The Effect of Moisture on the Frequency Domain Dielectric Characteristics of Transformer Oil-Paper Insulation Over a Wide Temperature Range

Stable operation of transformers is critical to ensure power supply safety in the grid. At lower temperature conditions, the physical state of moisture inside oil-paper insulation changes significantly, significantly changing the dielectric properties. The traditional oil-paper insulation state assessment method does not consider the impact of changes in the physical state of moisture, which lead to inaccurate assessment results. In this paper, laboratory tests were conducted on oil-immersed pressboard samples with varying moisture content to analyze the frequency dielectric response across a temperature range of −40 to 100 ℃. The influence of changes in the physical state of moisture on the relaxation activation energy of oil-paper insulation was analyzed. The double translation calculation method for the relaxation activation energy of damp oil-immersed pressboard over a wide temperature range was proposed. It provides an essential theoretical basis for assessing the insulation state of the transformer at low temperatures.