Research Of Electromagnetic Environment Calculation Methods In±800kV UHVDC Transmission Lines

With the rapid development of economy in China, electricity demand continues to grow,development of extreme distance, large capacity of power transmission has become inevitable. ±800kV UHVDC transmission lines with high transmission voltage, large transmission capacity, long transmission distance, low line loss of many advantages,therefore,development of ±800kV UHVDC transmission project is of great significance.When the electric field intensity on the surface of the conductor exceeds the corona inception field strength, the corona discharge will appears,triggering related field effect. DC corona and DC field effect is the main causes of the environmental impact of ±800kV UHVDC transmission lines. The electromagnetic environment of DC transmission lines can be characterized by:DC corona, total electric, ion current field, radio interference(RI) and audible noise(AN).First of all, this paper analyzes the corona mechanism,studies the calculation methods of the DC corona inception field strength. Then introduces the three methods on calculating the electric field intensity on the surface of splitting wire,which are the Markt-Mengele method,successive image method, simulation charge method, and the three methods and the computing results are compared. In the end, we studies the surface electric field intensity affected from the lines structure parameters, which draws the conclusion: changing the number of bundled conductor, Cross-sectional area of conductor and bundled spacing could effectively reduce the biggest electric field intensity on the surface of the conductor.Secondly, this paper analyzes the characteristics of total electric and ion current field,introduces the limit of total electric and ion current field of ±800kV UHVDC transmission lines in our country. The four methods on calculating total electric and ion current field are summarized, which are Deutsch assumption numerical method, half experience formula method, the finite element method, the Galerkin least square mesh-less method.In the end, we calculates the total electric of ±800kV UHVDC transmission lines based on the the Galerkin least square mesh-less method, uses iterative method to calculate ion current field. Then analysis of the calculation results and the result proves that this method has good accuracy.Finally, this paper analyzes the radio interference and audible noise of UHVDC transmission lines,introduces the limit of he radio interference and audible noise of ±800kV UHVDC transmission lines in our country in detail,gives the recommended calculationformula of radio interference and audible noise at the same time. Then, we studies the radio interference and audible noise affected from the lines structure parameters, which draws the conclusion:through changing the wire to ground height, conductor bundled spacing, and the number of bundled conductor could reduce the radio interference and audible noise level reasonably.