measurement
today almost exclusively voltage compen-
sated electronic resistance bridges are
used (measurement method according to
Wenner) with connection contacts, of
which are for current electrodes and for
voltage probes.
By increasing distance the current
penetrates deeper into the ground and
the measured resistivity can fall in-
crease depending the resistivity the
ground layer metre’s depth.
All power suppliers must have approved
earth connections their installations.
A customer who buys power takes
earthing for granted. The techni-
cal specifications and requirements for
earthing demonstrate the advantages of
deep-earth connections, both techni-
cal and economic solution, relation to
surface-earth connections.
Soil conditions external conditions?
The importance the soil conductor
of electric current great.
Resistivity different soil conditions.
An approved earthing should have: (1)
low electrical resistance, (2) ability to
conduct voltage stably (despite weather
changes) and (3) long service life, i.11:8
System structure and function deep earthing
Earthing
An earth connection conductor
placed the soil, with the aim divert-
ing electrical current from installation
connected the earth connection and
into the surrounding soil.
Current conduction occurs the soil
through electrolytic processes, known as
ionic conduction. Earthing thus functions as, among
other things, personal protection, proper-
ty protection, signal transfer protection,
lightning protection and the like.
Soil resistance relation humidity.
The connectors are connected verti-
cal metal tips that are driven down a
row about 0. Solid particles such as
gravel are not usually conductive.
Measurement ground resistance.5 deep metre apart. Soil with
good electrical conductivity thus has low
resistivity: 100 Ωm.e.3-0. The
most efficient earthing thus reached
when the electrode placed deep
enough not affected chang-
es soil humidity and temperature.
The water deeper lying ground layers
usually has higher salinity than the
water the surface layer. great impor-
tance that all this taken into account
for earth connections earth connection
systems.
Weather conditions cold, heat, rain and
wind mainly affect the upper layer of
the soil 1.
The electrical conductivity the soil
therefore mainly depends the propor-
tion saline water bound capillary
forces and osmotic pressure the pores
between grains sand and hygroscop-
ic humus particles (e. The higher the
moisture content the soil, the better
the conductivity.
(See image)
If the instrument reading the resis-
tivity the soil calculated according to
the following equation:
p Ωm
In unlayered soil, resistivity inde-
pendent the electrode distance a.5 m), which therefore ex-
hibits the most powerful variations.
Resistivity
The electrical properties the soil are
quality declared means its resis-
tivity, which measured (former
unit Ωcm, =100 Ωcm).
This means that voltage surges that can
occur for various reasons are led into the
ground that they not cause dam-
age. This despite the
fact that the use power without, or
with poor, earthing incurs great risks. When
calculating approximate earthing resist-
ance the earth connection when the
depth the resistivity the soil must
be measured with electrode distance ≈
0.
Measuring earthing resistance the
earth connection
.
good resistance corrosion.
For each case different soil type, soil
resistance must measured and prefer-
ably during several seasons and differ-
ent weather conditions.
Soil resistance relation temperature. Soil humidity normal-
ly varies between 5-40%.
Cold (frost) significantly impairs the
ground’s conductivity.75 l.clay). variations
below 14-18%, conductivity deteriorates
significantly.g
