To automate the operation of equipment that is powered by electricity, use special oil switches.
An oil switch is a device that switches individual circuits on or off in an electrical system, in its normal mode of operation or in an emergency, in manual mode, or from an automatic system command. A similar device is used in the organization of many power supply networks.
Equipment classification
To ensure the stable operation of electrical equipment, the following types of oil circuit breakers can be used:
- A system with a large capacity and oil in it is a tank system.
- Using dielectric elements and a small amount of oil - low-oil.
The circuit of the oil circuit breaker has a special device for extinguishing an arched arc during an open circuit. According to the principle of operation of arcing devices, such equipment is divided into the following groups:
- Using forced blasting of the working environment. Such a device has a special hydraulic mechanism for creating pressure and oil supply at the point of open circuit.
- Magnetic quenching in oil is carried out using special electromagnets of elements that create a field that moves the arc into narrow channels to break the created circuit.
- Oil circuit breaker with auto-blowing. The circuit of an oil switch of this type provides for the presence of a special element in the system that releases energy from the formed arc to move oil or gas in the tank.
Tank type system
Tank circuit breakers are very popular due to the simplicity of design. The oil switch consists of an input, an arrester and a contact system, 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 index 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 embodiment it is possible to use the manual mode, and for the second it is necessary to have an automatic switch-on.
In the single-tank type, when all three phases are in the same container with oil, the used working medium isolates the contact from each other and from the tank body, which must be grounded. Oil, in addition, serves to extinguish the formed arc and isolate the phases of power supply from each other at the time of network breakdown.
The principle of operation of single-tank switches
When the system is triggered, the contact of the arcing chamber breaks first. When the contact of the mains with a high voltage breaks, an arc arises that decomposes the oil due to exposure to high temperature. When the arc affects the oil, a gas bubble forms, 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 result in deionization of the formed arc during contact breaking. In a similar way, the oil switch breaks the circuit.
The principle of operation of a three-tank switch
The three-tank switch has a slightly different operating principle, which is associated with its use in a high voltage network. The oil switch, which is used in networks with voltages higher than 35 kV, has a special mechanism in the arc quenching chamber that creates blast. The arcing system used may consist of several operating modes. They allow you to increase the speed of arc extinction during contact breeding.
In order to secure this process, the elements transmitting electricity are placed in a special tank with oil, and a separate tank is used for each phase. Various actuators of oil circuit breakers are also used, allowing 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.
Advantages of the system
The arc extinguishing system of this type has a number of features, because of which it is used in many power supply circuits. The advantages of the system include the following:
- High efficiency circuit interruption, which allows the use of similar equipment 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 the implementation of an important command from an automatic control system or operator. Also, this quality leads to a relatively low cost of this type of equipment.
System flaws
Despite the great popularity of this system of extinction of the electric arc, which is formed when the contacts break, it has some disadvantages:
- The use of a large volume of oil to ensure reliable performance of tasks.
- Large dimensions of the arrester associated with the need to use oil in large quantities.
- Fire hazard. 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 may boil and catch fire.
Low oil type equipment
The oil switch VMP, or in other words low-oil, in addition to the working fluid to ensure isolation of the system elements from each other, has special elements made of dielectric materials. In this case, 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. In this case, a special drive is used in the system, which provides transverse blasting.
Due to the small amount of oil during the off state, the contacts are above the level of the oil used in the chamber, which increases the reliability of a power outage. Due to contamination of the working environment, it may lose its basic dielectric properties over time. Also, when creating such a system, designers took into account the fact that decomposition products are formed over time. Oil separators have been specially created for them.
Advantages and disadvantages of the system
An oil circuit breaker of this type is often used to provide a reliable break in the power supply circuits of short length and power. Its advantages include the following:
- Use a small amount of oil.
- The 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 in the arrangement of power supply to enterprises, offices or other industrial buildings where there is a high-voltage network.
The disadvantages include the following:
- To ensure reliable operation, it is necessary to 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.