The Development Of Large Current Vacuum Circuit Breaker And Research On The Key Technologies

The sustainable development of china total installed generating capacity results in an increase of generation protection circuit breaker. Vacuum circuit breaker is widely concerned of its friendly environment. The large generator vacuum circuit breaker is great significant to raising equipment protection capability and system stability. However, its rated current and short circuit current are far greater than average circuit breaker in power systems. Hence, it is much more difficult to be come true. So, development large capacity vacuum circuit breaker is one of the studying hotspots on power project.Targeting on a new type of large-current vacuum circuit breaker, its performance parameters is17.5kV /10000A /80kA . This paper makes a systematic and deep research on the key problems of development including breaking, the current transfer process, temperature rise and coordination between mechanical properties and load characteristics. The main works and achievements are as following:A new type of"dual-contact"structure of vacuum interrupter is proposed in the paper. It consists of main contact and arc contact, which are used to break short circuit current and carry rated current, respectively. Using double-bellows, the contact bounce can be substantially reduced. In order to increase short circuit current breaking capacity of large-current vacuum interrupter, an optimal design of"iron magnetic ring"is put into arc contact to improve its magnetic performance. In terms of the new type large current vacuum interrupter, simulation results show that it is excellent in axial magnetic density and radial magnetic uniformity at current peak, and the contact area is effectively utilized.The new structure vacuum interrupter has two pairs of contact, namely arc contact and main contact. During the closing/opening of vacuum circuit breaker, arc contact is first closed and post breaking, however, main contact is post closed and first breaking. So there must be the current transfer process. In this paper, during the breaking process of vacuum circuit breaker, a model of current transfer is used in the investigation of current transfer, and the maximum possible current transfer time when breaking short circuit current is obtained. On the basis, combining the dynamic and thermal stability with temperature ascension requirement, the load characteristic curve of new type large current circuit breaker is given in this paper. Through building dynamic analyses simplified model of contact bounce, the spring stiffness and instantaneous opening/closing speed of main and arc contacts are proposed.In order to deal with temperature rise problem of large-current vacuum interrupter, rectangular radiator is optimum design, and the functional relationship between heat transfer coefficient of natural cooling and substrate can be obtained by curve fitting approach. In the paper, ANSOFT software is used to simulate the long-term steady-state temperature field of new type large current vacuum circuit breaker, and implanted in the acute experiment.