SF6 circuit breakers: device, principle of operation, purpose

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

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

An SF6 high-voltage circuit breaker is a device, the purpose of which is to control and monitor a high-voltage power supply line. The design of such equipment resembles the mechanism of an oil device, only for extinguishing a gas compound is used instead of an oil mixture. Sulfur is usually used. Unlike an oil device, a SF6 device does not require special maintenance. Durability is considered its main advantage.

SF6 circuit breakers are divided into:

1. Columnar. The use of such a structure is optimal only for a 220 kV network. This disconnecting device operates on one phase. The design includes two systems that are placed in a container with SF6 gas. This is a contact and arcing system. They can also be both manual and remote. This is believed to be the main reason for their large size.
2. Bakovy. It is smaller in size than the core ones. The design has an additional drive, which has several phases. Thanks to this, you can smoothly and gently adjust the voltage on and off. And due to the fact that a current transformer is built into the system, the mechanism is capable of carrying heavy loads.

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

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

Principle of operation and scope

How does a high voltage SF6 circuit breaker work? Due to the isolation of the phases with each other by means of SF6 gas. The principle of operation of the mechanism is as follows: when a signal is received to turn off the electrical equipment, the contacts of each chamber open. Built-in contacts create an electric arc that is placed in a gas environment.

This medium separates the gas into individual 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 is operating at low pressure. The compressors then 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 breaker mechanism:

As for the tank-type models, control is carried out in them using drives and transformers. What is the drive for? Its mechanism is a regulator and its purpose is to turn the electricity on or off and, if necessary, keep the arc at a set level.

Actuators are divided into spring and spring-hydraulic. Spring loaders have a high degree of reliability and have a simple operating principle: 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 switches additionally have a hydraulic control system in their design. Such a drive is considered to be more efficient and reliable, because the spring device can itself change the level of the retainer.

Advantages and disadvantages of equipment

As with any structures and mechanisms, SF6 circuit breakers have their own 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. Action speed. SF6 reacts to the presence of an electric arc in a matter of seconds. Thanks to this, in the event of an 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 change gas mixtures. Contacts that come into contact with the mixtures are almost not subject to wear, and the outer case has high protection rates.
5. They can be used on high voltage networks. Their counterparts, such as vacuum devices, are not able to do this.

But these switches also have their drawbacks. For example:

1. Since the production of devices is very complex and SF6 gas mixtures are expensive, the price of the construction itself is high.
2. The device does not work at low temperatures.
3. Specific equipment should be used for the required maintenance.
4. The device must be installed on a special platform or foundation, and for this you must have experience and special instructions.

Finally, we recommend watching a video that describes in detail how the equipment filled with SF6 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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