How to determine whether the sealing problem of the current transformer needs to be repaired or replaced?

1. Determination of the degree of leakage
Minor leakage: If only a small amount of oil stains or gas leakage is found through inspection, for example, there are only tiny oil stains on the filter paper at the bottom of the oil-immersed current transformer, or the leak detector around the gas-insulated current transformer only occasionally issues a weak alarm, this may be a minor leak. For minor leaks, you can first mark and monitor the leaking part to see if the leakage situation worsens. If the leakage volume remains stable for a period of time (such as a few weeks or months) and does not have a significant impact on the performance of the transformer (such as normal indicators such as insulation resistance and dielectric loss factor), you can temporarily not repair it, but you need to strengthen monitoring.
Moderate leakage: When there is a more obvious leakage phenomenon, such as the oil level of the oil-immersed current transformer drops to a certain extent (for example, the oil level is 10% - 20% lower than the normal oil level), or the pressure drop rate of the gas-insulated current transformer exceeds half of the specified value, this may pose a potential threat to the performance of the transformer. At this time, it is necessary to further check the cause of the leak and consider repairing it. For example, check whether the sealing gasket is damaged, replace the damaged sealing parts, and recheck the leakage.
Severe leakage: If a large amount of oil or gas leaks, for example, the oil-immersed current transformer has a continuous oil dripping, or the pressure of the gas-insulated current transformer drops sharply and cannot maintain normal operation, it indicates that the sealing problem is very serious. In this case, the operation of the transformer must be stopped immediately and a comprehensive repair or replacement must be carried out. Because severe leakage will cause the insulating material to be directly exposed to the external environment, it greatly increases the risk of insulation damage, and may also affect the measurement accuracy and protection function of the transformer.
2. Judgment of performance index changes
Degradation of insulation performance: If the insulation resistance, dielectric loss factor and other indicators are significantly reduced when monitoring them, and it is suspected that it is caused by a sealing problem (such as moisture or impurities inside the transformer), it is necessary to consider repair or replacement. For example, if the insulation resistance drops below half of the specified value, or the dielectric loss factor exceeds 1.5 times the specified value, and there are signs of poor sealing (such as aging of the sealing gasket, leakage marks on the shell, etc.), this indicates that the sealing problem has seriously affected the insulation performance of the transformer, and the sealing components need to be repaired or replaced, and the insulating materials may also need to be processed (such as drying, cleaning, etc.).
Affected measurement accuracy: For current transformers used for metering or measurement, if the measurement accuracy is found to be deviated, and other factors (such as secondary circuit load changes, winding short circuits, etc.) are excluded, it may be that the sealing problem causes the internal components to be damaged or damp, affecting the performance of the transformer. For example, by comparing with other accurate measuring equipment, it is found that the measurement error of the current transformer exceeds the allowable range, and oil or gas leakage is found, it is necessary to check the seal and repair it to restore its measurement accuracy.
3. Judgment of operation stability
Increased partial discharge: If a significant increase in partial discharge is detected, and it is suspected that air, moisture or impurities have entered the interior due to poor sealing, the sealing problem needs to be dealt with. For example, if the partial discharge increases from the normal tens of pC to hundreds of pC, and there are signs of leakage around the transformer, this may be because the sealing problem has caused the deterioration of the internal insulation environment, resulting in an increase in partial discharge. In this case, it is necessary to repair the sealing components and deal with the partial discharge problem, such as finding the discharge point and cleaning impurities.
Abnormal sound or vibration: When the current transformer makes abnormal sounds or vibrations during operation, and the inspection finds that there is a sealing problem, it may be due to the internal components being affected by external factors (such as moisture, impurities, etc.) and causing failure. For example, if you hear a "hissing" gas leakage sound or a louder "buzzing" sound inside, and there are signs of gas or oil leakage, this may be caused by a sealing problem and needs to be repaired or replaced in time to ensure the normal operation of the transformer.