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What is the function of vacuum circuit breaker



When the vacuum circuit breaker is in the closed position, its insulation to earth is undertaken by suitable insulators. Once a permanent ground fault occurs in the route connected to the vacuum circuit breaker, and the ground fault point is not cleared after the circuit breaker trips, the vacuum gap at the break of the circuit breaker should also be responsible for the ground insulation of the electrical bus. The vacuum insulation gap between the contacts should withstand various repair voltages without breakdown. Therefore, the insulation characteristics of the vacuum gap have become the current research content to improve the fracture voltage of the arc extinguishing chamber, and to make the single-break vacuum circuit breaker develop to a high voltage level. Vacuum circuit breakers are:

1. The contact opening distance is small. The contact opening distance of the 10KV vacuum circuit breaker is only 10mm. The operating mechanism has small up and down operation power, small stroke of the mechanical part, and long mechanical life.
2. The arc burning time is short, regardless of the size of the switching current, generally only half a cycle.
3. Due to the small wear rate of transmission and conduction when breaking the current, the electrical life of the contacts is long, the full volume is broken 30-50 times, the rated voltage is broken more than 5000 times, the noise is low, and it is suitable for frequent operations. 4. After the arc is extinguished, the repair speed of the contact gap material is fast, and the fault characteristics of the near zone of the breaking are better.
5. Small and light in size, suitable for breaking capacitive load current. Due to its many advantages, it is widely used in distribution stations.

How vacuum circuit breakers work “Vacuum circuit breaker” is famous for its arc extinguishing medium and the insulating medium of the contact gap after arc extinguishing. It has the advantages of small size, light weight, light weight, etc. It is suitable for frequent operation. Therefore, it is widely used in distribution network. The working principle of vacuum circuit breakers is not complicated:

1. Cathode-induced breakdown: Under a strong electric field, the temperature of the protrusions on the negative electrode surface increases due to the Joule heating effect of the field emission current, and when the temperature reaches a critical point, the protrusions melt to generate steam, leading to breakthrough.

2. Anode-induced breakdown: The bombardment of the anode heats up a point due to the ion beam sent by the anode, producing melting and vapor, and a gap breakdown occurs. The conditions of anode breakdown are related to the electric field rise and fall index and the gap spacing. In addition, the circuit resistance of the vacuum circuit breaker is the main pyrogen that affects heating, and the circuit resistance of the arc extinguishing chamber usually accounts for more than 50% of the circuit resistance of the vacuum circuit breaker. The contact gap circuit resistance is the main component of the circuit resistance of the vacuum interrupter. Since the contact system is sealed in the vacuum interrupter, the heat generated can only be dissipated to the outside by the moving and static conducting rods. The breakdown principle of these vacuum gaps shows that the material of the vacuum stage and the surface of the stage are the key factors for the insulation of the vacuum gap.