How to deal with water in transformer oil?

Excessive moisture in transformer oil will seriously affect its insulation performance and cooling effect and must be dealt with promptly. The following are the system's treatment plans and precautions:

Moisture detection and evaluation

1. Moisture content determination

- Use the Karl Fischer method (ASTM D1533) to accurately determine the moisture content

- Portable moisture sensors can be used for rapid screening on-site

- Warning value:

≤15ppm (500kV and above equipment)

≤25ppm (220kV equipment)

≤35ppm (110kV and below equipment)

2. Determination of pollution degree

- Mild pollution (water content <50ppm): can be processed online

- Moderate pollution (50- 100ppm): offline purification is required

- Severe pollution (>100ppm): oil change is recommended

Professional dehydration technology plan

(I) Physical dehydration method

1. Vacuum hot oil circulation

- Working parameters:

Oil temperature: 60-65℃ (maximum not exceeding 70℃)

Vacuum degree: ≤50Pa

Processing cycle: 8-12 hours/time

- Equipment requirements:

Two-stage vacuum oil filter (ultimate vacuum ≤10Pa)

Equipped with a three-dimensional flash degassing tower

2. Centrifugal separation technology

- Applicable scenarios: when free water content is greater than 0.1%

- Treatment effect: can quickly remove more than 90% of free water

Chemical adsorption method

1. Molecular sieve adsorption

- ｓｅｌｅｃｔ a 3Å pore size molecular sieve (specially absorbs water molecules)

- Treatment capacity: 1kg adsorbent/ton oil

- Need to cooperate with the online monitoring system to prevent over-drying

2. Silica gel treatment

- Dynamic circulation treatment:

Silica gel addition amount: 2-3% oil weight

Contact time > 4 hours

- After treatment, fine filtration is required to remove particulate matter

Key control points

1. Temperature management

- Heating rate ≤5℃/h

- Oil temperature monitoring points are not less than 3

2. Vacuum system maintenance

- Regularly check the oil quality of the vacuum pump

- Roots pump + rotary vane pump combination is better

3. Quality verification

- Post-treatment inspection:

Breakdown voltage ≥ 60kV/2.5mm

Dielectric loss factor tanδ ≤ 0.005 (90℃)

Micro-water content meets the standard

Preventive measures

1. Respiratory system modification

- Install a double-layer silica gel respirator

- It is recommended to use a membrane dryer (dew point ≤ -40℃)

2. Operation monitoring

- Online micro-water monitoring system alarm value setting:

Warning value: 80% of the standard value

Alarm value: 120% of the standard value

3. Maintenance cycle

- Comprehensive oil quality inspection at least once a year

- ｒｅｐｌａｃｅ respirator desiccant every 3 years

Precautions

1. Direct heating with an open flame is strictly prohibited

2. The hydrocarbon gas content needs to be continuously monitored during the treatment process

3. For oil products that have produced acidic substances, regeneration treatment is required first

4. Equipment needs to be preheated in advance during winter operation

The transformer oil treated by the above method should reach GB/T 7595-2017 "Transformer Oil Quality in Operation" standard requirements. For large and important transformers, it is recommended to establish oil treatment files to record the parameters and effects of each treatment to provide data support for subsequent maintenance.