When to do oil filtration on the transformer?

Transformer oil filtration should be performed based on the condition of the oil, operating conditions, and specific maintenance schedules. Key indicators and situations where oil filtration is necessary include:

 1. Regular Maintenance Intervals

   - Transformer oil filtration is typically part of a preventive maintenance schedule, often performed every 2 to 3 years. The exact frequency depends on the transformer's operational environment and the manufacturer's recommendations.

 2. High Moisture Content

   - If oil testing indicates high moisture content (above 10-20 ppm), filtration should be carried out. Moisture in the oil can degrade the dielectric strength and cause insulation problems.

 3. Decreased Dielectric Strength

   - The dielectric strength of transformer oil should typically be above 30 kV. If it drops below this level, it indicates that contaminants like moisture or particles are present, and filtration is needed to restore the oil's insulating properties.

 4. Presence of Gases

   - Dissolved gas analysis (DGA) can reveal the presence of certain gases that indicate electrical or thermal faults within the transformer. If gases such as hydrogen, carbon monoxide, or acetylene are found in high concentrations, oil filtration with degassing may be required.

 5. High Acid Number

   - Over time, the oil can become acidic due to oxidation, which can lead to sludge formation and corrosion of transformer components. If the acid number (TAN) exceeds 0.3 mg KOH/g, filtration, or even oil regeneration, is recommended.

 6. Increased Particle Count

   - If the oil contains high levels of suspended particles, it can indicate contamination from solid impurities, aging insulation, or corrosion. Filtration helps remove these particulates and maintain oil quality.

 7. After Transformer Faults or Repairs

   - If the transformer has experienced a fault, repair, or oil leakage, the oil may become contaminated and require filtration. This ensures the oil is clean and restores the transformer's operational safety.

 8. Before Commissioning or After Long Storage

   - New transformers, or those that have been in storage for an extended period, may require oil filtration to ensure the oil is clean and free from contaminants. 

Regular monitoring and testing of transformer oil can help identify the appropriate time for oil filtration, ensuring the transformer operates efficiently and has a longer service life.