Mohammadreza Mohammadiyan asiabar - Master's degree, Faculty of Mechatronics, Islamic Azad University, Karaj Branch

An externally applied electric field that causes a sudden increase in electrical conductivity is called a threshold electric field. And the information of this threshold electric field is very important for the reliable insulation design of the dc power device because the distribution of the dc electric field is controlled by the electrical conductivity of the insulating material. There are several reports on the threshold electric field of XLPE and polymeric materials used for dc. Power cables that work at room temperature. However, there is no previous work on the threshold of cryogenic insulation materials, which is essential for the reliable insulation design of a superconducting dc cable. Therefore, in this study, by changing the number of layers of polypropylene multilayer paper, we tried to determine the threshold electric field characteristics of a polypropylene multilayer paper (PPLP) sample in liquid nitrogen. From the experiments, we can see that there is a threshold electric field of polypropylene laminated paper in a cryogenic environment. In addition, it was found that despite the different number of layers of polypropylene multilayer paper, there was no difference in the measured threshold electric field. In addition, it was found that if the electric stress exceeds the threshold field in the polypropylene laminated paper sample, the conductivity can change according to the number of layers of the polypropylene laminated paper.

electrical conductivity, polypropylene laminated paper, space charge, threshold electric field