Research On The Thermal Model Of Power Transmission System

In order to cope with climate change and protect the ecological environment,people started to adjust energy structure.Renewable energy is being vigorously developed,especially for wind energy and solar energy.However,traditional electric power transmission mode cannot deliver the renewable energy safely and efficiently.Thermal model of power cable system is one of the most important foundations for smart grids to control the cable system to perform the safe and efficient transmission.Therefore,I carried out the research to analyze the thermal model of the power transmission system under the supports from the projects:Sichuan province human resources and social security department project "the research of the method of strong paroxysmal power transmission"(N0.CHUANCAIJIAO[2013]203),Chinese Ministry of Education project " research on highly efficient delivery of power with strong intermittency "(No.Z2012015),and Sichuan Provincial Department of Education project“research on highly efficient delivery of power with randomness”(No.13ZA0025).Firstly,this paper introduces the type,structure,the laying way of the cable and basis of heat conductivity.These factors and the cable thermal temperature field are closely related.On the basis,I analyzed the heat transfer model which is based on the principle of heat transfer,thermal network model of cable system which is based on the similarity between the equivalent cable heat path and the circuit,and Finite Element model which is based on finite element analysis.Then I researched the calculation methods of the parameters in the models.As for the thermal network model,the thermal characteristic parameters are traditionally worked out according to the cable system structure,material and laying conditions.Generally,the calculation result is not enough precise to meet the requirement of the power delivery control.So we worked hard and explored an experimental approach for analyzing thermal characteristic parameters with recursive regression method to solve this problem.Then,according to the thermal model of the power transmission system,I analyzed model mathematically and worked out the thermal response of the power transmission system,and deduced the mathematical relationship between the system temperature and the system thermal characteristic parameters.The analysis results are very valuable to obtain the parameters conveniently,economically and without mechanical damage.Finally,the feasibility and precision of the thermal model characteristic parameters are analyzed by using the recursive regression method.At the same time,the correctness of the expression of the mathematical response of the step response of the thermal model is verified by Matlab software.The experimental results show that the maximum absolute error,mean absolute error and the variance of the absolute error of the temperature of each structural layer of the cable are calculated based on the thermodynamic parameters of the recursive regressionmethod are smaller than that of the IEC standard and have a good precision.The maximum difference of one cable system thermal step response is within 0.04? between the physicalthermal network model and the mathematical expression.Therefore,the power transmission system can be analyzed by the mathematical expression.