Discussion on Protection of Power Supply System and Electrical Equipment in Coal Mines

High-tech, new technologies and new products based on the discussion of coal mine power supply system and electrical equipment protection Deng Jianzhong (Wangan Coal Mining Group, Changzhi, Shanxi 046031) Although the situation has greatly improved, but overall it is still not optimistic. Coal mine power supply systems and corresponding electrical equipment protection have a direct impact on the safety of coal production. Doing a good job of protecting the corresponding electrical equipment is of great significance for ensuring the safety of coal companies. The article discusses the protection of the coal mine power supply system and electrical equipment.

With the continuous development of our country's economy, the consumption of coal is continuously increasing, which makes the production of the coal industry face significant pressure. Although the security situation of China’s coal production has been greatly improved, overall, it is still not optimistic. Coal mine power supply systems and corresponding electrical equipment protection have a direct impact on the safety of coal production. Doing a good job of protecting the corresponding electrical equipment is of great significance for ensuring the safety of coal companies.

During the daily production and operation of coal mines, power supply systems and corresponding electrical equipment play a very important role. With the continuous development and progress of related technologies in the coal industry, the use of intelligent electrical equipment in coal production enterprises is increasing. The more common is the microprocessor, which has strong data processing capabilities, and has strong protection for the power system of coal production enterprises, and can ensure the safety and stability of electricity supply in the coal production process.

The relay is a relatively common electrical equipment protection device in the coal mine power supply system. The extensive use of relays as protective devices in the power supply system of coal mines can respond to corresponding electrical anomalies and equipment failures in a timely manner, isolate corresponding faulty devices, or issue alarms in time, which can reduce electrical equipment as much as possible. Loss caused by failure.

With the continuous development of science and technology, a large number of corresponding technologies and intelligent equipments have been used in power supply equipment protection devices, making the coal mine power supply system develop in the direction of automation. In the actual work of coal mines, due to the continuous increase of current, the use of relays in the power supply system is very extensive, and the relays have more types, but its basic structure mainly includes the following aspects: 1.1 Live signal input part. Corresponding processing of the signal in the circuit is carried out and then transmitted to the relay protection device, so that the relay can understand the situation of the circuit in the current year.

1.2 Measurement section. The relay implementation has already set certain parameters, measured and detected the conditions in the circuit, and compared with the preset values, and found that if a certain range is exceeded, corresponding actions are taken.

1.3 Logical judgment section. According to the result of the comparison, a corresponding logic decision is made, then a corresponding action signal is issued and then executed by the executing agency.

2 Types of protection for common electrical equipment in underground mines Electrical equipment used in coal mines In addition to general electrical equipment, due to the special nature of mine production, there are also explosion-proof electrical equipment. Due to the relatively high safety requirements under the mine, this makes the safety requirements for electrical equipment very strict, and flameproof electrical equipment is mainly used. Because the power of the working equipment under the mine is relatively large, this makes the use of high voltage electrical equipment in coal mines more common. The common protection methods mainly include the following types: In the power supply system of coal mines, the insulation layer is prone to wear and aging due to the relatively harsh working environment for a long period of time, which makes the circuit often suffer from electrical leakage. Once the underground workers accidentally touch, it will lead to electric shock accidents. At the same time, there are often a large number of flammable gases and dusts in the mine. Once the electric spark occurs, it is very prone to an explosion. Therefore, measures must be taken to prevent leakage of the power supply lines downhole, detect leakage at any time, and find out where the leakage occurred in a timely manner so as to prevent serious accidents.

During the downhole production process, the power supply system often causes over-current, which leads to the occurrence of fire, and the cause of over-current is more complicated, common is short circuit or overload. This requires the adoption of appropriate measures to prevent over-flow, mainly by the following measures: The current below the mine exceeds the rated current of the electrical equipment, which is the so-called overload, which may be shortened if the overload is severe The life of an electrical device may also cause the electrical device to burn out. The causes of the overload of electrical equipment are relatively complex, mainly in the following situations: The load increases instantaneously, phase-to-phase operation or the voltage of the power grid decreases. This requires the use of time relays to effectively protect the overload. In the event of an overload condition, the time relay is turned on by the current relay to complete the delay operation and disconnect the power supply of the circuit.

Because the electrical equipment in the mine is in a relatively complex working environment for a long time, the aging or wear of the insulation layer is often serious. At this time, it may cause a short circuit. During the short circuit, the current in the circuit will increase instantaneously. As a result, the electrical equipment in the circuit is damaged. In severe cases, it also causes fire. In order to effectively prevent damage caused by a short circuit, electronic or electromagnetic relays can be used.

Under normal circumstances, the insulation layer inside the electrical equipment can effectively prevent the internal current from charging the metal shell. However, once the internal insulation layer is damaged, the insulation layer of the electrical equipment may be charged, resulting in personal injury. In order to prevent the electrical equipment housing from being charged, it is necessary to ground the electrical equipment so as to prevent the damage caused by excessive current flowing through the human body and effectively protect the life safety of the operator.

In the normal operation of the electrical equipment, if the power supply voltage disappears and stops working, when the power supply voltage recovers, the electrical equipment can be started or put into operation to cause personal injury or equipment damage. For the power supply system, many electrical devices start up and work at the same time, and they may also cause impermissible over-currents and excessive pressure drops. Thermal electrical equipment may cause fires. In order to prevent the electrical equipment from being started or put into operation when the voltage is restored, the contactor and the button are used to control the starting, the stopping and the stopping of the motor, so that it has a function of the pressure loss protection.

It adopts the principle of amplitude protection. When the voltage of the power supply system drops to 75% of the rated voltage in some applications, the motor or electrical component should be able to automatically cut off the power and stop working, so as not to damage the motor and mechanical equipment. The undervoltage protection method can use not only the contactor and the button control mode, but also low voltage circuit breakers or special electromagnetic voltage relays for undervoltage protection.

It adopts the principle of amplitude protection. When the voltage of the power supply system is greater than 115% of the rated voltage, it should be able to automatically cut off the power and stop working so as not to damage the motor and mechanical equipment. The overvoltage protection method is to connect a resistor, a resistor string capacitor or a diode string resistor in parallel across the coil to form a discharge loop to achieve overvoltage protection.

It is one of the important parts to achieve a safe and reliable system. Commonly used lockouts are leakage lockouts, mechanical lockouts, and wind power lockups. Leakage blocking adopts the principle of additional DC power supply detection. It is often used in explosion-proof vacuum type electromagnetic starters and low-voltage feeder switches. High-voltage distribution boxes are equipped with mechanical locking devices to ensure safety; Wind power blocking functions are provided by branch feeder switches. Used in conjunction with the fan's control switch, the normally closed contact of the fan's control switch is connected to the CPU circuit of the shunt switch to control the shunt switch.

The coal mine power supply system plays a decisive role in the smooth production of coal mines and the safety of production maintenance. This requires the relevant technical personnel to fully consider the special use environment of the coal mine power supply system and electrical equipment during the design and installation process, do a proper protection work, and ensure the safe and stable operation of the electrical equipment. 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.