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Earth leakage trips when power restored


Bobster.

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In the current bout of load shedding, coupled with gloomy weather, I am running my system in back up mode. 

Twice now since load shedding was reintroduced it has happened that when COJ turn the juice back on. the earth leakage on my DB has tripped. That's a 50% rate at present (remember that in Jhb, load shedding is down in 4 hour chunks, so we get less outages but longer). 

This never used to happen.

The first time it happened after power restoration I went through the routine of turning off all breakers on the DB, resetting the earth leakage and then turning the circuits back on one by one to narrow the problem down to one circuit. Unhappily, nothing caused a trip.

My thoughts are that it must be something to do with the solar system itself. If it were, say, a kettle then it could trip at any time. But then maybe this is just coincidence.

I'm a computer programmer by trade. When a system that has been behaving itself suddenly gives problems I always ask "what changed?" So what has changed at my house (that I know of)?

Since the solar system was installed and signed off
1) New DB to replace the ugly wart that had been left behind. I'm pretty sure that we had outages since that was replaced and with no problems when the grid supply came back up.
2) At the same time the feed from the solar to the DB was chased into the wall. 
3) Kitchen was gutted and rebuilt. During this the earth leakage did trip when a plasterer got some wet plaster into a wall socket. The socket has since been replaced even though it seemed to be working OK. In fact all the sockets were replaced to ensure that they all looked the same (I used CBI). 
4) New light switch fitted in one of the outbuildings (also CBI). I did this.

1,2 and 3 done by an electrician. 4 done by me.

It could be co-incidence, of course, but since we replaced the aforementioned socket the trips have always been when COJ restores power. Except only 50% of the time. The other 50% nothing happened at all.

 

Edited by Bobster
Clarity
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My solar setup is described in my sig. I'll add that I have timer switches
1) For outside lights (backed up)
2) For 2nd geyser (not backed up)
3) For swimming pool (not backed up)
4) For heat pump (backed up)

1-3 are mounted in the main or the sub (outbuildings) DB. (4) is on board the heat pump with just a display unit inside the house.

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7 hours ago, Bobster said:

Twice now since load shedding was reintroduced it has happened that when COJ turn the juice back on. the earth leakage on my DB has tripped.

Had a similar problem on an installation in JHB this week, it tripped every time the power came back on, I just meggered the all the circuits and eventually found  the culprit circuit. 

With the power coming back on and the NE relay opening, it must have amplified the already existing fault current to a level where it exceeded the trip point.   Fixing the circuit also fixed the problem. I suspect you have a similar situation. 

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Suddenly I have this exact or almost the same situation, will have my electrician look into it, already let him know about the issue.

1st I thought it was because when I was on the grid that I ran both geysers simultaneously, but I have done it before for a couple mins, without any problems. Currently in USB mode because of load shedding, I don’t even know when load shedding kicks in.

Yesterday it tripped and I only realized something was wrong when my inverters showed the grid is gone but the igniters on the stove top worked. Found that a trip switch linking the grid to my inverters tripped. Had to pull them all the way down in off position and push them back up in on position to restore grid to my inverters. 

Only the incoming grid feed is cut-off with this trip switch.


This afternoon, same thing, switch tripped. I can only imagine that it happens when the grid is restored after load shedding. I forgot to bypass the geysers, was also not aware that we will have load shedding and Only realized this when I was at the shops and no one had power.

We have had load shedding for more than 2 days in a row, don’t know what changed in the 2 days other than before these two days. If I think about it, it might be the loads running at the time, as our load shedding the past two days was during 10am-2pm, before the two days it was at nigh time, when my loads are basically a tv or two and a couple lights. 


Been fun and games this last couple days as everything running on timers etc is set for when there are suppose to be sunshine :)

I have been running around switching off high load items during 10am and 2pm.
With full sunshine I don’t have this issue, guess it is because I am on USB at the time and not SBU. 
Any thoughts?

 

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10 hours ago, Bobster said:

what changed?"

Same issue. On Friday night at 8PM (ish), the power comes back on and the RCD trips. What changed? Aaah yes... I replaced the garage door opener. I happen to know there's three MOVs in there and I have also proven in the past that it causes enough transient leakage to cause a trip.

Surge arrestors and EMI filters and the way they interact with the bonding relay. That is my issue.

Moved the motor off the backup circuit and the issue is gone again. The house is sold. The whole solar system is coming out soon. I'm not spending time on this again.

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11 hours ago, Bobster said:

Twice now since load shedding was reintroduced it has happened that when COJ turn the juice back on.

This was discussed in a previous issue with earth leakage trips. You might have a earth leakage that easily trip due to the transient leakage when switch over happens. The solution might be to replace the earth leakage with a better type like a ABB or Merlin Gerlin. I had a similar problem with a Onesto earth leakage some months back, I fitted a M&G and the problem disappeared. 

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Thank you all for your input. This is demystifying the issue for me.

@Gerrie I just checked, the earth leakage is branded Onesto. 

I'm an example of a person with a little bit of knowledge being dangerous. After all, I used to repair cash registers. So I had concluded that it couldn't be anything on a backed up circuit as they wouldn't "see" any difference when the power is restored.

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15 minutes ago, Bobster said:

Any opinions?

Have you looked at how much they cost? I looked at them back in the day, but since the type APR RCD was actually cheaper (and avoids tripping for me... mostly), I went with that.

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11 minutes ago, plonkster said:

Have you looked at how much they cost? I looked at them back in the day, but since the type APR RCD was actually cheaper (and avoids tripping for me... mostly), I went with that.

Yes. I did see some fairly scary numbers, and thank you for the information.

My electrician is a bit offended at the suggestion that he may have supplied a dicky device, but is going to test it for me. He says (and I don't understand this) that the municipal infrastructure in our area is old, the technicians have to reconnect "under load" and so there is likely a momentary over voltage. 

I don't understand the technical explanation, but it does make some sense to me because
1) The trip always comes at time of restoration
2) Immediately after I do the time honored test of switching off all circuits and turning them on one-by-one and the thing never trips.

My concern is this happening whilst we are away on a holiday.

Edited by Bobster
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2 minutes ago, Bobster said:

My concern is this happening whilst we are away on a holiday.

Yeah, Auto-reclosers are good for that.

2 minutes ago, Bobster said:

supplied a dicky device

Nobody is being malicious or anything... it's just that even a good quality RCD (I tried an ABB type-A too) can't always deal with a transient.

I tested mine using a good old earth leakage tested and it tripped somewhere between 15mA and 20mA. Within spec.

Then I measured with an earth leakage clamp meter, during normal operation and during a power restore.

First I measured the standing loss, which is the normal small amount of leakage caused by modern appliances (due to said filters and stuff). That leakage was uncomfortably high so I hunted down the culprits. One was an EMI filter installed on the iron transformer of the alarm system (why? Those things don't make noise). I removed it. The second was in the plug of a fancy socket-strip, a thing with neon lamps and surge arrestors. Chopped it off and put on a straight normal plug. Once I did that, the standing loss came down to a more acceptable 5mA.

Then I temporarily removed the RCD, put in a normal isolator (just for the test of course!), and measured the peak leakage current while restoring the power. If you leave the RCD in place you don't get a proper reading as it trips before the peak. I had a 40mA transient.

Which is why I am really really REALLY starting to loathe all the cheap MOVs people stick into everything. If this trend continues the only answer will be to use an RCBO on every circuit.

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1 hour ago, plonkster said:

Nobody is being malicious or anything... it's just that even a good quality RCD (I tried an ABB type-A too) can't always deal with a transient.

It's nothing anybody here has said, and he doesn't read this forum. He's a family member. He also gets a fair number of people telling him how to do his job, so he's not fond of laypersons sticking their nose in.

Anyway, the problem has been traced to the outbuildings. He was able to reproduce the fault by throwing the main municipal circuit breaker. He then found that if he ran JUST off the grid or JUST off the inverter there was no trip. Then he isolated the outbuildings and the problem went away - no trip regardless of what combination of mains and inverter he had turned on.

Edited by Bobster
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I went back to what was changed.
Found that when we were informed of coming load shedding, I pushed the amps up from 10A on each inverter to 40A on each inverter coming from grid as I wanted to get the batteries charged as quickly as possible on that 1st day (due to great rainy weather), I never turned it back down, so when the power went out during the daytime with loads running and it came back the load/s was too much to handle and tripped the switch coming back in from grid to inverters.
This only happens when my system is in USB as the grid kick in and want to charge the batteries at 80A as well as supply the load, it is too much for the 32A breaker. 
Had to manually stop loads such as geysers when load shedding occur during daytime, if and when load shedding happens at night time we don’t have any issues as our load is below 1000w after 16:00 and the system is in SBU mode anyway.

So in short, the trip was because of me :)

 

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7 hours ago, Bobster said:

My electrician is a bit offended at the suggestion that he may have supplied a dicky device

I use the Onesto allot as it is my preferred cheap brand. I always give the customers two quotes, One being Onesto and the other a “brand” name. The dicky devices wins 99% of the time.🙂 

 

 

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6 hours ago, Bobster said:

the problem has been traced to the outbuildings

@Bobster. Just out of interest, your earth leakage might also not trip when you switch “on” only outbuildings and switch “off” all the other loads. Unless you have tried this scenario.

I remember my system did not trip easy when half of my loads were switched off, when change over occurred. 

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I know you're all dying to hear the end of the story.

I can't give it to you completely. But

1) The electrician was able to simulate the problem by turning the main breaker for the municipal feed on and off
2) If he bypassed the solar system then there was no trip
3) If he turned off the CB that feeds the local DB in the out buildings there was no trip under any conditions
4) Last time I spoke to him he was in the middle of working on said local DB and said something about the neutral being improperly connected.
5) Last night when load shedding ended there was no EL trip at our house.

When I was talking to the electrician about what had changed he did point out that it might have been something that had been there all along, exacerbated by the very damp conditions.
 

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  • 1 year later...

Hi Guys

Need Help.  I have got the earth tripping only when municipal power returns.  I have tried installing the ABB Type APR (F202 A-63/0.03 AP-R) RCD but it did not resolve the issue for me.  Can anyone reccommend an electrician able to trace and resolve this issue in the Morningside/Kelvin Area in Sandton.

The fault can be simulated by tripping the municipal supply to the property on the boundary line.

Call/Message me on 0824515786

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  • 8 months later...
1 hour ago, Scubadude said:

Until the power came back and the earth leakage tripped.

It could be a real fault, the earth leakage will trip when earth leakage current of about <24mA is detected. In most cases if it trips when power turns back on, it could just be due to transient current (spikes) that occur when loads are turned on from municipality. To resolve this you could fit another high quality earth leakage like the ABB or Merlin Gerlin type, but these are expensive. Another option if you have space in the DB is to add a second cheap earth leakage and split your loads over two earth leakages, this will give you double the tolerance of 60mA instead of just the 30mA. I prefer the later but it requires more labour as you also need another neutral bar.

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