Internal temperature measurement and conductor temperature calculation of XLPE power cable based on optical fiber at different radial positions

Abstract To investigate the optimal radial-arranged-position of the optical fiber in the cross-linked polyethylene (XLPE) power cable, the fibers were arranged into three positions, including segmental conductor center, the insulation shield surface, and the waterproof compound center, respectively, and temperatures were measured based on the Brillouin optical time-domain reflectometry (BOTDR) technology while the thermocouples were arranged at the same positions mentioned above for comparison, respectively. Four cases of cable temperature rising experiments under the laying environments of duct and water were carried out. The conductor temperatures were calculated using the temperatures measured by the fibers at the insulation shield surface and waterproof compound center, and the differences between the calculated values and the measured temperatures by thermocouples were analyzed and compared. Results show the temperature differences at different axial positions of fibers at the insulation shield surface or the waterproof compound center were less than 0.22 °C. These were much less than the differences in different axial positions of thermocouples, among which the maximum is 4.8 °C. The maximum temperature differences between the fibers and the thermocouples at the three positions mentioned above were 4.9 °C, 3.2 °C, and 3.7 °C, respectively. The maximum transient relative differences of the conductor temperature between the calculated and measured values do not exceed 7.6% and 7.1%, respectively. And the steady-state relative differences do not exceed 2.6% and 4.7%, respectively. The insulation shield surface and waterproof compound center are recommended as the optical fiber arranged-position for calculating the conductor temperature.