Maintenance-free Vacuum Circuit Breaker Theory And Practice

In the field of medium voltage switch apparatus, vacuum circuit breaker has been widely used for its advantage of oil-free, miniaturized and easy access. But because vacuum circuit breaker's using amount and using area are very large, and at the same time, its function is very important, its reliability has been greatly paid attention by the department of designing, manufacture and user. For many years, amount of work for improving its reliability has been done. In this paper, from the intention of improving the whole circuit breaker reliability and on the basis of absorbing most advanced technology, the method of improving its reliability and the way of reaching maintenance-free are proposed, which should be considered from the following aspects: high reliability for interrupting character, insulation character, resistant to environment and so on. In this paper, the main tasks are proposed as following:1 The path and technology of realizing maintenance-free and high reliability for vacuum circuit breaker are proposed. Especially associated with national switch manufacturing condition, manufacture technique, user's request and the standard request of WTO, development direction and handling measure of our national electrical apparatus are put forward. On the basis of analyzing present operation mechanism's advantages and disadvantages, the concept of one type of vacuum circuit breaker, which is with new integral layout spring operation mechanism is presented, and its whole structure is also designed.2 Miniaturized vacuum arc quenching chamber which is with CuCr25 contact material,cup shape and longitudinal magnetic field contact structure, intensive interrupting ability is used. Vacuum arc quenching chamber is laid in a sealed insulating cylinder, which significantly improve the ability of enduring environment and phase-phase insulation character. With the software of ANSYS, the electric field of arc quenching chamber is calculated, and the insulating structure is also optimized. The electric field of phase-phase, phase-earth of three-phase arc quenching chamber of the circuit breaker is calculated, insulation character is analyzed and the circuit breaker's whole insulating structure are ensured.3 Each critical component of the operation mechanism is researched from theory andpractice: accumulation energy, driving motion, buffering, tripping. Each acting force of the operation mechanism is considered, especially the dynamic mathematic model of the moving parts is established. With numerical calculating method, the speed character of opening and closing is also calculated. On the basis of analyzing in theory, the operation mechanism structure is optimized, which makes the better fit between output character and arc quenching chamber's counterforce during switching and closing, very appropriate structure design and very little distortion amount, so the character is kept better and the reliability is improved. 4 On the basis of the research, vacuum circuit breaker's model machine is developed, and every character is examined through test. Finally, all type approval tests are passed on national standard in National High Voltage Electrical Apparatus Test Detection Center:...