Study On Electrical Parameter Inversion Method Of Distribution Line Based On Power Frequency Electromagnetic Field Inverse Problem

With the national grid to establish a robust smart grid,promote the construction of power grid facilities and a series of development policies have been put forward,the scale of power grid construction continues to expand.As an essential public infrastructure for national economic and social development,distribution lines accurately and reliably monitor their operating status and avoid line accidents under various factors,which is of great significance to the safe and stable operation of the power grids.The parameters such as the amplitude and phase of the operating voltage and current of AC distribution lines can directly reflect the line’s operating state.It is also the primary basis for evaluating power quality,calculating transmission power,judging the switching capacity of reactive power compensation,starting relay protection and performing fault diagnosis.Nowadays,the electrical parameters detection of distribution lines is mainly realized by contact transformers.However,the commonly used transformers have many problems such as poor flexibility,complex installation procedures,high insulation requirements and easy to cause ferromagnetic resonance.Therefore,seeking a safe,effective and non-contact electrical parameter detection method for distribution lines is necessary.In view of the above problems,this article uses the safety and convenience of non-contact measurement to apply the relevant theory of electromagnetic inverse problem to the detection of electrical parameters of distribution overhead lines,and then studies how to invert the electrical parameter information through the power frequency electromagnetic field of distribution lines.The research content can be mainly divided into the following four parts:Firstly,the catenary equations of distribution overhead lines under different conditions are established.The electromagnetic field distribution law of the near space below the line is explored by finite element simulation,which provides a reference for the layout of subsequent electrical parameter inversion measurement points.Meanwhile,according to the source-field relationship of distribution lines,a mathematical calculation model of three-dimensional power frequency electromagnetic field in distribution overhead lines is built.Secondly,the algorithm is improved under the basic framework of the NSGA-Ⅲ algorithm,the difference operator and adaptive operator are introduced.An improved adaptive NSGA-Ⅲ-DE algorithm based on the difference operator is proposed.Combined with TOPSIS method,the screening problem of inversion solution set is solved,and the solution efficiency of inversion method is improved.Thirdly,focusing on how to invert the electrical parameter information through the electromagnetic field data around the distribution overhead line,the theoretical derivation is carried out and the inversion optimization model is established.The improved algorithm is applied to the inversion of voltage and current under various operating conditions of distribution overhead lines,and the effectiveness and accuracy of inversion method proposed are analyzed and verified.Finally,the simulation test platform of AC distribution line is built.By measuring the field data and analyzing the electrical parameter inversion value,it is verified that the electrical parameter inversion method proposed in this article can effectively detect the operation state of distribution overhead line,which has great detection performance.