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5.5 Earth-termination systems an earth-termination system, in which no perceptible voltages
arising from the earthing current occur between two arbitrary
A detailed description of the terms related to earth-termina- points (Figure 5.5.1).
tion systems can be found in IEC 62305-3 (EN 62305-3) “Pro-
tection against lightning – Physical damage to structures and Earth electrode
life hazard”, IEC 61936-1 (EN 61936-1) and EN 50522 “Power is a conductive part or several conductive parts in electrical
installations exceeding 1 kV” as well as IEC 60050-826 and contact with earth which provide(s) an electrical connection
IEC 60364-5-54 (HD 60364-5-54) “Erection of power instal- with the earth (also foundation earth electrodes).
lations with nominal voltages up to 1000 V”. In Germany,
DIN 18014 must be additionally observed for foundation earth Earth-termination system
electrodes. In the following, only the terms are explained all conductively interconnected earth electrodes which are
which are required to understand this chapter. physically separated or metal components acting as such (e.g.
reinforcements of concrete foundations, metal cable sheaths in
Terms and definitions direct contact with earth).
Earth
is the conductive ground and the part of the earth in electrical Earthing conductor
contact with an earth electrode whose electric potential is not is a conductor which connects a system part to be earthed to
necessarily zero. The term “earth” also describes both a place an earth electrode and which is installed above the ground or
and a material, e.g. humus, loam, sand, gravel and rock. insulated in the ground.

Reference earth Lightning protection earthing
(neutral earth) is the part of the earth, especially the surface of earthing of a lightning protection system to discharge light-
the earth outside the area influenced by an earth electrode or ning currents to earth.

U E Earth potential
U B Touch voltage
U B1 Touch voltage without potential control
(at the foundation earth electrode)
U B2 Touch voltage with potential control
(foundation and control earth electrode)
U S Step voltage
ϕ Earth surface potential
FE Foundation earth electrode
CE Control earth electrode (ring earth electrode)

CE
FE
1 m

ϕ U B2

ϕ FE + CE
U B1 ϕ FE U E
U S

reference earth

Figure 5.5.1 Earth surface potential and voltages in case of a current carrying foundation earth electrode FE and control earth electrode CE

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