ERICO EST401 ERITECH Clamp-on Ground Resistance Tester - Manual (Page 19)

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Field Applications
Transmission Towers
Observe all safety requirements - Dangerously high voltage may be present!
Locate the ground conductor at the base of the tower. Many different configurations exist.
Care should be taken when searching for the ground conductor. Fig. 19 shows a single leg
mounted on a concrete pad with an external ground conductor. The point at which you
clamp the instrument should be above all splices and connections that allow for multiple
rods, butt wraps, or butt plates.
Note: Current flowing to ground may be high.
Central Office Locations
The main ground conductor from a ground window or a ground plane is usually the
location to clamp the tester. Due to the wiring practices within the central office, there
are many locations at which you can look at the water pipe or counterpoise from within
the building. An effective location is usually at the ground buss in the power room, or
near the backup generator.
By measuring current and resistance at several points and comparing the readings, you
will be able to identify neutral loops, utility grounds and central office grounds. The test
is effective and accurate when the ground window is connected to the utility ground at
only one point.
Figure 19
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