Which description correctly matches the TT, TN-S, and TN-C-S earthing systems?

• A. TN-S uses separate neutral and earth conductors from the source.
• B. TT uses a local earth electrode
• C. TN-C-S combines neutral and protective conductors (PEN) in part of the system.
• D. TT uses a local earth electrode; TN-S uses separate neutral and earth conductors from the source; TN-C-S uses PEN conductor

Answer: (C)

Understanding earthing schemes means knowing how fault current returns and how neutral and protective earth are arranged.

In a TT system, the installation relies on a local earth electrode at the consumer’s premises for fault return. In a TN-S system, the protective earth and neutral are kept as separate conductors from the source to the load. In a TN-C-S system, the supply can use a single PEN conductor in part of the system, which is later separated into individual neutral and protective earth conductors for the installation.

The description that correctly matches all three describes each one: TT uses a local earth electrode; TN-S uses separate neutral and earth conductors from the source; TN-C-S uses a PEN conductor. This captures the full set of arrangements across the three systems. The other options describe only one system at a time, so they don’t provide the complete mapping.