24KV high voltage vacuum circuit breaker parameters

Under different rated voltages

Rated opening distance of high-voltage VS1-24 Vacuum Circuit Breaker The rated opening distance is the shortest distance between the moving and static contacts when the vacuum circuit breaker contacts are in the maximum disconnected position. It is determined by the rated voltage of the vacuum circuit breaker, the nature of the breaking current under the use conditions, the contact material and its withstand voltage requirements. Under different rated voltages, the selection range of the contact opening distance of different types of vacuum circuit breakers is different. The contact opening distance of the vacuum circuit breaker is selected to be smaller, mainly to meet the needs of frequent operation, so as to improve the electrical life and mechanical life of the vacuum circuit breaker, but at the expense of a certain withstand voltage strength. The circuit breaker contact opening distance is relatively larger, but the vacuum circuit breaker contact opening distance and withstand voltage strength are not linearly related. When the rated voltage exceeds a certain value, two breaks or multiple circuit breakers are often used in series to solve the withstand voltage problem. Each type of vacuum circuit breaker contact opening distance has technical conditions. Too large or too small an opening distance will cause a decrease in breaking capacity and reduce the mechanical life of the circuit breaker.

The main functions of overtravel are as follows

Overtravel of high-voltage vacuum circuit breaker Overtravel is the distance that the moving or static contact can move after the vacuum circuit breaker contacts are closed. The main functions of overtravel are as follows:

1) Ensure that the contacts can still maintain a certain contact pressure after electrical wear.

2) When the contacts are closed, the contact spring force can be used for buffering and reducing bounce.

3) When the contacts are opened, the moving contact obtains a certain initial kinetic energy, breaks the fusion welding point, increases the initial opening speed, reduces the arcing time, and thus increases the speed of medium recovery.

Contact working pressure

Contact working pressure When the vacuum circuit breaker is in the closed working state, the operating mechanism must also give an external spring pressure to make the moving and static contacts in good contact. This external pressure is called the contact working pressure. When selecting and debugging the contact working pressure, the following situations should be considered:

1) Since the contact resistance between the contacts of the vacuum circuit breaker is related to the pressure between the contacts, within a certain range, the greater the pressure, the smaller and more stable the contact resistance. Therefore, the contact resistance of each phase of the general vacuum circuit breaker should not be greater than 100 ΜΩ.

2) The closing short-circuit current test is the most stringent condition for assessing whether the contact working pressure meets the requirements, and the working pressure of the contact is determined by this working condition. Therefore, in the closing short-circuit current test, the pressure between the two contacts of the selected vacuum circuit breaker must be greater than the arc and electric repulsion to be generated after the breakdown of the dry contact, otherwise, it will lead to the failure of the test and damage to the circuit breaker.

3) The closing bounce must be suppressed.

4) After the vacuum circuit breaker is opened, it will make a mechanical oscillation with attenuated vibration at the rated opening distance. This situation is called opening bounce. It not only has an adverse effect on the mechanical life of the vacuum circuit breaker, but also increases the probability of reignition and re-breakdown when the vacuum circuit breaker is working. Therefore, in order to reduce the spring vibration, the following aspects must be considered: try to reduce the mass of the contact and its connection parts; select the appropriate opening spring; use the appropriate buffer rubber to reduce the instantaneous speed of the contact when the opening is at the bottom; select the appropriate contact compression spring parameters.

Opening speed The opening speed will directly affect the recovery speed of the dielectric strength between the contacts after the current passes through zero.

If the recovery rate of the dielectric strength between the contacts is less than the recovery voltage after the arc is extinguished, it will cause reignition. The opening speed cannot be too low. Too low will not only affect the arc extinguishing, but also accelerate the electrical wear of the contacts to cause reignition and produce serious overvoltage. When the rated voltage and contact opening distance are constant, the adjustment range of the opening speed depends on factors such as the size of the breaking current, the nature of the load, and the recovery voltage. When the breaking current is large, the opening speed should also be large. At this time, due to the high recovery voltage, in order to reduce the probability of reignition, the opening speed should also be large. But it is not the case that the higher the opening speed, the better. When the opening speed is too high, the vibration during operation will be more severe, and the vibration compression of the vacuum circuit breaker bellows will be more severe, and the bellows may even be damaged in advance and leak. At the same time, the greater the vibration of the whole machine, the easier it is to cause damage to the parts of the whole machine. Therefore, it is also necessary to make appropriate choices according to the working tasks of the vacuum circuit breaker.

Related closing speed

Closing speed usually refers to the average closing speed when the contact is closed. Since the static withstand voltage level of the vacuum circuit breaker at the rated opening distance is relatively high, the closing speed of the vacuum circuit breaker is lower than the opening speed, but it must have a certain closing speed to reduce the electrical wear caused by the breakdown of the contact during the closing process and avoid contact welding. However, too high a closing speed not only increases the closing work of the vibration mechanism, but also increases the closing impact on the circuit breaker, reducing its service life. Usually, the closing speed of a 10kV vacuum circuit breaker is 0.4~0.7m/s. According to the working task, it can be 0.8~1.2m/s when necessary.

Related Bounce time

Bounce time refers to the attenuation vibration time when the contact is closed. The smaller the closing bounce time, the better the performance of the whole machine. If the closing bounce time is too long, it will cause contact burning and overvoltage. When doing short-circuit closing test, it may cause contact welding. For 10kV vacuum circuit breakers with copper-chromium as contact material, it is generally required that its closing bounce time shall not exceed 2ms, and the closing bounce time of copper-tungsten contacts shall not exceed 3ms.

Related Three-pole synchronization

The three-pole synchronization of the vacuum circuit breaker indicates the degree to which the three poles are not closed or separated at the same time. Poor three-pole synchronization has a certain impact on the breaking capacity of the vacuum circuit breaker, and the measured arcing time is also long. It is usually stipulated that the synchronization of closing or opening does not exceed 1ms. The numerical difference between the closing and opening synchronization is not large. Since the opening speed of the vacuum circuit breaker is large and the opening distance is small, it is not difficult to achieve this parameter through its manufacturing process and accurate debugging.