meggering romex

[76nemo]

so if i get a bad reading on a piece of UF cable does it mean the cable is bad or is it because its in the ground?

Can you reword that again?

 

[76nemo]

Smokie the Bear

Smokie the Bear

Here's a little trick I learned from another story. Take some tracing paper or the thinest paper you can find. Take a pencil and scribble very thick, thick lines on the paper, clip your leads on each end of the scribble and throw it a 1000V. No, I did not say indoors, nor camping:grin:

 

[480sparky]

Didn't someone post a video of doing just that lately?

 

[electricalperson]

Can you reword that again?

well that guy said that if you megger a uf cable thats been underground for a long time you will probably get a bad reading. im wondering if that reading actually means the cable its self is bad or if you get a bad reading caused by the ground and water and the cable is still good

 

[76nemo]

well that guy said that if you megger a uf cable thats been underground for a long time you will probably get a bad reading. im wondering if that reading actually means the cable its self is bad or if you get a bad reading caused by the ground and water and the cable is still good

Try thinking of it as the test is labeled, insulation resistance testing. You are pushing voltage and comparing the leakage to another conductor, conduit, etc.. You can run cable through conduit, fill it with water, and as long as the ends of the conductor are seperated and out of the conduit on the other end, she'll still megg almost infinite as long as the insulation is sound.
Does that help? Bottom line is,... the more you ask, the more you learn, the more you experiment, the more comfortable you'll feel. There's some great people here who are more than willing to help you with your questions, don't be afraid to ask.

 

[electricalperson]

thanks for that..only way people will learn is by asking and experimenting. no one knows everything and im learning something new every day from this website

 

[frenchelectrican]

Didn't someone post a video of doing just that lately?

Ken,

Yepper i am sure if i nailed right BrianJohn did that and also have a photo i am not sure if he post it here but i know he did allready on other forum that i know for sure.

Merci, Marc

 

[76nemo]

Ken,

Yepper i am sure if i nailed right BrianJohn did that and also have a photo i am not sure if he post it here but i know he did allready on other forum that i know for sure.

Merci, Marc

That, I didn't see. Where is it Marc?

 

[frenchelectrican]

frenchelectrician posted:
"MDshunk or myself ??"

My apology Marc, I will be more specific in the future.

Did not know you had to 'isolate' when using the thumper also. That is why we are all here, to share and learn.

Always located my voltage 'leaks' using the VOM 'probe de dirt' method.

Best Wishes Everyone

Sure i am glad we can help you with this.

now speaking of plainjane VOM not always can find the voltage leakage with that because some ground is " bone dry " and it will not really conduct low - med voltage range so your reading will varies a bit.

that the reason why most electricians rather used the megger or thumper to find the fault.

now keep in your mind there will be two common fault is either open fault
or short fault [ the short fault will have 2 diffrent way to determed this it will be either arc fault or bolted fault.]

hope this will clear up some info

if you want more details you can goggle search " megger " it will provide more info there than try to fill this page up.

Merci, Marc

 

[frenchelectrican]

That, I didn't see. Where is it Marc?

Hold your pants for a min let me find it.

if my cat get off from me lol

Merci, Marc

 

[cschmid]

you got the crank megger..sweat tool, I remember working with a guy (Scott) and we were meggering motor leads but we were in different rooms he said go ahead and I started to crank the megger.. Joe the mechanic with Scott had to call and tell me to stop between laughs I guess it was kind of funny..But I would never encourage you to play pranks..

 

[electricalperson]

today i was testing the romex again..i skinned an insulated wire and had it as close to the bare copper as i could without actually touching. i had the tester on the 1000v scale and noticed it arcs across and reads almost 0 ohms of resistance. then i put it on the ohm scale and noticed it was reading over 5000 ohms of resistance

 

[masterelect1]

Megger Usage

Megger Usage

Hope this helps. I cut my teeth in the shipyard doing ship repair. An inherent problem aboard ocean going vessels(re: electrical systems) is water-go figure.

Anyhow, learning how to use a megger was of the utmost importance. I used a Biddle 500 volt crank type megger. Aboard ship the electrical dist system is ungrounded as a ground on one phase does not interrupt the system from functioning. Last thing you want is to be dead in the water. So, as soon as a ground appeared on the monitoring sys. an electrical person was dispatched to find the culprit and clear it if possible as a ground on another phase would cause system failure.

Many of the older ships were DC (240/120 volt) and had ungrounded systems also. Most shorebird electricians have trouble understanding this concept (understandably) but if shipboard lighting/receptacle circuits had an intentionally grounded conductor most of the circuits would be compromised, i.e. not working, due to water in fixtures, etc...

The point of this is that a megger in the right hands is a very useful tool and has multiple uses such as phase to phase insulation testing, phase to ground insulation testing, and continuity of conductors from point A to B. On the ohms scale it can be used to measure resistance between conductors and of component parts, such as coils but is not as accurate as a VOM ,IMO.

 

[brian john]

 

[cschmid]

nice brian I especially like the slide show feature..I also like the picture of the emt couplings in the panel..:grin:

 

[Energy-Miser]

Hey, that's a very nice demo. What was the applied voltage? e/m

 

[Krim]

Is a thumper the same as a megger ?
If not what is the proper name for a thumper ?
I'm familiar with and have used a couple different meggers but have never actually seen what others consider to be a thumper .
Pictures anyone ?

Carl

 

[electricalperson]

a thumper is used to find cable faults underground. the power company uses them if im not mistaken. they put a high voltage and it creates a short circuit underground and you use a hearing device to hear it underground.

 

[Krim]

a thumper is used to find cable faults underground. the power company uses them if im not mistaken. they put a high voltage and it creates a short circuit underground and you use a hearing device to hear it underground.

So, it is a good sized piece of equipment on a tow behind trailer ?
Carl

 

[brian john]

Thumper 14"X14"X40" and a control unit 24"X18"X18" as I remember, owned by utilities and some testing companies.

#2 pencil on notebook paper and 1000 VDC, though thinner paper does works better