Study On The Current-Temperature Thermal Circuit Model Of Overhead Line Based On Parameter Identify

Overhead line Current-Temperature model is often used in transmission lines design and other fields, such as assessment of line running state and current carrying capacity. In recent years, the effect of conductor temperature on power system operation becomes a hot topic. As a result, the model was also applied to modified the equivalent line parameters, improving of the accuracy of power flow calculation, realization of the electrothermal coordination scheduling, calculation of the optimal power flow, and so on. Overhead line Current-Temperature model have important effect on the further development of the traditional power system analysis and scheduling theory, and has important theoretical significance and practical value.The traditional Current-Temperature model usually sees wire as isothermal body. However, overhead line generally form by a number of twist harness, cannot be regarded as a good heat conductor. Besides, many parameters required in the model, it is difficult to obtain exact and will bring error to the calculation. In addition, the model failed to reflect the axial temperature characteristics of overhead line, and is not conducive to the development of the theory of power system analysis. In this context, this essay, based on parameter identity, study on the calculation methods of the parameters of Current-Temperature model, and overcome the difficult problem of determining the model parameters. Meanwhile, creates a distribution parameters Current-Temperature model which considering the axial temperature distribution. Contribute to promote the further development of research on the effects of wire temperature on power system operation.First of all, the traditional Current-Temperature model is studied in this paper, which includes IEEE model, IEC model, thermal circuit mode, and the numerical simulation model. Then analyzing the calculation methods of the parameters of the model were, comparing the advantages and disadvantages of each model, and provide a theoretical basis for the follow-up study.Then, this essay designed an experiment platform of Overhead line carrying current temperature rise. The data acquisition device of platform has features real-time monitoring conductor temperature, operating current, ambient temperature, and wind speed, wind direction, sunshine intensity data. Data analysis software has the functions of analysis, storage, and display monitoring data. This experiment platform can be used in the model validation of Current-Temperature model and provide necessary data for model parameter identification.In order to overcome the difficult of determining the parameters on traditional lumped-parameter thermal circuit model, this essay put forward a method of calculating lumped-parameters based on linear regression parameter identity, and analyzed the change rule of parameters. The identification results show that, the environmental thermal resistance of LGJ-240/30 and LGJ-400/35 is decrease with the increases of current. Current-Temperature calculation shows that after the results of parameter identification was fed into lumped-parameter thermal circuit model, the maximum relative error is less than 1.5%, the average relative error is less than 0.6%, and the accuracy is contented to the requirements of project calculations. Compared with the parameter calculation method of traditional thermal circuit, the parameter calculation methods based on linear regression parameter identity improved the calculation accuracy of the lumped-parameter thermal model.On the basis of lumped-parameter thermal circuit model studies, this essay creates a distribution-parameters Current-Temperature model which considering the axial temperature distribution, and put forward a method of calculating distribution-parameters based on interior point methods parameter identity. The identification results show that, with the increasing of current, distribution thermal resistance and environmental thermal resistance of LGJ-240/30 is decreasing, but thermal capacity is increasing. Current-Temperature calculation show that after the results of parameter identification was fed into distribution-parameter thermal circuit model, the maximum relative error is less than 3.0%, the average relative error is less than 1.0%, and the model can accurately calculate axial thermal dynamic process of overhead line.