Arc extinguishing technology of vacuum circuit breaker, how to ensure that the arc can be extinguished quickly?
Vacuum arc discharge is formed in the metal vapor evaporated from the contact electrode. At the same time, the characteristics of the arc performance are different with the size of the breaking current. We generally divide it into small current vacuum arc and large current vacuum arc.
1. Small current vacuum arc
When the contact is broken in a vacuum, a cathode spot with concentrated current and energy is generated, and a large amount of metal vapor is evaporated from the cathode spot. The density of metal atoms and charged particles is very high, and the arc burns in it. At the same time, the metal vapor and charged particles in the arc column continue to diffuse outward, and the electrode also continuously evaporates new particles to supplement. When the current passes through zero, the energy of the arc decreases, the temperature of the electrode drops, the evaporation effect decreases, and the density of particles in the arc column decreases. Finally, the cathode spot disappears when it passes through zero, and the arc is extinguished.
Sometimes, the evaporation effect cannot maintain the diffusion speed of the arc column, the arc is suddenly extinguished, and the current is cut off.
2. High-current vacuum arc
When the contact disconnects a large current, the energy of the arc increases, the anode also heats up severely, and a strong concentrated arc column is formed. At the same time, the effect of the electromotive force is also obvious. Therefore, for a high-current vacuum arc, the magnetic field distribution between the contacts has a decisive influence on the stability and arc extinguishing performance of the arc. If the current is too large and exceeds the limit breaking current, it will cause a breaking failure. At this time, the contact heats up severely, and the current still evaporates after passing zero. The medium is difficult to recover and the current cannot be disconnected. How to ensure that the arc can be extinguished quickly?
1. Lengthen the arc
After the arc is lengthened, the arc voltage increases, changing the arc's volt-ampere characteristics. In a DC arc, its static volt-ampere characteristics move upward, and the arc can be extinguished. In an AC arc, due to the increase in the arc burning voltage, the arc is difficult to reignite.
2. Arc extinguishing hood
The arc extinguishing hood is a commonly used device that allows the arc to contact with a solid medium, reduces the arc temperature, and thus accelerates the arc extinguishing. Its structural type is varied, but its basic unit is "slit". We call the gap between the arc extinguishing hood wall and wall "slit". According to the number of slits, it can be divided into single slit and multiple slits.
3. Oil-cooled arc extinguishing device
Oil-cooled arc extinguishing is to place the arc in a liquid medium (generally transformer oil), and the arc vaporizes and decomposes the oil to form oil gas. This is oil blowing arc extinguishing. Since the arc extinguishing ability in oil is much greater than the arc stretched in the atmosphere, this method is generally used in high-voltage electrical appliances, such as oil switches.
4. Gas blowing arc extinguishing device
Gas blowing arc extinguishing uses compressed air to extinguish the arc. Compressed air acts on the arc, which can cool the arc well, increase the pressure in the arc zone, and quickly take away the residual free gas, so it has a higher arc extinguishing performance. According to the direction of the airflow blowing the arc, it can be divided into two categories: horizontal blowing and longitudinal blowing.
ZW7-40.5 Outdoor Miniaturized Vacuum Circuit Breaker have a reasonable structure and easy maintenance. Current transformers can be selected to achieve multiple changes and multiple windings to meet the needs of metering, measurement, and protection. It is used in outdoor 110KV or 220kV substations, 35KV transmission and transformation lines, agricultural power grid power systems, and transmission and transformation SVG protection systems.
It has many product advantages:
1. Circuit breaker performance: E2-C2-M2
2. Simple and convenient maintenance: It adopts a special modular mechanism. The replacement of the closing and opening coils does not require the removal of other components. Users can easily replace it, and no test and adjustment are required after replacement, making later operation and maintenance more convenient.
3. Miniaturized design: The product volume is significantly smaller than other users in the industry, which is convenient for transportation and on-site installation;
4. Wide range of use: Adapt to harsh environments, the product can withstand low temperatures of minus 15°C. Meet the use requirements of 1,000 meters above sea level. Under special requirements, the lowest temperature can reach -40°C, and special requirements can meet the use requirements of 2,000 meters above sea level.
