| With the development of ultra-high-voltage (UHV) power grid, people pay more and more attention to electromagnetic pollution caused by power equipments. Therefore evaluation on electromagnetic field of power equipments becomes increasing important. Researches on the forward problems, inverse problems of power frequency electric field, which are involved in the evaluation on power electromagnetic field, are performed in this paper, following are the main contents:(1) Calculate the forward problem of electric field in the vicinity of high voltage (HV) transmission lines based on charge simulation method (CSM).(2) An improved CSM based on genetic algorithm (GA) is presented, and numerical calculations were carried out to verify the feasibility of it. Forward problem of insulators is calculated and its application in the detection of insulation state of power apparatuses is described.(3) To solve problems coming up in the evaluation on power frequency electromagnetic field, inverse problem of HV transmission lines is put forwarded, and method for its solution is described. Examples regarding a 500 kV two loops transmission lines are presented, and results indicate that with the solution to inverse problem, practical electric field distribution in the vicinity of the transmission lines can be obtained by measuring electric field at some points under the transmission lines.(4) A wireless transmission based power frequency electromagnetic field measurement system is developed, which avoids the weaknesses of present measuring devices, such as, not convenient to move, disturbance caused by human body. Tests in a 500kV transformer substation were carried out to verify the stability of the system in HV electromagnetic field environment.(5) To get the power frequency electromagnetic field distribution in the transformer substation, measurements were carried out in Zhengzhou 500kV Xiaoliu transformer substation with shielding coat on and off a body model, analysis on the measured data is presented.(6) Present methods to compute power frequency electromagnetic field in transformer substation are described, and merits and weakness of each method is summarized. Then a method based on boundary element method (BEM) and CSM is presented to calculate power frequency electromagnetic field in substation, in which influences form apparatuses in the substation are taken into account. The indirect boundary integral equation on the surface of insulators and floating conductors are derived. Numerical calculations for a 500kV substation are carried out with method in this paper and IES-Coulomb respectively, good agreement has been obtained.(7) A software (EMPF) computing electric field in substation is developed, which offer an easy model building compared with present commercial software.The main original contributions of this paper are as follows:(1) In the IGA-CSM presented in this paper, the count of matching points is equal to the total count of matching points and testing points in traditional CSM (TCSM) therefore the testing information is transformed to the matching points, which avoids the tedious testing and adjusting work. It's obvious that the number of matching points N is greater than that of simulation charges M in IGA-CSM, so according to the principle of CSM an overdeterminated equation can be formulated. Real number coded GA is adopted to search the solution of it. Different from the current GA-CSM, the initial population firstly is created randomly, then improvement is made according to the boundary condition of M matching points selected from N matching points, which accelerates the convergence of searching.(2) Inverse problem of HV transmission lines enectric field and insulators electric field are put forwarded and global regularization is adopted to deal with the ill-posed of its solution caused by error in the measurement. Damped Gauss-Newton method is used to compute the inverse problem. Electric field distribution in the vicinity of transmission lines can be obtained by firstly measuring electric field at several points near to the ground and then solving the inverse problem, in this way, some measuring work can be replaced by calculation. Application of the inverse problem of insulators electric field in the detection of faulty insulators are described, in which electric field at points near the insulators are measured, and by solving the inverse problem of them, whether there exist faulty insulators can be confirmed.(3) The wireless transmission based power frequency electromagnetic field measurement system can work stably under HV electromagnetic field, the maximum transmission distance is 48m. Compared with most imported equipments, it can avoid the disturbance caused by human body to the original electric field, and only the probe need to be moved when the measuring points change.(4) A method based on BEM and CSM is presented to calculate power frequency electromagnetic field in substation, in which influences form apparatuses in the substation are taken into account. The indirect boundary integral equation for the surface of insulators and floating conductors are derived. BEM is used to calculate the electric field produced by charges on the surface of supporting and insulating devices, and CSM is used to compute the electric field produced by the busbars. Compared with single BEM, less mesh work is carried and extra equations are avoided compared with single CSM. A software computing electric field in substation is developed, which offer an easy model building compared with present commercial software.
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