Temperature Field Calculation And Dynamic Capacity Increase Of Direct Buried Power Cable

In recent years,urban power grid has developed rapidly,and cables are widely used in the field of transmission and distribution.After ensuring the safe operation of the cable,the temperature change of the cable core should be monitored in time to make full use of the cable.Due to the diversity of cable laying methods,the temperature field is affected by many factors.For the direct buried cables laid in clusters,the influence of surrounding soil on the temperature field is particularly obvious,which has high engineering practical value for the correct modeling of soil.In the existing temperature field calculation methods,the finite element method can accurately calculate the temperature field,but it takes a long time.IEC standard cannot be used to calculate the transient temperature field of cables.Based on the single circuit direct buried cable thermal path model,this paper analyzes the steady-state temperature and transient temperature rise of the cable,and verifies them by the finite element method,overcoming the shortcomings of the traditional thermal path model which cannot calculate the transient temperature of the cluster-laying cable,and finally realizing the dynamic capacity increase calculation of the cable under constant load and variable load,so that the cable transmission capacity can be fully utilized.Firstly,the loss of each layer of the cable is calculated by IEC-60287 standard.Combined with the cable temperature field control equation and boundary conditions,the COMSOL finite element simulation method is used to analyze the influence of ambient temperature,cable buried depth,phase spacing,soil thermal resistance coefficient,external heat source and backfill soil on the cable temperature field,and reasonable suggestions are given to reduce the cable core temperature.Secondly,combining the cable thermal circuit model with the soil trapezoidal layered model,the new model can quickly and accurately calculate the steady-state temperature distribution and transient temperature distribution of cables.,and verified by finite element method.The new model extends the application range of traditional thermal circuit model and can be applied to the working conditions of cable cluster laying,that is,the model considers the effect of mutual heat between cables.Finally,the new model is applied to the dynamic capacity increase calculation of cables,and the dynamic capacity increase calculation is carried out for constant load and periodic daily load,respectively.The capacity increase time under different emergency loads is calculated,which provides reference for power dispatching.In summary,the thermal circuit model can be used to quickly and accurately calculate the temperature field of the directly buried cluster laying cable,and then the temperature rise curve of the conductor can be obtained.Based on this,the dynamic capacity of the cable can be increased to ensure the economy and reliability of the cable operation.