  This paper describes the use of survival analysis and simulation to model the
lifetime of high voltage instrument transformers in the Dutch transmission
sys-tem. To represent asset aging, the non-parametric Kaplan-Meier method is
used to enable the fitting of Weibull distribution. Such an approach is
implemented on three different voltage levels, namely 110kV, 150kV, and
220/380kV. Real failure and inspection data is used to achieve a realistic
failure model of the instrument trans-formers. Failure and maintenance data
occurring between 1989 and 2021 have been used for this study. In spite of
missing and low-quality data, a rich failure database could still be prepared.
This study also offers insights into factors (i.e., voltage level, in-service
age) influencing the remaining life from both graphical survival function and
parametric Weibull distribution analysis. Based on the derived statistics,
future possible maintenance planning scenarios are simulated under a complex
system modelling framework in a digital twin enabled platform. Eventually, the
scenarios are evaluated in terms of replacement costs (CAPEX), inspection
hours, and unavailability hours.
