Study On Large Hydro Generator Internal Fault Transient Simulation And Engineering Application

In the"11th Five-Year"plan and long-term planning for year 2020 of China, the"vigorously developing hydropower"policy would continue to implement. A number of large hydropower stations have begun to build and gradually put into operation. The internal short-circuit faults of large hydro generator are highly destructive. To allocate effective protection has great significance for the generator itself and the safe and stable operation of the whole electric network. This paper studies internal faults and rotor eccentricity of the generator, then demonstrates the main protection schemes and the effect of rotor eccentricity to generator operation.In the actual operation, varying degrees of rotor eccentricity always exists in large generator; obvious eccentricity will affect the normal operation of the generator. China had a hydropower station in which a generator happened rotor eccentricity and caused the malfunction of the zero-sequence transverse differential protection. On the basis of engineering practice and the generator internal fault transient simulation model which is established on stator single-turn coil and equivalent damp loops, this paper starts from the expressions of the equivalent air-gap length and puts forward a method of calculating the inductance parameters under rotor eccentricity, then establishes a generator rotor eccentric simulation model. Base on mathematics model and calculation method, the MATLAB simulation program is modified and perfected.Use the modified MATLAB simulation program to calculate and simulate the self-inductance and mutual inductance of the stator and rotor, the stator branch current and the corresponding zero-sequence transverse differential current when the generator is running under different rotor eccentric degrees, then analyzes the inductance changing rules under rotor eccentricity, points out the current distribution of stator branches influenced by the rotor eccentricity and studies on the characteristics of the zero-sequence transverse differential unbalance currents of different rotor eccentric degrees under several typical neutral point modes. By quantitative analysis, useful reference for the safe operation of generators and proper application of zero-sequence transverse differential protection is provided.This paper uses the generator internal fault simulation and protection arrangement analysis software developed by our group to do the transient simulation analysis to all the faults in the generator fault set of the ALSTOM 700MW generator in the right bank station of Three Gorges, then compares and analyzes the protective effect of various main protection under the neutral point separated branches mode which is actually used in generators of right bank power station of Three Gorges. Finally, the main protection optimal scheme is put forward. The scheme is already applied to the practical operation of right bank power station of Three Gorges. But also the effect of rotor eccentricity to the zero-sequence transverse differential protection of ASLTOM generator in right bank power station of Three Gorges is analyzed according to the generator eccentric simulation model.It the end, all the work and the results are summarized, and further research direction is forecasted.