Electric Field Strength Influence on Frequency Domain Spectroscopy Characteristics of Transformer Oil-Paper Insulation

Oil-paper insulation is the main insulation structure of transformer. The existing national and industrial standards specify various electrical characteristics parameters of transformers. But the oil-paper insulation inside the transformer is complex. The study of experimental performance of oil-paper insulation under high voltage is still lacking. Therefore, it is necessary to study the oil-paper insulation under high voltage. The frequency domain dielectric spectroscopy (FDS) tests are carried out on oil-paper insulation under high voltage, and the changes of the real part of the complex capacitance and the dielectric loss value $\tan\delta$ at different voltages are obtained. The experimental results show that the real part of the complex capacitance of mineral oil increases with the increase of voltage, but the results of the mineral oil are opposite for the oil-immersed pressboard and oil-paper insulation. The dielectric loss increases with the increase of voltage in the specific frequency band, and the test results under different voltage values vary widely.