The purpose of filtering insulating oil (transformer oil) is to remove moisture and impurities in the oil, improve the insulation strength of the oil, protect the paper insulation in the oil, and also improve the physical and chemical properties of the oil to a certain extent.
Most distribution transformers are installed in the open air. The insulating oil (transformer oil) is affected by external impurities, contact with the air, and the high operating temperature of the equipment itself, which gradually deteriorates the quality of the oil. Insulating oil (transformer oil) after deterioration will not play the role of insulation and cooling. In order to prevent the safety operation from being affected due to the deterioration of oil quality, the regular oil samples of the power distribution in normal operation should be tested and analyzed, and the oil should be treated accordingly according to the analysis results. The inspection period for the oil chemical supervision of distribution operation is stipulated at least once every 3 years.
Routine inspection items include: acid value, water-soluble acid, flash point, breakdown voltage, appearance. It should be noted that if the equipment is often loaded with high loads, the number of inspections should be increased on the basis of the specified test period; if some indicators of the inspected items are obviously close to the controlled limit value, the number of inspections should also be increased; The quality of running oil varies greatly with conditions such as the degree of aging and impurities contained. Usually, a single test item cannot be used as the basis for evaluating the oil quality status. A comprehensive analysis should be carried out based on the measured main characteristic indicators.
1. Acid value-its limit value is greater than 0.1mg KOH/g. There are 4 possible reasons for exceeding the limit value: overload operation; consumption of antioxidants; incorrect oil supplement; oil contaminated. The following countermeasures can be taken for the acid value exceeding the limit value: investigate the cause, increase the number of tests, measure the antioxidant content and add it appropriately, and carry out the regeneration treatment of the transformer oil. If the economy is reasonable, the oil can be changed.
2. Water-soluble acid-its limit value is less than 4.2. There are two possible reasons for exceeding the limit value: oil is aging and oil is contaminated. The following countermeasures can be taken for the water-soluble acid exceeding the limit value: increase the number of tests and compare with the acid value to find out the cause. Carry out oil regeneration treatment, if economical and reasonable, you can do oil change treatment.
3. Breakdown voltage-its over-limit value is less than 20KV. There are two possible reasons for exceeding the limit value: excessive water content in the oil; contamination by impurity particles in the oil. The following countermeasures can be taken for breakdown voltage exceeding the limit value: find out the cause, carry out vacuum oil filter treatment, plate and frame pressure oil filter treatment or replace with new oil. Generally, the breakdown voltage of the oil after TPZGL series vacuum filtration treatment is greater than 50KV.
4. Flash point-its over-limit value is less than 130℃. Or it is 5°C lower than the previous test value. There are two possible reasons for exceeding the limit value: the equipment has a local overheating fault; the oil is compensated for. The following countermeasures can be taken for the flash point exceeding the limit value: find out the cause and eliminate the fault; carry out vacuum oil filter degassing treatment, or carry out oil change treatment.
5. Appearance-If the oil is opaque by visual inspection, there are visible impurities or suspended matter. Or the oil color is too dark, the oil appearance is abnormal. The possible reasons for the abnormal appearance are: the oil contains moisture, fiber, carbon black and other solids. The following countermeasures should be taken for oil with abnormal appearance: If the oil is fuzzy, turbid and white, it indicates that the oil contains water, and the water content should be checked. If it is found that the oil contains carbon particles, the oil is black, or even has a burnt smell, it may be that there is an arc or partial discharge fault inside. It should be combined with other tests to investigate the cause and eliminate the fault. If the oil color is dark and the color of the oil changes significantly, attention should be paid to whether the aging of the oil is accelerated, which can be combined with the acid value test and analysis of the oil, or strengthen the monitoring of the operating temperature of the oil.