Underground centralized reactive power compensation device

Abstract

The invention belongs to the technical field of mining power supply and distribution equipment, and particularly relates to an underground centralized reactive power compensation device which comprises an explosion-proof shell, and a three-phase cable connector is arranged on the explosion-proof shell. A vacuum alternating current contactor, a water-cooled reactor, a power unit, a buffer alternating current contactor, a buffer resistor, a control cabinet, a first current transformer and a power supply module for supplying power to the whole device are arranged in the explosion-proof shell, the whole reactive power compensation device is arranged underground, and each underground bus section is provided with one reactive power compensation device; according to the invention, centralized compensation is carried out on the underground reactive load generation source, so that the total load and the total current of an underground power supply system can be greatly reduced; through accurate reactive compensation, the device can improve the power factor of an underground power supply system and reduce voltage fluctuation and current harmonics, thereby improving the stability and reliability of the power supply system. The method is of great significance in guaranteeing safe production of mines.

Description

Technical Field

[0001] The invention belongs to the technical field of mine power supply and distribution equipment, and in particular relates to an underground centralized reactive power compensation device. Background Art

[0002] In the mine power supply system, the application of reactive compensation devices is of great significance for improving power supply efficiency and reducing energy consumption. However, there are many shortcomings in the current reactive compensation methods for mine power supply, especially in the underground power supply link. Traditional reactive compensation methods, such as centralized compensation on the ground high-voltage side, local low-voltage power supply compensation on the ground, and terminal compensation for underground remote power supply, are used to solve the low power factor on the mine power supply side and realize energy-saving operation of mine power supply transmission lines; local low-voltage power supply compensation on the ground is used for centralized power supply of high-power low-voltage equipment on the ground, reducing transformer capacity and operating current; terminal compensation for underground remote power supply mainly solves the startup problem caused by excessive voltage drop of long-distance power supply equipment. This reactive compensation method mainly focuses on compensation for transmission lines and specific equipment, while ignoring the problems of major reactive power sources such as underground mining and transportation equipment.

[0003] As the main power source for mine production, underground mining and transportation equipment generates a large amount of reactive power during operation, which not only leads to a low power factor for underground power supply, but also causes a series of problems such as excessive reactive power transmission loss and excessive selection of underground power transmission equipment. These problems not only increase the operating costs of the mine, but also limit the improvement of the mine's power supply capacity.

[0004] In addition, the existing underground main power supply mode mostly uses multiple, large-section power supply cables to meet power supply needs, especially in deep mines. This power supply method not only requires huge capital investment, but is also subject to multiple restrictions such as the shaft cross-sectional space and the maintenance space for power supply equipment. For old mines undergoing technical transformation, with the improvement of mining efficiency and the increase in the power supply load of underground equipment, the original power supply technical measures can no longer meet the needs. If the large-section power supply cables are replaced or new underground power supply cables are added in the original way, they will be severely restricted by the cross-sectional space of the shaft equipment, making it difficult to improve the power supply capacity. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides an underground centralized reactive power compensation device to solve the above-mentioned technical problems.

[0006] A concentrated reactive power compensation device underground comprises an explosion-proof housing, a three-phase cable connector is arranged on the explosion-proof housing, a vacuum AC contactor, a water-cooled reactor, a power unit, a buffer AC contactor, a buffer resistor, a control cabinet, a first current transformer and a power supply module for supplying power to the entire device are arranged inside the explosion-proof housing, and the entire reactive power compensation device is arranged underground, and a reactive power compensation device is arranged for each bus section underground; The first end of the three-phase cable connector is connected to the busbar to be compensated, the second end of the three-phase cable connector is connected to the first end of the main contact of the vacuum AC contactor and the first end of the main contact of the buffer AC contactor, the second end of the main contact of the vacuum AC contactor is connected to the first end of the power unit through a water-cooled reactor, the second end of the main contact of the buffer AC contactor is connected to the second end of the main contact of the vacuum AC contactor through a buffer resistor, and the second end of the power unit is star-connected; The current collection end of the control cabinet is connected to the external incoming switch cabinet, the first current transformer is installed on the connection line between the current collection end of the control cabinet and the external incoming switch cabinet, and the output end of the first current transformer is connected to the input end of the control cabinet; the voltage collection end of the control cabinet is connected to the secondary side of the voltage transformer on the bus to be compensated; the power unit, the vacuum AC contactor and the buffer AC contactor are all connected to the output end of the control cabinet; When in use, the control cabinet analyzes the reactive component of the line segment where the bus to be compensated is located based on the current parameters of the load side collected by the first current transformer and the voltage parameters of the bus to be compensated collected by the voltage collection terminal of the control cabinet, and controls the on and off of the power unit according to the analysis results to complete the adjustment of the reactive compensation capacity.

[0007] A further improvement of the technical solution is that the power module includes a high-voltage circuit breaker and a three-phase transformer, the first end of the high-voltage circuit breaker is connected to the second end of the three-phase cable connector, the second end of the high-voltage circuit breaker is connected to the first end of the three-phase transformer, and the second end of the three-phase transformer is connected to the electrical components to be powered in the device.

[0008] A further improvement of the technical solution is that it also includes a second current transformer, which is arranged on the star connection line at the second end of the power unit.

[0009] A further improvement of the technical solution is that the control cabinet is connected to the external main control terminal through a first RS485 communication line, and the control cabinet is connected to the reactive compensation devices corresponding to other bus sections underground through a second RS485 communication line.

[0010] A further improvement of the technical solution is that a water cooling pipe is provided on the inner plate of the explosion-proof housing, and both ends of the water cooling pipe are connected to an external liquid cooling unit.

[0011] A further improvement of the technical solution is that the water inlet and outlet of the water-cooled reactor are also connected to an external liquid cooling unit, and a water cooling pipe is arranged in parallel with the inner disk of the explosion-proof housing.

[0012] A further improvement of the technical solution is that temperature sensors are installed in the explosion-proof housing and on the water-cooled reactor, and the temperature sensors are connected to the input end of the control cabinet.

[0013] A further improvement of the technical solution also includes an electromagnetic starter, wherein the input end of the electromagnetic starter is connected to the output end of the control cabinet, and the output end of the electromagnetic starter is connected to an external liquid cooling unit. When the temperature data collected by the temperature sensor is higher than a preset temperature threshold, the control cabinet controls the start of the external liquid cooling unit.

[0014] A further improvement of the technical solution is that a liquid crystal control panel is arranged on the side panel of the explosion-proof housing, and the liquid crystal control panel is communicatively connected with the control cabinet.

[0015] The beneficial effects of the present invention are: Significantly reduce the total load and current of underground power supply: By centrally compensating the source of reactive load in the mine, this device can significantly reduce the total load and total current of the underground power supply system. This not only reduces the transmission loss of reactive power, but also improves the overall efficiency of the power supply system.

[0016] Reduce the need for cable loops in the mine: Due to the reduction of the total power supply current, this technical solution can significantly reduce the number of cable loops required for going down the mine. This is particularly important for deep mines, because the cross-sectional space of the shaft is limited, and reducing the number of cables means lower installation difficulty and less capital investment.

[0017] Improve the stability and reliability of the power supply system: Through accurate reactive power compensation, this device can improve the power factor of the underground power supply system, reduce voltage fluctuations and current harmonics, and thus improve the stability and reliability of the power supply system. This is of great significance for ensuring safe production in mines.

[0018] In addition, the invention has a reliable design principle, a simple structure and a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The schematic diagram of the circuit of the device is shown in Figure 2.

[0021] Figure 2 This is the connection schematic diagram of the control cabinet of the device.

[0022] Figure 3 This is a schematic diagram of the connection between the device and the external liquid cooling unit.

[0023] 100 is an explosion-proof casing, 110 is a three-phase cable connector, 120 is a vacuum AC contactor, 130 is a water-cooled reactor, 140 is a power unit, 151 is a buffer AC contactor, 152 is a buffer resistor, 160 is a control cabinet, 170 is a first current transformer, 181 is a high-voltage circuit breaker, 182 is a three-phase transformer, 190 is a second current transformer, 200 is an external incoming line switch cabinet, 300 is a voltage transformer on the bus to be compensated, and 400 is an external liquid cooling unit. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] The key terms appearing in the present invention are explained below.

[0027] RS485, also known as TIA-485-A, ANSI / TIA / EIA-485 or TIA / EIA-485, is a standard that defines the electrical characteristics of drivers and receivers in balanced digital multipoint systems. The standard is defined by the Telecommunications Industry Association and the Electronic Industries Alliance. Digital communication networks using this standard can effectively transmit signals over long distances and in environments with high electronic noise. RS-485 makes it possible to connect local networks and configure multi-branch communication links. RS485 has two types of wiring: two-wire and four-wire. The four-wire system can only achieve point-to-point communication and is rarely used now. The two-wire wiring method is mostly used. This wiring method is a bus topology structure, and up to 32 nodes can be connected on the same bus. In the RS485 communication network, the master-slave communication method is generally used, that is, one host with multiple slaves. In many cases, when connecting the RS-485 communication link, simply use a pair of twisted-pair cables to connect the "A" and "B" ends of each interface, while ignoring the connection of the signal ground. This connection method can work normally in many occasions, but it has buried great hidden dangers. Reason 1 is common-mode interference: The RS-485 interface uses a differential signal transmission method and does not need to detect the signal relative to a reference point. The system only needs to detect the potential difference between the two lines, but it is easy to ignore that the transceiver has a certain common-mode voltage range. The common-mode voltage range of the RS-485 transceiver is -7 to +12V. Only when the above conditions are met can the entire network work normally; when the common-mode voltage in the network line exceeds this range, it will affect the stability and reliability of communication, and even damage the interface; Reason 2 is the EMI problem: the common-mode part of the output signal of the sending driver requires a return path. If there is no low-resistance return channel (signal ground), it will return to the source end in the form of radiation, and the entire bus will radiate electromagnetic waves outward like a huge antenna.

[0028] PLC (Programmable Logic Controller) is used to store programs internally, execute user-oriented instructions such as logic operations, sequence control, timing, counting and arithmetic operations, and control various types of machinery or production processes through digital or analog input / output. PLC is essentially a computer dedicated to industrial control. Its hardware structure is basically the same as that of a microcomputer, and its basic components are: CPU, I / O board, display panel, memory, and power supply.

[0029] The purpose of the present invention is: since the main reactive load of the coal mine is generated by the terminal equipment of the mining face, the high-power motor of the raw coal transportation system, and the high-power hoist of the auxiliary transportation, such equipment is directly and centrally powered by the underground central substation or the mining area substation. The existing method is to install a mine flameproof low-voltage reactive compensation device on-site at the end of the equipment, which is often used to solve the problem of excessive voltage drop caused by excessive current of a single long-distance power supply equipment. However, the reactive power compensation capacity of the existing mine flameproof low-voltage reactive compensation device is limited, and the overall optimization effect on the underground power supply system is relatively small; therefore, the present invention installs an underground centralized reactive compensation device (a mine flameproof high-voltage SVG reactive compensation device) in the underground central substation or the mining area substation, which can change the blind increase of underground cables, and realize the reduction of reactive current at the source of reactive power generation, thereby reducing the power supply current from the underground central substation to the mining area substation, from the mine ground main substation to the underground central substation, or from the ground mine main substation to the underground mining area substation, and reducing the demand for large cross-section or quantity of underground cables.

[0030] like Figure 1 As shown, the present invention provides an underground centralized reactive power compensation device, which is installed in a central substation or a mining area substation. The underground centralized reactive power compensation device includes an explosion-proof housing 100, on which a three-phase cable connector 110 is arranged. The explosion-proof housing 100 is provided with a vacuum AC contactor 120, a water-cooled reactor 130, a power unit 140, a buffer AC contactor 151, a buffer resistor 152, a control cabinet 160, a first current transformer 170 and a power supply module for powering the entire device. The entire reactive power compensation device is arranged underground, and a reactive power compensation device is arranged for each bus section underground. Among them, each phase of the power unit 140 includes 10 IGBT power tubes connected in series, for example, A1 to A10 are connected in series on the A phase.

[0031] Specifically, the first end of the three-phase cable connector 110 is connected to the bus to be compensated, the second end of the three-phase cable connector 110 is connected to the first end of the main contact of the vacuum AC contactor 120 and the first end of the main contact of the buffer AC contactor 151, the second end of the main contact of the vacuum AC contactor 120 is connected to the first end of the power unit 140 through the water-cooled inductor 130, the second end of the main contact of the buffer AC contactor 151 is connected to the second end of the main contact of the vacuum AC contactor 120 through the buffer resistor 152, and the second end of the power unit 140 is star-connected.

[0032] Among them, the function of the buffer AC contactor is to pre-charge the built-in capacitor components in the power unit cabinet through the current limiting circuit of the matching buffer resistor when the underground centralized reactive compensation device is powered on for the first time. After the pre-charging is completed, the buffer contactor is cut off, the buffer resistor in the circuit is removed, and the main contactor is switched to normal power-on operation. No secondary switching is performed during normal operation.

[0033] like Figure 2 As shown, the current collection end of the control cabinet 160 is connected to the external incoming switch cabinet 200, the first current transformer 170 is installed on the connection line between the current collection end of the control cabinet 160 and the external incoming switch cabinet 200, and the output end of the first current transformer 170 is connected to the input end of the control cabinet 160; the voltage collection end of the control cabinet 160 is connected to the secondary side of the voltage transformer 300 on the bus to be compensated; the power unit 140, the vacuum AC contactor 120 and the buffer AC contactor 151 are all connected to the output end of the control cabinet 160; when in use, the control cabinet 160 analyzes the reactive component of the line segment where the bus to be compensated is located according to the current parameters of the load side collected by the first current transformer 170 and the voltage parameters of the bus to be compensated collected by the voltage collection end of the control cabinet 160, and controls the on and off of the IGBT in the power unit 140 according to the analysis results to complete the adjustment of the reactive compensation capacity. Among them, a PLC is set in the control cabinet 160, and the data calculation and control command issuance in the device are all realized by the PLC.

[0034] Among them, the power supply module includes a high-voltage circuit breaker 181 and a three-phase transformer 182, the first end of the high-voltage circuit breaker 181 is connected to the second end of the three-phase cable connector 110, the second end of the high-voltage circuit breaker 181 is connected to the first end of the three-phase transformer 182, and the second end of the three-phase transformer 182 is connected to the electrical components to be powered in the device.

[0035] In order to improve the safety of the device, a protection module and a second current transformer 190 are also provided in the device, and the second current transformer 190 is provided on the star connection line at the second end of the power unit 140. When the second current transformer 190 detects an abnormal current in the device, the control cabinet 160 controls the start-up of the protection module to perform fault protection on the device.

[0036] In addition, the control cabinet 160 is connected to the external master control terminal through the first RS485 communication line, and the control cabinet 160 is connected to the reactive power compensation device corresponding to other bus sections underground through the second RS485 communication line. The external master control terminal can realize data communication or command issuance with the control cabinet 160 through the first RS485 communication line, and the control cabinet 160 can control the underground centralized reactive power compensation device corresponding to the faulty bus to perform reactive power compensation operation through the second RS485 communication line when other bus sections fail.

[0037] In order to improve the service life of the device, a water cooling pipe is provided inside the explosion-proof housing 100, and both ends of the water cooling pipe are connected to the external liquid cooling unit 400. The water inlet and outlet of the water-cooled reactor 130 are also connected to the external liquid cooling unit 400, and are arranged in parallel with the water cooling pipe provided inside the explosion-proof housing 100. Correspondingly, temperature sensors are installed inside the explosion-proof housing 100 and on the water-cooled reactor 130, and the temperature sensors are connected to the input end of the control cabinet 160.

[0038] In order to achieve automatic control, the device also includes an electromagnetic starter, the input end of the electromagnetic starter is connected to the output end of the control cabinet 160, and the output end of the electromagnetic starter is connected to the external liquid cooling unit 400. When the temperature data collected by the temperature sensor is higher than the preset temperature threshold, the control cabinet 160 controls the start of the external liquid cooling unit 400.

[0039] In order to facilitate the staff to change the relevant parameters of each device in the device, a liquid crystal control panel is provided on the side panel of the explosion-proof housing 100 , and the liquid crystal control panel is communicatively connected with the control cabinet 160 .

[0040] For example, the power supply system of an existing mine needs to build a new +420m level central substation and a second level mining area substation. The original plan was to use the ground direct power supply mode for the mining area substation. The two downhole power cables were respectively powered by MYJV22-8.7 / 10kV-3×240 type 10kV different busbars from the ground 35kV substation. The power supply distance is about 2.3km. The second level mining area power supply and the +420m level central substation do not interfere with each other.

[0041] During the implementation process, two MYJV22-8.7 / 10kV-3×240 cables were installed at the +420m horizontal central substation, which were drawn from the 35kV substation on the ground mine. The mining area substation used two MYJV22-8.7 / 10kV-3×185 power cables installed during excavation, which were drawn from different busbar sides of the +420m horizontal central substation, which was inconsistent with the original design. After calculation and verification, the existing power supply mode of the second horizontal mining area substation resulted in the main power cables of the mining area substation and the +420m horizontal central substation being unable to guarantee safe operation requirements under single-circuit cable faults, and the underground power supply capacity was seriously insufficient. In order to meet the requirements of the regulations and take into account the on-site conditions of the completed construction, the power supply system of this mine must be optimized and adjusted. Taking into account the existing implementation situation, three power supply schemes are proposed for comparison and optimization, namely: Scheme 1: According to the original power supply process idea, continue to use the ground centralized reactive compensation method, do not consider the underground reactive compensation, according to the principle of increasing the underground power supply capacity, add the third busbar of the +420m horizontal central substation, improve the capacity of the second-level central substation, and meet the second-level power supply needs. Scheme 2: Continue to use the original design power supply process, adopt the ground centralized reactive compensation method, according to the principle of increasing the underground power supply capacity, do not consider the underground reactive compensation, restore the ground direct supply cable of the second-level mining area, and meet the second-level power supply needs. Scheme 3: According to the process of the present invention, adopt the underground nearby centralized reactive compensation method, install a mine-used explosion-proof high-voltage capacitor compensation device in the second-level mining area substation, improve the capacity of the existing underground power supply equipment, and use the existing equipment to meet the second-level power supply needs.

[0042] Specifically, Plan 1: Add a third busbar section to the +420m horizontal central substation.

[0043] (1) Adaptability modification of power cables and power supply equipment: This scheme increases the load of the +420m horizontal central substation due to the connection of the mining area substation load to the +420m horizontal central substation. The existing two MYJV22-8.7 / 10kV-3×240 power cables cannot meet the power supply demand. The design adds the third section of power distribution equipment to the substation and lays a new MYJV22-8.7 / 10kV-3×240 power cable from the 10kV side of the ground 35kV substation, forming a three-section busbar split operation power supply mode at the +420m horizontal central substation. The power supply of the second horizontal mining area substation must be changed from the laid MYJV22-8.7 / 10kV-3×185 cable to two MYJV22-8.7 / 10kV-3×240 cables drawn from the +420m horizontal central substation.

[0044] This method requires adding one set of power equipment in the third section of the +420m horizontal substation, a 3km single-loop +420m horizontal central substation 240mm power circuit, and a 1.4km 240mm power circuit from +420m to the second mining area substation, for a total of approximately 4.4km.

[0045] (2) Calculation of transmission loss: The transmission loss of the +420m horizontal central substation and the second horizontal mining area substation is: ①、+420m main substation power cable transmission loss: The substation uses a single busbar to supply power in three sections. In normal operation, the substation load is 8678kVA (see Appendix 1 for details), and the power factor is 0.75. According to the maximum load utilization time of 6000h, the maximum load loss time is about 4750h.

[0046] According to calculation, the current carrying capacity of each power cable is 167A. The substation power cable uses 3 MYJV22-8.7 / 10kV-3×240 cables, the line resistance is 0.091Ω / km, and the power supply distance is 3km. The annual power loss of each power cable is: W=3I2Rτ×10-3=3×1672×0.091×3×4750×10-3=108495kW·h; The annual power loss of the three-circuit cable line is 3×W≈325486kW·h.

[0047] ②. Transmission loss of power cable in the second horizontal mining area substation: The substation uses a single busbar to supply power in two sections. In normal operation, the substation load is 7790kVA (see Appendix 1 for details) and the power factor is 0.74. According to the table, the maximum load utilization time is 6000h, and the maximum load loss time is about 4750h.

[0048] According to calculation, the current carrying capacity of each power cable is 225A. The substation power cable uses 2 MYJV22-8.7 / 10kV-3×240 cables, the line resistance is 0.091Ω / km, and the power supply distance is 0.7km. The annual power loss of each power cable is: W=3I2Rτ×10-3=3×2252×0.091×0.7×4750×10-3=45954kW·h; The annual power loss of the two cable lines is Wtotal = 2×W≈91907kW·h.

[0049] ③. Conclusion: The total annual power cable transmission loss of the two substations is 417,393 kW·h. Based on the average electricity price of 1.9 yuan / kW·h in the mining area, the annual energy loss of the two substations is about 793,000 yuan.

[0050] Option 2: The power supply of the second horizontal mining area substation is directly supplied by the ground 35kV substation.

[0051] (1) Adaptability modification of power cables and power supply equipment: This plan abolishes the existing two MYJV22-8.7 / 10kV-3×185 power cables in the mining area substation, and lays two new MYJV22-8.7 / 10kV-3×240 power cables with a length of 4.6 km. These cables are directly drawn from the 10kV side of the ground 35kV substation and directly supplied from the ground. They do not interfere with the power supply system of the +420m horizontal central substation, and the existing power supply equipment of the +420m horizontal central substation does not need to be modified.

[0052] (2) Calculation of transmission loss: The power line loss of the +420m horizontal central substation and the second horizontal mining area substation is: ①、+420m main substation power cable transmission loss: The substation uses a single busbar to supply power in two sections. In normal operation, the substation load is 1277kVA (see Appendix 2 for details) and the power factor is 0.8. According to the table, the maximum load utilization time is 6000h, and the maximum load loss time is about 4500h.

[0053] According to calculation, the current carrying capacity of the power cable of section 1# is 58A, and the current carrying capacity of the power cable of section 2# is 16A. The power cable of the substation uses 2 MYJV22-8.7 / 10kV-3×240 cables, the line resistance is 0.091Ω / km, and the power supply distance is 3km. The annual power loss of each power cable is: W1=3I2Rτ×10-3=3×582×0.091×3×4500×10-3=12398kW·h; W2=3I2Rτ×10-3=3×162×0.091×3×4500×10-3=943kW·h; The annual power loss of the two cable lines is Wtotal≈13341kW·h.

[0054] ②. Transmission loss of power cable in the second horizontal mining area substation: The substation uses a single busbar to supply power in two sections. In normal operation, the substation load is 7790kVA (see Appendix 2 for details) and the power factor is 0.74. According to the table, the maximum load utilization time is 6000h, and the maximum load loss time is about 4750h.

[0055] According to calculation, the current carrying capacity of each power cable is 225A. The substation power cable uses 2 MYJV22-8.7 / 10kV-3×240 cables, the line resistance is 0.091Ω / km, and the power supply distance is 2.3km. The annual power loss of each power cable is: W=3I2Rτ×10-3=3×2252×0.091×2.3×4750×10-3=150990kW·h; The annual power loss of the two cable lines is Wtotal = 2×W≈301981kW·h.

[0056] ③. Conclusion: The total annual power cable transmission loss of the two substations is 315,322 kW·h. Calculated based on the average electricity price of 1.9 yuan / kW·h in the mining area, the annual power loss is approximately 599,000 yuan.

[0057] Option three: Add reactive power compensation equipment to the substation in the second horizontal mining area.

[0058] (1) Adaptability modification of power cables and power supply equipment: Based on the power supply system structure currently under construction in the mining area, this plan adds two sets of mine-use flameproof high-voltage reactive compensation devices (with water cooling devices) in the substation of the second horizontal mining area. After the reactive compensation device is installed, the calculated power factor of the substation of the second horizontal mining area is increased from 0.74 to 0.99, and the apparent power is 5798kVA (see Appendix 3 for details), and the calculated power factor of the +420m horizontal central substation is increased from 0.75 to 0.99, and the apparent power is 6602kVA. In the event of a power outage at the two substations, the current carrying capacity of the power cables is 334.8A and 381.2A respectively. The two-circuit MYJV22-8.7 / 10kV-3×185 cable of the second horizontal mining area substation and the two-circuit MYJV22-8.7 / 10kV-3×240 cable of the +420m horizontal substation under construction can meet the power supply demand. This power supply scheme makes full use of existing power supply and distribution equipment, reduces the use of cables, reduces capital construction investment, improves power factor, and suppresses harmonics generated by underground equipment, thus achieving energy-saving operation of the underground power supply system.

[0059] (2) Calculation of transmission loss: Under this method, the power line loss of the +420m horizontal central substation and the second horizontal mining area substation is: ①、+420m main substation power cable transmission loss: The substation uses a single busbar to supply power in two sections. In normal operation, the substation load is 6602kVA (see Appendix 3 for details), and the power factor is 0.99. According to the maximum load utilization time of 6000h, the maximum load loss time is about 4000h.

[0060] According to calculation, the current carrying capacity of each power cable is 190A. The substation power cable uses 2 MYJV22-8.7 / 10kV-3×240 cables, the line resistance is 0.091Ω / km, and the power supply distance is 3km. The annual power loss of each power cable is: W=3I2Rτ×10-3=3×1902×0.091×3×4000×10-3=118264kW·h; The annual power loss of the two cables is Wtotal = 2×W≈236527kW·h.

[0061] ②. Transmission loss of power cable in the second horizontal mining area substation: The substation uses a single busbar to supply power in two sections. In normal operation, the substation load is 5798kVA (see Appendix 3 for details) and the power factor is 0.99. According to the table, the maximum load utilization time is 6000h, and the maximum load loss time is about 4000h.

[0062] According to calculation, the current carrying capacity of each power cable is 167A. The substation power cable uses 2 MYJV22-8.7 / 10kV-3×185 cables, the line resistance is 0.118Ω / km, and the power supply distance is 0.7km. The annual power loss of each power cable is: W=3I2Rτ×10-3=3×1672×0.118×0.7×4000×10-3=27644kW·h; The annual power loss of the two cable lines is Wtotal = 2×W≈55287kW·h.

[0063] ③. Conclusion: The total annual power cable transmission loss of the two substations is 291,814 kW·h. Based on the average electricity price of 1.9 yuan / kW·h in the Shanghai Temple mining area in Inner Mongolia, the annual electricity loss is about 554,000 yuan.

[0064] Appendix 1: Load statistics of Scheme 1 (addition of the third busbar section in the +420m horizontal main substation):

[0065]

[0066]

[0067] Appendix 2: Load statistics of Scheme 2 (the power supply of the substation in the second horizontal mining area is directly supplied by the ground 35kV substation)

[0068]

[0069]

[0070] Appendix 3: Load statistics of Scheme 3 (additional reactive power compensation device in the substation of the second horizontal mining area)

[0071]

[0072]

[0073]

[0074] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. An underground centralized reactive power compensation device, characterized in that: It includes an explosion-proof housing, on which a three-phase cable connector is arranged, and inside the explosion-proof housing are arranged a vacuum AC contactor, a water-cooled reactor, a power unit, a buffer AC contactor, a buffer resistor, a control cabinet, a first current transformer, and a power module for supplying power to the entire device, and the entire reactive power compensation device is arranged underground, and a reactive power compensation device is arranged for each busbar section underground; The first end of the three-phase cable connector is connected to the busbar to be compensated, the second end of the three-phase cable connector is connected to the first end of the main contact of the vacuum AC contactor and the first end of the main contact of the buffer AC contactor, the second end of the main contact of the vacuum AC contactor is connected to the first end of the power unit through a water-cooled reactor, the second end of the main contact of the buffer AC contactor is connected to the second end of the main contact of the vacuum AC contactor through a buffer resistor, and the second end of the power unit is star-connected; The current collection end of the control cabinet is connected to the external incoming switch cabinet, the first current transformer is installed on the connection line between the current collection end of the control cabinet and the external incoming switch cabinet, and the output end of the first current transformer is connected to the input end of the control cabinet; the voltage collection end of the control cabinet is connected to the secondary side of the voltage transformer on the bus to be compensated; the power unit, the vacuum AC contactor and the buffer AC contactor are all connected to the output end of the control cabinet; When in use, the control cabinet analyzes the reactive component of the line segment where the bus to be compensated is located based on the current parameters of the load side collected by the first current transformer and the voltage parameters of the bus to be compensated collected by the voltage collection terminal of the control cabinet, and controls the on and off of the power unit according to the analysis results to complete the adjustment of the reactive compensation capacity.

2. The underground centralized reactive power compensation device according to claim 1, characterized in that: The power module includes a high-voltage circuit breaker and a three-phase transformer, wherein the first end of the high-voltage circuit breaker is connected to the second end of the three-phase cable connector, the second end of the high-voltage circuit breaker is connected to the first end of the three-phase transformer, and the second end of the three-phase transformer is connected to the electrical components to be powered in the device.

3. The underground centralized reactive power compensation device according to claim 1, characterized in that: It also includes a second current transformer, which is arranged on the star connection line at the second end of the power unit.

4. The underground centralized reactive power compensation device according to claim 1, characterized in that: The control cabinet is connected to the external main control terminal through the first RS485 communication line, and the control cabinet is connected to the reactive power compensation devices correspondingly set up in other bus sections underground through the second RS485 communication line.

5. The underground centralized reactive power compensation device according to claim 1, characterized in that: The inner disk of the explosion-proof housing is provided with a water cooling pipe, and both ends of the water cooling pipe are connected to an external liquid cooling unit.

6. The underground centralized reactive power compensation device according to claim 5, characterized in that: The water inlet and outlet of the water-cooled reactor are also connected to the external liquid cooling unit, and are arranged in parallel with the water cooling pipes provided on the inner disk of the explosion-proof housing.

7. The underground centralized reactive power compensation device according to claim 6, characterized in that: Temperature sensors are installed in the explosion-proof housing and on the water-cooled reactor, and the temperature sensors are connected to the input end of the control cabinet.

8. The underground centralized reactive power compensation device according to claim 7, characterized in that: It also includes an electromagnetic starter, the input end of the electromagnetic starter is connected to the output end of the control cabinet, and the output end of the electromagnetic starter is connected to an external liquid cooling unit. When the temperature data collected by the temperature sensor is higher than a preset temperature threshold, the control cabinet controls the start of the external liquid cooling unit.

9. The underground centralized reactive power compensation device according to claim 1, characterized in that: A liquid crystal control panel is arranged on the side panel of the explosion-proof housing, and the liquid crystal control panel is communicatively connected with the control cabinet.

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