When a cable or its internal components experience a breakpoint failure, it is challenging to intuitively determine the exact location of the breakpoint due to the external insulation covering.
Here are several methods to quickly determine the breakpoint of wires and cables:
Non-Damaging Cable Method
Digital Multimeter Method:
First, connect one end of the faulty cable to a 220V live wire and leave the other end suspended. Set the multimeter to the AC 2V voltage range. Starting from the live wire connection point of the faulty cable, hold the black probe with one hand while slowly sliding the red probe along the insulation of the faulty cable. The voltage value at points without a breakpoint is approximately 0.445V. When the red probe moves to a certain point, if the multimeter displays a voltage drop to 1/10 of the normal voltage (i.e., 0.04V), it can be determined that the breakpoint is approximately 15cm before that point (towards the live wire connection end).
If the shielding layer of the shielded wire is undamaged, this method cannot be used.
Induction Pen Method:
First, ensure that there is no power supply around the faulty cable. Then, connect the faulty cable to the live wire and slowly move the induction pen vertically to the cable. When the AC signal of the induction pen disappears, it can be determined that the breakpoint is at that detection point, with an error margin of no more than 10cm.
Bending Method:
For shorter cables, the bending method can be used to test for breakpoints. Connect both ends of the cable to the red and black probes of the multimeter. Start bending the cable back and forth from one end; if the multimeter shows intermittent connectivity, the breakpoint is at that location. Continue this method until the breakpoint is found.
Damaged Cable Method
Needle Piercing Method:
This method uses the continuity of the cable to locate the breakpoint. Insert steel needles at intervals along the faulty cable and use a multimeter to measure the continuity status. The point where continuity differs indicates the location of the breakpoint. However, this method will damage the insulation layer and can easily cause other issues during later use of the cable.
Professional Instrument Testing Method
Additionally, for determining fault points in underground cables, audio detection instruments can be used to locate the fault point.
For determining the entire length of the cable as well as short circuit and open circuit points, a cable fault locator can be used.
Different methods should be used based on the actual situation to determine the location of the breakpoint. The above methods can generally identify the location of the cable breakpoint.
Source: Distribution Communication
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