High-yield working surface power supply system and electrical equipment

With the development of high-yield, high-efficiency and intensive coal mines, coal mine electrical equipment is constantly being updated. This paper mainly describes the requirements of high-yield work in the face of power supply and electrical equipment, high-yield working surface power supply and electrical equipment.

High-yield working face; power supply system; electrical equipment With the development of high-yield, high-efficiency and intensive coal mines, coal mine electrical equipment is also constantly updated. Large-capacity, high-power, new high-efficiency and high-reliability automated electromechanical equipment, computer control, condition monitoring and other automation technologies and modern communication technologies are continuously applied to coal mines, which has accelerated the technological progress of electrical equipment on the working surface.

1 High-yield and high-efficiency work Facing the requirements of power supply and electrical equipment to improve coal mine production efficiency and efficiency, generally adopt high-power fully mechanized mining units, which can improve work surface yield and labor efficiency, improve the production capacity of shearer and transport capacity of transport equipment. . In order to meet the production capacity and suit high productivity and high efficiency, it is necessary to increase the cutting depth while increasing the coal cutting speed of the shearer. Increase the length of the work surface. In order to maintain continuous and stable production and high yield, and reduce the number of moving backs, this should extend the length of the advancement. This puts new requirements on the power supply and electrical equipment of the working face, requires the electrical equipment on the working surface to continuously increase the power capacity, improve the power supply voltage level, and has perfect, reliable and sensitive electrical protection and monitoring, control and information transmission functions.

From the early 1960s to the early 1970s, the world's major coal mining countries generally used 1100V to supply electrical equipment to the working surface. The installed capacity of the working surface is generally around 500kw. The power of fully mechanized mining equipment increased rapidly, and a double-motor shearer appeared. The power of the single machine was doubled. The power of the shearer increases, the capacity of the conveyor on the working surface also increases to more than 225kw, and the installed capacity of the working face is nearly 2000kw. At the same time, with the increase of the power of the mining and transportation equipment, the advancement speed of the working surface is accelerated, and the trend of the mining area is required to be increased. The length, China's own mining area to the long-term 6000m working face length of 350m high-yield high-efficiency working face into production, but also increase the power supply distance, which puts higher requirements on the power supply of the mining area. The original 1100V power supply system can not meet the requirements. The main reason is: after the working surface size is increased, the power supply distance is longer, and the motor power is increased, if the power is supplied with 1100V, the power of the conveyor motor on the working surface is more than 2x 300kW. If there is enough starting torque, it will be reduced by more than 40% in severe cases; if the power of the shearer increases, the control switch and cable and other equipment will exceed the reasonable current limit. If double cable or large section cable is used, the cable will be dragged. The difficulty of moving and bending, the cost, maintenance cost and loss are also relatively high; under the condition that the working face size increases, the equipment power and production capacity gradually increase, if the old system is used to increase capacity, it will not be worth the loss, uneconomical and unreasonable; With large-capacity transformers, high fault currents are prone to occur when cables are damaged. Therefore, the effective use of the 1100V voltage should be: the maximum power of the shearer single machine (multi-motor installed power is 485kw), the scraper conveyor motor power is 300kw. The equipment above the above power value should use a higher voltage. Power supply, the main advanced coal mining countries will increase the power supply voltage of the working surface to more than 2kV, the highest is 5kV. The analysis and calculation of 3.3kV shows that the power supply voltage of this level can meet the single-machine power of the working surface up to 750kw, multi-motor The installed power of the equipment is up to 1200kw and the transmission distance is 500~1000m. The 5kV power supply has twice the transmission capacity than the 3kV, and the working motor starting torque reduction rate is less than half of the 3kV.

2 High-yield working face power supply and electrical equipment 2.1 Working surface installed capacity and power supply voltage With the introduction of foreign advanced equipment, high-yield working faces appear in some domestic coal enterprises, which makes the installed power of fully mechanized mining equipment continuously increased, the largest coal mining machine The installed capacity has reached 1530kw, the maximum power of the drive motor is 610kw. The maximum installed power of the working plane conveyor is 1125kw, the driving motor power is 525kw, the maximum working surface conveyor power will reach 3x522=1566kw; the maximum installed power of the slot conveyor Up to 1350kW, the maximum power of the drive motor is 420kw; the maximum installed power of the emulsion pumping station is 3x 190kW; the maximum installed power of the transfer machine and the crusher is 200kw. Thus, the total installed power of the modern high-production working face is above 3000kw.

With the increase of the installed capacity of the working face, the high-yield and high-efficiency working face also requires an increase in the length of the working face and the extension of the length. The length of the "super" working face in China is 6000m, which requires increasing the transmission distance and improving the power supply of the working surface equipment. Voltage.

The power supply mode of the working face and the power supply mode of the high-yield working face of the main equipment, one is the conventional power supply mode, that is, two cable lines from the ground substation are supplied to the underground central substation, and then the cable is used by the central substation to be The mobile substation working in the trough is powered by the starter, load center, etc., respectively, to the shearer, scraper conveyor, transfer machine, crusher and belt conveyor; there is also a power supply method represented by the United States. The ground is substation, so the 6~12.5kV voltage goes down, and the incoming cable is sent directly to the mobile power supply center of the mining area. The power supply center is a large multi-circuit outgoing mobile substation device, and one working surface is equipped with an electromechanical device that can be divided into multiple different voltages.

With the increase of the installed capacity of the working face and the increase of the supply voltage, the mobile substation and the switching device are also developed to combine large capacity and high voltage. Now the maximum 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 the high voltage switch. The multi-coil transformer and the low-voltage control switch are combined. The capacity is 1000~3000kvA. France uses 5kV voltage to enter the well. The working surface equipment is also powered by 5kV. The working surface is equipped with an explosion-proof dry isolation transformer. The primary side voltage is 5000V500V. The secondary side no-load voltage is 5250V, and the transformer capacity is above 1000kVA. Its function is to isolate the working surface 5kV power grid from the mine power supply system, effectively limiting the harm of its relative short-circuit current.

The mobile substation is equipped with a vacuum circuit breaker on the primary side, and a standard spiral-arc SF6 circuit breaker with overcurrent, short circuit protection, grounding protection and leakage monitoring device and low air pressure protection on the primary side, and some surge shunt resistors. To avoid surge voltage and switching transients; SF6 or vacuum circuit breakers on the secondary side, with perfect overcurrent, short circuit, phase failure, voltage loss, ground and leakage protection, low air pressure protection and fault finding Functions such as latching and pilot protection, some with 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, and are provided with leakage monitoring and blocking. Device. In order to reduce the working face downtime, some mobile substations also have automatic reclosing devices. The vacuum contactor for mining switches has an electrical life of 1 million cycles.

On the first and second side switch boxes, set the observation window to check the working status of the circuit breakers and other protective devices.

The cable cross-section of the load is generally below 95mm, usually six or seven cores. For example, the 5kV soft cable for mining is a six-core cable, the power line section is 3x (6-95) mm2, and the core conductor is 0.3mm in diameter. The copper wire is twisted, wrapped with PVC insulation, and then 0.3mm tinned copper wire braid and semi-conductive rubber are used as the component of the fuse line and the jacket double shield structure. On the outside are several layers of tinned steel wire and rayon reinforced. Rubber and neoprene jacket. It can be used for semi-fixed cables that are not frequently rolled, such as work surface conveyors, and is also reinforced with a steel wire armored braid in the rubber sheath. Some national coal mine standards stipulate that the cables for feeding mechanical equipment on the working surface are generally flexible rubber cables, the core wires are flexible or bismuth-tin-copper wires, and the EPR standard medium-size ethylene propylene rubber or chloroprene is used for insulation between core wires. The sulfonated polyethylene is extruded. Typical shielding types are: TAC with semiconductor layer, semi-conductive rubber, copper wire nylon braid and ordinary soft copper wire braid; also with flexible steel wire armor to ensure the mechanical strength and flexibility of the cable. The liner and jacket are made of heavy duty polychloroprene PCP, which is flame retardant, soft, abrasion resistant, impact resistant and impervious.