Overview of vacuum circuit breaker, working principle of vacuum circuit breaker, advantages of vacuu

The "high-voltage vacuum circuit breaker" is named because the arc extinguishing medium and the insulating medium of the contact gap after arc extinguishing are both high vacuum; It has the advantages of small size, light weight, suitable for frequent operation, and no need for maintenance for arc extinguishing, and is widely used in the distribution network. A Brief History In 1893, Rittenhouse in the United States proposed a vacuum interrupter with a simple structure and obtained a design patent. In 1920, the Swedish company Phogat made the first vacuum switch.

The results published in 1926 and others also showed the possibility of breaking the current in a vacuum, but due to the small breaking capacity and the limitation of the development level of vacuum technology and vacuum materials, it could not be put into practical use. With the development of vacuum technology, the United States only made the first batch of vacuum switches suitable for special requirements such as cutting off capacitor banks in the 50s, and the breaking current was still at the level of 4,000 amperes. Due to the progress of vacuum material smelting technology and the breakthrough in the research of vacuum switch contact structure, in 1961, the production of 15 thousand volts and 1,000 amperes of breaking current vacuum circuit breaker began.

In 1966, 15 thousand volt, 26 thousand amperes and thousand amperes were trial-made, so that the vacuum circuit breaker entered the high-voltage, large-capacity power system. In the mid-80s, the breaking capacity of vacuum circuit breakers reached 100 kiloamperes. China began to develop vacuum switches in 1958, and in 1960, Xi'an Jiaotong University and Xi'an Switch Rectifier Factory jointly developed the first batch of vacuum switches with a kV and a breaking capacity of 600 amps; Subsequently, a 10 kV three-phase vacuum switch with a breaking capacity of 10 kV was made.

In 1969, Huaguang Electron Tube Factory and Xi'an High Voltage Electrical Appliance Research Institute made a 10 thousand volt, 2 thousand ampere single-phase fast vacuum switch. Since the 70s, China has been able to independently develop and produce vacuum switches of various specifications.

Vacuum circuit breakers are usually available in multiple voltage levels. The low-voltage type is generally used for explosion-proof electrical use. Like coal mines and so on.

The "high-voltage vacuum circuit breaker" is named because the arc extinguishing medium and the insulating medium of the contact gap after arc extinguishing are both high vacuum; It has the advantages of small size, light weight, suitable for frequent operation, and no need for maintenance for arc extinguishing, and is widely used in the distribution network.

The main domestic standards are based on:

JP3855-96 "General Technical Conditions for AC High Voltage Vacuum Circuit Breakers".

DL403-91 "Technical Conditions for Ordering 10 35KV Indoor High Voltage Circuit Breakers".

It should be noted here that there is no special standard corresponding to JB3855 in the IEC standard, but only the "IEC56 AC High Voltage Circuit Breaker" is applied. Therefore, the standard of vacuum circuit breaker in China is higher than or stricter than the IEC standard in at least the following aspects:

1) Insulation level: test voltage IEC China.

1min power frequency withstand voltage (kv) 2842 (between poles, poles to ground) 48 (between fractures).

Impact withstand voltage (kv) 7575 (between poles, poles to ground) 84 (between fractures).

2) The withstand voltage level of the vacuum interrupter fracture after the electrical life test: not specified in IEC56. China's JB3855-96 stipulates that:

After completing the electrical life test, the insulation capacity between the fractures of the vacuum circuit breaker should not be less than 80% of the initial insulation level, that is, the power frequency and impact 60kV.

4) Test current of temperature rise test: In IEC standard, the test current is equal to the rated current of the product. China's DL403-91 stipulates that the test current is 110% of the rated current of the product.

Vacuum circuit breaker, English: vacuum circuit breaker is named because the arc extinguishing medium and the insulating medium of the contact gap after arc extinguishing are high vacuum;

It is an indoor power distribution device in 3 10kV, 50Hz three-phase AC system, which can be configured in the central cabinet, double-layer cabinet and fixed cabinet as a control and protection of high-voltage electrical equipment.

The vacuum circuit breaker has a short arcing time, high dielectric strength, high electrical life, small opening distance and stroke of the contact, small operating energy, and high mechanical life.

In daily operation, the maintenance workload is very small, and it can be used for the protection and control of electrical equipment in industrial and mining enterprises, power plants and substations, especially suitable for places that require oil-free, less maintenance and frequent operation.

When the vacuum circuit breaker is in the closing position, its insulation to the ground is borne by the support insulator, once the line connected to the vacuum circuit breaker has a permanent ground fault, so the working principle of the vacuum circuit breaker is very important. What are the advantages of vacuum circuit breakers? Let's briefly introduce the working principle and advantages of vacuum circuit breaker.

The working principle of a digital slip and vacuum circuit breaker.

The working principle of the vacuum circuit breaker is: when the dynamic and static contacts are opened under the action of the operating mechanism, the arc is generated between the contacts, and the steam is volatilized on the surface of the contact at high temperature, because the contact is designed to be a special shape, a magnetic field is generated when the current passes, and the arc moves rapidly along the tangential direction of the contact surface under the action of this magnetic field, and some metal vapor is condensed on the metal cylinder (shielding cover), and the arc is extinguished when the natural zero is crossed, and the medium strength between the contacts is quickly restored.

Second, the composition of the vacuum circuit breaker.

The main structure of the vacuum circuit breaker is composed of a vacuum interrupter, an operating mechanism and an insulating support baseframe.

Vacuum interrupter.

According to the different types of switches, there are outer shielding cover type ceramic vacuum interrupter, intermediate sealing cup-shaped longitudinal magnetic field miniaturized vacuum interrupter, inner sealing glass bubble interrupter, and its basic structure is as follows:

Hermetically sealed insulation system (enclosure).

The airtight insulation system consisting of an airtight insulating cylinder made of ceramic, glass or glass-ceramic, a moving end cover, a fixed end cover, and a stainless steel bellows is a vacuum-tight container. In order to ensure air tightness, in addition to strict operation procedures in the sealed type, it is also required that the material itself has air permeability and small internal air release.

Conductive systems. It is composed of a fixed conductive rod, a fixed running arc surface, a fixed contact, a moving contact lead Kai, a dynamic running arc surface, and a dynamic conductive rod. There are roughly three types of contact structures:

Cylindrical contacts, transverse magnetic field contacts with spiral groove arcing surfaces, longitudinal magnetic field contacts. At present, the longitudinal magnetic field technology is adopted, and this kind of arc extinguisher has a strong and stable arc breaking ability.

Shielding system. The shield is an indispensable element in the vacuum interrupter, and there are various types of shields such as the main shield around the contacts, the bellows shield, and the shielding cover for equalizing pressure. The purpose of the main shield is:

aPrevent arc products from splashing on the inner wall of the insulated shell during arcing, thereby reducing the dielectric strength of the shell. bImprove the uniformity of the electric field distribution inside the arc extinguisher, which is conducive to reducing the local field strength and promoting the miniaturization of the vacuum interrupter. c. Condensate arc products, absorb part of the arc energy, and help to restore the strength of the medium behind the arc.

3. Advantages of vacuum circuit breaker.

1) The vacuum arc extinguishing effect is good in the sealed container, and the arc and hot gas are not exposed.

2) There are very few contact gaps.

3) The arcing time is short, the voltage is low, the energy is small, the contact wear is less, and the allowable breaking times are more.

4) The inertia of the moving conductive rod is small, and it is suitable for frequent operation.

5) The operating mechanism is small and the structure is simple, the overall volume is small, and the potato exacerbation is lightweight.

6)) Low noise during operation.

7) There is no danger of fire and **ignition.

8) The contact head is divided into a completely sealed structure, which is not easy to reduce its performance due to the influence of moisture, dust, harmful gases, etc., and operates reliably.

Answering the case of dry matter]: a, b, c, d

The advantages of vacuum circuit breaker are small size, light weight, fast action, long life, low noise operation, safe and reliable sock liquid, and easy maintenance.

The role of vacuum circuit breakers.

When the vacuum circuit breaker is in the closing position, its ground insulation is borne by the support insulator, once the line connected by the vacuum circuit breaker has a permanent grounding fault, after the circuit breaker trips, the grounding fault point is not cleared, then the ground insulation of the electric bus should also be borne by the vacuum gap of the circuit breaker break; When various faults are interrupted, the vacuum insulation gap between the pair of contacts at the fracture must withstand the action of various recovery voltages without breakdown.

Therefore, the insulation characteristics of the vacuum gap have become the current research direction to increase the fracture voltage of the interrupter and make the single-break vacuum circuit breaker develop to a high voltage level.

The functions of vacuum circuit breakers are:

1. The contact opening distance is small, the contact opening distance of the 10kV vacuum circuit breaker is only about 10mm, the work of the working mechanism is small, the stroke of the mechanical part is small, and its mechanical life is long.

2. The arcing time is short, and it has nothing to do with the size of the switching current, and there is only half a cycle per mu.

3. After arc quenching, the contact gap medium recovers quickly, and the fault performance in the near area of the breaking is good.

4. Due to the small amount of wear and tear when the dredging is interrupted at the current breaker, the electrical life of the contact is long, the full capacity is broken for 30-50 times, the rated current is broken for more than 5000 times, and the noise is small and suitable for frequent operation.

5. Small size, light weight, suitable for interrupting capacitive load electric denier delay.

Due to its many advantages, it is widely used in substation in the mold coarse plum, the current models are: ZN12-10 type, ZN28A-10 type, ZN65A-12 type, ZN12A-12 type, VS1 type, ZN30 type, etc.