Diagnosis of Rotor Winding Interturn Short-Circuit in Turbine Generators Using Virtual Power

Rotor winding interturn short-circuit (RWISC) occurring in turbine generators has been plaguing power producers with respect to production safety and economy. RWISC is characterized by impaired fundamental component of the exciting magnetomotive force and resultantly reduced no-load electromotive force E₀. In this paper, an inverse reasoning method is proposed to analyze RWISC. First, it is assumed that the generator´s rotor winding is running in good condition and the generator´s electromagnetic power (virtual power, VP) is inversely calculated from the obtained operational data on generators. Second, the difference between the virtual power and the actual electromagnetic power is calculated and then used to determine whether an RWISC occurs on the turbine generator. Three real cases of severe rotor winding shorts have demonstrated that this method proposed in this paper not only enables to diagnose RWISC, but also allows determining the RWISC level and its trending accurately. The method is appropriate for RWISC diagnosis, whether offline or online, and can be applied to make the generator sets in the power plant run safer, more economical, and more stable.