Ensuring the reliability of turbogenerators on the basis of the control of discharge processes in the stator winding insulation

Abstract

Issues related to the reliability of the electrical insulation system of high-load powerful turbogenerators with indirect gas cooling are considered and analyzed. The mechanisms of aging of the main components (main insulation, slot filling elements) of the insulation system under operating conditions exposed to electrical and thermal fields, and mechanical forces are studied. Modern ideas about the mechanisms of aging of main insulation and slot filling elements under the action of internal and external impacts (slot and spark discharges) are analyzed. The degradation of insulating materials during operation begins, first of all, in a weak local area of the main insulation, characterized by a large number of technological defects (cavities filled with gas), in which internal partial discharges occur. However, thermosetting insulation of high-voltage electrical machines can function normally throughout its lifetime in the presence of rather intense internal discharges. At the same time, no service life deterioration is observed due to the specific properties of modern main insulation, which contains a mica barrier. The greatest danger is posed by slot partial discharges (SPD) and vibration spark discharges (VS) that occur in the slot area of the stator winding. To reduce the intensity of these discharge processes, it is necessary to optimize the design of the anti-corona coating. On the basis of the performed analysis, a scheme was developed of the aging of the electrical insulation system of the stator winding of air-cooled turbogenerators. Based on the results of prototype tests, an estimated assessment of the "lifetime" of the electrical insulation system of the stator winding, developed using promising electrical insulating materials, was carried out.