Dissolved gases are byproducts of electrical and thermal stresses inside the transformer. Their type and growth rate indicate possible developing faults. Hydrogen can suggest partial discharge, methane and ethane often relate to low to medium temperature overheating, ethylene points to higher temperature thermal faults, and acetylene is strongly associated with arcing. Carbon monoxide and carbon dioxide relate to paper insulation decomposition. Trending DGA over time is crucial because rate of change often signals worsening conditions even if absolute levels are moderate.
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