| With the hydro-generator of Three Gorges Project being put into operation and many large and huge hydro-generator stations being constructed, the unit capacity of hydro-generator trends to become larger. The unit capacity of hydro-generators in Three Gorges Power Station, Longtan Power Station and Xiaowan Power Station is 700MW, and the design capacity for planning Xiluodu Power Station is also 700MW. In the Xiangjiaba Power Station, the unit capacity of generator will be 750MW. Theses huge generators are key equipment, which play important roles in the safety and stability of the hydropower stations, even for the whole electric power grid. Therefore, it is attractive to study on the internal fault simulation for huge hydro-generators and the new protection technology for generator-transformer unit. Digital Simulation has been an important tool in the research of electric power system. In the system fault research field, many fruits have been obtained. On contrary, study on generator internal fault with digital simulation is relatively weak. Furthermore, compared with the power grid protection, the rate of right trip for generator-transformer protections is not high. After reading plenty of literature, the dissertation introduces the history and development of the internal fault simulation for generators and protection technology for generator-transformer protection. The study necessity and problems needed to resolve in this field are also proposed. According to the structure characteristic of the generator, the mathematic model for transient simulation has been set up, which is based on the physical structure and winding connections. In addition, to meet the engineering need of batch simulations and protection checkouts, the model of double D and double Q damper windings is proposed and the transient simulation program for generator internal fault is also developed. The dissertation discusses the possible fault set of Alstom and VGS hydro-generators in Three Gorges left bank project. Adopting the developed transient simulation program, plenty of internal fault simulations and calculations have been carried out. The fault law and the main protection sensitive degree are also studied for Alstom and VGS hydro-generators. As for large generator, the neutral point is always connected to the ground by distributed transformer's high resistor or arc suppression coil. The stator ground fault simulation based on fundamental wave and 3rd harmonic is not fully consistent with the fact of fault process. Therefore, The mathematic model for stator ground fault has been set up, of which the fraction order harmonic and high order harmonic in the air magnetic field are taken into consideration. The model can fulfill the whole process transient simulation from normal operation to fault state. In the same time, the dissertation also discusses the ABB's injected stator ground protection for Three Gorges hydro-generator. Although the detection of turn fault for generator field winding is very difficult, the probability of turn fault is not low. Because the fault characteristic is not obvious, many faults are neglected. On the other hand, the electric feature for double point ground fault is similar to the turn fault of field winding. The research work of mathematic model for turn fault and double point ground fault is relatively weak. In this dissertation, the mathematics model has been set up with the harmonic magnetic field considered; in addition, the simulation program is developed. Based on the simulation study, a new protection scheme for turn fault and double point ground fault is proposed, which bases on the wavelet transform and modulus maximum. More attention is being paid on the sampled value differential protection due to its abilities of interference and CT saturation resistance, which has been put into engineering application for the bus-bar, short transmission line and power transformer protections. This dissertation studies the operating characteristic of sampled value protection, an...
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