How Often Should Transformer Oil be Changed

A transformer oil filtration machine is used to purify and restore the dielectric strength and insulating properties of transformer oil by removing contaminants such as moisture, gases, dirt, and sludge. The working principle of a transformer oil filtration machine involves several processes, including heating, degassing, filtering, and dehydration. Here’s a detailed look at how it works:

### 1. **Oil Inlet and Heating**

   - The contaminated transformer oil is drawn into the filtration machine through an inlet pump. The pump transfers the oil from the transformer tank to the filtration system.

   - The oil is then passed through a heater where it is heated to a specified temperature (usually around 60-70°C or 140-158°F). Heating the oil reduces its viscosity, making it easier to remove contaminants and improving the efficiency of subsequent degassing and dehydration processes.

### 2. **Degassing and Dehydration Chamber**

   - The heated oil enters the degassing and dehydration chamber, where it is exposed to a vacuum environment. The vacuum reduces the pressure within the chamber, which allows moisture and dissolved gases in the oil to evaporate at lower temperatures.

   - The oil is often distributed over a large surface area, such as a series of baffles or a thin-film spreader, to increase the exposure of the oil to the vacuum and enhance the removal of moisture and gases.

   - The evaporated moisture and gases are then drawn out of the chamber by a vacuum pump and discharged, while the purified oil continues to the next stage.

### 3. **Filtration**

   - After degassing and dehydration, the oil is passed through a series of filters to remove solid contaminants. These filters typically consist of coarse and fine filtration stages:

     - **Coarse Filtration**: The oil passes through a coarse filter that removes larger particles and sludge.

     - **Fine Filtration**: The oil then goes through fine filters (with pore sizes usually ranging from 1 to 5 microns) to remove smaller particles and achieve high oil cleanliness.

   - The filtering process ensures the removal of solid impurities that could impair the insulation properties of the oil.

### 4. **Polishing (Optional Step)**

   - Some filtration machines have an additional polishing step that uses activated clay or special adsorbents to remove any remaining trace impurities, such as acids or polar compounds that may degrade the oil.

### 5. **Reheating (Optional)**

   - In some systems, the oil is reheated after filtration to ensure that any residual moisture is fully evaporated and to help maintain the oil's temperature during the return to the transformer.

### 6. **Oil Outlet and Return to Transformer**

   - The purified and filtered oil is then pumped out of the filtration machine through the oil outlet and returned to the transformer. The machine can be set up in a continuous loop where oil is continuously drawn from the transformer, filtered, and then returned, or it can be used in batch mode.

### Key Processes in Transformer Oil Filtration:

1. **Heating**: Reduces the viscosity of the oil to improve filtration and enhances the removal of dissolved gases and moisture.

2. **Vacuum Degassing and Dehydration**: Uses a vacuum to extract gases and moisture from the oil, restoring its dielectric strength.

3. **Filtration**: Removes solid impurities to improve oil cleanliness.

4. **Optional Polishing**: Uses adsorbents to remove any remaining trace impurities.

### Benefits of Transformer Oil Filtration:

- **Improves Dielectric Strength**: By removing moisture, gases, and impurities, the oil's insulating properties are restored.

- **Extends Transformer Life**: Clean oil helps protect transformer components from overheating and electrical breakdown.

- **Reduces Maintenance Costs**: Regular oil filtration reduces the need for oil replacement and other costly maintenance.

In summary, a transformer oil filtration machine purifies contaminated oil through heating, vacuum degassing, and filtration processes, helping to restore the oil's insulating properties and extend the lifespan of the transformer.