Vacuum Arc recovery of Vacuum Circuit Breaker
High vacuum possesses extremely high dielectric strength. At zero current the arc is extinguished very quickly, and the dielectric strength is established very quickly. This return of dielectric strength is because of the vaporized metal which is localized between the contacts diffuses rapidly due to the absence of gas molecules. After arc interruption, the recovery strength during the first few microseconds is 1 kV/µs second for an arc current of 100A.
Because of the above-mentioned attribute of vacuum circuit breaker, it is capable of handling the severe recovery transients associated with short-line faults without any difficulty.
Property of contact material
The contact material of the vacuum circuit breaker should have the following property.
Working Vacuum Circuit Breaker
When the fault occurs in the system, the contacts of the breaker are moved apart and hence the arc is developed between them. When the current carrying contacts are pulled apart, the temperature of their connecting parts is very high due to which ionization occurs. Due to the ionization, the contact space is filled with vapour of positive ions which is discharged from the contact material.
Maintenance cycle of vacuum circuit breaker
The vacuum circuit breaker has the characteristics of high reliability, long service life and relatively long maintenance and repair cycle, but it can not be mistaken that the vacuum circuit breaker does not need maintenance. The maintenance cycle should be flexibly controlled according to relevant regulations and in combination with the actual operating conditions.
1. The arc is extinguished in a sealed container, and the arc and hot gas are not exposed. As an independent component, the arc extinguishing chamber is easy to install and debug.
2. The contact clearance is very small, usually about 10mm, with small closing power, simple mechanism and long service life.
3. The arc extinguishing time is short, the arc voltage is low, the arc energy is small, the contact loss is small, and the breaking times are many.