Comparison of Methods for Estimating the Remaining Useful Life (RUL) of Generator Insulation

Predicting the reliability of a generator system remains a significant challenge, requiring appropriate methods to estimate the remaining useful life (RUL) of its critical components, particularly the insulation system. This paper presents a comparative study of two existing methods used to estimate the RUL of generator insulation. The first method is based on dielectric test results, including leakage current measurement (in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{m A}$</tex>), tan delta test, and offline partial discharge analysis. The second method estimates RUL using the Equivalent Operating Hours (EOH), calculated from the total operating hours and the number of start-stop cycles of the power plant. The two methods produce different RUL results: Method I yields a remaining life of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 4. 2}$</tex> years, while Method II estimates <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 5. 2}$</tex> years-a difference of only one year. This small discrepancy suggests that both methods can be utilized complementarily, each offering distinct advantages. Method II, with its ease of implementation and continuous data availability, is well-suited for trend analysis of generator aging. Meanwhile, Method I provides more accurate and condition-based insights when dielectric testing is feasible, particularly during major equipment outages. Combined, these approaches offer a more comprehensive and practical framework for insulation health assessment and maintenance planning.