Research on the Requirements for the Break Time of DC-RCD Under Different Voltage Levels and Grounding Modes in LVDC System

Abstract

Personal safety in LVDC system is very important. By installing the DC-residual current device (DC-RCD), the impact of electric shock on human body can be effectively reduced. Since the specific value of the break time of DC-RCD has not been accurately concluded in LVDC system, and the break time is closely related to the voltage levels and grounding modes of the system. In this paper, a method of determining the break time of DC-RCD considering personal safety under different voltage levels and grounding modes in LVDC system is proposed. First of all, referring to IEC standards, the main influencing factors of human ventricular fibrillation caused by DC electric shock are analyzed and summarized. Secondly, the restriction conditions of the relationship between the break time of the RCD and voltage levels in different grounding modes are proposed. Finally, combining with the restriction conditions and using polynomial fitting method to process data, the specific requirements for the break time of DC-RCD under different voltage levels and grounding modes in LVDC system is presented. And by taking the nominal voltages in GB/T 35727-2017 as examples, the requirements for the break time of DCRCD in different grounding modes and some suggestions are given.