Talk:Definition of standardised earthing schemes/Archive 1

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Mistake in the following sentence ? "The TN-S system (5 wires) is obligatory for circuits with cross-sectional areas less than 10 mm2 for portable equipment."

Is the following sentence related to TN-C System  correct with or without "OR"?

This system is not permitted for conductors of less than 10 mm2 OR for portable equipment.

To be precise, the IEC60364 states:
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.

543.4.1: A PEN conductor may only be used in fixed electrical installations and, for mechanical reasons, shall have a cross-sectional area not less than 10 mm2 in copper or 16 mm² in aluminium.

So TNC can not be used for portable equipment, and when used for fixed installation PEN shall have S>=10mm2 If active conductors' size is lower, it's usually cheaper to go to TNS.

Mathieu GUILLOT 08:42, 30 April 2010 (UTC)

In that case sentence related to TN-S system should be: The TN-S system (5 wires) is obligatory for circuits with cross-sectional areas less than 10 mm2 OR for portable equipment.

Yes and no, I think we should remove from TNS scheme description the sentence related to 10mm2 section or portable equipment. That's not the TNS that is obligatory but PEN that is forbidden and it's clearly described in TNC scheme description. TT could be used for instance for portable equipment.

I propose: (TN-S E5-scheme)

"The protective conductor and the neutral conductor are separate. On underground cable systems where lead-sheathed cables exist, the protective conductor is generally the lead sheath. "

Mathieu GUILLOT 12:27, 30 April 2010 (UTC)