Study on the transformer insulation design and insulation margin verification under extremely cold conditions

Abstract Under extremely cold conditions, the property of insulation materials will change with the decreasing of the temperature. Therefore, the research on the dielectric property of insulation materials under unknown extreme cold conditions and the verification on the insulation margin of the insulation materials shall be conducted to ensure that the insulation margin of key transformer parts can meet operation requirements and to avoid the discharge or breakdown failures. The paper studies the main insulation of transformer winding, the insulation of high-voltage connection and the electric field distribution of high-voltage lead model under ambient temperature and low temperature conditions. In addition, the insulation margin curve of the transformer under different temperature conditions is obtained through breakdown characteristic experiment and simulation experiment.