Study On EM Environment Of HVDC Transmission Projects

High voltage direct current(HVDC) transmission project generally consist of converter ststion, transmion lines and ground electrode, Compare to high voltage alternative current(HVAC) transmission system, it has much advantage, as far as bulk, long distance power transmission and interconnection of the grid are concerned, the advantage of the HVDC is incomparable. It plays very important rule in the construction of the grid ,especially in the project of"western electricity energy to eastern"and"northern electricity energy to southern"in our country.With high voltage, large current and great electrial potential gradient, high voltage transmission projects will have a impact on the nearby environment, the environmental impact factors of HVDC includes not only power frequency electrical field, magnetic field, radio interference(RI) and audible noise(AN), but also DC total field, ion current, DC magnetic field, for its special DC transmission mode. Much studies on the EM environmental impact have been finished abroad, the domestic study is still nonsystem, although±500kV Gezhouba-nanqiao HVDC transmission project constructed in 1980's.The paper objectively reports the present EM condition of the HVDC projects running in this country first time by investigating the±500kV Gezhouba-nanqiao, Longquan-zhengping, Tianshengqiao-guangzhou, Gaopo-zhaoqing HVDC projects all round. According to the requirements of the design and assessment of the HVDC project, biulds the calculate programs for the DC total field, densitity of the ion current, and DC magnetic field. Inorder to study the EM environment of HVDC transmission lines, the instruments for measurement of the groud total field and ion current is made. The measurement of the factors for the four projects is finished in different place. With the test result, the reasonableness and accuracy of the program is proven.The result of the investigation shows the little impact of HVDC line to the nearby inhabitant, but the great impact of the converter station noise. The normal measurement of DC total field under the line is less-than 30kV/m, and affected by the groud ion distribution. All the measurement of the ion current are less-than 100 nA/m2. Based on the investigation and the measurement, conbine with the abroad expirence, the paper gives the technical limits for assessement of EM environment of HVDC projects, and the technical norm for assessment is accomplished, which would guide the design and the assessment of the EM environment of the HVDC projects.