Research On The Coal Mine 6 KV Power Cable On-Line Insulation Monitoring System

Cable is widely used in the coal mine power supply system, the cable insulation quality is the key factors that influence the safe and reliable operation of the cable, the reliability of the power supply line depends largely on the insulation of the cable. Due to the special environmental conditions of the coal mine, the electrochemical aging and the effect of partial discharge for a long time, easy to cause the cable insulation aging. if not timely identify and cut off the insulation aging line, may make the power supply system in the significant security hidden danger. for a long time, lack of perfect online testing device, the traditional measuring method need to stop the operation of the power grid, process is trival, error is big, and affect the normal production.Detailed research and analysis on the current domestic and international power cable insulation on-line detection methods, the detection principle of each kind of detection method, operation method,advantages and disadvantages are compared, finally selected the superposition method of low frequency signal as the main research method of this topic. Using the vector equation combined with The Fourier algorithm, the line impedance and transformer impedance is avoided compared with traditional algorithm. because this method adopts the AC signal as excitation signal, compared with other methods can be more close to the field work condition of power cable, more scientifically reflected the actual insulation properties of the power cable.According to the principle of superposition method of low frequency signal, monitoring system hardware implement circuit is designed. The hardware part of the device including measuring terminal, signal source and upper machine. Measurement unit including voltage transformer, current transformer, signal conditioning circuit, A/D conversion circuit. Data processing and control unit, including the DSP processor, peripheral display and alarm circuit, CAN bus communication circuit, low-frequency signal source, etc. Analyzed the selection principle of main components and circuits, work characteristics and work principle. Using the multisim12.0 software for part of the circuit and device for electronic circuit simulation analysis.Designed the detection mechanism software. Designed the whole software system work flow chart and the subprogram flow chart, on this basis, compiled the c language and assembly language program of the system. In order to improve the electromagnetic compatibility of device, the anti-interference has designed, from two aspects of hardware and software designed several effective anti-interference measures, ensure the normal operation of the monitoring device.The laboratory and simulated field installation and debugging. The scientific test content is planned, test divided into two categories, laboratory test and field simulation experiment, through the test verifies the performance of the device, found that the defect of system, to find the causes of defects and to modify the system hardware and software, and improve the performance of the device. Experimental results show that, under the simulated field the test equipment can monitored the power cable insulation resistance parameters on-line with relative error less than 3%.