Diagnosis of Short Circuit Faults Within Turbogenerator Excitation Winding Based on the Expected Electromotive Force Method

Short circuit faults in an excitation winding pose a potential threat to the safe and stable operation of turbine generators. Some turbine generators are forced to shut down for an overhaul whenever a fault occurs, and the economic losses can be serious. In this paper, a 2-D simulation model has been established using the basic electromagnetic and structural parameters of a generator. Here, the generator's excitation current at normal working conditions is calculated, and two binary function is used for the calculation of no-load electromotive force (EMF) expectations on the excitation current and active power is derived. Based on the fundamental characteristics associated with the reduction of effective turns in the excitation winding after a short circuit, the excitation winding short circuit fault can be determined using the deviation between the actual value and the desired value of generator no-load EMF. Fault examples showed that this method can achieve higher diagnosis accuracy, and that it can be used for the real-time monitoring and diagnosis of an overall excitation winding health inside a turbine generator.