Fast Calculation for Temperature Rise of Trench Laying Cables Based on Thermal Circuit Model and Assessments of the Cable Life

The quantitative evaluation of the cable life has always been a technical problem. An equivalent thermal circuit model of multi-loop trench laying cables is proposed for the fast calculation of the conductor temperature rise. The thermal coupling between multiple loops of the cables is characterized by the mutual thermal resistance. The relationship between the current of cable and the conductor temperature rise is derived. A numerical model used to calculate the conductor temperature rise under real-time current is put forward based on thermal circuit model. Then, Arrhenius equation is used to calculate the thermal aging life of the insulation material under different currents. By comparing the result of the proposed thermal circuit model with that of the FEM and IEC standard, the correctness of the thermal circuit model has been verified. It is shown from the results that the thermal aging life of the XLPE cable decreases obviously at high conductor temperature with the increasing current. The more cable loops and larger current applied in adjacent cables will also cause a decrease of the cable life.