| The continuation project in this thesis is one important part of the major project "Study on the system of Condition Monitoring and Fault Diagnosis&Early-warning for Ventilation and Security of the Power Supply System in Coal Mines", which is the sub-project of "safety Status Monitoring and Fault Diagnosis Forecast of Mine Ventilation Power Supply System"(No:2007BAK29B05), sponsored by the National Key Technology R&D Program of China during the Eleventh Five-year Plan Period. The project is also one of main parts of National Natural Science Foundation of China of Study on Insulation Evaluation Method for Failure Mechanism and Life of Mine High Voltage Cables (51377113). The work is proposed in accordance with lack of online monitoring system for insulation of mine high voltage cables and failure to judge health status of cables.With high yield and efficiency mechanized mining technology and gradually establishment of large or extra large modern mine and widely used of mining mechanized equipment, the power supply load of coal mine has a significant increase, the shearer capacity up to3000kW, and the power distance gradually becomes longer. In order to improve the power supply capacity of coal mine power grid and reduce energy consumption, a voltage of10kV power supply has been extended. Mine high voltage cable is an important medium for underground power transmission, it plays a vital role on the stability of coal mine production safety and load stability. Because the running environment of mine high voltage cable is special, the cables always encounter water, moist, roof fall, drag and drop environment, suffering electrical, thermal, chemical and other stress influence, which causes water tree or tree appeared. Over time, it will make cable insulation aging, resulting in reducing the level of cable insulation and shorting the service life of cables. The worst thing is causing gas, coal dust explosion accidents. According to statistical data of many years, cable fault has a high incidence, which accounted for about2/3of mine power supply accidents. Therefore, it is important and significant for improving supply reliability of coal mine cable and ensuring power supply safety of coal mine and avoiding the accident caused by cable insulation deterioration to study online monitoring methods for mine high voltage cable insulation, develop online monitoring system for insulation condition of mine high voltage cable to detecting the operation state in real-time.This thesis discusses fault types and fault reasons and extract methods for fault feature, develop a online monitoring system of mine high voltage insulation based on insulation resistance and conductor temperature. It achieves online monitoring insulation and provide a guarantee to continuous, reliable, safe operation of mine high voltage by detecting and extracting the voltage signal and current signal and temperature signal. The main contents of this thesis are as follows:A brief introduction to the basic structure of the mine MYPTJ high voltage cable and underground10kV supply line connection of deep well power supply system, on the basis of consulting a large number of domestic and overseas relevant and fieldwork investigation. The fault types and fault reasons of cable is studied, the classification method of cable fault is discussed, the relationship between fault type and fault characteristic quantity is determined, which provides basis for effective assessment and monitoring on cable insulation considering comprehensive amount parameter.On the basis of in-depth discuss cable insulation properties, it analysis faults feature quantity of ground current, insulation resistance, dielectric loss and others, investigates the relationship between fault feature and insulation deterioration degree, studies the existing online monitoring methods for cable insulation. Combined with fieldwork situations of cable line, the insulation resistance and conductor temperature are selected as insulation characteristics of online detection, the parameter identification model of cable insulation resistance and temperature transient model are established, online monitoring system solution of mine high voltage cable insulation is designed.Based on the characteristics of the detection signal, the voltage signal conditioning circuit, current signal conditioning circuit, temperature signal conditioning circuit, power supply circuit and the minimum DSP281system are designed, and do test for the designed hardware circuit. The tests show that the hardware circuit designed has high reliability and stability, realizing the desired design goals.Based on design of the hardware circuit, it designs the system software program, which mainly includes data collection procedures program, such as voltage signal RMS acquisition program, current signal RMS acquisition program, average temperature signal acquisition procedures, identification procedures of model parameter, projections procedures of core temperature and communication program. Application program is designed based on the C language, using a modular approach, which has a simple structure and a high execution efficiency. The software debugging showed that the program designed meets the design requirements.According to the system design scheme, under laboratory conditions, online monitoring experimental platform of mine high voltage cable are builded, to make joint debugging of hardware circuits and software programs. The commissioning results show that the hardware circuit can accurately capture fault characteristics signals, achieve monitoring implementation characteristics. The software program is designed reasonably, having strong portability. The system realizes online monitoring of insulation resistance and core temperature of mine high voltage cables. It laid a solid foundation for further work. |
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