During the operation of high-voltage electrical equipment such as transformers, oil circuit breakers, oil filled cables, power capacitors and oil bushings, the performance of insulating oil will gradually deteriorate due to the effects of oxygen, high temperature, high humidity and sunlight. Strong electric field and impurities. The insulating oil must be tested regularly to determine whether its performance has deteriorated. The quality of insulating oil is closely related to the breakdown voltage.
The breakdown voltage is a measure of the ability of a medium to withstand voltage without being damaged. It is one of the main indicators for testing the performance of transformer oil. Dry and clean oils have very high breakdown voltage values. The main factors affecting the breakdown voltage of transformer oil are water, impurities, temperature, etc. The relationship between temperature and breakdown voltage is complex. For dry and impurity free oil, the breakdown voltage is maintained by the non dissociation of neutral particles of the oil.
However, when the oil contains free water, dissolved water or solid pollutants, these impurities have higher conductivity and dielectric constant than the oil itself, they will form a conductive bridge under the effect of the electric field to reduce the breakdown voltage of the oil. The dielectric strength tester of insulating oil can judge whether there is water, impurities and conductive particles in the oil, but it cannot judge whether there is acid or sludge in the oil.
Generally, the breakdown voltage of transformer oil can reach 70kV, and then it is added to the transformer after vacuum filtration and degassing. Insulating oil is an important dielectric material in electrical and industrial production. It is widely used for cooling and insulation of electrical and electrical equipment such as transformers.