Surface Electric Field Intensity Analysis Of Shielding System For HVDC-Light Converter System

The building model and the calculation results of electric field of valve surface in HVDC-light play important directive roles in the design of shielding case for valve towers and the control of its surface field intensity. By use of Galerkin indirect boundary element the shielding effect on shielding system of the ideal converter valve has been analyzed.First build the ideal converter valve model and the electric field intensity at the surface of converter valve without grading rings and the model with grading rings are analyzed. The influences of height,position and distance between grading rings on electric field intensity on the surface of valve body structure are studied and get some rules. By comparing design cases of different grading rings,the suitable parameters of grading rings to meet some conditions are determined. The field intensity of vlave structure is reducing greatly with appropriate grading ring and there is no corona on the grading ring either. The results turns out that the field intensity of midpoint on relevant edges for converter valve body structure is increasing while the distance between grading rings around is getting bigger,the sharp corner of converter valve structure is effectively shielded with grading rings around and the field intensity of relevant sharp corner for converter valve body structure is decreasing while the height of grading ring is getting bigger.The shielding effect of shielding system in the real converter valve for an actual project is also analyzed in detail. By changing the parameters of the model like the size of shielding case and the distance between the shielding cases,we can conclude the suitable model which is satisfied with insulation requirments in engineering. Insulation system structure in the insulation design process is being adjusted and to get the calculation results with much more accuracy,the paper makes the calculating model with valve body and column and plate and sphere.The results shows that the electric field on the circular plate can not be ignored. Taking account of the electric field,the side of circular plate can be made to the shape of smooth ring. According to the applying voltage,choosing different cases on different moment to build the calculating model with full consideration.The principle and the applying voltage of every case is introduced definitely. The results confirm that the insulation design is feasible and also solve the problems of insulation in the egineering by calculating the surface field intensity on some key parts of vlave tower and grading rings.