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Do you know how to measure the earth resistance? if so
explain it
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Answer Posted / yogesh
the current being supplied from the AC power lines.
Alternatively, a bridge may be
used for measurement. Most often, the ground resistance is
measured with selfcontained
instruments such as the Megger ground resistance Tester.
The resistivity of earth may vary over extremely wide
limits, depending on the
composition of the soil and the moisture content.
Representative values are:
General average 100 ohm-meters
Swampy ground 10-100 ohm-meters
Sea water 0.01-1 ohm-meters
Dry earth 1000 ohm-meters
Pure slate 107 ohm-meters
Sandstone 108ohm-meters
Fig. 2 Equivalent radius A of groups of ground rods of
radius "a"
I current
V voltmeter
Ground under test Reference ground Auxiliary ground
Fig. 3 Fundamental method of ground resistance measurement
TYPE 3235 Earth TESTER
Adequate earthing systems for telecommunications,
electronic and electrical
equipment, power lines and lightning arresters of steel
towers and high buildings are
of extreme importance. Good earthing systems safeguard
personnel and equipment
during fault conditions. They are also frequently necessary
in minimising electrical
noise and for normal, reliable operation of electrical and
electronic equipment. The
resistance of any earthing system should be periodically
checked to ensure that it is
within limits.
The Type 3235 Earth Tester can be used to check almost any
earthing system. It
incorporates a test for earth voltage. AC voltage up to 30V
may be measured. High
S S S
S S S S
A=SQRT(a S ) S
A= cube root of(aS2) A= fourth root of(sqrt(2)aS2)
S
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