Detecting cable and wires fault location is a multi-step process. This method is used where the faulty wires or cables can’t be seen. It must be performed as quickly and safely as possible to prevent people from going without an electric supply for a prolonged period.
There is an extensive range of methods to locate the break or short point in an underground wire or cable. You may use any desired method as per your requirement and availability. But, in case you aren’t sure about how and what are the procedures for cable fault location, don’t fret.
We have detailed the most popular methods for locating faulty cable and wire and the step-by-step guide to performing it effectively.
The 3 most popular techniques for fault cable and wire location
1. Cable thumping
It is a portable high voltage surge generator. This method is used to inject a high voltage surge of around 25 kV into the faulty wire.
Upon supplying the high voltage surge, the open circuit fault breaks. As a result, it creates a high current arc. This high current arc produces the characteristic thumping noise at the faulty wire location.
The procedure involves:
- Setting a thumper to thump continuously
- Afterward, walking along the route listening to the generated thumping noise
The higher the applied DC voltage, the louder the thumping. However, it is relatively more effective for shorter cables route.
2. time-domain reflectometer (TDR)
This method sends low-energy signals of around 50 V for a shorter duration but at a higher repetition rate to locate the faulty wire and cables. When the signal senses a change in impedance, it gets reflected. This way, the faulty cable location is spotted using TDR.
The process measures the time the signal takes to reflect from a point where there is a change in impedance. Afterward, such signal reflections are plotted on graphs. Then, the graphical display is studied to decode the results.
3. The high voltage radar method
This is another popular method to locate underground faulty cables and wires. This method further includes several processes like:
- Arc reflection
- surge pulse reflection
- voltage decay reflection
A step-by-step guide to finding a break or short point in underground cables
1. Isolating cable and adhering to safety protocols: Generally, a cable fault is permanent. So, the protection devices at either one or both ends would have been tripped. This leaves the faulty cable isolated but never grounded or earthed.
So, make sure to isolate and earthing the ends to make them safe for testing.
2. Identification of cable: Keep in mind to confirm the cable for which the testing has to be done. So, in a place where multiple cables run parallel, begin with cable identification before rushing to cut the cable to start the test.
3. Tracing the cable: Remember, an underground cable is never straight, rather varies in-depth and directions. This step is to ensure the cable route follows the most expected path.
4. Identification of the fault: First, identify the phase and whether the fault is low or high resistance. You need top-quality equipment for the correct diagnosis of the fault—for example, Noyafa NF-816L Underground Wire Locator. This is an excellent helper in cable tests with a 1000 ft. cable length and 2 ft. of detection range.
5. Pre-location of the fault: Carry out a precise and reliable pre-location test for quick and efficient fault location. It reduces the length of the full-fledge cable route to a few percent and the extensive timings to just a few minutes.
6. Pinpointing the fault: Using the test mentioned above, you will get to a distance of around 5 percent to the faulty cable. After that, you may use acoustic pinpointing methods like shock discharge generators to pinpoint the cable fault margin to 0.1 percent.
7. Re-energizing the cable: After the testing and necessary repairs are made, hand over the cable to the operators. They reinstate and re-energize the loads.
Endnote
By now, you must have known the steps and the different methods to find a fault in underground wire and cable. This complete process might seem tricky and daunting on the surface. However, with the right tools and methods, it is easily doable.
Keep in mind to be cautious dealing with the underground cables and wires and ensure to start with the test only after you have cut the flow of the electricity.
