Exploring Possibility to Enhance DGA Interpretation Accuracy for EHV/UHV Power Transformer

Abstract

Power transformers play a vital role in power transmission and distribution system. Modern high voltage transformers to keep their size in acceptable range are built with relatively tight insulation tolerances compared to older equipment and are consequently subjected to increasingly high stresses in service. It is therefore very important to closely monitor their in-service behavior to avoid incipient faults, catastrophic failures, costly outages and losses of production.

Dissolved gas analysis of transformer oil is used to asses the insulation condition by periodic sampling the oil samples and measuring amounts of gases dissolved in oil by gas chromatography. Different types of interpretation of DGA data is analyzed to and the root cause of production of the gases, the accurate method is considered for predictive measures to be taken depending on gas concentration and rate of increase of levels of gas. The gas concentration levels in oil is effected by so many factors and they play an important role in the DGA based diagnosis process. Rate of rise of gas level can be considered as a factor for determination of cause of failure but other factors that are associated with it are stray gassing and change in solubility of the gas in oil. A mathematical approach is then proposed in the areas of stray gassing and change in solubility that is helpful for removal of the bad data from the preprocessing stage of the DGA data interpretation there by increasing accuracy of the interpretation.