Megger Limited PWS / Nov 06
DET4TC/R Launch
5
THIS PRODUCT (DET4TC/R) IS USED FOR?
This product is used for both soil resistivity testing (4 pole) and earth electrode (2 and
3 pole) testing. Methods such as ART allow earth electrodes to be tested without
disconnection. The addition of Stakeless testing will allow testing of electrode where
the use of test stakes is impractical.
WHY?
• Soil resistivity testing. (4 pole)
o Used to locate the best lowest resistance location for a new earth
system.
o Obtain earth resistance values required to design the earth system
o Geophysics – locating changes in geology
• Earth Electrode testing (2, 3 pole)
o Earth electrode / system resistance must be low and reliable. Why?
• To ensure enough current to flow in fault conditions to ensure
the circuits’ protective device trips out in time. Failure to trip or
trip too slowly can result in expensive damage to equipment,
fire or serious injury.
• Lightning strike protection.
• Improve equipment performance by reducing noise levels.
• Static electricity dissipation.
• Prevent dangerously high step or contact voltages present
during fault or high load conditions, another safety issue.
o Earth systems require testing both immediately after installation, and
at regular intervals thereafter as part of a maintenance program.
• ART – Attached Rod Technique
o This method is an additional feature used when performing the
standard 3 pole method when testing earth electrode resistance.
o The main problem associated with testing an electrode resistance is
the requirement to disconnect it. This is because the test current from
the instrument will flow, not just down the electrode being tested, but
also through any other parallel paths. E.g. other electrodes in the
system or back through the building earth.
• ART uses a clamp to measure only the current flowing down
the electrode being tested; the instrument then uses this
measurement to calculate the resistance of electrode.
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