The Study On Powerhouse Vibration-related Problems Of A Large-scale Pumpde Storage Power Station In China

With the rapid development of hydropower industry in our country, the construction scale of hydropower station becomes larger and larger, and the single-output and the size of the spiral case also improving continually, which brings great challenge to the operation safety of power station. The observation at home and abroad towards the hydropower station which have been put into operation showed that the vibration of hydraulic turbine set and powerhouse is the fundamental and universal problem that affects the safe and efficient operation of hydropower station and related systems, and is also one of the key technical issues which needs concern in the large hydropower station construction and opration. The vibration is more outstanding than conventional hydropower station, especially for pumped storage power station which posesses the characteristics of high speed, large capacity, high head, and frequent shift of pumping and generate electricity. The key technical problems of hydropower station’s safe operation should be further researched because of the complexity of the vibration. Faced with this issue, hydropower stations generally restrict operating head and avoid instable area, which greatly reduces the efficiency of hydraulic turbine set.This paper studied a certain large-scale pumped storage power station in our country combining with practical engineering. ①The review of powerhouse vibration was carried out from the perspectives of analysis on vibration source, natural characteristics, vibration response. ②Signal processing program was written with a core of FFT, and the comparison of programs is carried out based on the measured vibration signals. ③The full size model of the pumped storage power station’s 4th hydroelectric set was established. Based on this model, the structure natural characteristics and vibration response were caculated and were compared with the test results. ④In order to find out the change rule of the powerhouse vibration with different hydroelectric set seam form from two aspects of natural characteristics and vibration response, two unit model is eatablished. And the thorough research of the influence of adjacent unit on vibration response was studied by setting the different ways of unit operation.⑤On the basis of 4th single-hydroelectric set model, the effect of floor structure on powerhouse vibration was analyzed through the change of the generator floor thickness.⑥The powerhouse vibration responses of 4th hydroelectric set were calculated in different unit rotation speed to analyze matching of powerhouse and unit. The conclusions are as follows:(1)Through analyzing the vibration signal, the correctness of the program written about vibration signal processing was able to accurately identify the frequency that contained in the vibration signal.(2) The floor area with larger hole and corresponding to the uprightly pillars are the most intense vibration response areas, and they are also the areas the maximum vibration will be in. Therefore, the big hole area and the area corresponding to uprightly pillars should be avoided and relatively small vibration response area should be chosen in the layout of the unit control instruments on the floor.(3) "Two unit a seam" can enhance the interaction between the units, increase the constraint effect of local structure of powerhouse, improve the natural frequency of structure. But the vibration response in local areas will increase as a result of the interaction of unit vibration sources. "One unit a seam", the energy could be propagated through joint filler to adjacent units, which caused the vibration of the adjacent units.(4) With the increase of thickness of generator floor, its structure stiffness increased, and the thick plate structure generated smaller vibration response than the slab-beam structure at the same vibration source.(5) From the aspects of powerhouse vibration response, the powerhouse of pumped storage power station was more adapt to high-rotation speed unit. The stagger degree between the natural frequency of pillar and excitation frequency was bigger with the unit high-rotation speed operation. At the moment, the excitation frequency avoided the frequency range that caused local response of the pillar and the powerhouse vibration acceleration of vertical decreased rapidly.