对于这个问题，尺总分析的比较透切了。
扩展到相距100米以外的A、B两建筑，远不是伸臂范围的问题了。A采用TT，接地后不立即切除，无论B采用TN-C还是TN-S，PEN、N、PE导线都会把中性点对大地零点电位带入到B建筑室内来。如果检修不断N线，不断PEN线（做总等与重复接地，仍然不可以消除与大地电位零点之间的电压），检修就存在电击风险。
治学以诚 发表于 2013-6-8 07:20 http://www.jzdq.net.cn/club/images/common/back.gif
411.4.1 In TN systems the integrity of the earthing of the installation depends on the reliable and effective connection of the PEN or PE conductors to earth. Where the earthing is provided from a public or other supply system, compliance with the necessary conditions external to the installation is the responsibility of the supply network operator.
411.4.3 In fixed installations, a single conductor may serve both as a protective conductor and as a neutral conductor (PEN conductor) provided that the requirements of 543.4 of IEC 60364-5-54 are satisfied. No switching or isolating device shall be inserted in the PEN conductor.
NOTE 1 Examples of conditions include:
− the PEN is connected to earth at a number of points and is installed in such a way as to minimize the risk of a
break in the PEN conductor;
− RB/RE ≤ 50/(U0 – 50)
where
RB is the earth electrode resistance, in ohms, of all earth electrodes in parallel;
RE is the minimum contact resistance with earth, in ohms, of extraneous-conductive-parts not connected to a
protective conductor, through which a fault between line and earth may occur;
Uo is the nominal a.c. r.m.s. voltage to earth, in volts.
NOTE 2 In Germany compliance with condition RB/RE ≤ 50 / (Uo – 50) is compulsory for the supply network
operator.
NOTE 1 Examples of conditions include:
− the PEN is connected to earth at a number of points and is installed in such a way as to minimize the risk of a break in the PEN conductor;
− RB/RE ≤ 50/(U0 – 50)
where
RB is the earth electrode resistance, in ohms, of all earth electrodes in parallel;
RE is the minimum contact resistance with earth, in ohms, of extraneous-conductive-parts not connected to a protective conductor, through which a fault between line and earth may occur;
Uo is the nominal a.c. r.m.s. voltage to earth, in volts.
NOTE 2 In Germany compliance with condition RB/RE ≤ 50 / (Uo – 50) is compulsory for the supply network operator.
狗屁，你给个电路，证明一下，PEN，重复接地与不重复接地，两者之间的危险性不就完了吗
治学以诚 发表于 2013-6-9 16:59 http://www.jzdq.net.cn/club/images/common/back.gif
“IEC_60364-4-41：2005”＝老诚破口大骂的 狗屁 ？
{:4_126:}
老诚自己画的图，早已经证明了的。{:1_274:}
德国供电公司是“狗屁”？
……
如TT系统，N线接地了，就不能再允许相线接地了。
治学以诚 发表于 2013-6-9 17:13 http://www.jzdq.net.cn/club/images/common/back.gif
如TT系统，N线接地了，就不能再允许相线接地了。
好的。
那么，如TN系统，N线接地了，就允许相线接地了?
