Variation Characteristics of Typical Electric Field of Non-uniform Aging Oil-paper Insulation Under Complex Operating Conditions
As the main insulation component of transformers, oil-paper insulation experiences non-uniform aging phe-nomena after a long-term operation, which can cause changes in the electric field distribution inside the main insulation under complex operating conditions (ambient temperature, moisture conditions, and voltage type). Therefore, it is crucial to identify the variation characteristics of the electric field changes at the feature location (where the maximum field in-tensity occurs) inside the non-uniformly aged oil-paper insulation under operating conditions. This paper conducts dielectric parameter tests on oil-paper insulation materials subjected to different aging and moisture levels. It elucidates the variations in the frequency-dependent dielectric constant and DC conductivity of aged oil-paper insulation materials under different operating conditions. A comprehensive multi-dimensional nonlinear quantitative representation of non-uniformly aged oil-paper insulation is achieved by constructing a GA-BP neural network-based model for the dielec-tric parameters of aged oil-paper insulation. Additionally, considering the influence of aging on the water content equilibrium in oil-impregnated paper, the distribution of moisture within non-uniformly aged oil-paper insulation is cor-rected. Furthermore, based on typical non-uniformly aged main insulation structures, a model for the typical electric field distribution of non-uniformly aged oil-paper insulation is established. Finally, considering the distinct operating condi-tions in ultra-high voltage power grids, where valve-side windings in converter transformers experience higher DC voltage components in addition to AC voltage, imposing higher insulation requirements. This paper sets two different ex-ternal voltages and conducts simulation calculations on the typical electric field distribution of oil-paper insulation models at different stages of non-uniform aging under complex operating conditions. It reveals the variation characteristics of the electric field in non-uniformly aged oil-paper insulation, identifies critical operating conditions to be considered during actual operation, and provides important theoretical support for transformer operation and maintenance strategies.
oil-paper insulationnon-uniform agingnonlinear dielectric propertiesvariation characteristics of electric fieldAC/DC composite electric field
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