Chengdu 35KV Boundary ZW32 Intelligent High Voltage Outdoor Circuit Breaker

Structure and working principle of circuit breaker

ZW32-40.5 outdoor high-voltage vacuum circuit breaker is mainly composed of integrated solid sealed pole, current transformer, operating mechanism, and box body. This model of circuit breaker is designed for miniaturization, with a high-quality steel casing. Current transformers can be selected according to user needs. At present, vacuum switches have been widely used in various fields at home and abroad. With the popularization and improvement of the use of vacuum switches, users are increasingly in urgent need of understanding and mastering the principles, vacuum circuit breakers, usage and maintenance of vacuum switches. Our company provides some technical references for users to better use vacuum switches.

1. Rated opening distance
When the vacuum circuit breaker is in the open state, the selection of the distance between the moving and stationary contacts of the vacuum switch tube is related to factors such as the rated voltage, operating conditions, nature of the breaking current, contact material, and withstand voltage strength of the vacuum gap of the vacuum circuit breaker. It mainly depends on the rated voltage and contact material. Due to the significant impact of the rated opening distance on the insulation performance of vacuum switch tubes, as the rated opening distance increases from zero, the insulation level will also improve. However, when the opening distance increases to a certain value, the impact of the opening distance on the insulation performance is not significant. If the opening distance is further increased, it will seriously affect the mechanical life of the switch tube. Through the installation, operation, and maintenance of vacuum circuit breakers, the general selection range for the rated opening distance of vacuum circuit breakers is: 4-8mm for 6kV and below, 8-12mm for 10kV and below, and 20-40mm for 35kV.
2. Contact stroke of contacts
The selection of contact stroke for the contact must ensure that the contact can maintain a certain pressure even after wear and tear; When opening the switch, the moving contact obtains a certain initial kinetic energy, increases the initial opening speed of the switch, breaks the welding point, reduces the arc time, and improves the medium recovery speed; When closing, the contact spring can be used to obtain smooth buffering and reduce bounce.
3. Contact working pressure
The working pressure of vacuum circuit breaker contacts has a significant impact on the performance of vacuum circuit breakers, and its pressure is equal to the sum of the self closing force of the vacuum switch tube and the contact spring force. The selection of working pressure for circuit breaker contacts should meet four requirements: 1. Keep the contact resistance of vacuum switch tube contacts within the specified range, 2. Meet the requirements of dynamic stability test, 3. Suppress closing bounce, 4. Reduce opening bounce. Due to the arc and electric repulsion generated by the contacts after pre breakdown when closing the short-circuit current of a vacuum circuit breaker, the contacts bounce and the closing speed of the mechanism is also slow. Therefore, closing the short-circuit current is a condition for assessing whether the working pressure of the contacts meets the requirements.
4. Opening speed
Due to the direct impact of the opening speed on the recovery speed of the dielectric strength between the contacts after the current crosses zero, if the recovery speed of the dielectric strength between the contacts is less than the recovery voltage after the arc is extinguished, it will cause arc reignition. In order to prevent arc reignition and shorten the arc ignition time, the opening speed must be met. The magnitude of the opening speed mainly depends on the rated voltage. When the rated voltage and contact distance are constant, the fluctuation range of the opening speed depends on factors such as the magnitude of the breaking current, load properties, and recovery voltage. When the breaking current is large, the opening speed should also be large. When breaking the capacitor current, due to the high recovery voltage, in order to reduce the probability of reignition, the opening speed should also be large. The opening speed of 10kV vacuum switch is usually taken as 0.8-1.2m/s, and can be higher than 1.5m/s if necessary.
5. Closing speed
Due to the high static withstand voltage level of vacuum switch tubes at rated opening distance, the closing speed of vacuum circuit breakers is significantly lower than their closing speed. In order to minimize the electrical wear and tear caused by pre breakdown of the contacts during the closing process and avoid contact fusion welding, it is necessary to have a certain closing speed. However, excessively high closing speed not only increases the closing power of the operating mechanism, but also increases the closing impact on the switch tube, greatly reducing its service life. Under normal circumstances, the closing speed of a 10kV vacuum circuit breaker is 0.4-0.7m/s, and if necessary, it can be taken as 0.8-1.2m/s.
6. Contact closing bounce time
The closing time of a vacuum circuit breaker is an important indicator of its performance, which is related to the contact bounce pressure, closing speed, opening distance, and contact material of the vacuum switch tube. It is also related to the structure of the switch tube, the structure of the circuit breaker, and installation and commissioning. The smaller the bounce time of the contact during closing, the better its performance. The longer the bounce time, the more severe the electrical wear of the contact, which is prone to overvoltage during closing. When closing short-circuit currents or capacitors, as well as during action and thermal stability tests, it will cause contact welding. In addition, the longer the bounce time of the contact closing, the more seriously it endangers the structural service life of the switch tube. The closing bounce time of vacuum circuit breakers with 10kV copper contact materials shall not exceed 2ms, while the closing bounce time of vacuum circuit breakers with other contact materials may be relatively larger, but shall not exceed 5ms.
7. Three pole synchronicity
The three pole synchronicity of a vacuum circuit breaker indicates the degree to which the three poles are not closed or separated at the same time. Since the synchronicity of opening and closing is relative and the numerical difference is not significant, in general, only the synchronicity of three pole closing is evaluated. Circuit breakers with poor synchronicity of the three poles will seriously affect the breaking ability of the switch, and are prone to excessive arcing time. Due to the fast opening and closing speed and small opening distance of the circuit breaker, it is not difficult to achieve the parameter requirements through accurate debugging. Generally, it is stipulated that the closing synchronization should not exceed 1ms.

Main featuresChengdu 35KV Boundary ZW32 Intelligent High Voltage Outdoor Circuit Breaker
This product is mainly composed of high-voltage porcelain bushing, vacuum arc extinguishing chamber, transmission system and operating mechanism, and can be equipped with electromagnetic or spring operating mechanism. It has the advantages of excellent breaking performance, short arc time, long electrical life, 20 times of full capacity breaking without maintenance, reliable insulation, simple structure, and high mechanical reliability.
1. Adopting outdoor vacuum arc extinguishing chamber, which has the advantages of safety, reliability, and long service life;
2. Adopting new insulation materials to avoid the impact caused by inflation, oil filling, etc;
3. Current transformers have the characteristics of high precision, variable ratio, and multiple stages;
4. Can be equipped with both electromagnetic and spring operated mechanisms;
5. Circuit breakers have three types of structures: horizontal, central, and CT external.