Time‐varying model for the effective diagnosis of oil‐paper insulation used in power transformers

The analysis of dielectric response function obtained from the power transformer is a well‐accepted technique in insulation diagnosis. A convenient way of analysing time‐domain dielectric response φ ( t ) is the formulation of simple resistance−capacitance‐based circuits like the conventional Debye model (CDM) or the modified Debye model (MDM) that are capable of modelling φ ( t ). However, available techniques do not guarantee unique branch parameters of such circuits for a given φ ( t ). In fact, the branch parameters are known to depend on the curve‐fitting procedure opted during model formulation. This makes accuracy of CDM and MDM parameter‐based diagnosis techniques less reliable. Furthermore, it seems logical to analyse the time‐domain dielectric response of oil‐paper insulation using a model containing time‐varying parameters. In this study, a methodology is proposed using which such an insulation model (containing time‐varying parameters) is formulated using time‐domain insulation response. Related analysis presented suggests that the proposed model is immune to problems associated with available insulation models (containing time‐invariant parameters). The performance of the proposed model in indicating insulation condition is tested on data obtained from several real‐life power transformers.