Research On The Numerical Methods Of Total Electric Field Under UHVDC Transmission Lines

With the rapid development of economic, the demand for electricity increaseddramatically. However, the economic development and the resource distribution ofChina is extremely uneven. Developing the UHVDC (Ultra-High Voltage Direct)transmission is beneficial to optimize energy supply and resource allocation. So, a seriesof electromagnetic problems are generated. So, at the same time of UHVDC powertransmission is developed, we need to consider environmental requirements. Therefore,it is very important to the accurate calculate of the ground electric field of UHVDCtransmission line and provide a reference for the environmental assessment.The numerical methods of the ground electric field of transmission line is studiedbase on charge simulation method(CSM) in this paper. The main work is as follows:(1) According to the basic principles of the charge simulation method, the groundelectric field of UHVDC line is calculated by the assumption Deutsch, and comparedthe measured data and the results of calculation.(2) For the ground electric field under AC and DC lines in parallel, the influence ofthe surface electric field and the power lines trajectory of UHVDC transmission linesare analyzed in this paper. This paper has improved the method of power lines trajectoryand calculated the ground electric field under UHVDC lines when the AC lines isadjacent DC lines. The relationship between the adjacent distance of hybrid lines andground electric field were analyzed.(3) The3-D electric field over ground under UHVDC line is calculated with CSMof line, the feasibility of this method is validated by measurement. The power towercalculation model is built by CSM, and the ground electric field is calculated by CSMwith tower. The character of3-D electric field under lines near the tower is analyzed anddiscussed.(4) The inverse problem of ground electric field of UHVDC lines is put forwarded.In order to solve the inverse problem, the iterative method of Pivot Element Weighting-Newton Corrector(PEW-NC) is described. Examples regarding a±800kV DCtransmission lines are presented, compared the results of Pivot Element Weightingalgorithm and Levenbery-Marquardt algorithm to verify the feasibility of it.(5) The number of measure points is analyzed by PEW-NC method. Practicalelectric field distribution can be obtained by measuring8points under lines. Themethod can reduce the workload of the environmental impact assessment measurement.