Research On Methods To Measure Capacitive Current In Coal Mine

In the mine power supply system, the power is supplied by cable. In recent years, withthe expansion of production capacity and upgrade supply voltage level in mine, the range ofmine power supply network is widening, and the length of cable is increasing at the same time,therefore, distribution capacitance effects between ground and cable is increasing, so as thecapacitive current of mine power grid. The equipment insulation damage caused by arcover-voltage, gas explosion and other accidents has occurred because of single-phasegrounded fault. In order to reduce the accidents in coal mines and ensure the safety of themine power supply system, it is very important to measure and compensate single-phasegrounded capacitive current in the mine power supply system. This paper analyzes andresearches that how to measure capacitance current.Firstly, the traditional methods of measuring capacitive current are analyzed based on theresearch capacitive current formation, offset capacitance method and artificial neutral methodare simulated, and their advantages and limitations are indicated. Then research the injectingsignals method of measuring capacitive current in detail, and complete many simulationexperiments, such as three-frequency method, two-frequency method and sweeping frequencymethod. Their advantages and limitations are also indicated in this paper.Finally, on the basis of analyzing capacitive current measurement, an improved injectingsignals method is proposed in this paper. This method can accurately calculate capacitancecurrent by respectively measure the capacitance to ground and insulation resistance.According to the principle analysis and the results of simulation, this method can accuratelymeasure capacitive current, predict the insulation level before ground fault occurs, andimprove the security of the system.