HT instruments MACROTEST 5035 - Manual (Page 77)

MACROTEST 5035
EN - 76
11.9. EARTH RESISTANCE MEASUREMENT, 3-WIRE AND 2-WIRE METHODS
Method for small earth plant
Let a current circulate between the earth rod and a current probe positioned at a distance
from the earth equipment outline corresponding to fivefold the diagonal of the area
delimiting the earth equipment. Position the voltage probe at half-way between the earth
rod and the current probe, then measure the voltage between the two.
Black
Green Blue
Red
Use several rods in parallel and moisten
the surrounding ground if the instrument
does not manage to supply the current
necessary to perform the test because
o f a n h i g h e a r t h r e s i s t a n c e .
Earth resistance measurement for small earth plant
Method for big earth plant
Also this procedure is based on the voltamperometric method, but it’s mainly used when
it’s difficult to position the auxiliary current rod at a distance corresponding to fivefold the
diagonal of the area of the earth equipment. Position the current probe at a distance equal
to the diagonal of the area of the earth equipment. To make sure that the voltage probe is
positioned outside the area affected by the rod under test, take more measurements, first
positioning the voltage probe at half-way between the rod and the current probe, then
moving the probe both towards the earth rod and towards the current probe.
Black
Green Blue
Red
Use several rods in parallel and moisten
the surrounding ground if the instrument
does not manage to supply the current
necessary to perform the test because
o f a n h i g h e a r t h r e s i s t a n c e .
Earth resistance measurement for big earth plant