E-mail sinonshseo@gmail.com
Time：2025-05-21 14:02:10 Reading volume：
When water enters transformer oil, it must be handled in time, otherwise it will lead to reduced insulation performance, equipment corrosion and even malfunction. The method of separating water needs to ｓｅｌｅｃｔ appropriate technology according to the degree of water ingress (free water, emulsified water, or dissolved water). The following is a systematic treatment plan:
- Free water: A clear water layer (milky white or transparent) can be seen at the bottom of the oil.
- Emulsified water: The oil is turbid as a whole (water and oil form a stable emulsion).
- Dissolved water: The oil looks clear, but the water content exceeds the standard (instrument detection is required).
- Moisture content (Karl Fischer method):
- Mild water ingress: ≤50 ppm
- Severe water ingress: >100 ppm (may be accompanied by free water)
- Breakdown voltage (GB/T 507):
- Qualified: ≥40 kV (new oil ≥60 kV)
- Unqualified: <30 kV Emergency treatment required
Recommended method: centrifugal separation + vacuum dehydration
- Steps:
1. Initial drainage: Let stand for 24 hours and drain free water from the valve at the bottom of the transformer.
2. Centrifugal separation: Use a high-speed centrifuge (4000~6000 rpm) to separate the remaining free water and emulsified water.
3. Vacuum dehydration: Deeply remove dissolved water through a vacuum oil filter (target ≤10 ppm).
- Advantages: Rapidly removes large amounts of water to avoid subsequent equipment overload.
Recommended method: Demulsification + vacuum dehydration
- Steps:
1. Demulsification treatment:
- Add demulsifier (such as polyether), heat to 50~60℃ and stir to destroy the emulsified state.
- Or use electric field demulsification (high voltage electric field to make water droplets coalesce and settle).
2. Vacuum dehydration: After demulsification, the water is converted into a free state and then treated with a vacuum oil filter.
- Note: The demulsifier must be compatible with the oil to avoid affecting the insulation performance.
3. Dissolved water (the oil looks normal, but the water content exceeds the standard)
Recommended method: Vacuum dehydration + adsorption filtration
- Steps:
1. Vacuum dehydration: Heat at a vacuum degree of more than -0.095 MPa (≤65℃) to evaporate the dissolved water.
2. Adsorption filtration: Adsorb residual trace moisture through a molecular sieve or silica gel filter.
- Key parameters: The higher the vacuum degree, the better the dehydration efficiency (such as -0.099 MPa water boiling point ≈ 30℃).
- Operation: Turn off the transformer, let it stand for more than 7 days, and drain it from the bottom regularly.
- Disadvantages: Only removes free water, which takes a long time and needs to be coordinated with subsequent treatment.
- Operation: Heat the oil to 50℃ (to avoid oxidation), accelerate water sedimentation, and drain it every 2 hours.
- Risk: High temperature may accelerate oil aging, and acid value and dielectric loss need to be monitored.
1. Moisture content:
- Target: New oil ≤15 ppm, operating oil ≤35 ppm (UHV equipment ≤25 ppm).
2. Breakdown voltage:
- Target: ≥40 kV (≥50 kV is recommended for equipment above 110 kV).
3. Dielectric loss (tanδ):
- Target: ≤0.5% at 90℃ (GB/T 5654).
1. Sealing system:
- Use nitrogen protection or a sealed oil storage cabinet (such as a corrugated oil tank).
2. Respirator maintenance:
- ｒｅｐｌａｃｅ expired silica gel desiccant (blue silica gel turns pink and expires).
3. Regular monitoring:
- Detect moisture in oil and breakdown voltage every 6 months.
| Method | Applicable situation | Dehydration depth | Time consumption | Cost |
|------------------|-------------------|----------------|----------|---------|
| Centrifugal separation | Large amount of free water | Free water | 1~2 hours | Medium |
| Vacuum dehydration | Dissolved water/emulsified water | ≤10 ppm | 4~8 hours | High |
| Adsorption filtration | Trace water | 20~50 ppm | Continuous | Low |
| Natural sedimentation | Emergency temporary treatment | Free water | Several days | Very low |
Summary
- Mild water ingress: Direct vacuum dehydration.
- Severe water ingress: First centrifugal separation of free water, then vacuum dehydration.
- Emulsified water: Needs to be demulsified before treatment.
- After treatment, indicators such as moisture and breakdown voltage must be tested to ensure oil quality recovery!
> Tip: If the transformer windings have been damp, the insulation system needs to be treated by combining hot oil circulation or short-circuit drying.
