How to determine whether the oil in the oil-immersed transformer needs to be replaced?
Time：2025-01-17 Auther：ZTelec-www.ztelectransformer.com
Transformer oil in oil-immersed transformer plays multiple roles. First of all, it acts as an insulating medium to prevent short circuit failure inside the transformer. Secondly, the transformer oil has good heat dissipation performance, which helps to dissipate the heat generated during the operation of the transformer in time to prevent the equipment from overheating. In addition, transformer oil can also play a role in moisture-proof, anti-corrosion, etc., to protect internal components of the transformer from the erosion of the external environment.
How to determine whether the oil in the oil-immersed transformer needs to be replaced?
Whether oil-immersed transformer need to replace the oil can be comprehensive evaluation from the following aspects:
1.Oil analysis
The dielectric strength test: Measure the insulation ability of the transformer oil. If the dielectric strength is below the specified value, it may indicate that the oil contains too much moisture or impurities and needs to be replaced.
Water content test: Moisture is one of the most common pollutants in the transformer oil. Moisture may lead to insulation performance degradation. If the water content exceeds the limit, the oil needs to be replaced.
Dissolved gas analysis (DGA) : Detect the type and concentration of dissolved gas in the oil to determine whether there is overheating, discharge or insulation breakdown inside the transformer. If abnormal gas levels are detected, such as hydrogen, methane, ethane, etc., it may indicate that the oil is aged or contaminated and needs to be replaced.
Oil color and appearance inspection: The color change of oil and whether there is suspended matter can directly reflect the pollution degree and aging of oil. If the oil appears dark brown or black, or there is a large amount of suspended matter, it indicates that the oil has been severely aged or contaminated and needs to be replaced.
2.The transformer performance evaluation
The electrical performance test: The insulation performance and electrical connection of the transformer are evaluated through insulation resistance measurement, AC voltage withstand test and ratio test. If the test results are abnormal, it may indicate that the oil is aged or contaminated and needs to be replaced.
Temperature rise test: Measure the temperature rise of the transformer winding and fuel tank to ensure that its cooling system can work effectively. If the temperature rise is abnormal, it may indicate that the oil has deteriorated or there is a problem with the cooling system, requiring oil replacement or other maintenance measures.
Precautions for replacing transformer oil
When replacing transformer oil, the following points need to be noted:
Choose the appropriate oil quality: Transformer oil that meets the national standard GB2536-2015 should be selected and tested in strict accordance with the relevant standards before use. Unqualified oil may cause the transformer insulation performance to decline, affecting the service life.
Disposal of used oil: The old oil replaced should be disposed of in time to avoid polluting the environment and affecting safety. Generally speaking, the collected waste oil should be sent to regular treatment unit or treatment plant for treatment.
Eliminate air bubbles: After replacing the oil, some air bubbles may appear in the transformer. In order to eliminate these bubbles, you can add an appropriate amount of defoamer in the process of oil replacement. But you need to pay attention to the amount of defoamer to prevent excessive and lead to transformer performance degradation.
Even refueling: In order to make the oil evenly distributed in the transformer, the oil should be added from the bottom when replacing the oil. And the refueling speed should be controlled to avoid too fast and cause bubbles. At the same time, the amount of oil refueling should not be too much each time, so as to avoid overflow.
Safety inspection: Before replacing the transformer oil, the transformer should be a comprehensive safety inspection to ensure that the equipment is in normal condition. During the replacement process, you should pay attention to safe operation to prevent accidents.
