Dissolved Gas Analysis

“The fundamental purpose of [Dissolved Gas Analysis] DGA is to discriminate between normal and abnormal conditions. More specifically, DGA aims to provide a reliable and economical method of detecting faults, which may present unacceptable possibility of damage or near-term failure. In transformers, a fault is revealed by the production of new gases. In many cases, active faults generate gases at such a high rate that detection and assessment do not require finesse. On the other hand, the gases generated by a subtle, incipient, or intermittent fault can sometimes be difficult to distinguish from the background of residual gases already present in the transformer during “normal” operation. This situation can arise because of normal variations in gas concentrations due to load and environmental conditions; unavoidable random “noise” from measurement uncertainty (method repeatability and reproducibility), as well as data quality issues arising from poor sampling technique, exposure of samples to air, or mislabeling of samples. As with any decision process based on data subject to “random” interference, a method must be developed to minimize the number of false positives while also minimizing the number of false negatives, i.e., failures to detect real abnormalities. DGA is one of the most widely used diagnostic tools for transformer condition assessment because experience has proven it to be an effective tool.”

(Quote from IEEE C57.104-2019)

What method is used to analyze the sample?

ASTM D3612

IEC 60567

How do you interpret the results?

IEEE C57.104
IEEE C57.139
IEEE C57.155
IEEE C57.146
IEC 60599

What do the results indicate?

“DGA has limitations that warrant some precautions in interpretation, such as:
Samples can be incorrectly collected, identified, or processed. The veracity of dissolved gas data should be checked before remedial or emergency action is undertaken (i.e., a confirmation sample).

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