Treeing of ethylene-propylene rubber in cryogenic temperature region

The authors report results on the treeing resistivity of EPR (ethylene-propylene rubber) at both liquid nitrogen temperature and room temperature, and the effect of fillers on treeing. A treeing test method was established for opaque sample based on the detection of partial discharges. At room temperature, fillers lower the tree initiation voltage slightly but the growth of tree channels is inhibited by fillers. The tree initiation voltage at liquid nitrogen temperature is about three times higher than that at room temperature. Fillers improve treeing resistivity slightly. EPR has sufficient resistance to treeing at liquid nitrogen temperature. High reliability is expected during the long term operation of extruded EPR-insulated superconducting power cables considered by the authors