Protection and Maintenance Methods for Oil Transformers

Prevention of Moisture

Oil transformers are highly susceptible to moisture, which compromises their insulation performance. To prevent moisture ingress, adhere to the following guidelines:

• Initial Testing: Upon receiving the transformer, request the power supply bureau to conduct an initial test.
• Desiccant Installation: Install a desiccant immediately, especially for transformers with a capacity of 100 kVA and above.
• Monitor Silica Gel: Regularly check the silica gel in the desiccant. Replace it immediately if it becomes damp, as indicated by a color change, to ensure it continues to absorb moisture effectively.
• Minimize Storage Time: Plan installations to reduce storage time before the transformer is powered. Prolonged storage increases the risk of moisture ingress.
• Maintenance of Small Transformers: For transformers below 100 kVA, which do not have desiccant devices, periodically check and replace the oil in the oil pillow to prevent moisture accumulation.

Prevention of Oil Leakage

Transformer oil leakage often results from poor sealing. To prevent this:

• Inspect Fasteners: Regularly check and tighten small bolts to prevent loosening due to vibration. Ensure even and appropriate tightening.
• Check Rubber Components: Replace cracked or deformed rubber seals with parts that meet the original specifications, and ensure the sealing surfaces are clean.
• Storage and Handling: When storing transformers or performing maintenance (lifting, transporting, refueling), drain dirty oil from the oil pillow, clean it, and seal it to prevent contamination.

Monitoring During Operation

Continuously monitor the oil level, oil temperature, voltage, and current. Address any abnormalities promptly through analysis and appropriate action.

Installation Precautions

Avoid connecting the copper guide rod of the transformer with aluminum stranded wire or aluminum bars to prevent corrosion.

Oil Change and Drying

Over time, transformer insulation can degrade due to moisture or deteriorated oil quality. In such cases, oil changes and drying treatments are necessary:

• Oil Change: Lift the transformer body, drain the dirty oil, and clean the oil tank. Rinse any oil on the body, dry the transformer, and refill with new oil. Replace all oil-resistant rubber seals and test before resuming operation.
• Drying Treatment: Use methods like zero-phase sequence, eddy current, short-circuit, or oven drying to dry the transformer body. For larger transformers (35 kV and above), consider vacuum drying by local power manufacturers to ensure thorough drying without causing insulation aging.

These protection and maintenance methods help ensure the reliable operation and longevity of oil-immersed power transformers. For more detailed information, feel free to contact us.