TDR'S for fault location

[dmagyar]

I've read some of the last threads (last year) on TDR'S, but wanted to know as far as the "Fluke TS90", which is marketed as a network tool. This seems to have the same capability (as far as a simple distance to a fault vs. a wave form display) and it's a lot less expensive. Has anyone used one of these for fault location? I've got a potential client with some U/F cable thats dead shorted, hot, neutral and ground. I've used a Schronsteadt mac 51bx locator to map the underground route, but needed something to zero in on the short.

 

[e57]

I'm unsure of that particular model - it may not have the right VPN adjustments for handeling larger cables... You should dig up it's manual and take a peek....

Otherwise - this megger CFL510F works well - it does take some interpetation, but IMO is better than a numeric model for fault finding... - But at 10X the cost.... $1700 I've used it - I like it - If my old shop were still scraping by I'd offer to come down and do it for you.... :roll: (Some liguidator has it now...)

 

[480sparky]

Is it faulted to ground, or are all the faults still contained within the (intact) sheathing?

 

[zog]

For larger cables you need a thumper.

 

[dmagyar]

Follow up on original TDR question

Follow up on original TDR question

I bought one of the more modest "distance to fault" TDR'S. It's a Psiber CT50. It gave me readings that were not quite as confidence inspiring as I was hoping for but I did find the underground fault at the first place I dug (total length 350' for the run). Next time in any similar situation I'm locating the u/g cable, cutting it to near the center of the run, then use a more normal divide and conquer procedure. When the cable fault was isolated and by cutting out the bad section and resplicing, then measured (by meggar)>1000 megohms to all conductors in both directions. A previous splice was the culprit, the factors involved were: a tight cable, that previous splice poured into concrete and ground movement did the rest.

 

[e57]

I have a post operational CT50 - same one, used it for years along with my old shops Megger waveform one - the later being the best of the two - since there are 'things' - you can 'see' that will factor into locating - like splices.... If it is a dead short on a run with out splices - the CT50 works great... Take reading from both ends and there you are... If there are other anololies the numeric models have some problems IMO.

Some time ago, I had a call to a place where there was a open on a 208 wye neutral - 3 other guys had been in there and said it needed to be replaced... I got called because I'm a little OCD... Technically... And found with the nemeric it gave some odd readings - from experiance it meant splices, but went back to the shop for the megger - and you could see all the splices... Pulled up the carpet to find a cut out in the sub-floor and a box with an abandon feeder tapped from it with a bad splice - saved customer at least 10K... And me a lot of embarasment if I went to re-pull it only to find a splice that wount pull through, or re-running conduit....

Otherwise the CT50 has it's uses... FWIW I have found stuff within inches on 200' runs with it.... But money is better spent on a waveform display model... JMSO.

 

[nhfire77]

I have the Cyber CT50. I have found it invaluable. It's not perfect and has limitations,but it makes me look like gold.

I had a fire alarm with an open NAC. No one could figure it out, I was he third guy to try. No as builts avaiable. It was a nursing home, 70,000 sq ft over two floors. I hooked up the TDR. The short was 10'. There was a closet behind the panel, behind the boxes in the closet, a NAC booster with low batteries.

The facilities manager said I had the golden touch, and all of his business. It's amazing more people don't troubleshoot in a manner like this.