The Stable Operation Experiment On Three Gorges Hydropower 21# Turbine

Three Gorges hydropower station, as the largest installed capacity hydropower station in the world, has made tremendous contributions to our country and economic development, which installed 32 single 700MW hydroelectric generating and generated about 1000 billion kWh every year. The stable operation of the Three Gorges turbine has been focused by the people for a long time. The working condition of the turbine has been challenged due to its large size, low stiffness and operating not in optimal conditions zone. So the stable operation experiment of Three Gorges turbine means significance for grasping the features of turbine under different water levels and zoning stable operation completely.The stable operation of turbine is a complex problem, which relates to hydraulic factors, mechanical factors and electrical factors. The problem of the stable operation is evaluated by several parameters such as vibration, swing and water pressure fluctuation. First of all, the article introduces the composition and working principles of the sensors, and illustrates the frequency domain analysis of the signal. Then the appropriate sensors have been used according to the needs of the test. The test dates are processed by means of oscillogram, changing amplitude trends and spectrum. The information of the test about spectral components and amplitude changes has been gotten. The operating characteristics of the turbine equipment are analyzed in the 174.8 meters water level emphatically. At last, the zones of turbine stable operation have been divided from 171.5 to 174.8 meters water level, which instructed the stable operation of the turbine.According to the amplitude and spectrum element of the signals, The turbine operating area in designed water level should been divided as three parts, which include small load area, vortex area and big load area. The small load area ranges from 0 to 350MW, and the signals of the tube pressure fluctuation and the shaft swing appear a peak in the area. The amplitude of the tube pressure fluctuation signal gets maximum and the frequency components mainly includes low frequency and high frequency of 160Hz. The vortex area ranges from 350 to 630MW. The lower part of the shaft swing gets maximum on 515MW and the middle and the high part of the shaft swing gets maximum on 495MW respectively. The vortex frequency is 0.3Hz. The pressure signal and vibration peak on 578MW which gets maximun between vortex area and big load area, and the frequency is 1.87Hz. The big load area ranges from 630 to 756MW. The turbine works well in big load area, and the signals of the tube pressure fluctuation, the shaft swing and the rack vibration get smallest and the fluctuation are not obvious. Besides, the text demonstrates the majority of signals have gotten a good effect in the condition of added air to the main shaft. The results show that Three Gorges 21# turbine work well under the design water level, which meets the requirements of the design and the contract.