Current leakage on residential service

[wptski]

That is still my postition with equipment that has what I find to be typical megger readings...that is in excess of 100meg. Sure there may be lab instruments that can read this very low current, but not something you can buy.
Don

Don:

Your stuck in analog, you need to upgrade! Lots of new products out there that aren't lab instruments, lots of features, take a look some time.

 

[wptski]

I said your meter could not read microAmps. I was partially wrong, your meter specs say it cannot read less than 10 microAmps.

I said the meter will read zero (in your case that is still .01mA) if you clamp it around all of the current paths. This is a basic law of physics and must always be true.



So far we have 59 discussions over 6 pages, that is a lot of questions and answers. The problem seems to be you are not getting an answer that you like.

Yes, leakage current is real. Yes, it is measurable. Yes, it can be dangerous. However, your meter shows there is leakage current from a 3 conductor cord connected appliance insulated (maybe even isolated) from ground but you have yet to identify the path that current is taking.

Jim:

My original question wasn't about current leakage in a appliance, it was a "extra" added statement that I made. That's when dam broke loose and the flood hit.

The path for current flow is through and over the insulation as the ECM article mentioned above states but nobody here seems to belive this. I read that long before my first post. Electrical contracting which is what this forum is about doesn't seem to deal with low current leakage just heavy current leakage.

 

[suemarkp]

But you're putting insulated wires in your clamp meter, so it should still be measuring that current. If current is jumping off the insulation, where is it jumping to (especially if you're isolated the chassis from earth)?

 

[wptski]

I assume that follows the insulation to where the conductor(copper) is! Have you ever seen a picture/graphic of how the molecules of insulation align themselves duing a dielectric/absorption tests? That's the 1 minute and 10 minute insulation tests, not sure about the names right now. Sorry, I foget where I read a good explanation of the two tests!

 

[jim dungar]

Bill,

If most of the current is flowing in the copper internal to the power cord and the rest is flowing "in or on" the insulation, but all of it is flowing through your clamp-on then the meter must read it's zero value.

I have not seen any discussion in this thread denying the fact that current can "leak" through insulation. This thread has had discussions about unacceptable NEC and hospital system leakage current levels. Personally, I don't agree with the definitions in the EC&M article though I have no problem with the basic concepts. Leakage current in and of itself may not be a problem, but the path that it follows always is.

 

[brian john]

{quote]My original question wasn't about current leakage in a appliance, it was a "extra" added statement that I made. That's when dam broke loose and the flood hit.

The path for current flow is through and over the insulation as the ECM article mentioned above states but nobody here seems to believe this. I read that long before my first post. Electrical contracting which is what this forum is about doesn't seem to deal with low current leakage just heavy current leakage.[/quote}

I ask again what is your QUESTION AND/OR POINT.

I deal with ground current when it is an issue. That is when ground current from what ever source results in life safety issues, Power Quality issues, power interruption issues, other than that NONE of my customers will pay me to chase something that is not a problem.

 

[wptski]

Jim:

Right, they all flowing through the clamp but what flows some gets cancelled out and what's left is leakage. I've seen graphics where the magnetic fields are shown. Since you don't agree with the ECM article which is a carbon copy of other articles I've read on subject, you'll never change your views.

 

[wptski]

Brian:

My point is that appears that unless current leakage gets to the point where somebody gets shocked or there is another electrical problem, it's not a issue! There's no such thing like perdictive or preventative maintainance in this industry, That's too bad.

 

[don_resqcapt19]

Bill,

Right, they all flowing through the clamp but what flows some gets cancelled out and what's left is leakage.

If all the current is flowing through the clamp then they sum to zero. If you meter reads other than zero it is wrong. If there is leakage via other paths not associated with the conductors then you meter will not read zero. I see nothing in the article that says the current flowing through the clamp will not be detected. It is only saying that there is no perfect insulator and there is leakage on all circuits and equipment.
For the resistance that I often find with a megger, the leakage current is far below the resolution of your meter and of most if not all field meters. A path with 100 megaohoms of resistance will only flow ~1.2 microamp at 120 volts. Often my megger will read at its maximum which is more than 1999 megaohms. At that resistance the leakage is about 6 nanoamps. Is there a field meter that will read at that level?
Don

 

[don_resqcapt19]

Bill,

There's no such thing like perdictive or preventative maintainance in this industry, That's too bad.

Sure there is, but leakage in the mircoamp range of even in the low milliamp range does not trigger any action, at least not in any ordinary applications.
Don

 

[dereckbc]

There's no such thing like predictive or preventative maintenance in this industry.

Yes there is, lots of people make a living out of it.

The path for current flow is through and over the insulation as the ECM article mentioned above states but nobody here seems to believe this.

Appears you do not listen very well and only hear what you want to hear. In my very first response I said most of the leakage currents found are from distributed capacitance in any electrical system and filters installed L-G for FCC purposes. This is from the dielectric strength property in any insulation.

Teflon has the highest dielectric strength used in the industry, but is rarely used except in extreme high temperature or corrosive environments. Otherwise its cost is prohibitive. However even Teflon has leakage.

The whole point is any conductor insulation will have leakage at AC frequencies from dielectric strength, that will never change. At 60Hz the leakage the leakage from capacitance is so low, it is meaningless.

 

[wptski]

Since some or maybe all don't agree with the ECM article, is there a link to any article that anyone agrees with?

So there is some sort-of preventative maintaince in electrical contracting or are you refering to post-construction business? That means that you make use of current technology like thermal imaging, correct?

derekbc:

Dielectric strenght never changes??? Are you kidding? You meg when it's new and monitor it.

 

[spsnyder]

Dereck "Appears you do not listen very well and only hear what you want to hear...."

Bill "Since some or maybe all don't agree with the ECM article,..."

Case in point.

 

[dereckbc]

Dielectric strenght never changes??? Are you kidding? You meg when it's new and monitor it.

You are taking things out of context, I never said "dielectric strength never changes", that is what you wanted to hear so you can argue.

 

[wptski]

I'd just like to a few articles that condradict the ECM article! Is that asking too much?

 

[plate]

About 7-8 years ago, I troubleshot a garbage disposer that was tripping GFI recpt after about 60-90 seconds of use. I don’t remember the age of the actual garbage disposer.. It was a hard wired unit using bx cable. I believe it was on a separate circuit. The disposer was replaced and problem solved. A current probe/meter capable of leakage measurements would have been nice to have.

I not sure how much I would use a leakage meter, but it might come in handy when trouble shooting the GFP (30mA) portion of AFCI circuits where someone tied into another circuits grounded conductor. I happen to thrive on information(when time and money permits). I find that in general, measurements make one question the physics of what is going on and therefore increase your understanding (by digging in deeper to the subject). That is what is also good about this site. Are we on are way to 100 posts?

Edit to make sense out of last sentence in 1st paragraph

 

[don_resqcapt19]

Bill,

I'd just like to a few articles that condradict the ECM article! Is that asking too much?

I don't see anything in the article that says what you seem to think it says. It says that all conductors have leakage....that is the same as everyone else here is saying. It even says that the leakage current follows ohms law. If you have an isolated appliance with no conductive paths other than the cord where is the current flowing? Yes, in reality there are always other paths, but the resistance of these paths are so high that the leakage current would be in pico or femto amp range...that means that any insulation leakage current would flow with the conductors and if you clamp around all of the conductors, the current will sum to zero.
Don

 

[wptski]

Don:

Your stuck on zero! Look at Post #10, the link to a Fluke PDF on current leakage. Look at Fig. 1, does it say that it's going to read zero? Why do it if it's going to read zero, right? If you get a reading, it's leakage.

 

[karl riley]

I have just read this entire thread since someone asked me to check it out. I can see the different dialogs going on and understand the frustration of the electricians who are used to dealing with problems that have an effect that needs correcting.

At the same time, the poster (Bill) is really in a more academic space, to which he adds a bristling response to having some of his statements contradicted or downplayed.

So let me add a couple of points from my experience. First, I am used to using mini clamp-on ammeters which measure accurately in milliamps. The setting I use is the 20mA scale, and there is a zero set button I push before each measurement. I have not had a need to read below 1 mA.

The leakage Bill first mentioned was evidently current on the grounding conductor which was not related to the circuit he was measuring. In my experience this is often due to neutral current which is flowing around the building on grounding paths. There are several causes for this, but is it a problem?

Yes, if there is enough of it flowing in any particular run. This brings us to the question of how much leakage is a problem. Around 5 mA the GFIs will trip. Other than that, EPRI is looking into the possible connection of small leakage currents in bathtubs between faucet and drain due to voltages on the water system and childhood leukemia. That research has a long way to go still.

My work deals with the concern (childhood leukemia) with magnetic fields of 3 or 4mG, shown by extensive research. What leakage current causes those fields? If the child is, say 2 feet from the circuit with the leakage (net current), one needs one amp net current to produce 3 mG.

With some sensitive electronic equipment, 2 mG might have an effect, so one is still looking at 1+ amps as a problem, unless the circuit is very close.

So this is really a question of what amount of leakage is significant, since as pointed out there is always some micro amount. If we can't identify the significant value, there is not much use of continuing this thread just as an academic discussion. OK?

Karl

 

[mattsilkwood]

But you're putting insulated wires in your clamp meter, so it should still be measuring that current. If current is jumping off the insulation, where is it jumping to (especially if you're isolated the chassis from earth)?

thank you i was wondering how long it would take for someone to say this