The document describes various electrical checks and measurements that can be performed on stator windings to assess the condition of the insulation system. These include:
1) Polarization-depolarization current analysis to evaluate time constants and indices related to insulation quality and moisture sensitivity.
2) Capacitance and tan delta measurements at different voltages to assess delamination, corona protection, and non-linear insulation behavior.
3) Analysis of partial discharge patterns to identify the nature of discharges.
4) Non-linear insulation behavior analysis to understand the effects of aging.
The results of these tests are used to evaluate the insulation system and estimate the remaining life expectancy of the windings.