy resins are combined as the main insulation for high-temperature superconducting (HTS) cable joint. In this paper, PPLP/epoxy resin interface discharge voltages in liquid nitrogen (LN2) and at room temperature were tested. Surface discharge voltages of PPLP and epoxy resin in the same conditions were taken as comparisons. Experimental results show that the interface discharge voltage is lower than that of the surface discharge voltages whether in air or LN2. The maximum electric field among air or LN2, epoxy resin and copper electrode is enhanced by the upper layer of PPLP, causing the discharge more easily to take place along the PPLP/epoxy resin interface. The redistribution of electrons among PPLP, epoxy resin and metal electrode due to the differences in their energy band structure forms space charge region, resulting in the increase of maximum electric field strength and causing the lower interface discharge voltage. The charges caught by the traps of PPLP and epoxy resin result in the electric field distortion during the development of discharge, which also promote the discharge of the interface under the coupling effects of PPLP and epoxy resin.