A REVIEW OF DISSOLVED GAS ANALYSIS AND TRANSFORMER HEALTH CONDITION

Electrical and Electronics Engineering

NATIONAL CONFERENCE ON TECHNOLOGICAL ADVANCEMENTS IN ENGINEERING

Power transformers are important equipment of power system. The fault free operation of power transformers is a factor of major economic importance. Dissolved Gas Analysis (DGA) of transformer oil is one of the most effective power transformer condition monitoring tools. It has been proven that the generation of certain gases within a transformer is an excellent indicator that a failure is pending. DGA is a sensitive and reliable technique for detecting incipient fault condition in oil-immersed transformers. The overall health condition of the transformer strongly depends on the quality of insulation system within the power transformer. This paper deals with different DGA approaches such as Key Gas, Dornenburg Ratio, Rogers Ratio, IEC Ratio, Nomograph and Duval Triangle Method. Key Gas Method uses individual gas levels for detecting faults. Dornenburg Ratio Method and Rogers Ratio method uses the ratio of gas concentrations to indicate fault types. IEC Ratio Method uses the same three ratios as in Rogers Ratio Method but suggests different ratio ranges and interpretations. Nomograph method improves the accuracy by graphically representing the fault gas data. Duval triangle method uses values of three gases and they are transformed into triangular coordinates. The life of a transformer mainly depends on the life of its insulation system. Degree of polymerization, amount of CO and CO2, amount of furans, interfacial tension and acid number, oxygen level and moisture are the potential factors that affect the quality of insulation in a transformer. This study compares the effectiveness of dissolved gas analysis methods and also different factors affecting the insulation strength of the transformer.

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