Use of Modified TVM Parameters for Reliable Estimation of Power Transformer Insulation Condition

A picoammeter or an electrometer is generally used for the measurement of low-amplitude polarization and depolarization current. The available interpretation scheme of time-domain response using time-varying model (TVM) assumes the relaxation process to be purely Debye in nature. Results presented in this article suggest that this leads to inaccurate diagnosis. A modification in the TVM has been proposed to address the issue. The use of the modified TVM also provides a unique insulation model for a particular dielectric response. The modified TVM is subsequently used for estimating insulation condition. The proposed method and the suggested modification in TVM formulation are based on the analysis of data recorded from several real-life transformers. A comparison of the proposed work with that of other available methodologies has been made.