Research On Cable Load Optimal Method And Simulation Under Heat-flow Coupling Field In Cable Trench

Cable is an important way for energy transmission in electrical system,and cable trench is one of the important ways of cable laying.With the increasing demand for electrical energy,the load that the cable trench needs to carry is also increasing.Due to the operation and maintenance requirements of the cable trench,most of the cables in the trench are arranged in the corner of the cable trench.When the cable load increases and is evenly distributed,this arrangement may easily cause part of the cables to run at an excessively high temperature which may affect the service life of the cable and even release flammable gas that causes fire accident.Therefore,to optimize the load distribution of cables is of great significance.The temperature of each cable in the cable trench is affected not only by the amount of load,but also by other cables and the environment in the trench.Therefore,studying the distribution of the temperature field in the cable trench is crucial to the optimization of cable load.In this paper,the distribution laws of heat-flow coupling field in the cable trench is studied,and on this basis,the particle swarm algorithm based on the penalty function method is used to optimize the distribution of the cable trench cable load,and finally the arrangement of load is obtained by the reverse locking optimization method.The optimal load distribution plan provides a reference for cable planning and construction.The main research work of the thesis is as follows:(1)Combined with electromagnetism,heat transfer theory and mass transfer theory,the mathematical models of temperature field and fluid field of cable trench are established respectively.The three heat transfer methods,heat conduction,convection heat transfer and heat radiation in the cable trench are analyzed,and the mathematical model of the temperature field of the cable trench is established.The flow process of air fluid in the cable trench is analyzed,and the mathematical model of fluid field is established.The heat-flow coupling relationship between the temperature field and the flow field is expounded,and the mass transfer characteristics under the condition of heat and fluid coupling in the cable trench are introduced.(2)Three-dimensional simulation models of linear cable trenches and corner cable trenches were established respectively for the simulation of the steady-state thermal-fluid coupling field in the cable trenches.The distribution laws of temperature field and fluid field in straight cable trench and corner cable trench under the condition of heat-fluid coupling are analyzed respectively.The temperature and fluid fields in the straight cable trench are distributed symmetrically along the cable axis,while the temperature and fluid fields of the corner cable trench are not uniformly distributed on the two sides of the corner.And the influence of ambient temperature and wind speed is discussed under heatflow coupling field.(3)Using the particle swarm optimization algorithm based on the penalty function,the loads of the straight cable trench and the corner cable trench were optimized and redistributed,and the partial optimal load distribution of the straight cable trench and the corner cable trench was obtained.After optimization,the total loads in the straight cable trench and the corner cable trench is greatly increased,and the total load in corner cable trench is greater than that in linear cable trench.When some cables with lower load after optimization are removed,the total load after optimization is still greater than the load before optimization.The effect of optimization is significant.(4)Aiming at the problem that the cable trenches of different structures have different loads after being optimized,a reverse locking optimization method is proposed to perform an overall optimization calculation on the cable trenches,and an optimized distribution plan for the cable trench overall is obtained.After optimization,the total load in the trench has increased significantly,and the core temperature of each cable will not exceed the maximum allowable temperature in all three kinds of structures.Aiming at the problem of the generation and diffusion of flammable gas,the study on the diffusion law of flammable gas in cable trench was conducted,which provided a certain foundation for the prevention and control of fire accident in cable trench.