Simulation of Residual Current in Low Voltage DC Systems

With the development of new energy industry, low voltage DC system (LVDC) has been developed rapidly in the municipal and residential field. DC residual current has become a key problem threatening the safe and stable operation of low voltage DC system. In the DC system, the voltage fluctuation generated by the rectifier and the system circulating net currents generated by the line with different positive and negative parameters would interfere with the detection of residual current operated protective devices (RCD). In this paper, the effects of current on human beings was analyzed firstly. Then the impedance model of human body was built for different electric shock conditions. Meanwhile, the representative electric shock simulation models of TN, TT and IT systems were established. And the characteristics of residual current caused by direct and indirect electric shock in different grounding modes were researched. Next, the influence of system factors on circulating net currents and the detection of residual current was analyzed. On this basis, the configurations of RCD in DC system were proposed finally, protecting human body from electric shock and preventing electric fire accident threats.