How to judge whether the sealing material of the current transformer needs to be replaced?

1. Appearance inspection judgment
Observe the surface condition of the sealing material: carefully check whether the surface of the sealing material (such as sealing gaskets, sealants, etc.) shows obvious signs of aging. If it is a rubber sealing gasket, it is likely to need to be replaced when cracking, hardening, softening, powdering or loss of elasticity occurs. For example, cracks with a depth exceeding a certain value (such as 0.5mm) appear on the surface of the rubber gasket, which will cause the sealing performance to deteriorate and need to be considered for replacement.
Check the integrity of the sealing material: check whether the sealing material has any damaged, detached or missing parts. For sealants, check whether there is cracking or peeling. If the sealing material is found to be damaged in key parts (such as around the inlet and outlet terminals and the seams of the shell), even small damage may cause leakage and should be replaced in time.
Check the color change of the sealing material: A significant change in the color of the sealing material may also be a sign of aging. For example, some rubber materials will turn yellow or brown during the aging process, or the originally transparent sealant will become turbid. When the color change is obvious and accompanied by other signs of aging (such as reduced elasticity), the sealing material may need to be replaced.
2. Leakage judgment
Check for liquid or gas leakage: If there are signs of oil (for oil-immersed transformers) or gas (for gas-insulated transformers) leakage in the current transformer, first check the sealing material. For example, if oil stains are found at the bottom of the transformer, or gas leakage is detected around the gas-insulated transformer, this may be caused by the failure of the sealing material. At this time, even if the sealing material does not look seriously problematic, it should be considered for replacement to prevent further deterioration of the leakage.
Monitor the trend of the leakage volume: For minor leaks, the leakage volume can be monitored. If the leakage volume gradually increases, it means that the sealing performance of the sealing material is constantly decreasing and needs to be replaced in time. For example, by regularly checking the oil level of the oil-immersed transformer or the pressure of the gas-insulated transformer, it is found that the oil level decreases faster or the gas leaks faster, indicating that the sealing material has been unable to maintain a good sealing state.
3. Performance test judgment
Insulation performance test correlation judgment: When conducting insulation performance tests such as insulation resistance and dielectric loss factor of the current transformer, if these indicators are found to have dropped significantly and it is suspected that they are caused by sealing problems (such as moisture or impurities), then consider whether the sealing material has failed. For example, if the insulation resistance drops below half of the specified value and there are signs of moisture ingress around the sealing material (such as water droplets on the surface), this may be due to aging of the sealing material causing moisture ingress, and the sealing material needs to be replaced to restore a good insulation environment.
Pressure test (applicable to gas-insulated current transformers): For gas-insulated current transformers, a pressure test can be performed to determine the condition of the sealing material. If the internal pressure drops more than the specified rate during normal operation, or falls below the specified minimum pressure value, the sealing material may be leaking and needs to be replaced. For example, if the internal pressure of the transformer drops by more than 10% in a short period of time (such as a week) without an external cause of leakage (such as pipeline damage), this indicates that the sealing material may need to be replaced.