Research Paper (postgraduate) from the year 2013 in the subject Engineering - Power Engineering, , course: POWER SYSTEM ENGINEERING, language: English, abstract: Breakdown behavior of a 10 mm point-sphere gap is investigated for R12, R12 (Dichlorodifluoromethane, CCL2F2), air mixtures for pressures of up to 60psi. It is shown that at high gas pressures, mixtures containing high R12 content can have breakdown voltages higher than the corresponding values in air. Furthermore, these voltages are compared with the SF6. And make a comparison of R12 and SF6 in different scenarios i.e. GWP, cost, dielectric strength. Then Ac voltage breakdown characteristics of various combinations of insulating filler in transformer oil for use in transformers were investigated, with the aim of reducing the amount of oil and thus the cost. Tests were conducted on a sphere–sphere electrode in a horizontal arrangement and a sphere–plane electrode in a vertical arrangement. The Breakdown characteristics were also investigated in a modal in which Nomex paper was inserted between filler and the high-voltage electrode. Based on the experiments, optimum conditions are proposed for the application of transformer oil to transformers. Detailed results of investigations of both gas and composite insulating oil are described and discussed in this paper.