Transformer Reliability and Dissolved-Gas Analysis

Authors: J.J. Dukarm and M. Duval
2016 CIGRE Canada Conference
October 17, 2016

Dissolved gas analysis (DGA) is widely used for transformer condition screening and assessment. Conventional DGA practice is to employ statistically derived limits for combustible gas concentrations and their increments or rates of increase for the purpose of classifying a transformer’s condition as acceptable, suspicious, or abnormal. The DGA condition assessment, in the form of numeric “condition codes,” is sometimes used as part of a transformer health index for prioritizing of testing and maintenance or for asset management functions such as replacement planning. The basis of this condition classification scheme is the seemingly reasonable assumption that higher fault gas levels must represent progressively worsened states of the transformer, with correspondingly reduced reliability. We show that this assumption is not supported by the data.

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