Rearch On The Carrying Capacity Of 500kV High Voltage Cable In Tunnel

In the background of rapid development of national economy,the demand for electricity is increasing.In the process of reforming and upgrading the power grid and constructing large power plants,China’s power grid has made great progress and breakthrough.At present,there are 3 independent provincial networks in xizang,xinjiang and hainan,as well as 6 trans-provincial networks in north China,northeast China,east China,central China,northwest China and south China.The 500kV line plays an important role in the major power systems,and the communication between the power grids is mainly through it.The XLPE cable is widely used in city power grid,and the voltage level is increasing.If the core temperature is higher than the rated value for a long time during the operation of high-voltage cable,the cable loss will be increased,the thermal aging will be accelerated,and even thermal breakdown will occur,resulting in shortened service life.Under the condition of known limit temperature which the cable core material can bear,the maximum current value which the cable can bear is clear.Measuring the conductor temperature during operation can determine whether the cable is in economic operation and whether there is room for capacity increaseUltra-high voltage grid gradually formed,electric power tunnel and the comprehensive utility tunnel is widely used,this study consider cable internal structure and thermal road model,the application of IEC-60287 standard to calculate the internal heat transfer,by IEC-60287,the IEC-60853 standard such as defined in the thermal path model and the calculation method of related parameters,laying in the tunnel,models for FY 500 1 x 2500-YJLW03-Z290/five divisions,large cross-section conductor.The cable transport capacity calculated under the limit temperature of the cable core and the periodic load factor M calculated under the condition of one day(24h)periodicity are studied respectively.Based on COMSOL Multiphysics,the electric-thermal-flow coupling field simulation was carried out for the "pin" type cable laid in the tunnel.The temperature rise experiment platform was built,the temperature rise experiment of large load current was carried out in 4 laying environments,and the temperature rise of cable copper conductor,each structural layer and intermediate joint was recorded under different loads.The thermal circuit model and theoretical calculation are verified to provide auxiliary reference for the operation of existing cable lines.