As integral components of any power plant, transformers supply the generated electricity to the grid. However, the transformer’s cellulose-based paper insulation and the mineral oil that it is immersed in break down over time, due to standard operating conditions—or more rapidly due to potential faults within the system. This technical brief exhibits a collection of diagnostic and prognostic techniques that can be incorporated into the utility’s maintenance routine. Additionally, the latest version of the Institute of Electrical and Electronics Engineers (IEEE) standard (IEEE Std C57.104TM-2019) for dissolved gas analysis (DGA) has been incorporated and expanded upon with prognostic models to estimate the time to maintenance. An additional improvement for estimating missing system parameters from monitoring data (i.e., a tool for parameter estimation utilizing Powell’s method) is explained, so the IEEE thermal consumption model can benefit not only the collaborating nuclear power plant (NPP) but also the nuclear power industry at large. Overall, five different methodologies are explained, each of which aid in determining a transformer’s state of health. These methodologies include the Chendong model, the IEEE C57.91-2011 thermal life consumption model, a diagnostic model for DGA, and a prognostic model for DGA using an autoregressive integrated moving average model.
