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发表于 2013-6-14 14:37:18
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回复 93# 治学以诚
老诚眼中,已无任何……只剩下“胡扯”、“瞎说”、“乱搞”……
411.5 TT system
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411.5.3 Where a residual current protective device (RCD) is used for fault protection, the following conditions shall be fulfilled:
i) the disconnection time as required by 411.3.2.2 or 411.3.2.4, and
ii) RA x IΔn ≤ 50 V
where
RA is the sum of the resistance in Ω of the earth electrode and the protective conductor for the exposed conductive-parts,
IΔn is the rated residual operating current of the RCD.
NOTE 1 Fault protection is provided in this case also if the fault impedance is not negligible.
NOTE 2 Where discrimination between RCDs is necessary see 535.3 of IEC 60364-5-53.
NOTE 3 Where RA is not known, it may be replaced by ZS.
NOTE 4 The disconnection times in accordance with Table 41.1 relate to prospective residual fault currents
significantly higher than the rated residual operating current of the RCD (typically 5 IΔn). |
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