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0 前言 低压三相供电系统在工业企业和高层建筑的用电中应用相当广泛,但在传统的低压供电系统中主要强调过载、短路保护,其目的是保护用电设备、供电线路不受损坏;近年,又提出了保障人身安全的观点。1 防止触电的技术措施1.1 保护接地:就是将电气设备的金属外壳通过接地装置与大地作可靠的连接,以保护人体的安全。1.1.1 在中性点不接地或经高阻抗接地系统应用保护接地,即构成IT系统,如图1所示。当发生相线碰壳事故时,短路电流I_k将同时沿着接地体和人体两条通路流过。在低压供电系统中,可忽略导线对地电容的影响,按纯电阻电路分析:
0 Introduction Low-voltage three-phase power supply system in industrial enterprises and high-rise buildings in a wide range of power applications, but in the traditional low-voltage power supply system, the main emphasis on overload, short circuit protection, which aims to protect the electrical equipment, power lines from damage; In recent years, it has put forward the viewpoint of safeguarding personal safety. A technical measures to prevent electric shock 1.1 Protection of grounding: that is, the metal shell of electrical equipment and earth through the grounding device for reliable connection to protect the safety of the human body. 1.1.1 Unearthed in the neutral or high-impedance grounding system grounding protection system, which constitutes the IT system, as shown in Figure 1. When a phase touch event happens, the short-circuit current I_k will flow through both the grounding body and the human body at the same time. In the low-voltage power supply system, you can ignore the conductor on the ground capacitance, according to pure resistance circuit analysis: