Stator Insulation Performance: Six Decades of Experience

This paper presents a fleet-based evaluation of dielectric dissipation factor (tan δ) and capacitance measurements obtained from more than 85 hydrogenerator stator windings over nearly six decades of operation. In total, 610 offline in-situ measurements were analysed, encompassing machines commissioned between 1957 and the present and covering both thermoplastic (asphalt- and shellac-based) and thermoset (epoxy-based) insulation systems.