系统中，故障电流流向电源中性点
通过牢固的金属连接，几乎不涉及地球
电极（图2）。
这些配电系统用于特定电厂，其中连续性
供应不足是一项基本要求，如果没有供应
对人员造成危害或相当大的经济损失，或
需要一次接地故障的值。在这些情况下，绝缘监测
应提供可能接地故障的光或声信号装置，
或供应设备故障。
图2:TN系统中的接地故障
图3:IT系统中的接地故障
IT系统没有直接连接到地球的带电部件，但它们可以
通过足够高的阻抗接地。外露导电部件应
单独、成组或集体接地至独立接地
电极
接地故障电流通过
接地电极和线路导体电容（图3）。

systems, the fault current flows towards the power supply neutral point through a solid metallic connection, practically without involving the earth electrode (Figure 2). These distribution systems are used for particular plants, where the continuity of supply is a fundamental requirement, where the absence of the supply can cause hazards to people or considerable economical losses, or where a low value of a first earth fault is required. In these cases, an insulation monitoring device shall be provided for optical or acoustic signalling of possible earth faults, or failure of the supplied equipment. Figure 2: Earth fault in TN systems Figure 3: Earth fault in IT systems IT systems have no live parts directly connected to earth, but they can be earthed through a sufficiently high impedance. Exposed conductive parts shall be earthed individually, in groups or collectively to an independent earthing electrode. The earth fault current flows towards the power supply neutral point through the earthing electrode and the line conductor capacitance (Figure 3).