Terminology - Gossen MetraWatt GEOHM C Manual De Instrucciones

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Terminology

In order to assure that the terminology used in these operating instruc-
tions is not misunderstood, the most important terms are defined below.
Earth: a term used as a designation for the planet Earth, as well as a
connection to ground.
Ground reference plane: the zone in the ground within which no significant
voltages occur between any two point as a result of earth current, espe-
cially the surface of the earth located outside of the sphere of influence of
an earth electrode or earthing system (see also Figure 1 on page 7).
Earth electrode: a conductor which is embedded in, and electrically con-
nected to ground, or a conductor which is embedded in concrete which
has a large surface area in contact with the ground (e.g. a foundation)
Earth cable: a cable which is used to connect the system component to be
grounded to an earth electrode, and which is laid above ground, or
underground if insulated.
Earthing system: a system of electrically connected earth electrodes which
is restricted to a specific local area, or other metal objects which have the
same function (e.g. tower footings, armoring, metal cable jacketing and
earthing blades).
Ground (verb): to connect an electrically conductive object to earth via an
earthing system
Earthing: all means and measures in their entirety, which are required to
ground an object
Earthing resistance R : resistance between the earthing system and the
E
ground reference plane
Soil resistivity ρ
: the specific electrical resistance of the soil. Usually
E
defined as Ωm 2 : m = Ωm, soil resistivity represents the resistance of a
cube of earth along an edge with a length of 1 meter between two
opposing surfaces of the cube.
Dissipation resistance R : earth resistance between the earth electrode and
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the ground reference plane. For all intense purposes R
resistance (same as R ).
E
Earth potential U : voltage which occurs between the earthing system and
E
the ground reference plane (see also Figure 1 on page 7)
Contact voltage U : the portion of earth potential which can be short-cir-
B
cuited by human being (see also Figure 1 on page 7), where the current
path over the human body runs from hand to foot (horizontal distance of
approximately 1 meter from the accessible part), or from hand to hand.
GMC-I Messtechnik GmbH
E
Figure 1
is an equivalent
A
Step voltage U
by human being over a single step of 1 meter, where the current path over
the human body runs from foot to foot (see also Figure 1 on page 7). No
allowable limit values have been established for step voltage.
Φ
U
B
U
S
approx. 20 m
B = Ground reference plane
E = Earth electrode
U = Contact voltage
B
U = Earth potential
E
U = Step voltage
S
X = Distance to the earth electrode
Φ
= Potential
Ground-to-electrode potential and voltages with
current carrying earth conductor
: the portion of earth potential which can be short-circuited
S
U
E
B
X
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