Ground Resistance Tester Models 3711 and 3731
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Commonly Asked Questions for
Clamp-on Ground Resistance Measurements
Q. Can the Clamp-on method be used effectively on high tension towers
despite the distance or spacing between them?
A. Yes. Extended distances will not adversely affect the measurement
results. The important factor is that it be a multiple electrode system.
Q. Does the grounding electrode have to be disconnected and isolated
as is required when using the “Fall-Of-Potential” test with auxiliary
electrodes?
A. No. Actually the electrode must be connected to the system to provide
the path for test signal injection as well as to provide the background
impedance necessary as the reference. Additionally, if the tested rod is
poorly bonded to the ground connector, a high reading will be present.
Q. Does this mean I am not able to test an independent electrode?
A. No, however as soon as the connection is made to a multiple
electrode system, usually provided by the connection to the system
neutral, you can clamp on and make a measurement.
Q. Must the instrument be clamped directly on the electrode?
A. No, the instrument will provide valid measurement results when
clamped on to the electrode or the conductor leading to the grounding
electrode. The reading through the conductor will also verify not only the
grounding electrode resistance, but connections of the ground wire to the
rest of the system.
Q. Does the system under test have to be energized or de-energized to
perform the test?
A. We are measuring the grounding network. The only requirements are
that ground connections be made to the system under test and that the
voltage-to-ground at the tested point not exceed the instrument rating.
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