Megger Limited PWS / Nov 06
DET4TC/R Launch
8
DET4TCR
The instrument and display layout are identical with the exception of the 12V input for
battery charging.
Principle of Operation
The principal of operation is fully described in the User Guide, a copy of which has
been provided as part of the launch pack. However since the DET4TCR is replacing
the DET5/4, just the pertinent parts covering the additional ART and Stakeless
capabilities have been reproduced in this document.
Principle of operation (three-terminal resistance measurement using
ART)
The classic three-terminal test method has a disadvantage, namely that the electrode
under test must be disconnected from the system it is supposed to protect in the
event of a power system fault. The reason for this is that the injected test current will
take all possible routes to ground and not all of it will necessarily flow through the
electrode under test. In this case, the instrument will make a reading
of the entire earthing network, not just the individual electrode.
By using a current transducer (the Megger ICLAMP) to measure the current flowing
through the electrode under test as a fraction of the total test current injected, the
instrument can determine the individual resistance. This arrangement is shown in
Figure 7.
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