A fundamental study on electrical insulation of N2/SF6 gas-insulated electric power apparatus

In this paper, we carried out a case study on fundamental insulation design for the application of N-2/SF6 gas mixtures to a 275-kV gas-insulated busbar. First, we investigated the impulse ratio in N-2/SF6 gas mixtures and point out that the insulation design might be based on the negative switching impulse voltage in the case of lower SF6 content. Second, we estimated the tank diameter and SF6 gas amount with consideration of the electric field strength on conductor surface and temperature rise in gas mixtures. We clarified that the tank diameter at the lower SF6 content is mainly determined by the electric field strength on the conductor surface and quantified the optimum gas pressure and SF6 content for a target reduction of SF6 gas amount. (C) 2002 Wiley Periodicals, Inc.