Hydro generators: inspecting stator windings

Today, maintaining hydroelectric power plants is fraught with challenges, especially because of aging equipment and fewer qualified workers. In an initial article entitled “Introduction to Stator Windings” (BBA, 2019), we established that stator windings are the part of hydroelectric generating equipment that has the highest operating and maintenance costs and carry the highest risk; the next logical step is to write an article outlining inspections and assessments.

Since stator windings in the North American fleet of generators have reached or exceeded their life expectancy, it is imperative to adopt an appropriate maintenance and management strategy. Replacing aging equipment with new equipment is an obvious and easier way to manage risk; however, this requires major investments and therefore might be delayed.

Rigorous and orderly inspection and assessment of stator windings can extend their lives by implementing effective strategies. This article simply explains the steps necessary to do this. In particular, we take an inventory of useful IEEE standards, typical tests and elements to consider when performing the visual inspection.

Assessing the remaining life of windings relies primarily on available site information combined with the results of the visual inspection and electrical tests. This information helps provide an overview of stator windings. After which, experts can develop a strategy based on experience and knowledge, as well as comparing other windings of the same type, from the same supplier or the same generation. This strategy includes a task schedule as well as the related cost estimate and risk assessment.