Island mode earthing - GivEnergy AIO off grid - TN-S, TT, IT ????
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- Опубликовано: 22 мар 2024
- Lets take a look at the power the AIO from GivEnergy brings in off grid mode. Along with taking a look at how earthing systems might behave in both grid tied and off grid mode.
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With varied guidance from manufacturers and industry it is ever harder for us as installers and consumers.
Hopefully this video is of some help to both myself and others.
Enjoyed the video Mark
Brave video Mark. It's something I think about a lot. In Ireland we put an earth for on every single house before DNO connection is allowed. Rarely do you get under 45 ohms as it's just a steel spike terminated in a green box with a 10mm CPC. This goes directly back to the CU, as does the PME earth, no switching. I think the Huawei automatic change over switches used to disconnect the pme earth, but we were told to stop using them. Maybe the answer is to use some kind of earth monitoring system, years ago we used them on public machines like railway ticket machines. It's a synthetic earth current that runs in a loop around and if it disconnects or spikes a contractor just cuts all power. We will all have to think about this a bit more now that earthing is our problem.
Mark I think you need to explain for new learners more about emergency power supply from all manufacturers battery hybrid systems. Many electricians don't fully read the manufactures recommendations and supply a double socket near the system connected to the eps of the inverter . Near all suggest adding an earth rod or matt but many don't. Maybe a dedicated video in basic terms. Good for newbies
Very interesting video. A couple of points. With a PME TNCS eathing system the whole point of PME is to provide a distributed multiple point earth - sort of safety in numbers - if one earth fails you still have others to rely on.
In the case of your PEN fault, the earth rod with 20A going through it was probably providing a neutral return path for your neighbour's and stopping alternate phases from going under or over voltage due to load imbalance. So it's a good thing it was there to help out with the other earth paths - is one way of looking at it.
One thing I did notice with your install - are they single insulated L+N wires coming from your conduit to the inverters? They should be double insulated or in flexible conduit sheath etc.
It is absolutely providing a neutral return path. Hence the danger to those inside that installation. We need to remember the neutral path is a live one.
We are electricians so it shouldn’t need to be said but yes they are coloured tails cabling. Which are never actually double insulated. It’s single insulation with outer sheath. Hope that helps.
Ah right, difficult to tell.
@@electrician247Presumably the neutral current from neighboring properties was coming in from the remaining part of the cable after the fault and/or metallic services bonded to the combined neutral earth and finding their way to your earth rod. Without the rod the potential could have been higher - and worse if they were touching the cooker whilst stood barefoot on a damp stone kitchen floor for example. Metal gas pipes can be plastic coated so not good ground contact but connect neighbours quite well through bonding.
The estates around me have plastic water and gas supply lines, every house has an intricate mesh of earth bonds. Tons of copper wasted.
Keep fighting the good fight Mark, documentation needs to be complete and responsibility needs to be shared.
This is sounding like the RCBO Type rating for EV chargers issue mentioned on eFixx last week.
Good point Mark about the metal consumer unit potentially becoming live under pen fault conditions. Maybe we were safer with plastic consumer units after all 😂😂😂
Great channel Mark, keep up the good work 👍
Who knew plastic was a good insulator 🤭. Shame it burns so easy as well lol
Thanks Mark. Great video
Very timely vid, thanks Mark. Had AIO+solar installed in Dec 23 and been struggling to understand since then why 1 of 2 RCDs in main consumer unit always trips in off-grid mode. Have recently started to suspect an earthing issue (2 earth rods installed as part of AIO install), so will go back to my solar installer and see what they say
Worth checking out the AIO neutral earth bond. That is not activated by default and can result in RCDs tripping downstream
Awesome, thanks for the tip, will move the investigation onto this area next!
Very interesting video. Earthing is abit of a minefield running in island mode. Ive not yet yet set my Victron system to run in Island mode yet because of all the questions. I live in a property thats all electric. And my water pipe to house is plastic. It runs on a TNCS supply/earthing.
I have installed 2 earth rods in preparation of going off grid.
So many things to consider but here are some of my thoughts.
True ground and equipment ground are 2 different things. True ground being the star point in DNO. All our equipment grounds should be connected to mass of earth or true ground which they are normally. But under PEN fault conditions or loss of that star connected earth we then rely on the earth rods and then creat this equalpotenial zone. Really one earth rod doesnt really create enough of a equalpotenial zone for whole are of your house to allow all your equipment earths to be at true earth potenial. Bearing in mine that the soil resistivity changes through out the year. Like a transformer you kinda want a earth rod on each corner of your property. Then in island mode be able to disconnect the DNO pme earth. Because lets face it. Off Grid is disconnected from grid. Like you have found under PEN fault conditions. Everyones other house will want to earth throug your grounding system. Which open up another can of worms.
Also PEN fault detection which uses voltage threshold limits (207-253) to mitigate this is not good enough. You could loose your pme earth and still be within the range so earth rods make senses for a step in the right direction. 👍
I agree that there is a need to educate solar installers. I personally think a good starting point is to imagine any standalone inverter what are the principles? Most inverters will have internal protection to limit short circuit currents which means you can never achieve tripping times of an mcb for example x 5for a type b
mcb. With this in mind all circuits have to be rcd protected to achieve tripping times. I will be interested on people’s experiences with the island or esp neutral earth link that is a must to allow the rcd to function. I think this link is provided internally on givenergy inverters.
Not on the AIO out of the box.
If you apply a short circuit to aio output with grid off what is max current??? On the aio where is the neutral earth link switched
Another insightful video from yourself Mark, as a non electrician (electronics background) I find them useful and thought provoking, a few things that were provoked out of my thoughts were:
. Probably better to try and have the earth bonds/references connecting together within the meter box outside, if there's 50+ amps of diverted neutral current I wouldn't want that going via a plastic consumer unit under the stairs.
. Shouldn't external equipment (including in meter cupboards) be plastic cased rather than exposed metal cased? The DNO/supplier equipment and cut out switches are plastic cased to avoid touch voltage in fault conditions (phenolic excepted), does the requirement for metal consumer units (for fire risks) in the house apply to these outside units?
No requirement for them outdoors in terms of fire resistance. Exactly the same thoughts as you in terms of plastic outdoors.
Hi Mark, just wondering how it can be called an "All in one" when it appears to need a separate inverter for the solar panel strings?
That’s one for GE to explain. However generally AC coupled batteries have separate inverters and battery modules. This is an all in one ac coupled battery system. Rather than all in one PV dc coupled inverter. Horses for courses
Mark great subject. Correct me please but tncs can be also connected to tt. As far as I am aware they connect both in new projects. I have 2 ev chargers both pen fault modles. When I go into island mod they don't work. They had to be connected to an earth rod. So the install is connected as tncs and tt. It's for me a good subject to char about.
Yes Gino. They can be connected together as shown in the video. Cheers
Many Thanks Mark found that information very interesting, what sort of ZE / Fault currents have you measured when in island mode. Kind regards Darren
I will have a look at the original video to be accurate but in the 100s of amps of fault current from memory 😳
When you say about disconnectiong the DNO earth in island mode (13:45) you'd be TNS, would it not be TT as you have your earth rods and earth farm? Colllege seems to make everything simple - TT, TNS, TNCS and rthats about it (IT excluded), and then you get into the real world and its really NOT that simple.
No it’s not TT. Your electrodes form the earthing of the supply and it becomes TN-S
Mark
If at home you have an earth farm with sub 2 ohm, why would you bother with the TN connection in the first place?
I appreciate your video’s. I really want a sub 2 ohm earth farm at home…
Because it’s what is provided and as shown in the video more for experimentation. We won’t get these same values on customer systems sadly. Plus the TN is 0.16
I have a question, I have a Givenergy Solar installed by E.on. Looking at the Schematic they sent of the installed solar. It uses the home main earth which is PME. Are you saying that the Solar installation should have its own earthing (earth rod)?
It would depend on the battery storage system you have installed and existing setup. Additional equipment isn’t always needed
On my own system I have completely disconnected from the grid earth as we have had a lost neutral and I didn't want any feed back from the grid via the earth
This is an option I’m toying with. But the huge upside is general incredible reliability and usefulness
@@electrician247 my system is totally off grid but I still use the grid to charge my batteries if they fall below a certain voltage the grid connected chargers start charging but only on power ups or on cheap over night electric
I don't know ... a thought experiment: if you're in the middle of nowhere, then I think you're definitely on a TT system with the GivEnergy in island mode. If you are nearby some power network then, in fault conditions, it's possible that you'd see a voltage through the earthing rod, even though you're still TT. Aren't you required to add an earth when you install GivEnergy's equipment?
Taking that a little further, if you're operating in island mode and connected to the DNO's earth then don't you have whatever the DNO supplies (TN-S or TN-C-S) - assuming that you haven't disconnected the DNOs earth (why would you?). In a DNO fault condition, I think that some voltage through your TT is possible. But, it's a fault, so all bets are off.
I thought the whole idea of adding earthing to existing properties was to add another earth to the PME system (or TN-S), This increasing the bonding to earth and helps in the event of a fault (otherwise you'd be potentially running an IT system which doesn't seem safe at all).
I seem to remember that John Ward did a few videos about earthing.
In island mode we are TN-S in text book form. The DNO earth forms no part in the fault path while islanding.
So it also can not form part of the earth arrangement in text book form.
The PME support electrodes are exactly as described in the video and as you laid out in your comment.
@@electrician247 I wasn't thinking clearly - you are right about the TN-S in island mode. It' right there in the on-site guide, p29.
If there was a DNO fault, directly outside the property where the live wire is touching the ground, isn't there a possibility of a potential difference in the (real) earth with distance?
What is the GivEnergy standard: are you supposed to completely isolate the property earth from the DNO's earth? Does this depend on what mode it is working in?
@@jchidley step voltages are always possible when the mass of earth is involved. GE have said a few things regarding the aio to myself and other installers.
1ST :)
You are getting fault currents because in high frequency inverters there is no galvanic isolation if you went to transformer based inverters this wouldn't be a issue
Sadly GE have lost my faith in them as a company with their continued false advertising of paralell AIO capabilites and their support team answers stating it's not a prioirty for them to fix their firmware issues. Recommending customers install one AIO and gateway in the hope they fix their issues allowing us to install more in the future is bad. Not your fault but as a manufacturuer thats pretty poor.
It’s far from ideal however from what I know it’s closer than ever and tbf they made clear at the start it will take time to get appropriate approvals in place and rock solid firmware to ensure all those aspects are satisfied. I would much prefer they delay a launch of that rather than rush something that is glitchy and potentially unsafe.