By hvhipot 
Insulation performance tests must be conducted on electrical equipment, especially high-voltage electrical equipment, during commissioning or after a period of operation. Test its electrical insulation performance. According to the international “Preventive Testing Regulations for Power Equipment”:
1. The phase insulation resistance of fully connected isolated phase enclosed busbars with a rated voltage of 15kV and above shall not be less than 50M Ω at room temperature. The phase insulation resistance of 6kV common box enclosed busbars shall not be less than 6M Ω at room temperature.
2. The insulation resistance of general busbars should not be lower than 1M Ω/kV. The insulation resistance of electrical equipment refers to the ratio of the DC voltage U applied to its electrical insulation material to the total conductive current passing through it, that is, R=U/I. By measuring the insulation resistance of electrical equipment, the insulation status of the equipment can be checked. For example, whether it has been affected by moisture, aging, etc. Due to the influence of some adverse factors, the data measured in the experiment is inaccurate and cannot truly reflect the actual insulation state of the equipment, which affects the correct judgment of the equipment condition by the staff. Therefore, the author will share with everyone the problems and improvement measures encountered in the actual work process.
1. The effect of temperature on insulation: As the temperature rises, the insulation resistance of many insulation materials will significantly decrease. This is because the increase in temperature intensifies the movement of atoms and molecules in the insulation material, causing the original molecular structure to become loose. Under the action of an electric field, charged ions move and transfer electrons, resulting in a decrease in the insulation ability of the insulation material. In response to this factor, the testing personnel should convert the test results to the same temperature for longitudinal and transverse comparison. If the test data differs greatly and does not comply with the test regulations, the insulation should be analyzed for aging or moisture based on the test results.
2. The effect of temperature on insulation (the HT2500 series high-voltage insulation resistance tester with temperature compensation function can be used to measure insulation resistance) When the insulation material is in a high humidity environment, its surface will absorb moisture to form a water film, causing an increase in surface conductivity current and a significant decrease in insulation resistance. In addition, some insulation materials have capillary action, which absorbs more moisture, increases conductivity, and leads to a decrease in overall insulation. In response to this situation, equipotential shielding should be added.
3. The impact of testing time on testing. During repeated measurements, due to the presence of residual charges, the charging current and absorption current obtained during repeated measurements are smaller than the previous one, resulting in a false increase in insulation resistance. Therefore, after each insulation resistance test, the tested object should be fully discharged to ensure that the discharge time is longer than the charging time, in order to facilitate the discharge of residual charges.
4. The impact of oil pollution on insulation resistance. The surface of the test sample is prone to dirt or oil stains, which can conduct electricity and reduce the surface resistance of the insulation material. However, this does not represent the true situation of the insulation material. In response to this situation, it is usually necessary to use cleaning methods to wipe the surface of the insulator clean, which will greatly increase the insulation resistance value of the tested object.
5. Improper use of the insulation resistance tester can result in inaccurate data. Therefore, it is recommended to choose an insulation resistance tester with an appropriate voltage level. The wiring of the pointer type insulation resistance tester should be correct (measuring the “L” end of the terminal meter, grounding the “E” end of the meter, shielding the “G” end of the meter), and the driving speed should be 120 revolutions per minute. This is the only way to obtain accurate data.
HV Hipot Electric Co., Ltd. is a high-tech enterprise specializing in the production of megohmmeters, insulation resistance testers, intelligent dual display insulation resistance testers, and pointer insulator testers. Our products strictly implement the ISO9001:2000 quality management system.