A Method Of Dynamic Thermal Ratting Of Transmission Line Based On Distributed Parameters

Firstly,based on the heat balance equation of transmission line,this paper introduces in detail the relationship between the current carrying capacity of transmission line and conductor temperature,climate conditions(wind speed,wind direction,light intensity,environment temperature).Secondly,the models of transmission lines are introduced,including general transmission lines without considering the characteristics of parameter distribution and long transmission lines with considering the characteristics of parameter uniform distribution.Based on the long transmission line model with uniform distribution of line parameters and considering the climatic environment parameters along the transmission line,a transmission line model considering the heat balance equation is established.Thirdly,under the condition of known PMU measurements at the head and end of transmission line,combined with the equations of the electric heat coupled power flow circuit of each section of the transmission line,the measurement equations of the transmission line are established;the resistance,voltage and current phasors of each section are selected as state variables and the state estimation model of transmission line is established,using weighted least square method to estimate and solve.Then,according to the coupling relationship between resistance and temperature,the temperature distribution of transmission line is obtained,the initial temperature of transmission line is determined and the dynamic thermal setting value of transmission line is calculated.Finally,taking a transmission line in Shandong Province as an example,under different parameter distribution scenarios,the operation truth value of the line is calculated by power flow,and the initial value of the transmission line state variable is estimated by adding error disturbance.The dynamic heat value of the centralized parameter model and the algorithm in different scenarios is compared and analyzed,which verifies the rationality and feasibility of the algorithm in this paper.