With the development of coal mines in the direction of high productivity, high efficiency and intensification, electrical equipment in coal mines is constantly being updated. This article mainly elaborates the problems of high-output work in the face of power supply and electrical equipment requirements, high-output power supply and electrical equipment.
High-yield face; power supply system; electrical equipment With the development of coal mines in the direction of high productivity, high efficiency and intensification, the electrical equipment in coal mines is constantly being updated. Large-capacity, high-power, new-type, high-efficiency and high-reliability automatic mechanical and electrical equipment, computer control, condition monitoring and other automation technologies and modern communication technologies are continuously applied to coal mines, which accelerates the technical progress of electrical equipment at the work surface.
1 High-yield and high-efficiency work Faced with the requirements of power supply and electrical equipment to improve the production efficiency and efficiency of coal mines, high-power fully-mechanized mining units are generally used to increase the productivity and work efficiency of the working face, and to increase the production capacity of coal mining machinery and the transport capacity of transport equipment. . In order to meet the production capacity and to be suitable for high production efficiency, it is necessary to increase the cutting depth while increasing the shearing speed of the shearer. Increase the length of the work surface. In order to maintain continuous and stable production and reduce the number of moving downs, this should extend the length of advancement. This puts forward new requirements for power supply and electrical equipment in the work surface. It requires continuously increasing the power capacity of the work surface electrical equipment, raising the voltage level of the power supply, and having complete and reliable, sensitive electrical protection and monitoring, control and information transmission functions.
From the early 1960s to the early 1970s, the world's major coal-producing countries generally used 1100V to supply electrical power to the working surface. The installed surface capacity was generally around 500kw. The power of the fully mechanized coal mining equipment increased rapidly, and a double-motor coal mining machine emerged. The power of the single machine doubled compared with the original. With the increase of shearer power, the capacity of face conveyor has also been increased to more than 225kw, and the installed face capacity has been nearly 2000kw. At the same time, with the increase of the power of mining and transportation equipment, the speed of working face has been accelerated, and it is required to increase the mining area. In the length, the high-yield and high-efficiency working face with a length of 350m long in the mining area in China has been put into production, which also increases the power supply distance. This raises high requirements for power supply in the mining area. The original 1100V power supply system can not meet the requirements, mainly due to the following: when the size of the working face is increased, the power supply distance is longer, and the motor power is increased, if the power is also supplied with 1100V, the power of the conveyor motor at the working face is above 2x300kW. , can not guarantee enough starting torque, in serious cases will be reduced by more than 40%; shearer power increases, the control switch and cables and other equipment will exceed the reasonable current limit, if the use of double cables or large cross-section cable, will increase the cable drag Difficulty in moving and bending, cost, maintenance costs and losses are also relatively high; under the conditions of increasing working face size, increasing equipment power and production capacity, if the old system is used to increase capacity, it will not be worth the gains and losses, and it will be uneconomical and unreasonable. With large-capacity transformers, high fault currents tend to occur when the cable is damaged. Therefore, the effective use of 1100V voltage should be: the single machine shearer power (multi-motor installed power is 485kw), scraper conveyor motor power is 300kw. Above the power value of the equipment to use a higher voltage Power supply, the major advanced coal mining countries will raise the working surface power supply voltage to 2kV or more, the highest 5kV. For example, 3.3kV analysis shows that this level of power supply voltage can meet the working plane of a single power up to 750kw, multi-motor Equipment installed power of 1200kw, transmission distance of 500 ~ 1000m need. The 5kV power supply has twice the capacity of 3kV, and the reduction rate of the starting torque of the working motor is less than half of the 3kV.
2 Power supply and electrical equipment for high-output working face 2.1 Installed capacity and voltage for working face With the introduction of foreign advanced equipment, high-yield face appeared in some domestic coal enterprises, which increased the installed power of fully-mechanized mining equipment, and the largest coal mining machine Installed capacity has reached 1530kw, drive motor maximum power 610kw. Face conveyor maximum installed power up to 1125kw, drive motor power up to 525kw, the largest face conveyor power will reach 3x522=1566kw; slot slot conveyor maximum installed power Up to 1350kW, the maximum power of the drive motor is 420kw; the maximum installed power of the emulsion pump station is 3x190kW; the maximum installed power of the loader and the crusher reaches 200kw. In this way, the total installed power of the modern high-output working face is above 3000kw.
With the increase of the installed capacity of the working face, the high-productivity and high-efficiency working face also requires increasing the length of the working face and extending the length of the working face. The length of the “super†working face in our country reaches 6000m, which requires increasing the transmission distance and improving the power supply of the working face equipment. Voltage.
Power supply for working face and power supply for high-output work face of major equipment. One is conventional power supply, which is provided by two sub-cable lines from the ground substation to downhole central substation, and then sent by the central substation cable to the The mobile substations with work-slots are powered by shearers, scraper conveyors, transloaders, crushers, and belt conveyors through starters, load centers, etc.; there is also a power supply system that is represented by the United States. The ground is transformed into a well with a voltage of 6~12.5kV, and the cable into the well is directly sent to the mobile power supply center in the mining area. The power supply center is a large-scale multi-circuit outlet mobile substation device. One work surface is equipped with an electromechanical device that can separate and sing several different voltages.
With the increase of the installed capacity of the working face and the increase of the power supply voltage, the mobile substation and the switchgear also develop towards large capacity and high voltage. Currently, the largest capacity mobile substation has exceeded 3000kV.A, the primary side voltage is 6~12.5kV, and the secondary side voltage is 5kV, 4.16kv, 3.3kV, 2.3kV, 1.1kv. The large mobile power supply center in the United States is a high-voltage switch. Multi-coil transformer and low-voltage control switch are combined together, and the capacity is 1000~3000kvA France adopts 5kV voltage into the well, and the work surface equipment also uses 5kV power supply. The working surface is equipped with explosion-proof dry isolation transformer, and the primary voltage is 5000V500V. The secondary side no-load voltage is 5250V, and the transformer capacity is all above 1000kVA. Its function is to isolate the working surface 5kV power grid from the mine power supply system, effectively limiting the damage of its relative short-circuit current.
The mobile substation is equipped with a vacuum circuit breaker on one side, and a standard rotary arc type SF6 circuit breaker. The primary side is equipped with overcurrent, short circuit protection, ground protection and leakage monitoring devices and low pressure protection, and some also have a surge shunt resistor. To avoid surge voltage and switching transients; SF6 or vacuum circuit breakers are used on the secondary side, with complete over-current, short-circuit, phase failure, voltage loss, ground and leakage protection, low pressure protection, and troubleshooting Functions such as latching, latching, and pilot protection. Some also have phase sensitive short circuit protection and surge absorbers. Neutral points are usually grounded through reactors or resistors to limit the ground current flowing through the neutral point. Leakage monitoring and latching are provided. Device. In order to reduce work surface downtime, some mobile substations also have automatic reclosing devices. The electrical life of vacuum contactors for mining switches reaches 1 million times.
On the first and second side switch boxes, an observation window is set up to view the working status of the circuit breakers and other equipment and various protection operation conditions.
The cable cross-section connecting the load is generally less than 95mm, usually six or seven cores, for example, the 5kV soft cable for mining is a six-core wire, the power line section is 3x(6-95)mm2, and the diameter of each core conductor is 0.3mm. The copper wire is twisted, covered with PVC insulation, and then a 0.3mm tinned copper wire braid and a semiconductive rubber are used as constituents. The double-shielding structure is composed of a tinsel wire and an outer jacket. On the outside are several layers of tinned steel wire and synthetic fibers. Rubber and neoprene sheath. It can be used for semi-fixed cables, such as work surface conveyors, which are not often rolled, and reinforced by a steel wire armored braid inside the rubber sheath. Some national coal mine code standards stipulate that the cable feeding the mechanical equipment in the working face is generally a flexible rubber cable whose core wire is a flexible or tin-bismuth-copper wire, and EPR standard medium-size ethylene propylene rubber or neoprene used for insulation between core wires. Sulfonated polyethylene extrusion. Typical types of shields are: TAC with semiconducting layers, semi-conductive rubber, copper wire braids, and plain soft copper wire braids; flexible steel wire armor is also used to ensure the mechanical strength and flexibility of the cable. The liners and jackets are made of heavy duty polychloroprene PCP. This material is flame-retardant, soft, abrasion-resistant, impact-resistant, and permeable.
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