In a TN-C-S installation, the PEN conductor is used in part of the installation to combine earth and neutral.

• A. It uses a separate earth conductor in all sections.
• B. It uses no earth at all.
• C. It uses a PEN conductor in all sections.
• D. It uses a PEN conductor in part of the installation to combine earth and neutral.

Answer: (D)

TN-C-S uses a single conductor that combines earth and neutral (PEN) for part of the installation. At a designated point, usually at the service head or main distribution board, this PEN conductor is split into separate protective earth (PE) and neutral (N) conductors. Up to that split, earth and neutral share the same conductor; beyond it, the installation runs with distinct PE and N conductors. This is exactly what the statement describes, making it the correct description of how TN-C-S is arranged.