Discharge activity simulation in turbogenerators stator windings insulation

The research goal is to numerically study the conditions for the initiation of partial discharge in the air gaps of the stator slot of a high-voltage turbogenerator in conditions that reproduce the actual design of the stator groove of a 220 MW air-cooled turbogenerator; taking into account the distribution of the field of operating temperatures and electrical voltage in the stator groove, changes in the electrophysical properties of materials such as dielectric constant, electrical resistance of basic insulation materials and elements of the corona protection system, depending on the local temperature. The criterion of the conditions for the initiation of the PD is the excess of the electric field strength level over the electrical strength of the air gap in any local zone of the stator slot structure, for which a nonlinear functional dependence of the electrical strength of the air gap is applied. The studies were performed by modeling the stator groove in a numerical environment in which the geometry of a fragment of the stator groove structure is reproduced. According to the results of the numerical study, the values of the permissible range of the specific volume electrical resistance of the external corona protective coating are determined, which make it possible to ensure the absence of conditions for the occurrence of PD during longterm operation of the turbogenerator, and it is also established, that the most dangerous defects are local damage to the external crown protection coating and local breakage of the ripple spring of the side seal, the results obtained are of an applied nature for use in engineering departments in order to study the operability of the structural elements of the crown protection system when working out design solutions during the detailed design of air-cooled turbo-generators.

Authors: E. R. Mannanov, A. M. Kostelov, V. O. Belko, A. M. Andreev, V. N. Zheleznyak

Direction: Electrical Engineering

Keywords: stator winding, insulation system, numerical simulation, slot partial

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