Analysis of Insulation Diagnosis for Generator-Motor Stator Winding in Pumped Storage Power Plant

Abstract

In this study, insulation diagnostic tests were conducted on pumped storage power plant (PSPP) generator-motor stator bars with artificially simulated defects in order to improve solutions to perform preventive maintenance and track insulation diagnostic data for generator-motors by proving the effectiveness of insulation indices. Moreover, ozone (O3) concentration was estimated in order to relate it to partial discharge (PD) in laboratory to ensure the effectiveness of ozone as another index for insulation deterioration. By performing an offline PD test and ultraviolet (UV) observation on one of the generator-motors during overhaul, and an ozone concentration measurement for the identical machine after the overhaul, it was concluded that ozone estimation could be a powerful index for insulation diagnosis under actual operational conditions. It was further developed that ozone measurement is useful to detect not only discharges in slots as mentioned in some studies but also discharges at the end-winding as proven in this study. The findings of this study are expected to contribute to more reliable maintenance of generator-motors in PSPPs by achieving elaborate insulation diagnosis via multiple diagnostic indices.