The Inversion Calculation Method of Core Temperature in 110 kV Cable Inter-mediate Joint

The heating of mid-joints is one of the common hidden dangers in cable systems, and temperature monitoring at the mid-joint is of significant importance for assessing cable operation status. In this paper, a method for inversely calculating the core temperature at the mid-joint of a 110 kV cable is proposed, based on the thermal circuit method for cable body from the standards IEC-60287 and GB/T-10181, as well as the temperature measurement method of distributed temperature sensing devices installed on the inner side of the outer sheath. This method aims to improve the accuracy of temperature calculations by considering the effect of contact resistance loss on core heating and comparing the results with simulation data to validate the accuracy of the proposed approach. The results show that when the cable operates under steady-state conditions and for different temperature conditions on the inner side of the outer sheath, the absolute errors between the calculated current and core temperature using the modified inversion method and the simulation results are within 5%, which basically meets the requirements for field application.