Dissolved Gas Analysis (DGA)
Standard Test Method for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas Chromatography, ASTM D3612
The primary use of dissolved gas analysis (DGA) is as a routine monitoring oil test for electrical equipment. Incipient fault conditions – disruptions in the normal electrical and mechanical operation of electrical equipment – cause the oil to break down, generating combustible gases. The profile of those gases can be interpreted to diagnose whether fault conditions exist, and how severe those faults may be. DGA is also used to determine the concentration of dissolved atmospheric gases (oxygen, nitrogen, and carbon dioxide) so that the operation of oil preservation systems such as conservators, continuous nitrogen systems, and nitrogen blankets can be evaluated.
Gas content of new oil installed in equipment is frequently run. Appropriate operation of new equipment may require an extremely low gas content in the newly installed oil – a typical specification value is 0.5% (5000 ppm) by volume of total gas dissolved in the oil. There are several methods for running this (ASTM D831, D1827, D2945), but a complete DGA by method D3612 gives a more useful result. Not only does the test quantify the total gas in ppm (the conversion to % can be easily done), it also tells which gases are present and in what quantities. DGA is also performed on samples drawn during factory heat runs (and sometimes during factory electrical testing) to monitor the integrity of newly manufactured units. Similarly, most installations of new, large transformers require close monitoring by DGA during the first days, weeks, and months of operation.
The primary use of dissolved gas analysis (DGA) is as a routine monitoring oil test for electrical equipment. Incipient fault conditions – disruptions in the normal electrical and mechanical operation of electrical equipment – cause the oil to break down, generating combustible gases. The profile of those gases can be interpreted to diagnose whether fault conditions exist, and how severe those faults may be. DGA is also used to determine the concentration of dissolved atmospheric gases (oxygen, nitrogen, and carbon dioxide) so that the operation of oil preservation systems such as conservators, continuous nitrogen systems, and nitrogen blankets can be evaluated.
Gas content of new oil installed in equipment is frequently run. Appropriate operation of new equipment may require an extremely low gas content in the newly installed oil – a typical specification value is 0.5% (5000 ppm) by volume of total gas dissolved in the oil. There are several methods for running this (ASTM D831, D1827, D2945), but a complete DGA by method D3612 gives a more useful result. Not only does the test quantify the total gas in ppm (the conversion to % can be easily done), it also tells which gases are present and in what quantities. DGA is also performed on samples drawn during factory heat runs (and sometimes during factory electrical testing) to monitor the integrity of newly manufactured units. Similarly, most installations of new, large transformers require close monitoring by DGA during the first days, weeks, and months of operation.