What is a vacuum switch

At present, replacement of oil and gas-insulated circuit breakers with vacuum switches is carried out everywhere. 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 breakers contribute 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. The 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 switch can be presented in tank and column version. In the first case, the role of insulation is played by dry air, which is pumped 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.

The vacuum switch can have one or more discontinuities per pole. This means that the electrical circuit will be interrupted in several places, so that the damping of the arcing arc occurs more efficiently.

The dry air pressure is equal to 5 atmospheres, because 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 widespread than the switch of the column design.

The process of extinguishing an electric arc in a vacuum switch takes place as follows: in a 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 the electrodes is carried out by a spring drive, the spring plating of which is carried out by means of an electromagnet.