What causes sludge formation in transformer oil?

Sludge formation in transformer oil is primarily caused by the oxidation of the oil due to exposure to heat, moisture, and oxygen. This process leads to the breakdown of oil molecules, resulting in the creation of insoluble compounds and particulate matter. Additionally, the presence of contaminants, such as dirt and metal particles, can accelerate sludge formation. Regular maintenance and monitoring of oil quality are essential to mitigate these effects and prolong transformer life.