| With the expansion of China’s power grid scale,the transmission voltage grade has been gradually increased from high voltage(110～220k V)to ultra-high voltage(500k V)and the scale,transmission distance and load capacity of transmission project are increasing rapidly.The problem of electric field environment in the space near the transmission lines has been paid more and more attention.In this paper,the electric field calculation and its inverse operation are analyzed and studied based on ultra-high voltage transmission line.The calculation and study of power-frequency electric field on transmission lines is of great significance to the problem of environmental electromagnetic limit and site selection of transmission projects.Firstly,this paper calculates the electric field distribution under the two-dimensional model of the transmission line by the method of simulated charge and analyzes the influence of different conditions on the offline electric field.The electric field calculation method of the three-dimensional model of the transmission line is proposed under the consideration of sag.The experimental results show that the3 d electric field can improve the accuracy of the calculation.In order to optimize the setting of simulated charge parameters in 3d electric field calculation,a method of optimizing simulated charge based on intelligent algorithm is proposed.Particle swarm optimization algorithm,genetic algorithm,simulated annealing algorithm were combined with simulated charge method respectively.The fitness function was established by using the error value of the finite element method and the error value of the test point.Experimental calculations are carried out in 2d and 3d electric field calculations.The computational efficiency of the three intelligent algorithms is compared through the optimization results.Based on the principle of the inverse operation of the power frequency electric field,a nondestructive method for detecting the voltage on the line is proposed.Kalman filter algorithm is introduced to preprocess the measured electric field value to reduce the instability caused by malformed data in the reverse operation.The inverse simulation experiments are carried out under the multi-media operation environment and Kalman filter algorithm.In addition,an actual ultra-high voltage transmission line is selected to establish two measurement schemes,and the advantages and disadvantages of the two measurement schemes are compared through the results of reverse operation.Based on the above work,the main innovations of this paper are:1.A three-dimensional electric field calculation model and method for transmission lines are proposed,which is more in line with the real situation of long span transmission of UHV transmission lines.The results show that the 3d method of offline electric field significantly improves the effectiveness and accuracy of electric field calculation.2.Combining with the intelligent algorithm,the optimization simulation algorithm is proposed.The optimal parameter setting and minimum error value of simulated charge are found by applying the method to two dimensional and three dimensional computing models.Compared with the traditional analog charge algorithm,the optimization analog charge algorithm has higher accuracy and robustness.3.Based on the principle of electric field inversion,a nondestructive voltage detection method is proposed.At the same time,the kalman filter algorithm is introduced to preprocess the electric field measurement data,which can effectively reduce the generation of ill-posed matrix and improve the accuracy and robustness of the inverse calculation.4.In the actual engineering application of the voltage on the electric field inversion line,two measurement methods are proposed.Based on the measured data,the voltage on line is calculated and compared.The discussion of measurementmethods has important guiding significance for the actual engineering operation of the voltage on nondestructive testing lines. |
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