One of the most common faults in the excitation system of synchronous generators is ground fault. Since the first ground fault doesn’t make any malfunctions in the generator, it can’t be detected by popular techniques. In this thesis, two techniques based on FFT for detecting ground faults in static excitation systems have been studied. The first technique can distinguish whether the fault occurs on the DC or AC side of the excitation system just when there is not another in excitation system. In second technique that has been proposed in this research, the ground fault occurred in the DC or AC side can be distinguished even though there is an open-circuit or short-circuit fault in the rectifier diodes. In addition to mentioned techniques, a techniques for locating the rotor winding ground fault in synchronous generators have been studied. In this technique, the ground fault is located by measuring the components DC and AC of excitation voltage and the components DC and the AC of the ground impedance voltage between the ground and the neutral terminal of excitation transformer in static excitation system.