Fault Finding & RD A frames

**GroundScope** · May 13th, 2011, 05:33 AM

Does anybody do Fault Locating. I didn't until a bloke called me to find a Fault in a 200 meter power cable on a Farm between House & Shed.
He said he had 2 electricians & they said it was stuffed but neither could find the fault.

I tested the ends of the cable first and it had low ground on both sides on both ends. I got an old CRT Pulse Echo Tester but its only good for phone lines & it showed the cable good for 200 meter, which was no help. So I did a locate & marked the cable path, and since I got no A Frame I put my TX on the lowest power @ 8khz then clipped Red lead on Red (A) & Black lead on Black (N) of the faulty power cable , Theory being the signal will cancel out until I hit the fault where it will leak to ground. Got a slight tone and no current reading for about 100 meters then the cable lit up & I said this it the spot. Customer with spade in hand dug down & found the cable direct buried in the dirt with no duct & It was quite obvious it had been hit by lightning.

I cut the faulty section out for a photo and Cable tests good both sides now. Leaving a happy customer to get it all patched up.

Got me to thinking, meybe I should buy one of those RD400 FFL2 A frames on ebay, I guess they will work ok with a RD4000T10 TX , anybody use one ???

**nrp3** · May 13th, 2011, 07:14 AM

I don't do a lot of locating, but I do fault locating. I find those kind of damages to light poles in the apartments I service. The wire was often times not buried deep enough or damaged when installed. I have an a frame for my Dynatel that I haven't tried yet. I have a stand alone a frame fault locator made by Progressive now Tempo/Greenlee. These can be found on Ebay for reasonable money. I would like to add a more powerful one made by either Timco, HJ Arnett, or Aquatronics for locating transformer secondary faults. I have a basic TDR (Riser Bond 1550) and a more advanced Bicotest T631 (been in their shop for almost a year for repairs, when they said months, they weren't kidding). TDR has gotten me within a couple of feet. I think we're talking the same thing pulse echo. I'll have to try your technique with the locator. Looks like that cables been hit and repaired before. Landscapers have been known to hit cables and patch them up with tape and wirenuts, which works for awhile and then fails again.

**1idejim** · May 15th, 2011, 01:47 PM

Originally Posted by nrp3

I don't do a lot of locating, but I do fault locating. I find those kind of damages to light poles in the apartments I service. The wire was often times not buried deep enough or damaged when installed. I have an a frame for my Dynatel that I haven't tried yet. I have a stand alone a frame fault locator made by Progressive now Tempo/Greenlee. These can be found on Ebay for reasonable money. I would like to add a more powerful one made by either Timco, HJ Arnett, or Aquatronics for locating transformer secondary faults. I have a basic TDR (Riser Bond 1550) and a more advanced Bicotest T631 (been in their shop for almost a year for repairs, when they said months, they weren't kidding). TDR has gotten me within a couple of feet. I think we're talking the same thing pulse echo. I'll have to try your technique with the locator. Looks like that cables been hit and repaired before. Landscapers have been known to hit cables and patch them up with tape and wirenuts, which works for awhile and then fails again.

same here, i do a lot of irrigation locating and fault finding, i have promoted the TDR for use in irrigation for a decade. use the dynatel 573d/l with an Aframe to find faults

**GroundScope** · May 17th, 2011, 10:40 PM

Originally Posted by nrp3

TDR has gotten me within a couple of feet. I think we're talking the same thing pulse echo.

Yep, PET is the old name for TDR, but same thing, Mine is an old Aegis CZ13202 all analog with a Cathode Ray Tube, internal 12v battery lasts just on 10 minuites. but it only really good for phone cable.

**Wingfoot** · May 18th, 2011, 12:22 AM

Hey Mate! - I'm stoked reading all your posts! Good onya!

I work closely with my local telephone company repairmen. Whenever they need to pinpoint an open (fault), whether it's a 2-pair service line or a copper cable, I am called. I have had success with the following technique:

I grab a ground with my black lead and I clip my red lead on the suspect dead wire or on the problem cable sheath. Even if I can't get transmitter continuity in f8 when I hook up, I still trace out my peak signal until my signal drops. (f8 and stronger frequencies are induction frequencies - Transmitter continuity not needed to trace line) I monitor the depth as I am tracing out. When the peak signal drops and the depth reading drops dramatically I usually find the fault. This works for me more times than not...................

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**nrp3** · May 18th, 2011, 06:24 AM

Drove about a hundred miles each way to fix something like the first post yesterday. A row of pole lights out. Found a bad splice. As you got close to it you could smell it. Using the A frame put me right on it. One of these times when I don't have to drive so far and have more time, I'm going to try these locator techniques.

**nrp3** · May 18th, 2011, 07:03 AM

I tried the TDR on this but was off by about 6 feet. It could see short (dip on the screen), but because I don't really know the VOP (velocity of propagation) of UF (underground feeder) I use this formula:

Distance to fault from one end of line/Distance to fault from one end of line+Distance to fault from opposite end of line x Total length of line. This comes from the manual. I may not have measured accurately enough. For pole lights you have to know not only the distance between poles but take a guess how far down into the ground it goes before turning horizontal and going to the next one. That and the fact that there was a piece of different brand cable spliced in. I have gotten within a couple of feet before though.

If want some light (kidding) reading on the subject get this guys book:

http://www.cablefaultlocation.com/index.html

A lot of it is way over my head, but an interesting read.

Another site you may want to check out:

http://faultlocating.com/default.aspx

**GroundScope** · May 18th, 2011, 09:14 AM

Originally Posted by Wingfoot

Hey Mate! - I'm stoked reading all your posts! Good onya!

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Hey Wingfoot, You must be half Aussie- you got the lingo down pat.

I guess you can tell I've had a slow week, not much work about at all, Too wet to dig perhaps ??

**Wingfoot** · May 20th, 2011, 12:47 AM

Originally Posted by GroundScope

Originally Posted by Wingfoot

Hey Mate! - I'm stoked reading all your posts! Good onya!

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Hey Wingfoot, You must be half Aussie- you got the lingo down pat.

Hey Mate! I have a couple blokes, Geoff & Bruce, who were born and raised there in Melbourne. It's interesting for me to listen to them talk. Both married Yanks and will probably stay here until they die. Geoff works in the school system here and gets almost 9 weeks a year vacation during our summer months; June, July and August. Geoff does part-time work as a field umpire for footie games played here in the United States. My buddy Geoff is always flying somewhere to officiate a game.

Every 2 years, Geoff flies to Australia for 8 weeks during the months of June and July to stay with rellies and visit friends. He tells me he finally survives the cold winter months in the States to travel half way around the world to endure more winter months in Melbourne!

Melbourne, Australia in July on the Yarra River.
Melbourne's first census (in 1836) reported 142 male citizens and only 35 females!
Oh my, how they’ve grown!

Anyway, Hoo-roo!

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**GroundScope** · May 21st, 2011, 08:20 AM

G'day Wingfoot,
Aint that pretty, Ya know sometimes I think I liked it better when there was only 142 people here, And of course we were all convicts. This was a Penal Colony ya know - Worlds Biggest penitentiary.
Better get Geoff & Bruce to have a butchers at this , they can zoom RIGHT into their backyard
http://www.nearmap.com/?ll=-37.77112...k&nmd=20110406

I find this This is WaaaaY better than Google Earth once you know how to drive it. Ive got the map centered over where I like to work. Naah not the big hole !
I like it because you can go back in time with the slider at the top , and you can view things from an angle with multi view. Its done with a Cessna & camera pod rather than satellite photos.

Heres some dude got an Airplane in his backyard http://www.nearmap.com/?ll=-37.76685...k&nmd=20101224

**Enjoythefall** · June 10th, 2011, 11:28 PM

I've never seen an A-frame. How does it work?

Since we're on this subject of my ignorance, I might as well ask this too... What is a groundscope useful for?

**nrp3** · June 11th, 2011, 07:32 AM

A frames and sometimes probes that look like ski poles are used for locating earth contact faults. That is when a conductor is touching the earth, for instance the sheath on a phone cable or when insulation is damaged on a power conductor. Many locators have an option for it. Sometimes they are stand alone units. Tempo/Greenlee makes a standalone unit that works pretty well. I have the A frame for the Dynatel, the Greenlee unit and just recently, the Aquatronics EG 3000, because it has more power.

As for groundscope, I'm not sure, but that may be TDR (time domain reflectometer). Also known as cable radar. Sends pulses down the cable and with it and you can see shorts and opens. Not quite as accurate as the a frame, but can get you close.