Besantek BST-GFL31, User Manual

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BST-GFL31 User Manual
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2.5.3 How to Locate Ground Fault?
After the reference setting, we will continue with the most important part for signal tracing with the help of
dual-range current clamp. Let us refer to the following diagram again:
Fig 2.5.3
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Solution for Online fault tracing
In most DC systems (like power substation), it could not be shut down. So the fault tracing will be carried
out when the system is working online. In this case, there will be high interference that is generated by
distributed capacitance from the circuit itself. With BESANTEK’s dual-range current clamp, it can
effectively cancel the interference and pinpoint the fault much faster.

Steps for fault location
Take the diagram in Fig 2.5.3 for example (supposed that positive busbar has ground fault).
1) Sectionalize the DC system
After setting for the first reference point in Point a, we will sectionalize the DC system as different
“Levels”. The first level will be Branches of b, c, d, e and f. The second level will be Branch g, h, i,
j, k, l, m and n. All these branches are connected with loads which has input (red line) and output
(black line). And you could consider all cabinets in power substation as bigger loads with many
smaller loads inside.
As the earth fault is on positive busbar, the signal tracing will follow all the way based on positive
busbar. We will begin the signal search from the first level.
During the process of signal tracing, it is very important to have a detailed record about the
wiring structure on how each load is connected in the system. This will help you trace the signal
effectively.
2) Use one-clamp or two-clamp tracing
Use one clamp to clamp around input and output of the load when these two lines are very close
to each other (like Branch b, c and e in Fig 2.5.3).
Use two clamps to clamp around the input and output line of load when input and output lines
are far away from each other (like Branch d and f in Fig 2.5.3).
Note:
If one load has more than one input line or output line, connect the clamp around all the
input and output lines.
One-clamp and two-clamp operation have the same purpose: to cancel the interference
generated by DC system itself. Also, the arrow mark direction (label on the clamp) should always