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¨ EN 50522: Earthing of power installations exceeding
1 kV a.c.
¨ IEC 62271-202 (EN 62271-202): High-voltage / low-voltage
prefabricated substation
¨ IEC 60364-4-41 (HD 60364-4-41): Low-voltage electrical
installations – Part 4-41: Protection for safety – Protection
against electric shock
Figure 5.8.7 Flashover along the DEHNiso spacer made of GRP ¨ IEC 60364-5-54 (HD 60364-5-54): Low-voltage electrical
installations – Part 5-54: Selection and erection of elec-
trical equipment – Earthing arrangements and protective
If the separation distance is calculated correctly and the re- conductors
quired components are properly selected and mounted on site, ¨ IEC 62305-3 (EN 62305-3): Protection against lightning:
an effective isolated lightning protection system can be imple- Physical damage to structures and life hazard
mented for the structure.
Components tested in conformity with the standard must be ¨ DIN 18014: Foundation earth electrode – General planning
used to be able to install a functional lightning protection criteria (German standard)
system. Installers of lightning protection systems must select ¨ DIN VDE 0151: Material and minimum dimensions of earth
the components according to the requirements at the place of electrodes with respect to corrosion (German standard)
installation and install them correctly. In addition to the me-
chanical requirements, the electrical criteria according to the Important terms and definitions
latest lightning protection technology must be considered and Earth electrodes are defined as non-insulated conductors in
observed. This also applies to GRP components used for light- contact with earth. A locally restricted system of conductively
ning protection systems. interconnected earth electrodes is termed earth-termination
In addition to the standards described before, international system. This earth-termination system is connected to the part
component standards e.g. for test joints or conductor holders of an installation to be earthed via the earthing conductor
have already been published. and the main earthing busbar. The earth resistance R E (remote
earth) can be determined depending on the earth resistivity ρ.
Earthing of a dead part is called protective earthing, while
5.9 Dimensioning of earth-termination earthing of a point of the operating circuit such as the neutral
systems for transformer stations of a transformer is called operational earthing. If currents flow
into the earth-termination system in the event of a fault, the
Earth-termination systems are vital for a functioning power earth potential can be calculated as follows:
supply. The main tasks of a properly functioning earth-termi-
nation are to form high-voltage protection and low-voltage U = I Z
ground, ensure protection measures and voltage limitation to E E E
permissible maximum values even in case of a fault, form the U E earth potential rise
basis for all equipotential bonding and lightning protection
measures and ensure the protection of persons and material I E current to earth
assets. Irrespective of this, experience and discussion about Z E impedance to earth
earth-termination systems took a back seat. Properly function- Depending on the distance, the earth surface potential ϕ arises
ing earth-termination systems are often taken as given with- between the earth-termination system and remote earth. A
out any question. Therefore, the most important physical and person approaching the fault location is exposed to step volt-
normative backgrounds and possible technical solutions will age and a person touching the faulty part of the installation is
be described in this chapter. exposed to touch voltage U T . To reduce possible step voltage,
potential control measures can be taken. All conductive parts
Normative references inside the electrical installation are integrated in the equipo-
The requirements of high-voltage and low-voltage systems tential bonding system.
typically go hand in hand in a transformer station. The follow- The term transferred potential means that potentials can be
ing standards apply: transferred into areas with a different or no potential rise by
¨ IEC 61936-1 (EN 61936-1): Power installations exceeding means a conductor (e.g. cable shield, PEN conductor) connect-
1 kV a.c. ed to the earth-termination system. Global earth-termination

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