What will break down under abnormal stresses in transformers, leading to gas production?

In transformers, the oil used as an insulating and cooling medium is susceptible to breakdown under abnormal stresses, such as high temperatures or electrical discharges. When the oil is subjected to these conditions, it can undergo thermal and chemical degradation, resulting in the production of gases. This phenomenon is often referred to as gas formation or gas generation in the context of transformer maintenance.

The presence of gas can indicate issues such as arcing or partial discharge within the transformer, which are serious concerns that require immediate attention. Monitoring the types and quantities of gases generated can provide valuable insights into the condition of the transformer and help predict potential failures.

While metallic components, cooling liquids, and plastic insulators can also experience stress and failure under certain conditions, they do not typically lead to gas production as a result of breakdown as oil does. Thus, the oil's role and its chemical properties make it the correct answer in this context regarding gas production under abnormal stresses in transformers.