Study on DC Conductivity Characteristics of Polypropylene Laminated Paper

DC electric field analysis should be carried out for the insulation design of dc high-temperature superconducting (HTS) equipment. For that purpose, the conductivity of PPLP was measured under room temperature and liquid-nitrogen temperature. The testing results show that the conductivity of single PPLP is 2.02 × 10
^-15
S/m at liquid-nitrogen temperature and 2.86 × 10
^-15
S/m at room temperature. The threshold electric field of PPLP insulation at liquid-nitrogen temperature and room temperature is 17.5 kV/mm. When the applied electric field is lower than 17.5 kV/mm, the conductivity of PPLP does not change with the electric field strength. When the applied electric field is higher than 17.5 kV/mm, the conductivity of PPLP increases with the electric field strength. Different layers of PPLP have the same electric field threshold, but the conductivity is not the same.