Fault locates

[ptonsparky]

We are working on a run of USE wire that tests @.3meg to ground. 1/4 mile plus in length. The other two conductors check out @ 4 - 10 meg with phase to phase about the same. We have found in the past that finding a fault with readings much more than 20k is about impossible, at least with the equiupment I have. Just wondering if anyone has better luck & if so what equuipment you are using.

The USE is 20+ years old and the .3M reading may just be the general condition of this conductor insulation along its entire length. I was there to check out a 75 hp motor that had considerable mice damage & just checked the underground to the pivot for the heck of it.

 

[electricalperson]

We are working on a run of USE wire that tests @.3meg to ground. 1/4 mile plus in length. The other two conductors check out @ 4 - 10 meg with phase to phase about the same. We have found in the past that finding a fault with readings much more than 20k is about impossible, at least with the equiupment I have. Just wondering if anyone has better luck & if so what equuipment you are using.

The USE is 20+ years old and the .3M reading may just be the general condition of this conductor insulation along its entire length. I was there to check out a 75 hp motor that had considerable mice damage & just checked the underground to the pivot for the heck of it.

that cable needs to be replaced. even 10megaohm is too low. it should be at LEAST 100megaohms. ill hook up 50megs until a repair can be done. i would not energize that cable.

they sell a tool called a TDR (time domain reflectometer or something like that) that can pinpoint faults, water damage, insulation damage etc with a location. i dont have one but im sure other people do here.

is this cable underground? if its 20 years old im worried that the pipe is rigid conduit and is rusted away. good luck pulling it out of thats the case. they make a special chemical to put in the pipe that will help loosen it up but i never used it before

is it possible the .3 meg is reading through a connection to ground? what megger did you use? hook up the guard terminal and see if it improves. my megger has a guard terminal that i use and that gives a more accurate reading if the insulation is dirty or whatever. im pretty sure im using it right. i hook the guard terminal to the insulation its self and megger from the conductor to ground or the sheath or the conduit. the guard terminal stops surface leakage

 

[Cow]

So the pivot is still running? I wouldn't mess with it to be honest until one of the wires blows clear and gives you an easier job of fault locating. We use a pinpointer made by Progressive, I believe this is the newer version of what we use:

http://www.stayonline.com/detail.aspx?ID=170

I believe 480sparky has this exact one, maybe he can shed some light on it. I've only fault located on wiring that blew or corroded apart, never tried it on something that just megged low so I can't really help you there as far as how effective it'll find the fault or bad spot.

 

[ptonsparky]

Change the name & age and it looks just like the one we use. I wonder if they have changed any on the inside?

I was proved wrong by my help. The corn is 4'-6' tall so the guy using the fault locater was right on the heel of the one with the cable locator and they found one fault about 800' out. It was slow going so they probed more often.

Owner opted to irrigate vs repair at this time.

 

[ptonsparky]

that cable needs to be replaced. even 10megaohm is too low. it should be at LEAST 100megaohms. ill hook up 50megs until a repair can be done. i would not energize that cable.

they sell a tool called a TDR (time domain reflectometer or something like that) that can pinpoint faults, water damage, insulation damage etc with a location. i dont have one but im sure other people do here.

is this cable underground? if its 20 years old im worried that the pipe is rigid conduit and is rusted away. good luck pulling it out of thats the case. they make a special chemical to put in the pipe that will help loosen it up but i never used it before

is it possible the .3 meg is reading through a connection to ground? what megger did you use? hook up the guard terminal and see if it improves. my megger has a guard terminal that i use and that gives a more accurate reading if the insulation is dirty or whatever. im pretty sure im using it right. i hook the guard terminal to the insulation its self and megger from the conductor to ground or the sheath or the conduit. the guard terminal stops surface leakage

Cable is direct bury. We use a Fluke megger. I have two TDRs but they aren't as user friendly as one would hope. We use them as 'last choice' for this type of locate.