具有变频器的矿井低压漏电保护研究

Research on mine low-voltage electric leakage protection with frequency converter

为了解决移动变电站低压侧为变频器供电时漏电保护装置误动的问题,提出了基于傅式算法的附加直流原理漏电保护新方法。通过理论分析和MATLAB/Simulink仿真,研究了具有变频器的矿井低压供电系统附加直流原理漏电保护,提出由傅式算法分解出采样电压直流分量以反映电缆绝缘水平的保护方法;同时分析了其他因素对直流分量的影响。研究结果表明:变频器对传统附加直流保护整定值有较大影响,易造成漏电保护装置误动且无法实现电缆的在线绝缘监测;所提出的直流分量法能准确测量电缆对地绝缘电阻,且可消除电缆分布电容、变频器载波频率、变频器输出频率等其他因素的干扰;采用该漏电保护方法,可承受变频器投入时对采样电压造成的较大冲击,不必在启动期间解除漏电保护装置,能够消除在此期间存在的人身触电安全隐患。

In order to solve the problem of the malfunction of electric leakage protection device when the low-voltage side of mobile substation provides power to the frequency converter, a new method of electric leakage protection with additional DC principle based on the Fourier algorithm was proposed. Through the theoretical analysis and MATLAB/Simulink simulation, the electric leakage protection of additional DC principle for the mine low-voltage power supply system containing the frequency converter was studied, and a protection method for decomposing the DC component of sampling voltage by the Fourier algorithm to reflect the insulation level of cable was proposed. At the same time, the influence of other factors on the DC component was analyzed. The results showed that the frequency converter had greater influence on the setting value of traditional additional DC protection, which was easy to cause the malfunction of electric leakage protection device, and the online insulation monitoring of cable could not be realized. The cable-to-ground insulation resistance could be accurately measured by the proposed DC component method, and it would not be interfered by other factors such as cable distribution capacitance, carrier frequency of frequency converter, output frequency of frequency converter, etc. The large shock on the sampling voltage when the frequency converter is put into operation can be borne by using this electric leakage protection method, and it is not necessary to remove the electric leakage protection device during the startup period, so that the safety hazard of personal electric shock existing in this period can be eliminated.