The detection of certain gases generated in an oil-filled transformer in service can be an indication of a malfunction that may eventually lead to failure if not corrected.  In a transformer, generated gases can be found dissolved in the insulating oil, in the gas blanket above the oil, or in gas collecting devices. The presence of gas and its quantity are dependent on equipment variables such as: type, location, and temperature of the fault; solubility and degree of saturation of various gases in oil; the kinds of material in contact with the fault; and finally, variables associated with the sampling and measuring procedures themselves.  The two principle causes of gas formation within an operating transformer are thermal and electrical disturbances. Gases are also produced from the decomposition of oil and insulation exposed to elevated temperatures.

Learning Objectives:

• Explain the purpose of dissolved gas analysis
• Determine types of faults
• Identify key gases
• Define influencing factors

Prerequisites:

Participants should understand basic electrical theory.