Research On The On-line Monitoring Of Insulation Parameter Of Mine Low Voltage Cables

A method of non-grounded neutral point is widely used in the power system of mine.We can quickly find out the faulty line via the online insulation monitoring system, and it's important to improve the security of performance and reliability of power system's supply.By analyzing the behavior of mine's power system, a new method based on additional low frequency signal is presented. A low frequency signal is injected into low voltage underground power system. By measuring low-frequency voltage and low-frequency current, insulation parameters can be calculated. And theoretical analysis shows that, this method can not only measure cable's insulation parameters, but also carry out faulty location of the insulation branch.By MATLAB/SIMULINK simulation technology, analysis result and the method of measuring insulation parameters are simulated. Simulation experiment shows that, modeling and theoretical analysis results are correct, the method of additional low frequency power measuring insulation parameters can exactly measure insulation resistance and capacitance to ground, the measuring accuracy is good, it can carry out not only on-line monitoring ,but also selective leakage protection of underground electric network, the value of distributed capacitor has effect on measuring precision, the selection of signal frequency has direct effect on measuring precision.In the end, the detection unit with C8051F020 as its core and adopting measuring method basing on additional low frequency signal, including hardware and software designs. Each model's hardware circuit and principle analysis of these circuit is given, and system software flow sheet is also given. Low frequency signal source is designed and realized.Theoretical analysis and simulation results show that the method is accurate, and it can apply to many areas. It has good prospects for engineering applications.