Investigation on Lightning Impulse Breakdown and Dissolved Gas Characteristics of the Novel Three-element Mixed Insulation Oil

As a kind of potential alternative of traditional mineral insulation oil, mixed oil gives rise to numerous researches on its physicochemical and insulation properties. On this background, a novel three- element mixed insulation oil was developed successfully by our team. Its key parameters meet the requirements of IEC 60296:2012. In order to promote the application of the novel three-element mixed insulation oil in transformers, the research on its insulation characteristics had been carried out under severe non- uniform electric field. In this study, the breakdown voltages and propagation velocities of the novel three-element mixed insulation oil under standard lightning impulse voltage were measured by the rising-voltage method, and the oil gap distance was adjusted from 5mm to 25mm. The dissolved gas characteristics after breakdown fault of the novel three-element mixed insulation oil were also studied at gap distance of 10 mm by gas chromatography. Compared the lightning impulse breakdown voltages of the novel three-element mixed insulation oil with that of mineral oil, the former exhibits much lower breakdown voltages under negative polarity than the latter, and slightly higher under positive polarity. The novel three-element mixed insulation oil also has lower propagation velocities than mineral oil at gap distances from 5 mm to 25 mm. Besides, H-2 and C2H2 are the main gaseous products after lightning breakdown fault of the novel three- element mixed insulation oil. With the increase of breakdown times, the contents of H-2 and C2H2 are obviously increased, which can be used as the characteristic gases of lightning impulse breakdown fault for the novel three-element mixed insulation oil.