How is oil in a transformer tested for moisture and dissolved gases?

Transformer oil is tested for moisture using Karl Fischer titration, which accurately measures water content in parts per million. Dissolved Gas Analysis (DGA) is used to detect gases such as hydrogen, methane, acetylene, ethylene, and carbon monoxide. These gases indicate overheating, partial discharge, or arcing inside the transformer. Oil samples are taken under controlled conditions and analyzed in laboratories or with online monitors to assess insulation health and detect developing faults early.