What causes hydrogen formation in transformer oil?

Hydrogen formation in transformer oil is primarily caused by the thermal decomposition of the oil, particularly at elevated temperatures. This process occurs due to the breakdown of hydrocarbon molecules, often accelerated by electrical discharges or arcing within the transformer. Additionally, the presence of moisture and contaminants can exacerbate this degradation, leading to increased hydrogen levels, which can indicate insulation failure or overheating issues in the transformer system.