Earthing systems

 The standards specify that:
IEC 62305-3
5.4 Earth-termination system
5.4.1 General

When dealing with the dispersion of the lightning current (high frequency behaviour) into the ground, whilst minimizing any potentially dangerous overvoltage’s, the shape and dimensions of the earth-termination system are the important criteria. In general, a low earthing resistance (if possible lower than 10 W when measured at low frequency) is recommended. From the viewpoint of lightning protection, a single integrated structure earth-termination System is preferable and is suitable for all purposes (i.e. lightning protection, power systems and telecommunication systems). Earth-termination systems shall be bonded in accordance with the requirements of 6.2.

What do we mean by an “earthing system”?

A detailed explanation of the terms used in the earthing-termination technology can be found in the standards (SANS/IEC 62305-3)

Terms.

  • Earth is the conductive ground and the part of the earth in electrical contact with an earth electrode whose electric potential is not necessarily zero. The term “earth” also describes both a place and a material, e.g. humus, loam, sand, gravel and rock.
  • Reference Earth is the part of the earth, especially the surface of the earth outside the area influenced by an earth electrode or an earth-termination system, in which no perceptible voltages arising from the earthing current occur between two arbitrary points
  • Earth Electrode is a conductive part or several conductive parts in electrical contact with earth which provide(s) an electrical connection with the earth (also foundation earth electrodes).
  • Earth-termination system all conductively interconnected earth electrodes which are physically separated or metal components acting as such (e.g. reinforcements of concrete foundations, metal cable sheaths indirect contact with earth).
  • Earthing Conductor is a conductor which connects a system part to be earthed to an earth electrode and which is installed above the ground or insulated in the ground.
  • Lightning Protection Earth earthing of a lightning protection system to discharge lightning currents to earth.