Effects of heat and radiation on the leakage current in flame-retardant XLPE-insulated cables

The leakage current was measured by the current integration method for cables insulated with flame-retardant cross-linked polyethylene (FR-XLPE), used as safety-related cables in nuclear power plants in Japan. As a result, it has been clarified that FR-XLPE is much more vulnerable to deterioration due to heating and radiation than non-FR-XLPE. Namely, after heating and gamma-ray irradiation, distinct leakage current flows in the FR-XLPE cables even at a low electric field. However, the insulation resistances of the cable insulator calculated from the leakage currents flowing through FR-XLPE cables variously treated are several orders of magnitude higher than the value required for electrical insulation of circuits. This means there are no concerns about the insulation characteristics for both cables insulated with non-FR-XLPE and FR-XLPE. (author)