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Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 5:08 AM

Hi everyone.

As per my knowledge the technology for locating cable fault in higher size cables above 16sqmm are available ( In India) where as that for lesser than 16sqmm or say 6sqmm cable not available . I hope as the technology advanced , there might be some kind of development in finding out the fault location in lower size cables.

If anyone aware of this kindly share.Thanks.

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#1

Re: cable fault locator for Lower size upto 16sqmm

07/13/2021 5:13 AM

Qualified Electricians can use elegant fault locator devices. These predict where on a cable the fault may be found and are invaluable in troubleshooting.

Most, if not all, will have access to one.

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#2

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 5:41 AM

What you are seeking is a Time Domain Reflectometer.

It can locate faults down to the foot or inches, if it is a good one.

You must know the capacitance of the cable,which should be provided by the manufacturer of the cable or wire.

It can also be done with a good oscilloscope when configured properly.It will require a little math though.

Here is an example,but there are other methods as well.

It is very simple to make one with a scope and battery.

Here is a link:

https://hackaday.com/2020/12/14/dead-simple-time-domain-reflectometry-with-just-a-battery-and-an-oscilloscope/

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#9
In reply to #2

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 5:13 PM

Here is a very good explanation of an oscilloscope used as a TDR.

https://www.youtube.com/watch?v=e9Z0VqZvrXo

Watch and learn and understand.

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#13
In reply to #2

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/14/2021 12:33 PM

Thank you ...I will go through it.

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#3

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 7:17 AM

...therefore if the capacitance-per-unit-length of the cable is known, it matters not a jot what the cross-sectional-area is and the <...16sqmm...> boundary suggested in the original post is irrelevant, as is the country of installation.

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#4
In reply to #3

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 8:40 AM

"Knowing exactly what to say,I said nothing." Mark Twain

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#5

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 8:47 AM

If the specifications of the wire or cable is unknown,use a 1 meter length cable and test it using a C-Meter and or Z-meter and calculate from that starting point.

Then use the very simple battery and 'scope method described in my link.

Use of a calculator is permitted.

(Before electricity reached my little corner of the world,we had to watch TV by candlelight)

Basically,we made do with what we had.

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#6

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 9:34 AM

Fluke make a test instrument.

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#14
In reply to #6

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/14/2021 12:34 PM

Thank you....I will go through it...This seems to be more interesting to me ..

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#7

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 3:26 PM

There are a number of ways to locate a fault. Which one is best depends on the characteristics of the fault. This document describes several methods.

Cable Fault Location Measuring Methods - HV Technologies

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#15
In reply to #7

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/14/2021 12:34 PM

Thank you for the detailed article with products...This also seems to be interesting to me. I will go through it.

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#8

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 3:44 PM

This app might work...worth a try....

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#10

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/13/2021 9:08 PM

https://www.epanorama.net/blog/2010/07/17/tdr-circuit-kit-available/

I made this several years ago. Works very well. You will need an O'scope of minimal specifications. Unlike commercial models you must divide the distance in half. To calibrate: Use a sample of the cable you need to measure say, 50 ft. Leave it open and then retest after shorting it. Coax lists velocity in per centage. Every thing else you will need to figure out on your own. Cable TDR's are rare at this point. Most are fiber.

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#11

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/14/2021 1:15 AM

Cable fault locators have been around since I started my apprenticeship in 1965 and the ones we used were valve powered back then and were used on power lines to narrow down the fault search area. They used the Time Domain Reflectometer principal, the modern ones I used could find faults on Decoron cable and small signal cables, coax, trailing cables and motor supply cables.

The fly leads from the machine were clipped onto one end of the cable between cores or core to sheath. All that was needed to get the right indication was the insertion of the dielectric constant of the cable into the device by way of thumbwheel switches.

If the constant wasn't known and the cable was of unknown length then a piece of the cable of a known length was connected to the device and the dielectric constant adjusted to get the cable length to correspond to the cable length. The remote end of the cable will show an open circuit on the CRO by a rising spike and if shorted by a lowering spike both of which are done to get the end correct. A discontinuity will show up as a small spike or a series of spikes for the joining plug socket ends, or a crimp link, as will partial breaks.

A moving cursor dot is moved along the trace by a knob and the digital length value is displayed according to the trace position. Accuracy is dependent on the operator but I have found faults in 2Km cables to 1/2m or about a backhoe bucket hole.

I have also used then to check tower antenna cables for damage or faulty connectors.

Brilliant pieces of kit and I dare say they have improved in the last 10 years since I had access to one.

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#12
In reply to #11

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/14/2021 4:03 AM

"Cable fault locators have been around since I started my apprenticeship in 1965..."

I've been around since before then & my grandfather is named on a UK Post Office patent for an improved cable fault finding system.

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#16

Re: Cable Fault Locator for Lower Size up to 16 sq mm

07/15/2021 7:43 AM
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#17

Re: Cable Fault Locator for Lower Size up to 16 sq mm

08/13/2022 3:08 AM

This instrument will help to pre-locate the fault and is suitable for almost all types of cable with an accuracy of 1 m.

http://www.telemetrics.in/PDF/TFL%206.pdf

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#18
In reply to #17

Re: Cable Fault Locator for Lower Size up to 16 sq mm

08/13/2022 5:27 AM

...For low resistance faults only( such as less than 20ohm )...Else we will have to use High voltage thumper also.

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#19
In reply to #18

Re: Cable Fault Locator for Lower Size up to 16 sq mm

08/13/2022 8:07 AM

A Thumper! I haven't heard that term in many years (1960's). We used to apply those to find intermittent faults in telephone cables.Basically,it discharged a large HV capacitor across the line, or to ground,which would weld a loose connection or make it totally open and make if easier to locate.

I had one such problem once,and called for a Thumper.My supervisor came out with no thumper.He took 2 pieces of #6 solid copper wire,about 1 meter long, and bent them into a 90 degree angle,like a large allen wrench shape, then hung the long end down toward the ground.He started walking the path of the cable and when the wires came together,he said"Dig here". I laughed,thinking it was a joke.

I felt silly digging ,but he insisted,so I dug.

Unbelievably,the fault was exactly where he indicated.

I have heard of water dousing,but not cable dousing.

I still don't understand it but in this case it worked.

Go figure.

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