A methodological approach for improvement of vacuum-insulated HV bushings

In this paper a methodological study is presented for the optimal design of a vacuum feedthrough to be used in HV direct current, with high electrical performances in terms of holdoff voltage. From general guidelines, widely described in the literature and relevant to simpler geometric configurations, summarized in few basic rules useful to design vacuum insulators, the authors have sketched an optimal insulator profile for a cylindrical axisymmetrical arrangement. The adopted assumptions have been validated by means of numerical tools based on the charge simulation method and the finite difference method. A prototype feedthrough has been realised, matching the constraints about the field distribution achieved theoretically with technological constraints due to the manufacturing process. High voltage experimental tests confirming the effectiveness of the suggested insulator design approach are reported