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Factors affecting the test results of the GB/T507 voltage withstand tester: As an insulating medium filled inside electrical equipment, transformer oil must possess good electrical properties in order to fulfill its intended functions properly. The main electrical properties of new oil include: breakdown voltage, dielectric loss factor, volume resistivity, and gas evolution tendency. The dielectric strength or breakdown voltage of transformer oil is a measure of its ability to withstand voltage levels within electrical equipment without being damaged; it is one of the main methods used to assess the quality of transformer oil. It actually measures the instantaneous breakdown voltage of insulating oil. In pure insulating oil, there are always some free electrons that are freed under the action of high-energy external rays, or ejected from the cathode due to strong local electric fields. Under the influence of an electric field, these electrons undergo impact ionization, which ultimately leads to the breakdown of the insulating oil. Since this breakdown is caused entirely by electrical effects, it is referred to as \"electrical breakdown\". Insulating oil used in engineering is never completely pure, containing various impurities. The breakdown of impure insulating oil occurs because impurities form \"bridges\" that span between the electrodes; these bridges have high electrical conductivity, which increases the leakage current and leads to severe heating. This in turn enhances the ionization process, ultimately resulting in ionization breakdown along the path of these bridges. This process is closely related to thermal processes, which is why it is called \"thermal breakdown\". Desiccant oils possess a fairly high breakdown voltage; generally, the breakdown voltage of domestically produced oils is above 40 kV, with some reaching over 60 kV. However, when the oil contains free water, dissolved water, or solids, since these impurities have higher conductivity and dielectric constants than the oil itself, they form conductive paths under the influence of an electric field (voltage), thereby reducing the breakdown voltage of the oil. This test can determine whether there is moisture, impurities, and conductive particles in the oil, but it cannot determine whether the oil contains acidic substances or sludge.