Measurement Uncertainty In The Determination Of Dissolved Gas Composition In Transformer Oil (Gas Chromatography)

It is very sensitive and effective when DGA is used in latent faults and early diagnosis about transformer. Uncertainty-evaluation could be helpful to judge the credibility, comparability and acceptability of the experimental results.The uncertainty-evaluation in measuring gases dissolved in transformer oil is illustrated in order to explain the method in details, while compliance is checked based on error theory, about the content of each component. The whole process of DGA should be taken fully into account first, including experimental principle, experimental procedure, required equipment and standard gas. Consequently, the sources of uncertainty is identified and quantified. Finally, the calculation of relative uncertainty, combined with uncertainty and expanded uncertainty (95%confidence interval) is finished. The relative uncertainty-evaluation consists of7aspects, that is measurement repeatability, concentration of standard gas component, atmospheric pressure, experimental temperature, sample volume of liquid, sample volume of gas and injection technique.Comparison of the results of measurement uncertainty assessment and error analysis, It is evident that1) error analysis could meet with the need of impact analysis for different factors;2) Impact analysis for different factors and uncertainty, which is more conducive to characterize the accuracy and reliability of the measurement results, could display dispersion of the measurement, check the compliance of results based on error theory as well.In the process of uncertainty-evaluation, from which we could draw experience and lessons, the analysis of uncertainty sources has increased the accuracy of measurement quality and credibility and has made significant improvement. By means of the judgment of uncertainty, the R&D and selection of laboratory equipment will be more targeted than before. In the future, dynamic uncertainty should be paid more attention to and be put into use, and thus the lab could earn a better reputation in the market.