How do I replace the insulating oil in a current transformer?

I. Preparation
1. Safety Measures
Disconnect the power supply and conduct an electrical test to ensure the equipment is fully discharged.
Set up fences and warning signs to prevent misoperation.
2. Tools and Materials
Prepare a vacuum oiler, oil filter, insulating oil (compliant with GB 2536), gaskets, and an oil level gauge.
II. Procedure
1. Oil Draining and Inspection
Use a vacuum oiler to recover the used oil until the oil level drops to 2-3 cm below the primary terminals.
Check the oil for moisture and impurities. If the oil is severely deteriorated, replace the entire oil.
2. Sealing
Remove the expander housing and terminals, clean the sealing surface, and replace the gaskets (compression should be maintained at 1/3).
3. Vacuum Oiling
Use the vacuum oiler to inject new oil to the mark corresponding to the current ambient temperature.
Let it sit for 24 hours to allow the oil to vent and ensure there are no bubbles remaining. 4. Performance Testing
Insulation resistance testing, dielectric loss (tanδ) measurement, and oil pressure testing are performed to ensure oil quality meets standards.
III. Precautions
Oil Quality Control: New oil must be filtered through an oil filter to ensure a water content of ≤20ppm.
Seal Check: After filling the oil, observe for 24 hours to confirm there are no leaks.