Study On Temperature Field And Ampacity For Tunnel Power Cables With Triangular Arrangement

In the conditions of the peri-urban,the substation,and crossing sea or river,the tunnel power cable has been applied more and more widely.Power cables’ triangle arrangement has advantages of balancing three-phase magnetic field and saving space,which make it a common arrangement in tunnel power cables.Therefore,the fast and accurate calculation of the temperature field and ampacity for tunnel power cables with triangle arrangement will help the power department to make an accurate judgement on the cables’ status and formulate maintenance plans.In addition,cable arrangement spacing is reasonably set according to the calculation results of the temperature field and the ampacity,and it also has some guiding significance for improving the transmission capacity and economy of power cables.In this paper,through the study on analytical calculation method of the temperature field and ampacity.A simplified temperature circuit model of single core high voltage power cables based on IEC-60287 standard was established.Depending on the analytic formula provided by the standard,the data of the temperature field and the ampacity are obtained.Through the study of the theory of finite element numerical calculation,the multi-physical field coupling simulation model of single-phase and one-circuit triangle compact power cables is established by ANSYS,and the corresponding temperature field and ampacity are calculated.Comparing the above two methods,the results are basically the same,and the error is less than 3%.It is proved that the coupled model can be utilized to simulate the temperature field and ampacity of the tunnel power cables with triangle arrangement.The coupled model is implemented to simulate the temperature field and ampacity of single circuit triangular power cables with different spacing.According to the study,when the phase spacing increases in a certain range,the temperature of the cable core decreases linearly,and the ampacity has a linear upward trend.When the phase spacing exceeds a certain limit,the changing speed of the core temperature and the ampacity gradually slows down.Combined with its laying environment and running state,it’s found that the best phase spacing between cables is 70～100mm.Due to the complex operational environment of multi-circuit power cables in tunnel,the analytical computation is difficult.In this paper,the coupling simulation model of power cables with different circuits,different laying form and different circuit spacing is established,and the temperature field and ampacity of multi-circuit power cables are calculated.The calculation results of the temperature field and ampacity are compared and analyzed.The optimal range of the circuit spacing in the form of the corresponding laying is given,and it provides a reference for the design and construction of power cables in tunnel.