What is a gas-insulated switch and why is it needed?

In order to extinguish an electric arc, many different gas mixtures are often used. According to this principle, equipment filled with SF6 gas is used, which is used for work in an emergency. In this article we will consider the device, the principle of operation and the purpose of SF6 circuit breakers.

What does the equipment consist of and what are the designs?

The gas-insulated high-voltage switch is a device whose purpose is to control and monitor the high-voltage power supply line. The design of such equipment resembles the mechanism of an oil device, only for extinguishing a gas connection is used instead of the oil mixture. As a rule, sulfur is used. Unlike an oil appliance, SF6 does not require special care. Its main advantage is durability.

SF6 equipment

SF6 circuit breakers are divided into:

  1. Column. The use of such a structure is optimal only for a 220 kV network. This tripping device operates on a single phase. The design includes two systems that are placed in a tank with gas. This is a contact and arcing system. They can also be both manual and remote. This is considered the main reason for their large size.
  2. Buck. It is smaller in size than core ones. The design has an additional drive, which has several phases. Thanks to this, you can smoothly and gently regulate the on and off voltage. And due to the fact that a current transformer is built into the system, the mechanism is able to carry heavy loads.

According to the method of extinguishing an electric arc, SF6 circuit breakers are divided into:

  • air, it is also called autocompression;
  • rotating;
  • longitudinal blast.

The principle of operation and scope

How does a high voltage SF6 circuit breaker work? Due to the isolation of the phases between themselves by means of SF6. The principle of the mechanism is as follows: when a signal is received about the disconnection of electrical equipment, the contacts of each camera open. Built-in contacts create an electric arc, which is placed in a gas environment.

This medium divides the gas into separate particles and components, and due to the high pressure in the tank, the medium itself is reduced. Possible use of additional compressors if the system operates at low pressure. Then the compressors increase the pressure and form a gas blast. Shunting is also used, the use of which is necessary to equalize the current.

The designation in the diagram below indicates the location of each element in the switch mechanism:


As for the tank-type models, they are controlled by drives and transformers.What is a drive for? Its mechanism is a regulator and its purpose is to turn on or turn off electricity and, if necessary, to keep the arc at a set level.

Drives are divided into spring and spring-hydraulic. Spring-loaded ones have a high degree of reliability and have a simple principle of operation: all work is done thanks to mechanical parts. The spring is capable of compressing and expanding under the action of a special lever, as well as being fixed at a set level.

The spring-hydraulic actuators of the circuit breakers are additionally equipped with a hydraulic control system. Such a drive is considered more efficient and reliable, because a spring device can itself change the level of the latch.

Arc extinction in vacuum

Advantages and disadvantages of equipment

As in any structures and mechanisms in SF6 circuit breakers, there are advantages and disadvantages. The advantages of the device include:

  1. Multifunctionality. The purpose and application of such a mechanism is possible for any voltage in the network.
  2. Speed ​​of action. SF6 reacts to the presence of an electric arc in seconds. Due to this, in case of emergency, it is possible to quickly turn off the controlled system.
  3. Possible use in vibration and fire hazard conditions.
  4. Longevity. There is no need to replace gas mixtures. The contacts that come into contact with the mixtures are almost not subject to wear, and the outer case has great protection.
  5. Can be used on high voltage networks. Their analogues, such as vacuum devices, are not capable of doing this.

But these switches have their drawbacks. For instance:

  1. Since the manufacture of devices is very complex and gas-insulated mixtures are expensive, the price of the construction itself is high.
  2. The appliance does not work at low temperatures.
  3. For the required maintenance, certain equipment should be used.
  4. The device should be installed on a special platform or foundation, and for this you should have experience and special instructions.

In the end, we recommend watching a video that details how the equipment filled with SF6 gas works and what it is used for:

So we examined the device, purpose and principle of operation of SF6 circuit breakers. We hope the information provided was useful and interesting for you!

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