2020 Vol. 46, No. 6

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Research on method of coal mine gas and coal dust explosion perception alarm and explosion source judgment
SUN Jiping
2020, 46(6): 1-5. doi: 10.13272/j.issn.1671-251x.17617
<Abstract>(82) <HTML> (14) <PDF>(15)
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Characteristics of coal mine gas and coal dust explosion are analyzed: Concentration of O2 in air decreases rapidly, while concentrations of CO2, CO and other toxic and harmful gases increase rapidly; Ambient temperature rises rapidly, and air pressure increases rapidly and then falls; Stronger infrared and ultraviolet radiation are generated; High-temperature, high-pressure, high-speed explosion shock wave and flame front are generated; Explosion sound and vibration are generated; A large amount of smoke and dust are generated; Wind speed increases rapidly and then falls, and wind flow reverses; Roadway collapses, electromechanical equipment is moved and damaged; A large number of casualties are caused. A coal mine gas and coal dust explosion perception alarm and explosion source judgment method based on multi-information fusion of gas (O2, CO2, CO)concentration, temperature, sound, vibration, air pressure, wind speed, wind direction, smoke, dust, infrared, ultraviolet and image is proposed: Gas and coal dust explosion can be identified through change of multi-parameters; Explosion source can be determined according to change range, change sequence of the parameters and sensor damage at different positions. Protection and setting methods of sensor are proposed: Sensor should be equipped with a streamlined or arc-shaped shell, and the sensor shell should use high-temperature resistant, fireproof and heat-insulating material; Sensor should be installed in center of roadway top; Sensor should be installed on mining face and heading face, and the sensor should be located 10-15 m away from the working face; Sensor should be installed in the middle of each roadway(without branches).Protection and setting methods of cable and optical cable are proposed: Armored cable and optical cable should be adopted, and the cable and optical cable should have properties of flame retardant, high-temperature resistance and impact resistance; Cable and optical cable should be buried at the angle between roadway side wall and floor; Cable and optical cable can also be protected by introducing into compressed air duct.
Design of hydraulic coal unloading device of belt conveyor in underground coal mine
DAI Shuangcheng, WANG Mudou, LI Zhengjia, REN Xiaopeng, XING Xudong
2020, 46(6): 6-11. doi: 10.13272/j.issn.1671-251x.2019120038
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Taking the 6-2116 fully mechanized coal mining face of No.2 shaft of Nalinmiao Coal Mine as the engineering background, in view of problems of large coal consumption and difficult coal transport in abandoned roadway backfilling on coal pillar recovery working faces, a hydraulic coal unloading device of belt conveyor in underground coal mine was designed. The device is composed of support device, redirection device and hydraulic system. It is installed at intersection of main transportation roadway and auxiliary retracement channel. Using hydraulic pump station as power, the coal is unloaded from the belt conveyor by the support device and the redirection device cooperatively,and then the coal is transported to the abandoned roadway. Through the coal unloading device, the raw coal does not need to be lifted into ground and then transported to underground by trackless rubber truck, which improves economic benefit and filling efficiency, and reduces safety risk. Field industrial test results show that when the shearing speed of shearer is 0.8 m/min, the speed of scraper conveyor is 0.4 m/s, the speed level of transfer machine is low, the speed of belt conveyor is 1.0 m/s, and the extension length of support cylinder and redirecting cylinder is 0.7 m, the coal unloading device can realize continuous coal unloading, which meets needs of coal backfilling for the test working face and ensures normal advancement of the coal pillar recovery working face.
Design of mine-used multifunctional thermal resistance type isolation safety barrier
ZHANG Yuxiang, SONG Jiancheng, TIAN Muqin
2020, 46(6): 12-16. doi: 10.13272/j.issn.1671-251x.2019090018
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Abstract:
In view of problems of poor anti-interference performance, low integration and single function of common thermal resistance type isolation safety barriers, a mine multifunctional thermal resistance type isolation safety barrier was designed. The safety barrier uses DC/DC isolated power supply module with two mutually isolated outputs to supply power to safety side and dangerous side circuits respectively, and realizes three-terminal isolation of power supply side, dangerous side and safety side combining with signal optocoupler isolation.It has functions of quadratic nonlinear error correction for thermal resistance, thermal resistance sensor disconnection fault alarm, high temperature alarm with hysteresis, voltage and current signal output conversion and so on. The prototype test results show that: two thermal resistances can work at the same time, and the threshold comparison circuit operates steadily; with the input temperature increases, the output current basically increases linearly, the linearity is as high as 0.15%, and the corresponding analog output transmission processing error is less than 0.5% , which meets requirements of relevant regulations; it effectively suppresses the interference of spikes and various noise, and has good anti-interference performance; the maximum relative error is only 0.667%, which is lower than the similar type of XX6071 safety barrier. The actual application results verify that the temperature measurement results of the safety barrier are accurate and the high temperature alarm action is stable, which meets the actual application needs of mine electrical equipment.
Design of intelligent detection system of gas environment in roadway of coal mine inspection robot
NIE Zhen, MA Hongwei
2020, 46(6): 17-22. doi: 10.13272/j.issn.1671-251x.17598
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Abstract:
At present, most underground gas inspection robots use lifting mechanism or fixed probe to sense gas environment, which influences robot's driving flexibility, and due to the limitation of robot body mechanism, most inspection robots can only detect local gas environment information within sensors installation range, and lack of gas concentration detection in any cross-sectional space of the roadway. In view of the above problems, an intelligent detection system of gas environment in roadway of coal mine inspection robot based on gas diffusion model was designed. The system is based on theory of gas diffusion, combined with gas environment characteristics of coal mine roadways, and introduces influence of wall rock, wind speed and gas diffusion coefficient on gas diffusion model, and establishes a gas diffusion optimization model in roadway by using virtual image source method and BP neural network intelligent algorithm optimized by genetic algorithm. The environmental information such as gas concentration at any point of the inspection robot in the moving process is obtained by the sensor detection system, and the gas diffusion optimization model is substituted to solve the optimal gas diffusion coefficient. The gas concentration distribution at the corresponding point can be calculated and solved by inputting the coordinate position of a certain point in the roadway. With movement of the robot, the gas concentration distribution data on different coal mine roadway sections under its displacement path can be obtained. The experimental results show that the system can calculate gas concentration at any point on any cross-section of the roadway that meets the detection error requirements, and achieve dynamic real-time detection; it overcomes limitations of traditional coal mine roadway gas detection methods. Using inspection robots to replace the manual inspection of coal mine gas can provide a new idea and method for intelligent detection of gas in coal mines.
Research on motion planning method of underground mobile robot
YANG Lin, MA Hongwei, WANG Yan, WANG Chuanwei
2020, 46(6): 23-30. doi: 10.13272/j.issn.1671-251x.17613
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In view of problems of overshoot, collision, discontinuity and unsmoothness in the trajectory generated by motion planning of existing underground mobile robot, a motion planning method of underground mobile robot was proposed, which consists of path planning, trajectory generation and trajectory optimization. Path planning is realized by A* algorithm based on graph search, and a passable global path is quickly planned as initial value of path generation through three steps of cycle iteration, namely start search, path sorting and continue search. Trajectory generation is realized by constructing objective function based on Minimum Snap and applying equality constraint.Trajectory optimization is achieved by applying inequality constraints on the basis of trajectory generation: by adjusting time allocation and building inequality constraints on Corridor trajectory planning, the overshoot phenomenon that occurs during solution process for Minimum Snap trajectory generation is resolved and the entire trajectory itself is constrained to avoid collisions; by introducing the harmonic function Bezier Curve, the trajectory optimization problem of the Minimum Snap based on Bezier Curve is constructed, which makes the solution of the high-order objective function simple and efficient, and finally generates a motion trajectory which is suitable for the underground mobile robot with minimum energy loss, continuous, smooth, collision free and executable.In the Matlab simulation environment, the random map is designed, and the optimal trajectory planning results including time allocation, location planning, speed planning and acceleration planning are generated.The experimental results verify the correctness and effectiveness of the motion planning method.
Environmental information data compression algorithm for coal mine four-rotor flying robot
LIANG Yan, MA Hongwei, CUI Yazhong, XUE Xusheng, NIE Zhen, ZHANG Li
2020, 46(6): 31-34. doi: 10.13272/j.issn.1671-251x.2019100047
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In view of problem that flight path and trajectory of four-rotor flying robot in coal mine roadway are changeable, which leads to great redundancy of environment information data collected by the robot in dynamic space, an environmental information data compression algorithm for coal mine four-rotor flying robot is proposed. The default threshold noise reduction method of wavelet analysis is used to reduce the noise of original data to improve signal-to-noise ratio; taking methane monitoring as an example to introduce data compression algorithm, the roadway space is split into several sections along the roadway direction, and the effective value of methane concentration of each split section is selected and used to reconstruct the detection data of methane concentration. The experimental results show that the methane concentration signal compressed and reconstructed by the algorithm has little error with the manual detection result, the data compression algorithm can extract the effective value of methane concentration data and remove the redundant environmental information collected by the robot, thereby improving the effectiveness and real-time performance of data transmission.
Research status and development trend of intelligent monitoring and early warning technology in coal mine
ZHENG Xuezhao, TONG Xin, GUO Jun, ZHANG Duo
2020, 46(6): 35-40. doi: 10.13272/j.issn.1671-251x.17530
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The research status of intelligent monitoring and early warning technology in coal mine in China was summarized from the aspects of Internet of things, big data, cloud computing and artificial intelligence.According to practical application of intelligent monitoring technology in coal mine, the problems of intelligent monitoring and early warning in coal mine was points out, including poor reliability of precursory information collection of underground coal mine monitoring equipment, insufficient depth of cloud platform integrated application and fusion, weak database security, and immature application of artificial intelligence technology in coal mine monitoring.The development trend of intelligent monitoring and early warning technology in coal mine was prospected: the application of graphene/graphene oxide optical fiber sensors in intelligent monitoring system of coal mine can realize multi-source information perception and improve the reliability of precursory information collection; studying multi-technology deep cross fusion to explore deep value of monitoring data; constructing coal mine monitoring database based on block chain technology, ensuring that the database cannot be tampered and has good read and write performance; developing intelligent safety monitoring and warning system with adaptive and deep learning, realizing mine automatic monitoring and intelligent early warning.
Research on intelligent evaluation method of health state of shearer
CAO Xiangang, LI Yanchuan, LEI Zhuo, LEI Yinan
2020, 46(6): 41-47. doi: 10.13272/j.issn.1671-251x.17596
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In view of problems of existing health state evaluation methods for shearer, such as low assessment accuracy due to the great influence of human factors on determination of evaluation index weight, weak local search ability and poor anti-interference ability and insufficient ability to find the global optimal value of the single evaluation algorithm, an intelligent evaluation method of health state of shearer based on principal component analysis(PCA) and BP neural network optimized by genetic algorithm（GA）algorithm (PCA-GA-BP algorithm) was proposed. Firstly，according to structure and working principle of shearer, the state monitoring points of the shearer are selected to obtain various state parameters of the shearer's health state. PCA is used to reduce data dimensions and extract the data characteristics of the shearer's state parameters to avoid complication of BP neural network input. Then，GA is introduced to find the global optimal weight for the traditional BP neural network. Finally, an intelligent evaluation model of shearer's health state based on GA-BP is established by training parameters, and the state parameters of the shearer are automatically input into the evaluation model. The test results is output through intelligent evaluation algorithm, self-learning, self-optimization and self-judgment of shearer's health state are realized. The experimental results show that the intelligent evaluation method of health state of shearer based on PCA-GA-BP algorithm can accurately, rapidly and intelligently evaluate the health state of shearer. Compared with evaluation method based on single BP algorithm, it has shorter training time, simpler evaluation process and higher evaluation accuracy, up to 97.08%.
Research on intelligent monitoring system of mine-used belt conveyor
MAO Qinghua, MAO Jingen, MA Hongwei, ZHANG Xuhui, LI Zheng
2020, 46(6): 48-52. doi: 10.13272/j.issn.1671-251x.17595
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In view of the friction and heating between conveyor belt and key components such as idlers and rollers, the internal damage and tear of steel conveyor belt, and high running power consumption in operation process of mine-used belt conveyor, an intelligent monitoring system of mine-used belt conveyor was designed. The system includes damage monitoring system of steel conveyor belt based on weak magnetic detection method, fault diagnosis and early warning system of key components of belt conveyor based on infrared thermal imaging temperature detection method, and coal flow monitoring, foreign matter monitoring, belt tear monitoring and personnel safety monitoring system based on visual detection method, and implementation principle of each system is introduced in detail. The internal damage identification of steel conveyor belt and fault diagnosis and early warning of key components of belt conveyor are verified by experiments. The results show that the system can accurately identify damage of steel conveyor belt with an accuracy of about 98%, and can accurately identify faults of key components of belt conveyor and give early warning.
Analysis method of mine ventilation difficulty degree based on ventilation equivalent area
WANG Yanping, FAN Jingdao, YAN Zhenguo, LI Chuan, CHANG Xintan, LI Xuewen
2020, 46(6): 53-58. doi: 10.13272/j.issn.1671-251x.17597
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In view of problems that equivalent orifice commonly used in current mine ventilation difficulty degree evaluation cannot effectively reflect details of ventilation difficulty degree, and ventilation resistance measurement cannot well measure effect of complex ventilation system in parallel, an refinement analysis method of mine ventilation difficulty degree based on ventilation equivalent area is proposed. According to obtained roadway ventilation information, the ventilation system network is solved to obtain wind pressure of each node in the system, and the ventilation system is segmented according to the wind pressure of each node. The roadways in each section are in parallel. According to characteristics of equivalent orifice, the equivalent orifice of each section are first calculated to obtain the equivalent area of each section comprehensively, so as to obtain corresponding ventilation equivalent area of each node. In order to visually and clearly express difficulty degree of ventilation in each section of the ventilation system, the ventilation equivalent area is represented graphically, including the wind pressure-equivalent area diagram, node-equivalent area diagram, wind pressure-equivalent energy consumption diagram and node-equivalent energy consumption diagram. According to the ventilation equivalent area diagrams, the mine ventilation difficulty degree is analyzed in detail including wind bottleneck, resistance distribution and ventilation energy consumption. The results of example validation show that the method can effectively distinguish resistance area and local resistance position and ventilation bottleneck location in the ventilation system, and it can be used for analysis and optimization of mine ventilation.
Intelligent leakage protection method of mine power grid based on equivalent conductance
WANG Qingliang, YANG Bo, GAO Mei, LIU Xinru, LI Lei, HAO Zhaoming
2020, 46(6): 59-64. doi: 10.13272/j.issn.1671-251x.17594
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The phenomenon of harmonic wave and arc light in mine power grid is increasingly serious, and leakage fault signal distortion and probability of arc light leakage increases, resulting in serious fault signal distortion and less fundamental wave component. However, the existing leakage protection methods of mine power grid adopt zero-sequence fundamental wave component as fault characteristic parameter, which has a low identification rate for arc light leakage. In view of the above problems, an intelligent leakage protection method of mine power grid based on equivalent conductance was proposed. On the basis of analyzing characteristics of leakage fault, the zero-sequence current is decomposed orthogonally with distorted zero-sequence voltage as reference according to non-sinusoidal power theory. The distortion equivalent conductance is adopted as fault characteristic parameter, and the leakage circuit is identified by comparing symbols and value of equivalent conductance of each feeder: the circuit with the maximum equivalent conductance and negative sign is judged to be leakage branch, and alarm and tripping command are issued; the equivalent conductance with a positive symbol represents current insulation level of corresponding non-leakage feeders to realize automatic monitoring of cable insulation state. The orthogonal reactive current is adopted to reflect capacitive current level of the grid, which provides data support for mine power supply safety analysis and fault warning. Simulation results show that the method can realize leakage fault identification, leakage branch location and automatic monitoring of cable insulation state, and meets requirements of selectivity, rapidity and sensitivity, especially suitable for arc leakage fault identification, which can effectively improve safety of the mine power supply.
Research on dynamic movement law of hydrogen sulfide on fully mechanized caving face of coal mine
JIN Yongfei, XU Yaqi, LIU Yin, ZHANG Dian, GUO Jun
2020, 46(6): 65-71. doi: 10.13272/j.issn.1671-251x.2019100051
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In view of problems such as difficulty in verifying reliability of research results, the single method is often used to study distribution law of hydrogen sulfide (H2S) concentration in fully mechanized caving face of coal mine, taking a coal mine working face in Shaanxi as research background, H2S concentration distribution and dynamic movement law of the working face is studied using Fluent software to build a numerical simulation model.Measurement points are arranged on the working face, and H2S concentration in the working face is measured on site with a CD4 gas detector. Both numerical simulation and field measurement results show that in the vertical direction, as the height from the floor increases, the H2S concentration first increases and then decreases; in the horizontal direction, as the distance from the coal wall of the working face increases, the H2S concentration gradually decreases; in the wind flow direction, as the distance from the shearer increases, the H2S concentration gradually decreases. The numerical simulation results are consistent with the field monitoring results, verifying feasibility of the numerical simulation method and providing reference for the field H2S movement law research.
Prediction of gas emission rate on fully-mechanized caving face with layered mining of thick coal seam
WANG Xiaopeng
2020, 46(6): 72-75. doi: 10.13272/j.issn.1671-251x.2019090079
<Abstract>(86) <HTML> (12) <PDF>(9)
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Due to the difference between fully-mechanized caving face and single stoping process face, there would be a big error in predicting gas emission rate on fully mechanized caving face by use of AQ 1018-2006 The Predicted Method of Mine Gas Emission Rate. Meanwhile, there is a lack of research on prediction of gas emission rate on fully-mechanized caving face with layered mining of thick coal seam at present, which results in weak technology base for gas control. For the above problems, a prediction method of gas emission rate on fully-mechanized caving face with layered mining of thick coal seam was proposed. By analyzing gas emission characteristics of the fully-mechanized caving face, gas emission sources were determined including gas from coal cutting, coal caving, goaf and adjacent layers. Corresponding calculation formulas of gas emission rate were obtained according to different gas emission sources, so as to get a calculation formula of gas emission rate on fully-mechanized coal-caving face with layered mining of thick coal seam. The method has been used to predict gas emission rate on fully-mechanized caving faces of Wudong Coal Mine and Jia'gou Coal Mine separately, and the results show that the error between the predicted result and the measured value is less than 5% to meet actual production needs.
Application of bedding directional long borehole in thick coal-seam along top excavating face
SHI Yongtao
2020, 46(6): 76-80. doi: 10.13272/j.issn.1671-251x.2019110071
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Due to large thickness of coal seam along top excavating face, normal borehole cannot effectively extract coal gas from roadway floor, which is easy to cause gas exceeding limit on the excavating face and affect efficiency of roadway excavating. Taking main transport roadway of a coal mine in Shanxi Province as an tested roadway，application of bedding directional long borehole in thick coal-seam along top excavating face was researched from three aspects of parameters design of extraction technology, borehole construction and extraction test by analyzing problems existed in gas control on excavating face. The field test results show that after adopting extraction technology of bedding directional long borehole, gas concentration in return air flow and excavating face of the main transport roadway is stable on the whole during roadway excavating. The average gas volume fraction of the return air flow is 0.34% and the one of the excavating face is 0.16%. Gas emission decreases obviously, which shows definite gas control effect. Compared with extraction technology of normal borehole, roadway excavating is accelerated from 150 m per month to 240 m per month, gas volume fraction of the excavating face is decreased from 0.53%-0.79% to 0.25%-0.48%, gas volume fraction of the return air flow is decreased from 0.63%-0.96% to 0.28%-0.69%, and the total time consumption of excavating 400 m roadway is reduced from 175 d to 138 d, which show that excavating efficiency is improved effectively.
Fault detection method for belt conveyor roller
CAO Guanqiang
2020, 46(6): 81-86. doi: 10.13272/j.issn.1671-251x.2018100035
<Abstract>(153) <HTML> (19) <PDF>(21)
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In view of problems that existing fault detection methods for belt conveyor roller use contact measurement, are not easy to install and operate, and are not suitable for underground large-scale fault detection, a roller fault detection method based on wavelet denoising and BP-RBF neural network is proposed. Audio signal during the operation of the roller is collected and denoised by a compromise method which combines soft threshold method and hard threshold method; energy sum of the wavelet decomposition signal of each layer is used as feature value of the layer, and low-frequency feature values are converted by processing coefficients to reduce their proportion in the total energy and make the fault feature more obvious;the extracted feature vectors are input into BP-RBF neural network model for fault detection. The test results show that fault recognition rate of the method reaches 96.7% for three cases of normal roller signal, crack failure on the roller surface, and wear failure on the roller surface. Compared with the traditional spectrum analysis and diagnosis technology, the proposed method requires less workload and has higher accuracy; compared with fault detection technologies based on temperature detection and other technologies, the proposed method uses a non-contact installation method, which is more convenient to install and has larger detection range and good application prospect.
Research on time-frequency characteristics of acoustic-electric signals in process of rock failure under load
LIU Yang, QIU Liming, LOU Quan, WEI Menghan, YIN Shan, LI Pengpeng, CHENG Xiaohe
2020, 46(6): 87-91. doi: 10.13272/j.issn.1671-251x.2019120045
<Abstract>(77) <HTML> (11) <PDF>(11)
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The analysis of time-domain characteristics of acoustic emission (AE) and electromagnetic radiation (EMR) signals in process of rock failure under load mostly draws qualitative conclusions from amplitude, ringing count, energy and other parameters, without directly giving time-domain correlation of AE and EMR signals, and parameters used in frequency-domain characteristics analysis of AE and EMR signals are relatively simple. In view of the above problems, monitoring experiment of AE and EMR signals of rock samples under uniaxial compression was carried out, and time-frequency characteristics of AE and EMR signals in different stages of rock failure under load were analyzed. The results show that: ① In compressionstage and elastic stage, amplitude of AE and EMR signals is basically zero. In accelerated failure stage, amplitude of AE and EMR signals increases gradually and the number of signals increases gradually. In stage of complete failure, amplitude of AE and EMR signals increases and decreases almost at the same time. When load reaches the peak value, amplitude of AE and EMR signals reaches the maximum at the same time. Amplitude of AE signal is larger than that of EMR signal in the whole process of failure under load. ② In accelerated failure stage, AE and EMR signals are significantly correlated. In stage of complete destruction, AE and EMR signals are highly correlated. In the whole process of failure underload, variation trend of AE and EMR signals with time is basically the same, and AE and EMR signals are highly correlated in time-domain. ③ In accelerated failure stage and complete failure stage, EMR signals are mainly low frequency and very low frequency signals. Compared with EMR signal, AE signal has wider frequency band and larger amplitude of main frequency. Main frequency concentration range of AE and EMR signals is similar but not completely consistent. Amplitude of main frequency of AE and EMR signals in complete failure stage is larger than that in accelerated failure stage.
Design of damage detection system for mine-used wire rope
WANG Hongyao, LI Xiaowei, HAN Yimiao, LYU Xi
2020, 46(6): 92-97. doi: 10.13272/j.issn.1671-251x.17546
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The broken wire on surface of mine-used wire rope would tilt during operation, which may lead to the situation that the wire rope in operation scratches or takes away the inner wall of aperture in flaw detector, and even causes secondary damage to the wire rope, so as to affect detection results. For the above problems, a damage detection system for mine-used wire rope was designed based on ultrasonic ranging principle and strong magnetic detection principle. The system uses ultrasonic ranging device to detect tilting height of broken wire on the surface of wire rope. If the detection value exceeds the limit distance, an alarm would be issued, or else damage of the wire rope would be further detected by strong magnetic detection device. The test results show that in view of the set 20,30,35 mm tilting height of the broken wire, the detection errors of the system are basically not more than ±2 mm, which verify that the system can effectively and accurately detect broken wire on surface of the wire rope as well as its tilting height, so as to avoid the broken wire to damage the strong magnetic detection device caused by too high tilting.
Adaptive coal flow detection method of belt conveyor
LI Yao, WANG Yiha
2020, 46(6): 98-102. doi: 10.13272/j.issn.1671-251x.2019090087
<Abstract>(247) <HTML> (40) <PDF>(26)
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For problems of existing coal flow detection methods of belt conveyor such as susceptibility of detection accuracy to environment, complex realization process, long time-consumption of information extraction and so on, an adaptive coal flow detection method of belt conveyor based on machine vision was proposed. Firstly, the original coal transportation image of belt conveyor is enhanced by a fusion algorithm based on wavelet transform and segmented by OTSU algorithm into belt image and coal image. Secondly, the segmented coal image is processed by cavity filling, contour detection and area calculation to obtain area information of the coal image. Finally, a coal flow detection algorithm based on mathematical modeling is used to obtain coal flow detection value through calculating transient volume of coal. The test results show that the average detection time of the method is about 30 ms, and error between detection results and the measurement ones of electronic belt scale is about 5%, which meets real-time and accuracy requirements for coal flow detection of automatic speed control system of belt conveyor.
A zero-crossing point prediction algorithm of short-circuit current for mine-used phase-controlled switching
YU Shuohang, RONG Xiang, YANG Fan, WEI Lipeng
2020, 46(6): 103-107. doi: 10.13272/j.issn.1671-251x.2020030074
<Abstract>(95) <HTML> (15) <PDF>(15)
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The existing zero-crossing point prediction algorithms of short-circuit current have some problems, such as complex calculation and big error. For three-phase short-circuit fault of coal mine power supply system, a zero-crossing point prediction algorithm of short-circuit current for mine-used phase-controlled switching was proposed. In the algorithm, DC component of short-circuit current is calculated by summing short-circuit current sampling data in one fundamental wave period after occurrence of three-phase short-circuit fault, which can reduce calculation amount and eliminate harmonic interference. AC component of short-circuit current is obtained by subtracting the DC component from the sampling data. Using periodicity of the AC component, the AC component at any sampling time after one fundamental wave period can be predicted. By adding the DC and AC components at any sampling time after one fundamental wave period, short-circuit current at any sampling time can be reconstructed to predict zero-crossing point of short-circuit current. The simulation and experimental results verify accuracy of the algorithm.
Influence factors analysis of discharge characteristics of compound intrinsically-safe circuit
SHI Yaping
2020, 46(6): 108-112. doi: 10.13272/j.issn.1671-251x.2019110048
<Abstract>(84) <HTML> (13) <PDF>(16)
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Existing researches on discharge characteristics of compound intrinsically-safe circuits may be lack of mathematical analysis, or consider influence factors incompletely. For the above problems, discharge principle of compound intrinsically-safe circuit was analyzed, and mathematical models of discharge current, power and energy of the compound intrinsically-safe circuit under non oscillating state were derived. The influence of power supply voltage, inductance, capacitance, resistance and other parameters on discharge characteristics of composite intrinsically-safe circuit was simulated by Matlab software. The results show that with the increase of power supply voltage, the stable values of discharge current and power increase, and the discharge energy increases at the same time. With the increase of inductance, the blocking effect on current increases, and the discharge power and energy decrease gradually. In the initial stage, the discharge current, power and energy do not change with capacitance, and then gradually increase with the capacitance increase. The smaller the resistance R is, the greater the influence on the discharge current, power and energy is. Discharge current, power and energy decrease with the charging resistance R1 increases.

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