Experimental Study on Dielectric Properties of Oil-Paper Insulation in Low-Frequency Transformers

Low-frequency power transformers are one of the key equipment in flexible low-frequency transmission. In this paper, a test platform for low-frequency dielectric properties of oil-paperboard insulation was established to test the dielectric properties of oil-paperboard insulation under low-frequency sinusoidal voltage, and the influence of different moisture content and temperature on the dielectric properties of oil-paperboard insulation at low frequencies was obtained. The results show that the relative permittivity of transformer oil and insulating paperboard increases slightly when the frequency is lowered at $100^{\circ} \mathrm{C}$, and there is a positive correlation between temperature and relative permittivity of insulating paperboard. The dielectric loss factor of transformer oil and insulating paperboard is positively correlated with temperature at low frequency relation. The test results and conclusions provide data support for the design and development of the insulation structure of the low-frequency transformer, and ensure the reliability of insulation structure.