Research On Torsional Vibration On-Line Monitoring,Analysis And Protection System Of Turbine-Generator Shafts

The purpose of this research is to develop an online monitoring, analysis and protection method for turbine-generator shafts torsional vibration. A shaft-blade coupling torsional vibration model was established in this paper. The fault reason, the characteristics and the fatigue life loss estimating method of torsional vibration was researched. Based on these researches, a torsional vibration monitoring, analysis and protection method was given. Furthermore, a torsional vibration monitoring, analysis and protection equipment was invented.In the aspect of shaft-blade coupling torsional vibration modeling and simulating method, the turbine generator shafts and blade disks were considered as a spring-mass system with a branched structure. The shaft-blade coupling torsional vibration response analysis method for the model was given. A vibration model for the long blades such as the LP last stage blades was proposed, and the parameter adjusting method was given. Based on the blade vibration model, a shaft-blade coupling torsional vibration model was established, and the response analysis method was proposed.To analysis the fault mechanism and characteristics of torsional vibration, FMEA method was used to analyze the most common torsional vibration faults which may cause serious fatigue damage to the turbine-generator shafts, such as subsynchronous oscillation, short circuit, asynchronous paralleling. The electromagnetic torque during torsional vibration was calculated, and the dynamic torque response of the shafts during the fault was analyzed, which have provided the basis for the torsional vibration diagnosis method and the dangerous section search.In the aspect of fatigue life loss analyze for turbine-generator shafts caused by torsional vibration, the shearing stress calculation method for the dangerous sections and the S-N curve and P-S-N curve calculation method for the rotor material was given in this paper. According to the torque-stress characteristics of the journals, couplings and the long blades, stress calculation method for each structure was presented. The tensile fatigue tests and S-N curve fitting results of the coupling bolt material 25CrMo were given in this paper. It has been proved that the high-cycle fatigue properties of the bolt material can be accurately described by the three-parameter exponential S-N curve model by comparing the fitting results based on different S-N curve models. The fatigue limit of the high-cycle P-S-N curve calculated by the traditional maximum likelihood method was proved to have a high probability of being higher than the accurate fatigue limit. Therefore, a modified method based on maximum likelihood method was proposed so as to calculate the high-cycle P-S-N curve more accurately. The P-S-N of 25CrMo calculated using the modified method was given in this paper.In the aspect of shafting torsional vibration on-line monitoring, analysis, protection strategy, based on the analysis of shaft-blade torsional vibration coupling model and failure mechanism of torsional vibration and shaft torsional vibration fatigue life loss, the on-line fatigue life loss calculation methods for analyzing the fatigue damage caused by electromagnetic torque impact and SSO have been proposed respectively. Based on fatigue life loss calculation, the method for calculating the threshold value for the protection was given as well. According to the FMEA analysis and the available signal from the power unit, a torsional vibration diagnosis method was brought out. Based on the above research, a torsional vibration on-line monitoring, analysis, protection method which could quickly and accurately evaluate the safety of shafting torsional vibration was presented, a torsional vibration on-line monitoring, analysis and protection system was invented to protect the turbine-generator shafts from torsional vibration damage. The introduction for the system was in the end of this paper.