Megger SMART THUMP ST16, User Manual

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M
AVTMST16 Rev 1 May 2016
22
The procedure called "COMED" in the configuration set up will perform the
following steps:
Pattern 2

low voltage trace to identify cable end (blue trace)

high voltage trace to identify fault (negative reflection in red trace)

low voltage trace to identify all transformers leading up to the fault plus one
additional transformer past the fault (blue trace) if there is a transformer past
the fault
How to Determine the Faulty Section
Proceed as follows to perform sectionalizing according to Pattern 1 :
Step Description
1
Select the menu item from the main menu or from the submenu (depends on the
system configuration).
Result: A LV pulse is fed into the cable. The reflection image is processed by the
transformer identification software. After a few seconds, the reference trace which shows
the distance to the cable end and, in addition, the approximate distance to each
transformer is presented in the display.
This reference trace is also called “live” trace as it is permanently refreshed.
2 Compare the indicated transformers with the actual plans of the cable system.
If necessary adjust the transformer search sensitivity and / or the propagation velocity in
the options.
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NOTE: Sectionalizing is a transformer prediction algorithm based of
impedance changes. If all transformers in a loop cause similar
signatures the prediction works very well. If there are impedance
changes for some other reasons (most likely joints) the software cannot
tell them apart in every case. Please always check the distances to
identify missing or "phantom" transformers.