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系統(tǒng)中，故障電流流向電源中性點
通過牢固的金屬連接，幾乎不涉及地球
電極（圖2）。
這些配電系統(tǒng)用于特定電廠，其中連續(xù)性
供應(yīng)不足是一項基本要求，如果沒有供應(yīng)
對人員造成危害或相當大的經(jīng)濟損失，或
需要一次接地故障的值。在這些情況下，絕緣監(jiān)測
應(yīng)提供可能接地故障的光或聲信號裝置，
或供應(yīng)設(shè)備故障。
圖2:TN系統(tǒng)中的接地故障
圖3:IT系統(tǒng)中的接地故障
IT系統(tǒng)沒有直接連接到地球的帶電部件，但它們可以
通過足夠高的阻抗接地。外露導電部件應(yīng)
單獨、成組或集體接地至獨立接地
電極
接地故障電流通過
接地電極和線路導體電容（圖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).