Conductor Current Carrying Capacity Of Traction Network Considering The Influence Of Electrothermal Coupling And Temperature Calculation Method

By analyzing the thermal balance equation of the transmission line of the traction network,it can be known that there are many meteorological and geographical environmental factors that need to be collected in the process of calculating the load capacity and temperature of the wire(wind speed,wind direction,sunshine intensity and ambient temperature,etc.),and it is difficult to monitor due to the complex and changeable environmental parameters of the wire,as well as the quality control problem of the monitoring device itself,which will lead to the accuracy of the monitoring results is not high,thus affecting the accuracy of the calculation results.Therefore,based on the IEEE-738 model,a thermal equilibrium equation based on equivalent parameters is derived.This method substitutes the convective heat transfer coefficient and the equivalent solar insolation radiative heat absorption power into the steady-state thermal equilibrium equation,and then analyzes the electrothermal coupling relationship of the transmission wire,so that the calculation process of the conductor ampacity and temperature becomes simple and the accuracy is within the allowable range.By comparing the calculation results of the equivalent parameter-based calculation model with the calculation results of other commonly used international calculation models,it can be seen that the ampacity and temperature calculation results of the equivalent parameter-based calculation model meet the calculation requirements,while simplifying the calculation process and reducing the monitoring cost.The main research work of this paper is as follows:(1)Based on the transient thermal equilibrium equation,the steady-state thermal equilibrium equation when the temperature change of the transmission line of the traction network is zero is derived.Based on the IEEE-738 model,the calculation process of convection heat dissipation power,radiant heat absorption power,radiated heat dissipation power and Joule heating power is carefully analyzed.Since the AC resistance calculation is very complicated,the AC resistance value is analyzed and properly simplified,and finally the calculation formula of the transmission wire load capacity and the calculation process of the temperature are obtained.(2)Through the study and analysis of the effect of temperature change of the air layer around the transmission wire on the convective heat dissipation coefficient under the meteorological environment of the same wind speed and wind direction angle,the temperature change of the air layer around the transmission wire is concluded that the effect of the temperature change of the air layer around the transmission wire on the convective heat dissipation coefficient under the same climatic geographical conditions is very small,and the same convective heat dissipation coefficient can be used under the same wind speed conditions to replace the convective heat dissipation coefficient calculated at different wire temperatures.The heat absorption power of solar insolation radiation was analyzed by the same method.Considering that in the case of the same lead wire diameter,the same equivalent solar insolation radiation heat absorption power can be used to replace the solar insolation radiation heat absorption power calculated under different conditions of other insolation radiation amounts.(3)Firstly,the coefficients in the convective heat dissipation power in addition to temperature are integrated to obtain the convective heat transfer coefficient,and then the convective heat transfer coefficient and the equivalent solar insolation radiative heat absorption power are listed by using the steady-state heat balance equation,and finally the unknown amount is obtained by solving the equation system.The resulting unknown quantity is then established into a thermal equilibrium equation based on the equivalent parameters.The process of calculating the carrying capacity and temperature of the traction mesh conductor by this method will be simplified.(4)The cigre model,IEEE model,Morgan formula and GB model commonly used at present are introduced in detail,and the advantages and disadvantages of these computing models are compared and analyzed.Finally,the calculation results of the above four models are compared with the calculation results of the equivalent parameter calculation method with the wire ampacity and temperature calculation results under the same geographical environmental factors,and the feasibility of the equivalent parameter method is verified.