| Due to the special work environment of the coal mine in China, the incidence of injuries are higher than any other industry sectors. Although coal mine casualty accidents in recent years, absolute number declined, but the mortality rate of coal mine accidents in China are significantly higher than the world average. After coal mine accidents, in such bad environment how quickly, safe rescue the trapped miners, become a new topic in the field of coal mine safety. The construction of coal mine emergency safety facilities, is an effective means to solve this problem. But in the coal mine gas emissions and other harsh environment after the accident, how to ensure the safety of coal mine emergency safety facilities of electric, make it not happen secondary explosions, become the key and technical difficulties of research coal mine emergency safety facilities. This team creative "high-speed power turned-off technology" as to ensure the safety of coal mine emergency safety facilities of the core and key. Through the study of " high-speed power turned-off technology ", this team successfully developed the" 127V,2kw" mining flameproof emergency safety facilities high-speed power turn-off switch device, improve the power supply system of emergency safety facilities for fire and explosion prevention performance, guarantee the reliability and security of the emergency safety facilities of power supply system, for the coal mine disaster rescue, security personnel life safety, improve the level of our country’s coal mine disaster relief has very important significance.The high-speed power turn-off safety technology is defined as a complete set of safety technique and electrical equipment that the protection equipment is able to cut off the power supply or utilize other means to avoid transferring energy to the fault location before possible fire or explosion happens on explosive medium thus to meet the anti-explosion safety requirements in all around way, when fault occurs in the low voltage power system under a mine. The essence of the high-speed power turn-off technology is to take all means to avoid exposing of leakage spark and short circuit arc thus to avoid the faulted spark or arc ignite the explosive medium around, when leakage of electricity or short circuit fault occurs in power system. This paper analyzes the existing coal mine electrical safety technology principle and insufficiency, points out that only adopting high-speed power turn-off safety technology can fundamentally guarantee the coal mine electrical safety of emergency safety facilities. This paper, based on the research of the cable by mechanical trauma simulation experiment and rubber cable fault fire form the analysis of the time, put forward the high-speed power turn-off safety technology total power outage time is less than 5ms conclusion, time metrics for high-speed power turn-off safety technology to find a theoretical basis. Adopting high-speed power turn-off safety technology to ensure the safety of coal mine emergency safety facilities of electric, thus to meet the requirements of safety of fireproof and explosion-proof for low voltage power supply system in a coal mine. This paper analyzes the coal mine of single-phase earth leakage fault transient process. Contrast analysis of the sampling a variety of electrical leakage protection device, sampling time, choice "3C" type zero sequence order filter sampling as earth leakage protection device, in order to improve the sampling time, sampling time adjustable was developed from the track sampling device, the leakage parameters can be 3ms fast sampling. Through the analysis of leakage fault instantaneous zero sequence network, the first derivative is presented based on the zero sequence voltage for the principle of setting method, can judge the degree of single phase leakage within 1.5ms, for 127V system, guarantee the action on limit value is not more than 3.5kΩ. Put forward least squares parameter identification method for multiple line high-speed selective leakage protection algorithm of transient, the distributed parameters of cables to the ground are mainly made up of distributed capacitors and isolated resisters. When a single-phase fault occurs, the identification mode based on the zero sequence current is started to account the time. Suppose there is no fault occurring on any feeders and the isolated resistor and distributed capacitor to the ground follow up the mode above, the equivalent resistor rΣ and the phase-ground distributed capacitor CΣ can be calculated based on the equation above. Taking the line 1 as an example, if results of rε and CΣ are reasonable, that means that the distributed parameters of the feeder are natural and there is no single-phase grounded fault occurring on the feeder; If the results are not reasonable (both values are negative), that means that the distributed parameters of the feeder do not follow the model and the assumption of’there is no single-phase grounded fault occurring on this feeder’is incorrect thus to draw a conclusion that there is fault occurring on the feeder. Through MATLAB simulation, compares the different grounding resistance and power supply voltage phase Angle at the beginning of the least squares parameter identification method, identified by the circuit parameters. Results show that the parameter identification results have obvious characteristics, namely the normal line of distributed capacitance and insulation resistance are all positive, and the identification of distributed capacitance values very close to the actual parameters; the parameters of the faulty line are negative. Implement the accurate and selective removal of leakage fault quickly.This paper analyzes the short circuit current in the process of change curve, and found that the impact of the short circuit current value not only the phase voltage and the power factor of circuit, the initial phase, and the influence of the short circuit instantaneous load current value, the dynamic stability check on equipment, should calculate the impact value, put forward using hollow transformer short-circuit current collection scheme, and calculate the hollow transformer resistance index of frequency characteristic and the sampling resistance. Study shows that after the occurrence of short circuit current will experience a mutation in the transient process, using the current variation in the process, can correctly distinguish normal current and fault current change, so in the process of short circuit current changes of first order and second order derivative formulas were derived, using the MATLAB simulation curves of the current, can be seen from the curves of current, Combining with the short circuit current first and second order derivative, a comprehensive criterion which can realize the whole cycle without blind spots short circuit fast monitoring judgment and reliable removal. Based on transient analysis of motor starting current, found that the starting current of the instantaneous maximum in other conditions under the condition of the same and the power factor of starting circuit and the initial phase of the phase voltage starting moment, when a high-speed short-circuit protection design, transient analysis method should be adopted, in order to ensure the correctness of the action. Based on motor starting current is proposed first and second order derivative of high-speed short-circuit protection setting method, and the setting method of sampling time analysis, analysis shows that the method is completely satisfy the high-speed short-circuit protection time index of the sampling time is less than 3ms, realize the purpose of fast, reliable, to cut off the short-circuit current. Put forward through the acquisition of terminal voltage and hollow secondary voltage of transformer short-circuit fault in loop time constant identification method, can achieve the goal of high-speed short-circuit protection. This paper, on the basis of the study of power electronic technology, the design of the coal mine based on power electronic components SSCB mining flameproof emergency safety facilities high-speed power turn-off switch device structure of main circuit, through to the N-SSCB and L-SSCB two kinds of topological structure of the simulation analysis, found that the circuit in the switch off time is shorter, a wider range of application. Eventually determine L-SSCB for the implementation of high-speed power turn-off technology. Through the simulation analysis and calculation to find the auxiliary switch device loop resistance capacity absorption equipment specific parameters. Analyzes the L-SSCB mechanism of conduction and shut off, and has presented equations to calculate the forcible turn-off time of L-SSCB, and the formula is verified by MATLAB simulation. Of flameproof shell power electronic device cooling was studied, and design the special heat pipe cooling device, the device can completely satisfy the requirements of industrial operation test, solve the SSCB in flameproof shell heat dissipation problem.Under the laboratory environment of mining flameproof emergency safety facilities high-speed power turn-off switch device conducted a series of dynamic and static simulation experiment, among them:characteristic experiment of hollow transformer, mastering the hollow transformer transient characteristics; hollow transformer and comparative experiments of ferromagnetic transformer, hollow transformer is verified in terms of transient signal extraction of superior performance; high-speed short-circuit protection experiments to verify the current higher derivative the veracity and reliability of high-speed short-circuit protection; high-speed algorithm for calculating leakage protection experiments to verify the veracity and reliability of multiple line high-speed selective leakage protection algorithm; switch device off three phase short circuit current and leakage current experiment.. Device running in the experiment, the newly developed system is able to identify all faulted feeders in, and completed the design of the indicators in advance. |
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