The Function of Vacuum Circuit Breaker - What Is Vacuum Circuit Breaker?

The function of vacuum circuit breaker - what is vacuum circuit breaker?

The function of vacuum circuit breaker

When the vacuum circuit breaker is in the closed position, its ground insulation is borne by the supporting insulator. Once a permanent ground fault occurs in the line connected to the vacuum circuit breaker, after the circuit breaker trips and the ground fault point is not cleared, there will be damage to the electrical bus. The insulation against ground must also be withstood by the vacuum gap at the break of the circuit breaker; when various faults occur, the vacuum insulation gap between a pair of contacts at the break must withstand various recovery voltages without breakdown. Therefore, the insulation properties of the vacuum gap have become the current research direction to increase the fracture voltage of the arc extinguishing chamber and develop the single-break vacuum circuit breaker to a high voltage level.

The functions of vacuum circuit breaker are:

1. The contact spacing is small. The contact spacing of the 10KV vacuum circuit breaker is only about 10mm. The operating power of the operating mechanism is small, the stroke of the mechanical part is small, and the mechanical life is long.

2. The arcing time is short and has nothing to do with the switching current, generally only half a cycle.

3. Since the dredge wears less when breaking current, the contact has a long electrical life, with a full capacity of 30-50 breaking times, a rated current breaking of more than 5,000 times, and low noise, suitable for frequent operations.

4. After the arc is extinguished, the medium in the contact gap recovers quickly and has good performance in breaking near-area faults.

5. Small size and light weight, suitable for breaking capacitive load current.

Because of its many advantages, it is widely used in substations. The current models mainly include: ZN12-10, ZN28A-10, ZN65A-12, ZN12A-12, VS1, ZN30, etc.

Working principle of vacuum circuit breaker

"Vacuum circuit breaker" is named because its arc extinguishing medium and the insulating medium in the contact gap after arc extinguishing are both vacuum. It has the advantages of small size, light weight, suitable for frequent operations, and no maintenance required for arc extinguishing. Therefore, it is widely used in power distribution Online applications are relatively common. The working principle of the vacuum circuit breaker is not complicated:

1. Breakdown caused by cathode:

Under a strong electric field, due to the Joule heating effect of the field emission current, the temperature of the protrusions on the cathode surface increases. When the temperature reaches the critical point, the protrusions melt and generate steam, causing breakdown.

2. Breakdown caused by anode:

Due to the electron beam emitted from the cathode, bombardment of the anode causes heating at a certain point to produce melting and steam, resulting in gap breakdown. The conditions for causing anode breakdown are related to the electric field enhancement coefficient and gap distance.

In addition, the loop resistance of the vacuum circuit breaker is the main heat source that affects the temperature rise, and the loop resistance of the arc extinguishing chamber usually accounts for more than 50% of the loop resistance of the vacuum circuit breaker. The contact gap contact resistance is the main component of the vacuum interrupter loop resistance, because the contact system is sealed in the vacuum interrupter, and the heat generated can only be dissipated to the outside through dynamic and static conductive rods.

The breakdown mechanism of these vacuum gaps shows that the material of the vacuum electrode and the surface condition of the electrode are very critical factors for the insulation of the vacuum gap.

HZ2611 Transformer Short Circuit Impedance Tester