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Time：2025-05-19 11:48:47 Reading volume：
The main purpose of transformer oil degassing is to remove gases (such as oxygen, nitrogen, carbon dioxide, etc.) and trace moisture dissolved in the oil, thereby restoring or improving the oil's insulation performance, chemical stability and equipment operation reliability. Specific goals include the following aspects:
- Key impact: Dissolved gases (especially oxygen and moisture) will significantly reduce the dielectric strength (breakdown voltage) of the oil.
- Mechanism of action:
- Gases may ionize under high-voltage electric fields to form conductive channels, causing partial discharge or breakdown.
- When moisture and gas coexist, insulation degradation will be further aggravated.
- Effect after treatment: The breakdown voltage of the oil after degassing can be increased by 20%~50%, meeting the standard (such as ≥60kV/2.5mm).
- Key impact: Oxygen and moisture are the main causes of aging of transformer oil and cellulose insulating materials.
- Mechanism of action:
- Oxygen: reacts with oil to generate acidic substances and sludge, corrodes metal parts, and blocks oil channels.
- Moisture: accelerates the hydrolysis of cellulose insulation (cardboard, windings), reducing its mechanical strength and insulation performance.
- Effect after treatment: Degassing can delay the aging of oil and solid insulation and extend the life of the transformer.
- Key impact: When high temperature or pressure changes, dissolved gas will precipitate to form bubbles.
- Mechanism of action:
- Bubbles are prone to partial discharge (PD) under high-voltage electric fields, causing insulation damage.
- In severe cases, it triggers the "bubble effect" (bubble breakdown), threatening equipment safety.
- Effect after treatment: After degassing, the gas saturation in the oil is reduced, and the risk of bubble precipitation is significantly reduced.
- Key impact: dissolved gas will reduce the thermal conductivity of the oil.
- Mechanism of action:
- Gas forms a thermal resistance layer in the oil, affecting the heat dissipation of the winding and the core.
- Overheating will accelerate insulation degradation and form a vicious cycle.
- Effect after treatment: The thermal conductivity of the oil is improved after degassing, and the temperature rise of the transformer is more stable.
- International standard requirements (taking IEC 60296 as an example):
- Oxygen content: usually required to be <3000ppm (new oil) or lower (such as below 500ppm).
- Moisture content: related to oil temperature, such as <10ppm at 20℃.
- Total gas content: Some standards require <1% (volume fraction).
- Degassing treatment: It is a necessary means to achieve these indicators.
- Application scenarios:
- Vacuum oil filling: Degassing treatment is a prerequisite for vacuum oil filling to ensure that there are no bubbles remaining in the oil.
- Hot oil circulation: Degassing is performed synchronously when the transformer is energized and dried to improve the drying effect.
- Post-fault processing: After an internal arc fault, the combustible gas (H₂, CH₄, etc.) generated by the decomposition of the oil is removed.
1. Vacuum degassing (most commonly used):
- By vacuuming (residual pressure ≤ 0.1kPa) and heating (50~60℃), the gas is precipitated from the oil.
2. Thin film degassing:
- The oil forms a thin film in a vacuum environment to increase the gas escape area.
3. Ultrasonic-assisted degassing:
- The ultrasonic cavitation effect is used to promote gas release (for high-viscosity oil).
- Temperature control: The heating temperature must be lower than 65℃ to prevent oil oxidation.
- Vacuum degree: The performance of the vacuum pump directly affects the degassing efficiency.
- Detection and verification: After degassing, the gas content (such as chromatographic analysis), moisture and breakdown voltage need to be tested.
Through degassing, transformer oil can be restored to a "clean and dry" state, ensuring long-term safe operation of the equipment.
