| The cable access corridor overcomes a series of problems,such as the occupation of urban space by the traditional laying way,the easy erosion of the cable,the influence of the outside world on the operating condition,and the low service life.With the rapid progress of urbanization in China,the construction of comprehensive pipe gallery has become the trend of modernization and renovation of urban infrastructure.Due to the continuous heating of the cable due to the load current,the heat is constantly accumulated in the cabin,and the temperature of the air in the cabin increases accordingly.Ventilation equipment is usually used to reduce the cabin temperature to maintain the normal operation of the cable.Some of the heat in the cable cabins is drawn into the surrounding soil through the walls,and some is carried away by ventilation.However,there are few studies on the numerical calculation method of "the calorific value of cables,the heat introduced into soil through the wall surface,and the heat taken away by ventilation equipment".For the sake of safety,low load is often used in engineering to ensure the safety of operation.At the same time,it is difficult to determine the carrying capacity of the cable due to the laying environment,arrangement mode,geometric section,etc.,so that the total heat output of the cable and reasonable ventilation volume are also difficult to obtain.With the significant change of voltage grade,if it is increased from 10 kV to 220 kV,the difference of cable calorific value will be greater.The calculation error of ventilation volume according to the estimation method in the previous specification is large,which is difficult to ensure the safety of cable operation.This paper summarizes the current calculation methods of carrying capacity,heat output and ventilation volume of power tunnel cables and power tunnel cables at home and abroad.Based on the comparison and analysis of the characteristics and theoretical analysis of common numerical calculation methods,the calculation idea of solving the cable cabin heating and ventilation volume by finite element method is put forward,and the COMSOL Multiphysics calculation software is determined to conduct simulation research on the 110 kV XLPE power cable.In this study,the three-field three-dimensional calculation model of cable's "electromagnetic-heat-flow" is decomposed into "electromagnetic-heat" and "heat-flow" two-field two-dimensional calculation model.The "electromagnetic-heat" heating model of power cable is established to solve cable carrying capacity,and then the cable heating capacity is solved according to the thermal effect of current.Secondly,the "heat-flow" thermal conductivity calculation model was established to solve the heat introduced into the soil considering the heat storage effect of the surrounding soil and the convection heat transfer effect in the cable cabin.At the same time,the radiation heat transfer between the cable and the surrounding inner wall is estimated.Finally,the results of various algorithms are compared and analyzed,and a set of calculation formulas for calculating the actual ventilation volume of 110 kV cable cabin are obtained. |
PDF Full Text Request