Study on the Influence of Aging Degree and Test Flow Velocity on Electrification of Ester Insulating Oil

The performance of insulating oil has a decisive significance for the single-limit capacity and operation reliability of the transformer. Compared with traditional mineral insulating oil, ester-based insulating oil belongs to low carbon/zero carbon emissions. The existing operating data of ester-based insulating oil transformers also shows that the transformer is stable and eco-friendly with almost zero carbon emissions. In this paper, a testing platform for electricity of oil flow was set up, and the effects of aging degree of oil paper and test velocity on electricity of oil flow of ester insulating oil were analyzed by selecting two kinds of commercial ester insulating oil and mineral insulating oil. The results show that the viscosity of the ester insulating oil is higher, and the friction contact between the oil paper is further increased under the action of oil flow, which accelerates the charge separation at the interface of the oil paper, resulting in the electricity of the oil paper is significantly higher than that of the mineral insulating oil, in which the natural ester is the highest, followed by the synthetic ester. With the increase of oil flow velocity, the charge separation at the interface of oil paper is intensified, and the charging tendency of ester insulating oil is enhanced. The increase in the aging degree of the oil paper accelerates the generation of aging polar products in the oil and then accelerates the dissociation of impure molecules; resulting in the increase of the number of intrinsic ions and impurity ions in the oil, and thus aggravating the electrification degree of the oil flow.