Applications - Gossen MetraWatt GEOHM C Manual De Instrucciones

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Applications

This instrument fulfills the requirements of the applicable European and
national EC guidelines. We confirm this with the CE marking. The relevant
declaration of conformity can be obtained from GMC-I Messtechnik
GmbH.
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The GEOHM C is a compact instrument for the measurement of earthing
resistance in electrical systems in accordance with the following
regulations:
DIN VDE 0100 Installation of power systems with nominal voltages of up
to 1000 V
DIN VDE 0141 Grounding in AC systems with nominal voltages of
greater than 1 kV
DIN VDE 0800 Installation and operation of telecommunications systems
including data processing systems: equipotential
bonding and grounding
DIN VDE 0185 Lightning protection systems
The instrument is also capable of determining soil resistivity which is
essential in calculating dimensions for earthing systems.
It can thus be taken advantage of for simple geological surveys, and for
the planning of earthing systems.
Beyond this, ohmic resistance can be measured at both solid and liquid
conductors, and internal resistance can be measured at conductive
components, as long as these are capacitance and induction-free.
Measured values can be transmitted from the GEOHM
integrated IR interface.
The following quantities can be measured and tested with the GEOHM
• Voltage
• Frequency
• Earthing resistance
• Soil resistivity
GMC-I Messtechnik GmbH
Correct Positioning of the Earth Electrode
Earth electrodes and earthing systems must always demonstrate the
lowest possible overall resistance relative to the ground reference plane
in order to assure safe operation of electrical systems, and to fulfill
applicable regulations.
This resistance value is influenced by the soil resistivity of the surrounding
soil, which depends upon the type of soil, how wet the soil is and the time
of year.
Before the location of an earth electrode or an earthing system is finally
established, it is advisable to examine prevailing soil characteristics. Soil
resistivity can be measured at various depths in different soil layers with
the earth tester. The results indicate, for example, whether or not it would
be more favorable to drive the earth electrodes deep into the soil, i.e. to
use long earth electrodes, or if additional electrodes may be necessary.
Beyond this, different types of earth electrodes are available, for example
earth strips, earth rods, mesh earth electrodes and earth plates, each with
varying dissipation resistance values (see chapter 5.6.2 on page 23). The
earth electrode with the most favorable geometry is selected depending
upon soil characteristics.
Earthing System Maintenance
Previously installed earth electrodes and earthing systems can be tested
to determine whether or not their resistance values exceed allowable
limits, and if so whether ageing of the system and/or changing soil
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C to a PC via the
characteristics have contributed to this situation.
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