Turbo generator stator winding condition assessment

Stator winding is a main component of generator. Electrical, mechanical, thermal and environmental stresses remain major factors for insulation degradation and accelerated aging. A large number of generators failed due to stator winding problems, mainly insulation deterioration. Insulation degradation assessment plays vital role in the asset life management. Mostly the stator failure is catastrophic causing significant damage to the plant and the environment. Other than generation loss, stator failure involves heavy repair and/or replacement cost. Early fault detection would be an important tool to implement condition-based maintenance (CBM) for asset better management. Condition based maintenance offers scheduled outages and reduces failure risks in old asset as well as premature failure in the new one. The winding insulation trend can be best analyzed by using online partial discharge monitoring. In windings insulation system, the energy discharge mainly occurs on the surface, slot, end winding, inter-turn and between bars. Slot discharge is dangerous in its kind and plays an important role in the accelerated insulation degradation. On the detection of partial discharge activity, accurate interpretation can establish insulation trending for stator insulation assessment. Hot spot can lead to catastrophic failure if not caught in time. Effective monitoring will reduce the life cycle cost with improved reliability and better asset management This paper presents a detailed case study of generator stator winding failure leading to core damage.