BST-GFL31 User Manual
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be the same (pointing towards the same load). The green arrow directions in Fig 2.5.3 indicate
the right direction for current clamp in different situations.
Important:
Arrow direction of the current clamp in the circuit should strictly follow these rules.
Suggestion:
When you connect the current clamp with input and output lines, please keep the
clamps steady for around 5 seconds to make signal stable.
3) Signal judgment
Follow the signal indication of signal strength, phase angle and current direction in the signal
receiver.
If receiver indicates , the faulty point is in the same direction with arrow in current detector.
You should follow the arrow direction. If it indicates
, then they are in the opposite direction
or current clamps are put in the wrong way.
4) The faulty branch has stronger signal
There is always big difference of signal strength, arrow direction and phase before and after the
branch of earth fault. In Fig 2.5.3, there is almost no signal or only weak signal in Branch f.
However, Branch e has stronger signal than all the other branches (c, d and f) in Level 1. As
there is no fault in DC power (Branch c) or battery string (Branch d), signal indication are very
weak or almost no signal there.
In the same way, Branch h has stronger signal than all the other branches (g, i and j) in Level 2.
Therefore, during signal tracing for the earth fault, we should always follow the stronger branch.
5) Use multi-setting of signal reference
For details, please refer to “2.6.1 Multiple Setting of signal reference
”.
Above are just general steps for signal tracing using the signal receiver. For further illustration of ground
fault location, please refer to Section 2.6 and 2.7 for the location theory and measurement tips.
2.6 Some Tips for Ground Fault Location
2.6.1 Multiple Setting of Signal Reference
Many DC systems contain hundreds of electric branches across 2 to 3 levels or even more, each level
might consist of dozens of branches. Due to the existence of distributed capacitance and sometimes AC
signal, there will be current leakage in the system. This can result in a very weak current signal in the
grounding branch. (Ex. Less than 10% of the reference point.)
1) Determine location of weak signal:
Take Fig 2.6.1.1 for example, the signals from Branch g, h, i, and j are very weak compared with Branch
e. It is difficult to judge which lower branch has the fault due to the weak signal. In this scenario, the
reference point should be adjusted on the lower branch.
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