NEN 1010 §312
TN-S system
TN-S stelsel
Also known as: tn-s
TN-S system: N and PE conductors are laid out as separate lines from the transformer station. Safest configuration against PE faults.
Practical example
TN-S system. An industrial site with its own MV transformer runs separate N and PE conductors to every distribution board.
Common mistake
TN-S system Common mistake: Connecting N and PE together somewhere in the installation 'just in case' — this creates a local TN-C fault in a TN-S system, causing fault current on the PE.
See also
Related terms
In-depth guides
- → Earthing and earthing systems (TN, TT, IT)
- → NEN-EN-IEC 61557-8 IT system and insulation monitoring (IMD) — first-fault detection
- → §411.6 IT system — disconnection on a second fault (§411.6)
- → §411.5 (IEC 60364-4-41) The TT system — why an installation's own earth electrode makes an RCD mandatory
- → §131 Protection Principles
- → §411.3.2 Automatic disconnection of supply (AUV)
- → §413.3 Electrical separation (§413.3) — an isolating transformer as a protective measure without earthing
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