UHVDC converter valve shielding case surface electric field calculation using hybrid-weight-function boundary element method

The calculation results of three-dimensional electric field of the valve towers in a DC converter station plays an important directive role in the design of the shielding case for the valve towers and the control of its surface field intensity. However, due to its enormous volume and complex structure, there are difficulties in the digital simulation of the shielding case for valve towers. To save computing resource, A new method, called hybrid-weight-function boundary element method (HWFBEM) was proposed. In this method, the Collocation and Galerkin procedures were synthetically employed to deal with the continuous integral equations. It makes full use of the advantages of the two procedures and provides a better trade-off between accuracy and efficiency. By using HWFBEM, the electric field in (800 kV converter systems was obtained, which could be employed to guide insulation design of valve hall in HVDC converter stations in China. Calculation results show that with the current design for the concerned scheme the maximum field intensity at the surface of shielding cases was no more than 16 kV/cm, so if 20 kV/cm is taken as the critical field intensity for corona onset, there will be no corona occurred on the shielding cases. In addition, the availability of this method is demonstrated by comparing the calculated results obtained using HWFBEM with that obtained using Galerkin boundary element method.