Copula based bivariate modelling of DGA and breakdown voltage in high voltage transformers and reactors

This paper aims at investigating the applicability of copula approach to accommodate the dependence structure between total combustible gases (TCG) and breakdown voltage (BDV). The TCG and BDV have been obtained from dissolved gas investigation and oil parameter testing respectively by utilizing the real-time data of transformer and reactors in service for more than a decade. In the proposed study, considering the negative association and goodness-of-fit measure, the Frank copula has been found satisfactory to model the bivariate joint distribution. Hence it has been used to develop the joint and conditional probability between them. Lastly, the outcome of this novel analysis validates the relationship between TCG and BDV which can be utilized for assessing the influence of total combustible gases on oil parameters. This will further help in taking precautionary measures for maintaining the quality of the oil for retaining the healthiness of transformers and reactors.