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Dissolved Gas Analysis

Dissolved Gas Analysis (DGA) is the single most broadly used test available today. This test is also the most effective test used to determine whether a transformer's operation is normal or not. Likewise, this test will determine all fault conditions. In conjunction with other tests, analyses and inspections DGA is crucial in determining the operating conditions of transformers.

When an oil sample is analyzed, dissolved gases are extracted from it. The gases are then separated and quantitatively indentified through gas chromatography. When a gas develops, it is due to temperature degradation of transformer oil and insulating materials. Transformer faults occur in internal environments of the insulating oil or in near proximity to cellulose insulation. In the event that a fault is active, the degradation rate can or will be substantial. Each fault, however, consists of various mixtures of degradation gases. Any of these mixtures can identify potential problems that one should avoid.

DGA (ASTM 3612-D) pinpoints the presence and levels of the following gases: Hydrogen, Nitrogen, Carbon Monoxide, Oxygen, Methane, Carbon Dioxide, Ethane, Ethylene, and Acetylene. The concentration level of these gases is measured in parts-per-million.

The three basic fault processes, Corona, Sparking and Arcing, can be identified by monitoring and analyzing the composition of mentioned gases. Finally, monitoring the rate in which gas generates permits PowerCom to assess the extent of each fault.

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