How to check whether the seal of the current transformer in operation is good?

1. Appearance inspection
Check around the sealing part: carefully check the sealing gasket, sealant and other parts of the current transformer. For oil-immersed current transformers, observe the connection between the shell and the cover, and around the inlet and outlet terminals; for gas-insulated current transformers, check the sealing parts of the gas chamber. Check these parts for signs of oil stains, water stains or gas leakage. For example, if small oil droplets are found in the sealing part, it is likely that there is a problem with the seal causing oil leakage.
Check the integrity of the shell: Check whether the entire shell of the transformer has cracks, holes or deformations. Damage to the shell may cause internal oil or gas leakage, and also destroy the sealing environment. You can touch the shell gently with your hand to feel whether there are any uneven or damaged areas. In addition, pay attention to whether the color of the shell changes abnormally. The color of the shell of some materials may change when it is affected by internal pressure changes or chemicals.
Check the status of the connecting parts: Check whether the connecting parts (such as bolts and nuts) are loose. For sealing parts connected by bolts, loose bolts may cause gaps in the sealing surface, resulting in leakage. The tightness of the bolts can be gently checked with a suitable tool (such as a wrench), but be careful not to use excessive force to avoid damaging the components. At the same time, check whether there are any signs of leakage around the connecting parts, such as oil stains or traces of gas escape.
2. Oil level or pressure check (applicable to oil-immersed and some gas-insulated transformers)
Oil level check of oil-immersed current transformer: Observe the oil level gauge of the oil-immersed current transformer. Under normal circumstances, the oil level should be within the specified scale range of the oil level gauge. If the oil level drops significantly and the normal oil level fluctuation caused by oil temperature changes is excluded (the oil level will rise when the oil temperature rises, and the oil level will drop when the oil temperature drops), it may be that the oil leaks due to poor sealing. For example, when the ambient temperature is stable, the oil level continues to drop, which requires further inspection of the sealing.
Gas insulated current transformer pressure check: For gas insulated current transformers with internal pressure requirements (such as SF6 gas insulated transformers), check the internal pressure through a pressure monitoring device. If the pressure drop exceeds the normal leakage rate range, or is lower than the minimum pressure value specified for the equipment, it is likely that there is a problem with the seal that causes gas leakage. Some transformers are equipped with pressure sensors and alarm devices. When the pressure is abnormal, an alarm will sound to prompt the operator to check the sealing condition.
3. Leakage test (applicable to oil-immersed and gas-insulated transformers)
Gas leak detection (taking SF6 gas as an example): For gas-insulated current transformers, professional gas leak detectors can be used for detection. A simple qualitative leak detection method is to bring the leak detector probe close to the sealing part of the transformer and the area where leakage may occur, such as valves, pipe connections, etc. If the leak detector sounds an alarm, it indicates that there may be a gas leak. Quantitative leak detection methods can also be used, such as local wrapping, that is, wrapping the suspected leaking part with an airtight plastic film for a period of time (usually 24 hours), and then using an instrument to detect the gas concentration inside the wrapping, and calculating the leakage amount based on the wrapping volume and the detected gas concentration.
Leakage detection of oil-immersed current transformers: For oil-immersed current transformers, a similar method can be used to check for oil leaks. Place white filter paper or oil-absorbing material at the bottom and around the transformer where oil droplets are likely to appear. If oil stains are found on the filter paper after a period of time (such as a week), it indicates that there may be an oil leak. You can also use a special oil leak detector and apply it to the suspected leaking area. If there is an oil leak, the color of the leak detector will change, indicating the leak location.