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SF6, an insulated gas with high dielectric strength, is widely used in the power system. However, SF6 is one of the six limited greenhouse gases specified with a GWP of 23500. Therefore, it is necessary to assess a candidate as alternatives to SF6 in electrical equipment.
In this paper, a new insulating media C5F10O with a GWP value of only 1 and a dielectric strength twice that of SF6 is studied. The discharge characteristics of C5F10O mixed with N2, CO2, and Air in different pressure, ratio are discussed in uniform field under AC voltage. An experimental platform for the discharge was designed, which consists of a 300 KV AC generator, divider, and a test chamber, where the Rogowski electrodes with the distance of 10mm are mounted. The breakdown experiments of 95%CO2/N2/Air mixed with 5% C5 at 0.1-0.5 MPa were carried out respectively. The experiments were repeated at least five times for each test condition. The results show that the insulation performance can be greatly improved by adding a small amount of C5 gas to CO2/N2/Air. Among them, C5 mixed with Air has the best insulation performance, followed by the mixture with N2 and CO2.The insulation strength of 5% C5 /95% Air at 0.5MPa can reach 78% of SF6 in the same experimental conditions. In addition, the breakdown voltage of 2%C5, 5%C5 and 8%C5 mixed with Air at 0.1-0.5 MPa were measured. The results reveal that the higher the mixing ratio of C5, the higher the discharge voltage of mixed gases is. At 0.5MPa, the insulation strength of 8%C5/92%Air is approximately 87% that of SF6.
Therefore, the mixtures of C5 and Air are expected to replace SF6 in terms of electrical strength. However, the liquefaction temperature of gases and the toxicity of products after decomposition need to be considered comprehensively.