What does the presence of gases in transformer oil indicate?

Gases dissolved in transformer oil indicate thermal, electrical, or insulation related processes occurring inside the transformer. Certain gases are associated with specific fault types, such as overheating, partial discharge, or arcing. Carbon monoxide and dioxide indicate paper insulation involvement. While small amounts of gas can be normal, rapid increases or abnormal gas ratios signal developing faults. Interpreting gas patterns and trends allows operators to detect problems early and plan corrective action.