Probability distributions of gases dissolved in oil of failed power transformers

The author collected about 300 sets of measured concentrations of gases dissolved in the oil of power transformers. All were obtained by chromatographic analysis of oil samples taken from transformers with known actual defect. Defects were classified into one of three basic types: dischargers, partial discharges and thermal faults. The probability distributions of the individual gas concentrations, depending on the type of fault present in the transformer were identified. The values of heterogeneity coefficient and parameters of probability distributions were given. It has been shown that the gases dissolved in oil of fault transformers are subject of log-normal or Weibull probability distributions regardless of the type of the defect.