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Earth leakage trips intermittently - cannot find reason


Antony
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Hi all,

 

I have read this article for the past 3 months in search of my own earth leakage problem.

 

gotten to the point where I can pinpoint it is originating on one my sub DB's (installed separate earth leakages for each dB)

now before I order the breaker in question I rather want to find the culprit appliance. so I need a suggestion on the cheapest meter that I can use to trace each point.

Can you guys recommend something here ?

 

cheers,

 

 

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  • 5 months later...
On 2018/11/19 at 9:50 AM, ___ said:

It could be caused by something on the grid side, though it is unlikely. I read at least one post somewhere on a forum where the trouble was in a lamp post on the street.

One thing it could be is that the RCD is simply on its way out. I had that once, some years ago. They have an electrical life, how many times they can operate, and for the cheap ones this could be a few thousand times. So you could just replace the RCD, its a cheap R250-R350 and it probably needs to be done anyway at some point.

(RCD == Residual Current Device, the more formal name for what we informally call an Earth Leakage).

It is also possible that you have what I had: You have all sorts of EMI-filters and surge arrestors in appliances in your home, and this causes a high standing earth leakage.

Let me first take a detour to explain standing leakage: Every house has a standing leakage to earth. There is always a couple of microamps (or even millamps) sneaking off to earth, because insulation is never perfect, some of it always finds alternative ways back to the supply and therefore bypasses the normal return path that is monitored by the RCD.

Most RCDs start tripping at around their 50% rating. So a 30mA RCD might trip as early as 15mA. The regulations simply state that they MUST trip within a very short time at 30mA.

Then inside your home you may have appliances that introduce more such leakage. One way to filter out EMI, for example, is to fit two capacitors between L/N and earth (and a capacitor is a frequency dependent resistor, so it passes a small bit of current to earth). The other culprit is the cheap-but-effective surge protection used almost everywhere: Metal Oxide Varistors. They pass a tiny bit of current too.

Now I can get to the meat of the argument: Sometimes when the power comes on, these filter devices can introduce a small spike (duration is literally in the microsecond range) and this causes nuisance tripping, especially if it is on top of a fairly high leakage. There is no actual leakage (other than the normal tiny bit of standing loss).

In my home I had a standing loss of a good 7mA.

44026573_10156534809275619_1659529355484725248_o.thumb.jpg.ed30928ea2ea405e5797c6d4bfc113cc.jpg

It took me weeks to solve it. These are the things I uncovered.

41922911_10156473202760619_6831740783935094784_o.thumb.jpg.eb92aba4603bad4683ee0b2414b13a38.jpg

This is the plug of a "Multiplug strip", with a surge arrestor built in. Note the MOVs (those green things). This introduced a good 1mA leakage. One of the neon lamps were burned out in any case, so I removed it.

44052883_10156539543745619_1922839584060735488_o.thumb.jpg.7000cbae672c3bd150d07840bc9fc97c.jpg

That's the transformer feeding the alarm system. It has a big EMI filter in front of the iron transformer (for what? Iron transformers don't introduce noise and are pretty effective at removing it... I ripped it out).

surge2.thumb.jpg.98489100a27bcdd05e0d7f11ee6609ee.jpg

That's the bottom side of the Garage door opener (ET DC-Blue). Again note the blue MOVs.

How did I find these appliances? Trial and error. Literally unplugging everything, faking power failures and first drilling down to which circuits had the problem, and then further down to the appliances. All the while the kids are unhappy because the internet is down 😉

And my solution...

44731917_10156558072885619_3896920155187314688_o.thumb.jpg.fa6a19d149c675ba7a831d546f0fd1a9.jpg

This is a type AP-R (ABB's lingo for impulse-resistant) RCD. I paid too much for it. It should cost about R1200, but apparently it is out of stock with the suppliers at the moment. Contact the guys at LiveCopper to find out how long until they have stock.

Hi

Having a similar issue, in that E/L trips on power restore only.  Currently a 40a E/L ACDC brand (refer photo) 

Where can I get this RCD? Could not find on Livecopper website?
 

Is a 25A RCD sufficient? (5000w/230v = 22A) 

4F37C967-0A3C-49D5-B5CA-ED33A77BC16F.jpeg

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Have a plug socket that will be fine for a few weeks, then out of the blue the rcd trips and even if I unplug the appliance and try to reset the circuit breaker, the rcd immediately trips and if I leave mcb in the off position and come back to it one day, switch on the mcb, all is fine and I can plug in the appliance and everything is good until one day the  rcd trips again and the process is repeated 

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If you can get hold of a Meggar meter, then you can hopefully see if/where the earth fault is. Sometimes you've got a couple of "small" earth faults which adds up to the max of your earth leakage and then it trips. 

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Welcome to my world 😉

Get a clampmeter (not too cheap but they also function as a multimeter) and read the ma between neutral and earth.

Remember they all add up.

I’ve a fancy borehole controller that gives a high 30ma reading. On its own it can cause a trip when it comes on - requests to the local factory on this issue go unheeded. Surge protectors also add to this load. And the current wet weather will help as well to show up poor insulation of cable cuts and connectors.

Sometimes my rcd also trips when the power comes back. If you have several rcds in sub db’s (seems you have them) the more sensitive one will trip first. Currently five rcds in five sub dbs. I’ve installations done this way, thinking each one will protect its own db, but their sensitivity vary widely. So it was actually just a waste of time and money. It also sends you on a wild goose chase untill you figure it out. I’ve bought a plug ma tester (useful to own for about R250) and it is usefull to show the trip sensitivity of an rcd - I’ve once returned a Hager rcd based on this and it was swopped out with not even a shoulder shrug. Makes one wonder hmmm...
The only real solution is to get an expensive slow trip rcd, do a seach for info in the forum. It is not legal to install a >30ma rcd in homes (you get them). I could never get hold of a slow trip 30ma and they sold for about R1700, not exactly ACDC prices. 
I also notice a wider variety of rcd’s nowadays.

Edited by Johandup
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  • 1 month later...
On 2018/11/19 at 9:50 AM, ___ said:

It could be caused by something on the grid side, though it is unlikely. I read at least one post somewhere on a forum where the trouble was in a lamp post on the street.

One thing it could be is that the RCD is simply on its way out. I had that once, some years ago. They have an electrical life, how many times they can operate, and for the cheap ones this could be a few thousand times. So you could just replace the RCD, its a cheap R250-R350 and it probably needs to be done anyway at some point.

(RCD == Residual Current Device, the more formal name for what we informally call an Earth Leakage).

It is also possible that you have what I had: You have all sorts of EMI-filters and surge arrestors in appliances in your home, and this causes a high standing earth leakage.

Let me first take a detour to explain standing leakage: Every house has a standing leakage to earth. There is always a couple of microamps (or even millamps) sneaking off to earth, because insulation is never perfect, some of it always finds alternative ways back to the supply and therefore bypasses the normal return path that is monitored by the RCD.

Most RCDs start tripping at around their 50% rating. So a 30mA RCD might trip as early as 15mA. The regulations simply state that they MUST trip within a very short time at 30mA.

Then inside your home you may have appliances that introduce more such leakage. One way to filter out EMI, for example, is to fit two capacitors between L/N and earth (and a capacitor is a frequency dependent resistor, so it passes a small bit of current to earth). The other culprit is the cheap-but-effective surge protection used almost everywhere: Metal Oxide Varistors. They pass a tiny bit of current too.

Now I can get to the meat of the argument: Sometimes when the power comes on, these filter devices can introduce a small spike (duration is literally in the microsecond range) and this causes nuisance tripping, especially if it is on top of a fairly high leakage. There is no actual leakage (other than the normal tiny bit of standing loss).

In my home I had a standing loss of a good 7mA.

44026573_10156534809275619_1659529355484725248_o.thumb.jpg.ed30928ea2ea405e5797c6d4bfc113cc.jpg

It took me weeks to solve it. These are the things I uncovered.

41922911_10156473202760619_6831740783935094784_o.thumb.jpg.eb92aba4603bad4683ee0b2414b13a38.jpg

This is the plug of a "Multiplug strip", with a surge arrestor built in. Note the MOVs (those green things). This introduced a good 1mA leakage. One of the neon lamps were burned out in any case, so I removed it.

44052883_10156539543745619_1922839584060735488_o.thumb.jpg.7000cbae672c3bd150d07840bc9fc97c.jpg

That's the transformer feeding the alarm system. It has a big EMI filter in front of the iron transformer (for what? Iron transformers don't introduce noise and are pretty effective at removing it... I ripped it out).

surge2.thumb.jpg.98489100a27bcdd05e0d7f11ee6609ee.jpg

That's the bottom side of the Garage door opener (ET DC-Blue). Again note the blue MOVs.

How did I find these appliances? Trial and error. Literally unplugging everything, faking power failures and first drilling down to which circuits had the problem, and then further down to the appliances. All the while the kids are unhappy because the internet is down 😉

And my solution...

44731917_10156558072885619_3896920155187314688_o.thumb.jpg.fa6a19d149c675ba7a831d546f0fd1a9.jpg

This is a type AP-R (ABB's lingo for impulse-resistant) RCD. I paid too much for it. It should cost about R1200, but apparently it is out of stock with the suppliers at the moment. Contact the guys at LiveCopper to find out how long until they have stock.

Hi Guys

Tried the above RCD (63A version) and did not resolve tripping after power failure restore.  Need an electrician that could help in the Morningside/Kelvin Area (Sandton) to conduct the above tests and trace the fault.

By the way the 25A and 40A RCD from ABB has been discontinued, only available in 63A.

Message or contact me on 0824515786

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Looking at the symbol on the ABB RCD in the post you quoted above and given there's no mention of a tripping curve indicates that it doesn't offer any overload protection, only residual current (earth leakage) so the 25A, or 40A or 63A rating just indicates the maximum load the internal contacts can make and break without being damaged. Often the wholesalers will charge you a much higher price for a 25A than a 60A when there's no reason not to install the 60A. Probably the reason they discontinued the two lower current rated options.

Edited by Marv
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