Comparison of the Electrical Conductivity of Polypropylene Laminated Paper (PPLP) and Kraft in LN2 According to the Number of Layers

As polypropylene laminated paper (PPLP) is usually wound around the high-voltage conductor of a dc high-temperature superconducting power cable several times, it is needed to determine whether electrical conductivity of PPLP could be increased according to the number of layers. In thin films without layers, electrical conductivity increases according to the thickness of materials. For this reason, the effect of the number of PPLP layers on electrical conductivity needs to be verified because the dc electric field distribution is highly influenced by electrical conductivity. In this paper, to determine the effect of PPLP layers on electrical conductivity, we measured the conductivity of specimens with single, double, and quadruple layers of PPLP in liquid nitrogen (LN2), and compared the results according to layer number. In addition, we measured the electrical conductivity of specimens with single, double, and quadruple layers of Kraft to verify if there was a layer effect or not. The electrical conductivity of the PPLP and Kraft specimens did not change with an increase in the number of layers. Therefore, we concluded that the electrical conductivity of single-layered PPLP and Kraft specimens can be used in dc electric field simulations.