Clean vs dirty earthing systems


Groot Woordenboek Industrie & Techniek (GWIT)

  • schone aarde [ELEC.ENG.] (met schone aardelektrode) = clean > earthing
  • schone aardelektrode [ELEC.ENG.] = clean earthing electrode

There are two reasons for my apparently dismissive responses. The first is; The reason there are two earthing systems provided is the so-called

(1) The 'dirty earth' has all the non-critical data equipment and general appliances attached to it.

(2) The 'clean earth' has all the critical data systems grounded on it in the hope that no noise will be found on this earth.

Schone aarding

Deze aarding staat los van veiligheidsaarding. Schone aarding wordt vaak toegepast om spanningsverschillen en [invloeden tussen apparaten onderling__] te voorkomen. Computersystemen en meetinstrumenten vragen vaak om schone aarding. Deze elektronica is erg gevoelig voor invloeden van buitenaf. Schone aarde is bekend onder verschillende namen:

  • Functionele aarde
  • Meetaarde
  • Instrumentatie-aarde
  • Procesaarde
  • Referentieaarde

Also worth considering that 'clean' (and 'dirty') earths are a concept that isn't particularly fashionable any more - any up to date standards - e.g. BS EN 50310 ("Application of equipotential bonding and earthing in buildings with information technology equipment") take the opposite approach and try to bond everything together as often and as solidly as possible and if there are any remaining worries about fault currents burning out sensitive little conductors or upsetting earth referenced data transmission (which is quite rare these days anyway) then they add more conductors (e.g. by-pass bonding conductors). Trying to keep two earthing systems separate isn't easy and if it is done successfully tends to undermine the 'equipotential zone' concept that's often needed for safety (shock protection) - especially in UPS protected environments and similar where supplementary bonding or similar may be relied on to compensate for longer than usual disconnection times.

I guess I'm saying it might be worth going back to whoever specified a 'clean earth' and asking them if they're really sure...

- Andy.