Analysis of Unrecoverable Breakdown Ground Fault Scenarios in the Internal Insulation of Large Generator Stators

Due to the complex physical structure and numerous equipment at the generator stator, the stator ground fault scenarios are complex and variable. The mechanism of single-phase ground fault breakdown is difficult to clarify. Starting from a typical stator ground fault scenario, this article explores the types of dielectric breakdown and degree of damage caused by internal grounding faults in large generators. These faults are mainly caused by excitation such as internal insulation defect discharge and slot gap discharge. As the internal insulation is mainly composed of solid insulation materials such as mica and semiconductors, such faults are often accompanied by permanent insulation damage. Analyze the theory of irreparable stator insulation grounding faults in typical scenarios. Study the effect of grounding residual current on core burning and melting. Compare and analyze the reliability of the allowable operating range of stator safe grounding current under different grounding methods. The simulation model is established to verify the effectiveness of the method.