Optimization On Hydraulic Operating Mechanism Of The Ultra-High Voltage Circuit Breakers

The high voltage circuit breaker, which plays an important role in control and protection, is the key equipment in the power transmission system. The hydraulic operating mechanism, with the characteristics of fast response, large instantaneous power and longtime to wait, is the core component of circuit breaker. As the driver of circuit breaker, the opening and closing performances of which is directly influenced by the operating mechanism. Therefore, in order to improve its capability and reliability, it is very necessary to optimize the key parameters and structure of the hydraulic operating mechanism.In this thesis, the hydraulic operating mechanism of 550kV ultra-high voltage circuit breaker was studied. The theoretical study on the opening and closing processes of circuit breaker was carried out. The mathematical models of arc-quenching chamber and hydraulic operating mechanism were derived. Combining the two models with three dimension (3D) multi-body dynamics model of the linkage, a co-simulation model of circuit breaker was established. By comparison of simulation and experimental results, it was proved that the co-simulation model is more accurate than former. Tow kinds of control valve systems were measured in the test rig. Based upon the simulation and experimental analysis, the method for improving the capabilities of the control valve system has been obtained. The cushion structure of high speed hydraulic cylinder was optimized by using the simulation models. The optimization parameters of the structure size were proposed, which can effectively reduce the peak pressure of hydraulic system. The influences of working pressure on opening and closing performances of the circuit breaker were investigated through experiments. The results revealed that the hydraulic operating mechanism have better capabilities with higher working pressure. The theoretical analyses and simulation researches on the hydraulic operating mechanism whose working pressure is 50MPa were carried out, and the optimization key parameters and structure were proposed. Then a new hydraulic operating mechanism with higher capabilities was developed.In Chapter 1, the aim and significance of the study in this thesis were discussed. The current research progresses on the circuit breaker and its hydraulic operating mechanism were reviewed. The main research subjects were presented. In Chapter 2, the theoretical study of the circuit breaker was carried out. Combining the models of arc-quenching chamber and linkage with the hydraulic operating mechanism, a co-simulation model was built, which was proved more accurate than former with the experimental results. The co-simulation model could be used as a reference to design new hydraulic operating mechanism. The characteristics of seals were investigated, and the conclusions could be as a guideline to desig the seal structures.In Chapter 3, the application of simulation model was discussed. Based on the datas of simulation and experiment, the performances of two kinds of control valve systems were analyzed to find the differences between them. The conclusions on lower velocity of closing process have been obtained, which was caused by the underlap and flow area of the main valve. The theoretical analyses and simulation researches on the cushion structure of high speed hydraulic cylinder were implemented. The optimization parameters of the structure size were proposed, which can effectively reduce the peak pressure of hydraulic system. The peak pressures in opening and closing progress were reduced by 16% and 12%. The opening and closing performances of circuit breaker with different working pressures of hydraulic system were measured. With the experiment results, it can be seen that the hydraulic operating mechanism have better capabilities with higher working pressure.In Chapter 4, the new hydraulic operating mechanism whose operating pressure was 50MPa was designed and optimized. In order to improve the capabilities of the operating mechanism, a newly developed hydraulic operating mechanism was investigated. On the basis of theoretical calculation, the hydraulic operating mechanism was simulated and optimized. The optimization key parameters and structure were obtained, which were accepted for high voltage circuit breaker.In Chapter 5, conclusions in this thesis were summarized and future research proposals were suggested.