To automate the operation of equipment powered by electricity, special oil switches are used.
Oil switch - a device that switches on or off individual circuits in the electrical system, in its normal operation or in an emergency, in manual mode or from the command of an automatic system. A similar device is used in the organization of many power supply networks.
To ensure the stable operation of electrical equipment, the following types of oil circuit breakers can be used:
- System with large capacity and oil in it - tank.
- Using dielectric elements and a small amount of oil, low oil.
The circuit of the oil circuit breaker has a special device to extinguish the arc formed during the break of the circuit. According to the principle of actionarc extinguishers such equipment is divided into the following groups:
- Using forced air blowing working environment. Such a device has a special hydraulic mechanism for creating pressure and supplying oil at the point of chain break.
- Magnetic quenching in oil is carried out using special electromagnet elements that create a field that moves the arc into narrow channels to break the created circuit.
- Auto blown oil circuit breaker. The scheme of this type of oil switch provides for the presence of a special element in the system, which releases energy from the formed arc to move oil or gas in the tank.
Tank system type
Tank circuit breakers are very popular due to their simple design. The oil circuit breaker consists of an input, an arc extinguisher and a system of contacts, which are placed in a tank with oil. When using equipment in a system with a voltage of 3-20 kW, all three contacts (phases) can be located in one tank, with an increase in the voltage indicator to 35 kV, the phase must be located in a separate tank. In two cases, an automatic or remote control system can be used, however, for the first version, manual mode can be used, and for the second, an auto-recloser is required.
In the single-tank type, when all three phases are in the same container with oil, the working medium used conducts contact isolation from each other and fromtank body, which must be grounded. Oil, in addition, serves to extinguish the formed arc and isolate the phases of the power supply from each other at the time of the network break.
The principle of operation of single-tank circuit breakers
When the system is triggered, the contact of the arc chute first breaks. When the contact of the high voltage network is broken, an arc occurs, which decomposes the oil due to the effect of high temperature. When the arc acts on the oil, a gas bubble is formed, in which the arc itself will be located. The created bubble consists of 70% hydrogen, and this gas in this state will be supplied under pressure. Exposure to hydrogen and artificially created pressure will deionize the formed arc during contact break. In a similar way, the oil switch conducts a circuit break.
The principle of operation of the three-tank circuit breaker
The three-tank switch has a slightly different principle of operation, which is associated with its use in a high voltage network. The oil circuit breaker, which is used in networks with voltages above 35 kV, has a special blowing mechanism in the arc extinguishing chamber. The arc extinguishing system used can consist of several modes of operation. They allow you to increase the speed of extinguishing the arc during the opening of the contact.
In order to secure this process, the electricity-transmitting elements are placed in a special oil tank, with a separate tank used for each phase. Various drives are also usedoil switches that allow you to supply the working fluid in the selected direction. The system has a special element for controlling the size of the arc, which is represented by a shunt. After the disappearance of the formed arc, the current supply stops completely.
This type of arc extinguishing system has a number of features, due to which it is used in many power supply circuits. The advantages of the system include the following:
- High circuit breaking efficiency, which makes it suitable for use in high voltage networks.
- The simplicity of the design makes it reliable and maintainable. Repair of oil switches should be carried out exclusively by professionals, since such equipment is responsible for carrying out an important command from an automatic control system or operator. Also, this quality determines the relatively low cost of this type of equipment.
Despite the great popularity of this system for extinguishing an electric arc, which is formed when the contacts are broken, it has some disadvantages:
- Using a large volume of oil to ensure reliable performance of assigned tasks.
- Large dimensions of the arc extinguisher, associated with the need to use a large amount of oil.
- Fire hazard. This is due to the fact that during the formation of an arc, the temperature of the oil rises. If the amount of working fluid is less than the recommended level, it mayboiling and ignition.
Low oil type equipment
The VMP oil switch, or in other words, low oil, in addition to the working fluid to ensure the isolation of the system elements from each other, has special elements made of dielectric materials. In this case, the oil is used only for the formation of gas. Each element of the system in which the circuit breaks has a separate chamber with an arcing device. This uses a special drive in the system, which provides transverse blast.
Due to a small amount of oil during the off state, the contacts are above the level of oil used in the chamber, which increases the reliability of power interruption. Due to contamination of the working environment, it may eventually lose its basic dielectric properties. Also, when creating such a system, the designers took into account the fact that decomposition products are formed over time. Oil separators were specially created for them.
Advantages and disadvantages of the system
This type of oil circuit breaker is often used to ensure a reliable network break in power supply circuits of small length and power. Its advantages include the following:
- Using a small amount of oil.
- Relatively small dimensions and weight of the structure, increasing the scope of its application.
Such positive qualities made it possible to use the network break system when arranging power supplyfactories, offices or other industrial buildings where there is a high voltage network.
Disadvantages include the following:
- To ensure reliable operation, you must constantly monitor the oil level and add it if necessary.
- The high cost of equipment is associated with the use of expensive dielectric materials in its manufacture.
The type of oil circuit breakers is selected according to the characteristics of the power supply circuit in which they will be used.