NEN 1010 §612.7
Earth electrode resistance measurement
Aardweerstand-meting (Re)
Also known as: aardweerstand, aardweerstand-meting, aardimpedantie, earth-resistance-test, pen-geleider, pen-conductor, pen-split
Three-point or clamp measurement of resistance between main earth electrode and remote earth mass. TT system with 30 mA RCD requires Re ≤ 1666 Ω; in practice ≤100 Ω is targeted for lightning discharge and SPD operation.
Practical example
Earth resistance measurement (Re). Using a 3-pen test on a foundation earth electrode, an Re of 12 Ω is determined, well sufficient for both the RCD requirement and good SPD operation.
Common mistake
Earth resistance measurement (Re) Common mistake: Measuring earth resistance during dry summer periods and considering that value representative — in wet soil Re can be significantly lower, and in drought just too high for the standard.
See also
Related terms
In-depth guides
- → Earthing and earthing systems (TN, TT, IT)
- → §531 Residual Current Circuit Breakers (RCD)
- → §712 PV installations — fire service switch and DC marking (§712)
- → Praktijk (IEC 60076-6 / IEC 60364 achtergrond) Resistance earthing (NGR) — low-resistance versus high-resistance star point, and why it differs from a Petersen coil
- → §411.3.2 Automatic disconnection of supply (AUV)
- → §413.3 Electrical separation (§413.3) — an isolating transformer as a protective measure without earthing
- → §442 Temporary overvoltage from an earth fault in the high-voltage network (§442) — why the substation voltage rise reaches the low-voltage installation
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