Dielectric frequency response of a MV stator coil: effect of humidity and thermal ageing

Abstract

The aim of this paper is to determine the influence of temperature, moisture content and thermal ageing on the dielectric frequency response of the insulation of a single stator coil. Measurements were made with a single medium voltage coil at different temperatures and percentages of relative humidity, generated inside a climatic chamber. Then, the coil was thermally aged by a current flow, reaching 120 °C, and the test was performed at different stages of ageing. This study presents the influence of temperature, humidity and ageing on the behavior of dielectric frequency response of a stator coil.