The thermal conductivity of crosslinked polyethylene insulation in aerial bundled cables

The calculation of the current rating of crosslinked polyethylene insulated (XPLE) aerial bundled cables is based on the temperature rise of the conductors, whereas the external thermal resistance depends on the temperature rise of the surface of the cable. It is necessary, therefore, to calculate the temperature difference between the conductors and the surface of the cable. This calculation requires knowledge of the magnitude of the thermal conductivity (or thermal resistivity) of the insulant and its temperature dependence, but values given in the literature for black XLPE are dispersed and are mostly for cast rather than extruded material. The radial temperature difference across the insulation of single-core, two-core, three-core, and four-core aerial bundled cables carrying various currents was measured in still and in moving air at velocities up to 8 m.s^-1. The internal thermal resistance, and hence the thermal conductivity of the insulant, is derived from these measurements for XLPE with and without carbon loading