Review of experiments investigating transformer insulation condition on bubble inception temperature

The power transformer is a vital asset within the electrical network and infrastructure. Hence, failures can cause large financial and societal impacts. One means of transformer failure occurs when the transformer is operated at excessively high load, for instance due to high user demand for electricity, or through circumstances such as failure of a parallel transformer. The overload increases the transformer operating temperature. This may generate bubbles within the transformer, which has been identified as one of the failure mechanisms. Better understanding of the scenarios where this may occur can arm the transformer operator to mitigate bubbling events, thus preventing premature transformer failures. Current knowledge regarding bubbling caused by loading and temperature is still not fully understood. Although a few studies have looked into this phenomenon, they have not yet determined a consistent or complete set of results for temperature versus condition or load. Within this study, the different experimental methods and designs used by different researchers are compared in order to draw out the reasons for variance between them, as well as to inform future studies as to the importance of these features to the temperature results.