The protection of electrical equipment and power supply systems is an important part of the entire coal mine safety and plays an extremely important role in the development and production of coal mining enterprises. In the coal mine production process, relay protection devices are widely used in the protection of coal mine power supply systems and electrical equipment.
However, with the continuous development of science and technology, especially network information technology, coal mining companies are increasingly paying attention to the application of high-tech technology, especially the application of intelligent electrical equipment and power supply systems is very extensive.
In addition, in some hardware facilities, microprocessors are also widely used and promoted in the safety production of coal mines. Microprocessors are environmentally friendly and have strong data processing. This will ensure the stability and reliability of the coal mine system and thus ensure the safe production of coal mines.
As we all know, the equipment used for the protection of power supply systems and electrical equipment in coal mines is relays. With the continuous development of science and technology, especially network information technology, its protection system has gradually developed toward intelligence and automation. In terms of coal mine hardware, microprocessors have also been widely used and developed, and relay protection devices are mostly used. With the rapid development of various science and technology, such as computer technology, microelectronic technology, information technology, and network communication technology, the reliability of the entire system has been greatly improved, thus ensuring the production quality. The relay of the protection system of the power supply system and the electrical equipment is an automatic device that can reflect the failure and abnormal state of the system when it is working, and that it can make timely processing or send an emergency signal through the equipment. Fuses, relays, relays, and other devices can all play a protective and emergency role, but due to the normal operation of the coal mine power supply system, the current in the circuit is in a rising state, so that the fuse can not effectively meet the demand, and the relay Contactors are widely used protection devices in power supply systems and electrical equipment protection applications in coal mines. There are many kinds of relay protection devices, and their basic structures include the following aspects: Field signal input part: On-site signal is sent to the relay protection device, and the necessary pre-processing is generally performed so that the relay can effectively detect the physical quantities of each site; the measurement part : Comparing with the given set value or automatically generated criteria in real time, the determination determines whether the protection is started or not; the logic judgment part: according to a certain logical relationship combination, operation, and finally determine whether the circuit breaker should be tripped or signaled , And pass the relevant command to the implementation part; Execution part: It is the key part that enables the relay protection device to work reliably.
2 Types of protection for common types of electrical equipment downhole The electrical equipment can be classified into general types and flameproof types depending on the model. Because underground environment is extremely complicated, in coal mines, explosion-proof type must be used to prevent explosion caused by gas. At the same time, electrical equipment can be divided into low-voltage electrical equipment and high-voltage electrical according to the operating voltage level. equipment. Most of the equipment used downhole belongs to high-voltage electrical equipment. When the equipment is in operation, the voltage is quite large. Under the current circumstances, overcurrent protection, leakage protection and grounding protection are the three most common protection methods downhole.
2.1 Leakage protection When the insulation resistance of the power grid is less than a certain value, the surrounding eyes of the person touching the power grid should be detonated at the same time as much as possible. When detonating, the blast effect of the inner ring borehole adjacent to the surrounding eyes must be strictly controlled.
6.4 Strictly control the degree of concentration of the explosives' arrangement. In order to overcome the production of clips for the fundus of the eye, the amount of the drug is usually enhanced at the fundus.
In the next 10 years, China’s energy structure coal will still account for 60% and 70%. As the depth of mining increases, the construction of mines is transitioning to deeper ones. The construction of deep mine roadways will encounter more complicated problems, giving full play to the first lane and light. The advantages of surface blasting, especially strengthening the study of blasting construction in deep mine tunnels, are the current problems that need to be solved by coal mine science and technology workers. Electric shocks will occur, which will cause accidents and dangers to the human body. Moreover, the leakage of electricity will also cause equipment damage and short circuits. ACCIDENT. Due to the existence of electric sparks, there is a danger of explosions such as gas and dust under coal mines. Therefore, in the entire power supply system in the downhole, it is necessary to provide a device for the leakage protection system so as to realize the insulation monitoring, leakage protection, and compensation of the capacitive current flowing through the borehole equipment. According to the requirements of coal mines, according to its protection function, it can be divided into two types of leakage protection methods: no selective leakage protection and selective leakage protection.
2.2 Overcurrent protection In the normal production of coal mines, the main cause of electrical fire accidents is the overcurrent of the power grid. The formation of overcurrent has a great relationship with short circuit and overload. Therefore, the best way to prevent electric fire is to take effective measures to prevent overcurrent.
Overload refers to the current generated during the operation of the motor or the current of the electrical equipment during normal operation is greater than its rated current, but it is more than the multiple of the rated current. Under normal circumstances, it is the rated current of 1.5 Less than. We all know that there are many factors that cause the motor or electrical equipment to be overloaded. For example, the most common ones are the following: sudden increase in load, operation in open phase, and reduction in grid voltage. The increase of the dynamic overload degree will directly lead to the shortening of the delay time. Conversely, if the overload degree is reduced, the delay time will be longer. This feature is called inverse time characteristics. The delay link is mainly realized by the time relay. When the overload occurs, the current relay acts, and the contact is connected to the time relay coil. After the time delay, the time relay contact is actuated to cause the actuator to act and cut off the main circuit power supply. Overload signal. Overload protection can be achieved by electromagnetic relays, electronic relays and thermal relays.
Short Circuit Protection Short circuit occurs when the electrical or line insulation is damaged, the load is short circuited, or the wiring is incorrect. The instantaneous fault current generated during a short circuit can reach ten to several tens times of the rated current, causing electrical power damage to electrical equipment or distribution lines due to overcurrent, or even causing fire due to arcing. Both electromagnetic relays and electronic relays can be short-circuit protected.
2.3 Ground Protection As we all know, under normal circumstances, because the outer shell of the electrical equipment is metal, the electrical equipment is in an insulated state and therefore will not be charged. However, when the metal shell is damaged, the insulation layer is damaged, and the outer shell of the electrical equipment is damaged. The frame will be charged. At this time, if the human body is in contact with electrical equipment, it will cause damage to the human body and cause an accident. According to our country's regulations, the safety current of the electric shock is 30mA. Therefore, only through the grounding protection makes the electric current when the limiting current passes through the person is safe and will not cause harm to the human body. In this way, the current passing through the human body can be made a safe current and will not cause harm to the human body, so that the occurrence of an electric shock accident can be avoided or reduced.
With the continuous development of science and technology, especially network information technology, coal mining companies are paying more and more attention to the application of high technology, especially the application of intelligent electrical equipment and power supply systems is very extensive. With the combination of PLC, hydraulic technology and intelligent electrical equipment, the reliability and safety of the entire system will be further improved and improved.
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