Selection of the operating mechanism of the hottes

2022-08-05
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Selection of operating mechanism of circuit breaker 1. Basic information of operating mechanism of circuit breaker 1. The circuit breaker realizes the preset purpose by changing the direction and action point of force through the transmission parts of the operating mechanism. Its energy sources generally include electric power and human power. In addition to the human power mechanism, electromagnetic mechanism, pneumatic mechanism, spring mechanism and hydraulic mechanism all rely on electric power, The action of circuit breaker is realized by instantaneous energy release. From the perspective of the new equipment used in the agricultural transformation, although the components have been newly improved, there is still no major breakthrough. There are still too many action links, dynamic and static lubrication and other aspects that cause the efficiency of the mechanism. At the same time, the components may be worn and damaged. Therefore, the failure rate of the mechanism is high

according to the practice and field operation experience in recent years, among the various faults of circuit breakers, the mechanism operation is the first, accounting for about 80%, and the operating mechanism fault accounts for the vast majority of these mechanism faults. The main reason is that the operating mechanism is in a static operation state, the working state of each activity link can not be monitored, and hidden dangers can not be found in time. In particular, outdoor equipment is more prone to failure due to the impact of environmental conditions. Therefore, the structural optimization of the operating mechanism, the adoption of new materials and processes for parts and components, and the improvement of processing accuracy are a long-term task to eliminate defects in the future

II. Basic requirements for operating mechanism

since whether the breaker can operate effectively and reliably depends largely on the performance and quality of the operating mechanism, the operating mechanism equipped with it should meet the required properties and reliability according to different circuit breakers, mainly including the following points:

1. The operating mechanism should have sufficient closing function

in actual work, The energy of the operating mechanism will not remain at the rated value, but will change within a certain range. According to the requirements of the original ministerial regulations, the lower limit value is 80%-85% of the rated value, and the upper limit value is 7. In case of abnormal operation or damage of parts, it is 110% of the rated value, that is, the operating mechanism can turn off the generating and short-circuit current at the lower limit value, while the upper limit value should not damage the relevant parts due to excessive operating force

2. It shall have the function of keeping closing

when the duration of the operation command is short and the cooperation of the operation function is short, it shall have the mechanism of keeping closing to ensure that the circuit breaker remains in the closing position after the closing command and operation function disappear

3. It has a relatively short opening time

the closing time shall be independent of the action speed of the pusher on the operator's guide rail and the length of the command issuing time. At least, the opening speed shall not cause arc reignition, that is, the opening time shall be shortened as much as possible to reduce the existence time of short-circuit fault, so as to improve the stability of the power system and reduce the fault range as much as possible

4. Anti jump device shall be provided.

in order to avoid continuous multiple closing and opening after the circuit breaker is closed, mechanical or electrical methods shall be adopted to prevent arbitrary opening and closing after the circuit breaker is opened, so as to reduce unnecessary actions

5. There must be a linkage device

the linkage device in the operating mechanism can ensure the reliability of the circuit breaker, so that when the circuit breaker is in a state, it will be affected by the misoperation of the operating mechanism, and the general operating mechanism should be interlocked at the opening position; Low pressure and high pressure interlock; Position interlocking in spring mechanism, etc.

III. advantages and disadvantages of actions of various operating mechanisms

1. The opening and closing speed of manual operating mechanism depends on the size of manpower and operation. 10. Displacement accuracy: ± 0.5% of the author's proficiency. That is, reliability varies from person to person. If there is a latent fault in the system, the contact of the circuit breaker will be fused or even exploded due to excessive electric power or too slow scab closing speed, which is very unsafe

2. It is difficult to express the essence of the problem in a simple and intuitive way by adopting the traditional teaching method. The advantages of energy spring mechanism are: fast opening and closing speed, small motor power, and AC and DC dual-use

disadvantages: the structure is complex, there are many parts, and the machining accuracy is too high

suitable for operating medium voltage circuit breakers, especially for small capacity distribution systems

3. Pneumatic operating mechanism

advantages: fast action, stable operation, low DC power supply, and can still operate for several times in case of short-term power loss

disadvantages: high price and strict process requirements

applicable to high-voltage circuit breaker and medium voltage circuit breaker

4. Advantages of electromagnetic operating mechanism: simple structure, reliable operation and low manufacturing cost

disadvantages: the closing coil consumes large power, the parts are easy to be damaged, the structure is bulky, and the closing time is long

IV. principle of selecting operating mechanism for circuit breaker

comparing the above operating mechanisms, their performances are different, but considering the requirements of operation reliability, the electric energy storage operating mechanism is the development direction. It is suitable for medium voltage circuit breaker, especially for circuit breaker of small capacity distribution system. The pneumatic mechanism is applicable to medium voltage, high voltage and ultra-high voltage operated circuit breakers. Pneumatic operating mechanism shall be phased out. For the transformed substation, the original AC and DC power capacity and the requirements for the characteristics and reliability of the circuit breaker should also be considered to put forward the selection scheme. For the new station, the selection shall be made after comprehensive consideration of the circuit breaker characteristic requirements and various conditions according to the design requirements and the importance of the tasks assigned to the circuit breaker in practice

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