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Lv Y.Z.,Beijing Key Laboratory of HV and EMC | Du Y.F.,Beijing Key Laboratory of HV and EMC | Zhou J.Q.,Beijing Key Laboratory of HV and EMC | Li X.X.,Beijing Key Laboratory of HV and EMC | And 4 more authors.
44th International Conference on Large High Voltage Electric Systems 2012 | Year: 2012

The electrical properties of oil insulation in transformers are of crucial importance considering the safe operation of existing units and also with regard to specification of the insulation system in new units. The performance degradation of oil insulation was considered to be a direct consequence of electrical and thermal stresses. A large number of experimental results have also revealed that excessive moisture content in the oil is one of the major factors accelerating degradation of the liquid insulation. Much effort has been devoted over the years for effectively improving the anti-aging property of oil insulation in order to extend the lifetime of transformers and increase the load capacity. In this work, we develop a new type of mineral oil-based nanofluid modified by semiconducting nanoparticles to improve its anti-aging properties and moisture resistance. The accelerated thermal aging tests were performed at the temperature of 130 °C for 6 days. The AC and impulse breakdown voltage, as well as partial discharge inception voltage (PDIV) of both the aged pure mineral oils and aged nanofluids with different moisture contents were studied according to the standards. We found that both the AC and impulse breakdown strength of the aged nanofluids are improved at the optimum composition. Especially, time to impulse breakdown of aged nanofluids is prolonged by more than 60% compared to that of aged pure oils, which will markedly reduce the propagation speed and prolong the propagation time of the streamer between the electrode gaps. It is noteworthy that the moisture resistance of the aged nanofluids is significantly improved at the high moisture content. All the test results demonstrate that semiconducting nanoparticles can not only improve the mineral oil's anti-aging properties but also dramatically strengthen its moisture resistance.

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