megging

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RHJohnson

Senior Member
duluthelectrical said:
Thank you everyone for your comments, on one job the pipe got so hot at a point it melted a hole in it . Ground size and methods wasn't sufficient to clear the fault current. Other jobs I believe it was the feeding point, i.e at the lb conduit body. If jacket gets slightly nicked at conduit body then after sitting there contracting and expanding it finally meets its melting point and boom. Megger testing is only so good. Verticle dropping conductors need to be supported by conductor strain relief in future.
You haven't been clear on your megger test procedure or your conduit layout. To begin, a megger test on new 600v cable, after installation, is usually required to be 100 meg or higher to be acceptable. That is from phase to phase, and phase to ground. What is your wire size? If a hole melted in conduit it must be a larger size, and you used an LB....bend radius!The insulation was stressed right there. Vertical drop on those conductors was how many feet? You state megger testing is only so good.....It's all you need if you know what you are doing....If the conductor melted a hole in the conduit you have more than a megger problem!
 

boboelectric

Senior Member
duluthelectrical said:
Just want some clarifications, what is the best way to test a 600 thwn conductor? I have been megger testing all of my wires and they test out ok, but later on i will find out that they were not ok. I use the fluke 1520 and test them to 1000v and wait till it reaches 3 meg ohms. They always test out but I am beginning to believe that this test isn't sufficient. Any suggestions?
I'd never energize those cables reading 3 Meg.
 
i am trying to fix the job with the hole in the pipe, re- pipe with 4 inch all the way,using mogul style lbs, and using a pull box, upsizing the ground wire, i never did this job, nor has any of my jobs blow up, i am the guy that is fixing
 

zog

Senior Member
Location
Charlotte, NC
duluthelectrical said:
The G is a gig ohm which everyone knows, the k is actually on the 1520 megger which is another test range.

There is no such thing as GkOhms, T Ohms would be the equivilant and I doubt your 1520 measures T Ohms and LV wire would never see T Ohms.
 

76nemo

Senior Member
Location
Ogdensburg, NY
Hi there duluth. I have the 1520 as well, and graduated to the 1507. The 1520 only measures as high as 4000M. Reread that, that's 4G's. You'll see 4000M on an open test/leads held apart on the 1520.

I can't really add anything more than what else has been stated. It seems like now you are responding that the tests showed 3G, not 3M. Am I correct here? If you EVER have any cabling that rings at 3M or anywhere near that, NEVER energize them, the insulation definetly has issues.

Please respond back with any further questions.
 

76nemo

Senior Member
Location
Ogdensburg, NY
duluthelectrical said:
The G is a gig ohm which everyone knows, the k is actually on the 1520 megger which is another test range.

Had to go look again before I opened my mouth any further:grin:

duluth, the only function on the 1520 that indicates "k" is the resistance mode, not the IR test. Can you follow up on this?
 

mdshunk

Senior Member
Location
Right here.
76nemo said:
Had to go look again before I opened my mouth any further:grin:
I'm still wondering what the results of the IR test were myself. 3M? 3G? Some made up 3gk thing? It's definitely not clear, and I'm personally doubtful whether any of those numbers are the real result or not even though it doesn't matter a hill of beans to me. If a guy told me any sort of megger readings and wasn't sure of something as fundamental as the units of the measurement, I might also wonder if the test itself was even properly conducted.

Who did these tests anyhow? The installer or a 3rd party? Was it documented or did someone just remember the numbers in their head?
 

76nemo

Senior Member
Location
Ogdensburg, NY
duluthelectrical said:
Sorry the 1520 will go up to 1000 gk ohms. Know knowing I got readings 200-300 gk ohms and they still blow what could be the problem?


In the matter of personal safety, we are all trying to help, but me, the dummy, am trying to clear up what I don't understand in your original question. duluth you said the 1520 will scale to 1000gK.
The 1520 has a maximum of a 1000V push, is this where you are getting 1000 from?
 

wptski

Senior Member
Location
Warren, MI
The 1520's analog scale has one point marked as "GK" because its used to read in either Gigohms or Kohms depending on the function used. Like "76nemo" stated at 1000V, it has a maximum of 4000M or 4G. I gather this from looking at the manual which is pretty lame if you ask me! I also have a Fluke 1507.
 

POWER_PIG

Senior Member
mdshunk said:
It sounds like you need some enhanced quality control on your installation methods and not some better fancy whiz-bang tester.
Agreed...............anyone have some input on where I can find a mirror that states that IM the purtiest of them all?
 

76nemo

Senior Member
Location
Ogdensburg, NY
duluthelectrical said:
reading at 4g not 4m

Than you are good to go. Are you just checking one leg to ground, or all around the fence? Now I have to go back and reread, lost again. They should just euthanize me:grin:
 

76nemo

Senior Member
Location
Ogdensburg, NY
Continuity is not stressing the insulation. This type of testing will eat $ in batteries, but it is something that is required, like it or not, unless you are hand crankin'.

Start the scenario over again. What other questions do you have about IR testing or the 1520 specifically?
 
I would like to know in detail how others test there wires with the 1520. I know that meggering is the most important test of the system and would like any input.
 
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