IMPACT OF POWER ELECTRONICS DEVICES ON LEAKAGE CURRENT IN MINE ELECTRICAL SYSTEMS: A CASE STUDY IN VIETNAM

Abstract

Purpose. To determine the impact of power electronic devices on leakage current in underground mine AC power network. The research results allow choosing appropriate leakage protection method to improve electrical safety in underground mining. Methodology. This study uses analytical methods and modeling methods on Matlab/Simulink software to determine, analyze, and evaluate the working current and leakage current in the mine power network containing power electronic devices. F ndings. A mine power network model containing inverter and electric motor was built by analytical method and simulated using Matlab/Simulink with model parameters U= 1,140 V, C = 0.19 uF/phase, R = 168 kQ/phase. The research results show that, with a leakage resistance of 1 kQ, the leakage current value in the AC network with a frequency other than 50 Hz after the inverter (467 mA) is 1.52 times higher than the leakage current value in the AC network with a frequency of 50 Hz before the inverter (307 mA), and at the same time, many high-order harmonie components appear in the 50 Hz AC network with THD = 1.77. In addition, the research results also show that the leakage current in the AC network before and after the inverter depends less on the insulation resistance of the DC network but depends mainly on the insulation of the AC network, the leakage resistance and the operating frequency of the AC network. Originality. Leakage current in AC power network containing power electronic devices in mining in Vietnam is studied. The research results show that when using a mine power network with an inverter, the leakage current on the AC side after the inverter has a larger value than the leakage current of the AC side before the inverter. Practical value. The research results allow choosing the appropriate leakage protection method to improve electrical safety in underground mining.