What is a vacuum switch
At present, there is a general replacementoil and gas-insulated circuit breakers with vacuum switches. This type of switching equipment is designed to protect power circuits against short-circuit and overload currents at various voltage levels from 10 kV to 220 kV. The reasons for the replacement of equipment are due not only to operational wear and obsolescence. Oil circuit breakers have a sufficiently small life of trips, it is necessary to control the oil level, and also to install powerful electric drives to ensure the required speed of operation. In addition, there is a risk of an explosion during the shutdown process.
In turn, SF6 circuit breakerscontribute to the development of the greenhouse effect, they are difficult to produce and maintain. Switches of this type are quite expensive, require control over the use of SF6 gas, and also place high demands on the quality of the injected gas.
The advantages that vacuum circuit breakers have are as follows:
1. Environmental safety.
2. A large number of commutations.
3. Low operating costs.
4. Ease of construction.
5. High reliability.
6. Small size.
7. Explosion and fire safety.
8. No noise pollution.
The disadvantages of vacuum switches include:
1. Relatively small rated currents and tripping currents.
2. Probability of switching overvoltages.
The development of vacuum switching devices is being handled by a number of countries, such as Japan, China, Russia, etc.
Vacuum circuit breaker can be provided intank and column version. In the first case, the role of insulation is played by dry air, which is injected under pressure. This design allows you to make the vacuum switch absolutely safe for the environment. The most important feature of the tank design is that during dismantling, it is not necessary to collect the gas of the insulating medium.
A vacuum switch can have one or morediscontinuities per pole. This means that the electric circuit will be interrupted in several places, so that the damping of the arcing arc occurs more efficiently.
The pressure of dry air is equal to 5 atmospheres,since at large values the arc chute chamber, which is installed in the vacuum switch, can lose its stability and can be irreparably deformed. Nevertheless, it is believed that the vacuum vacuum switch has become more widely used than the column design switch.
The process of extinguishing an electric arc in a vacuumswitch occurs as follows: in the vacuum arc chute the longitudinal magnetic field is superimposed on the passing arc. This creates the effect of so-called longitudinal magnetic blasting, due to which the length of the arc increases. As you know, the longer the arc length, the easier it is to extinguish it. In this regard, the voltage of the electric arc has a large influence on the dimensions of the switch, since the higher the voltage, the larger the dimensions of the arc chute and, consequently, the larger the overall installation should have.
Opening of electrodes is carried out by a spring drive, a spring cocking of which is carried out by means of an electromagnet.