Measurement ground resistance. variations
below 14-18%, conductivity deteriorates
significantly.
The connectors are connected verti-
cal metal tips that are driven down a
row about 0.e.5 m), which therefore ex-
hibits the most powerful variations.75 l.g.
This means that voltage surges that can
occur for various reasons are led into the
ground that they not cause dam-
age. great impor-
tance that all this taken into account
for earth connections earth connection
systems.
Soil conditions external conditions?
The importance the soil conductor
of electric current great.clay). Soil humidity normal-
ly varies between 5-40%.
Cold (frost) significantly impairs the
ground’s conductivity.
A customer who buys power takes
earthing for granted. 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.5 deep metre apart.
The water deeper lying ground layers
usually has higher salinity than the
water the surface layer.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.
All power suppliers must have approved
earth connections their installations. When
calculating approximate earthing resist-
ance the earth connection when the
depth the resistivity the soil must
be measured with electrode distance ≈
0.
An approved earthing should have: (1)
low electrical resistance, (2) ability to
conduct voltage stably (despite weather
changes) and (3) long service life, i.
For each case different soil type, soil
resistance must measured and prefer-
ably during several seasons and differ-
ent weather conditions.
Resistivity different soil conditions.
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. The
most efficient earthing thus reached
when the electrode placed deep
enough not affected chang-
es soil humidity and temperature.
Weather conditions cold, heat, rain and
wind mainly affect the upper layer of
the soil 1.
Soil resistance relation humidity.
Measuring earthing resistance the
earth connection
.
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.
Soil resistance relation temperature. The higher the
moisture content the soil, the better
the conductivity. Solid particles such as
gravel are not usually conductive. Earthing thus functions as, among
other things, personal protection, proper-
ty protection, signal transfer protection,
lightning protection and the like. Soil with
good electrical conductivity thus has low
resistivity: 100 Ωm.
(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.
good resistance corrosion.3-0.
Current conduction occurs the soil
through electrolytic processes, known as
ionic conduction. This despite the
fact that the use power without, or
with poor, earthing incurs great risks. 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.
Resistivity
The electrical properties the soil are
quality declared means its resis-
tivity, which measured (former
unit Ωcm, =100 Ωcm)
