Comparison of Field Winding Inter-Turn Short Circuit Fault Idendification Methods in a Salient Pole Hydro Generator

This paper presents the results of an investigation into the failure of a salient pole hydrogenator. The rotor poles are observed to have undergone significant overheating and several poles are likely to have suffered from resultant interturn short circuit. In order to identify the source of the fault, conventional voltage drop methods and recurrent surge oscillograph results are compared with a new approach proposed in this paper - injecting higher frequency currents (3rd harmonic and 6^th harmonic). Analysis of fault identification methods demonstrates the difficulty of identifying the location of field winding faults, even when they are clearly present. The results demonstrate that the method proposed in this paper, injection of a 180Hz current in the field winding, offers superior ability to identify which poles may have faulted in a generator with a high number of salient poles.