Mark fantastic video. Mark in any island mode hybrid inverter or generator, I was under understanding that we can join a tncs system to earth rods. New homes have dual connections. If you have any pen fault devices connected, say an ev charger, it will not work in any island mode unless it's connected to the earth rod because of the change over to the island. Earth can never be put on a switch like a change over. This subject is very interesting.
That is correct Gino. We either swap the grid mode earth to TT and ditch the dno earth entirely or maintain them all as a collective of earth's for varied uses depending on grid or off grid modes. Thanks
Brilliant content thanks very much for sharing this ! , Bruno is doing a marvelous job love him 🤩 Great to see that Polar include the N/E bond relay for island mode , is there anything in the regs which states that any EPS/UPS downstream overcurrent protection device should be of a lower value than the maximum inverter output current ? EG if the inverter is rated at 16A maximum we shouldn't be using 32A Mcb's to protect EPS/ups ring final circuits . Currently It looks like we're more reliant on the internal electronics for current protection rather than any MCB's which rely on a high PFC for quick disconnection . Thanks again this is all very helpful
Excellent mark fills in some of the gaps in knowledge between the 2 operating modes. I do agree that some grey areas might still exist particularly when using less common battery & inverter systems and the floating non referenced earth they might output on island mode & whether the RCD/RCBO will operated under all Enviromental conditions:) and any generated reference point from the electronics of the inverter.
Another thing you could do as well as use an appropriate RCD /RCBO is Limit any items you run on essential circuits as 1 item of class 1 equipment & make sure other items are of class 2 construction.😀
Great video Mark, Looks like a great piece of test kit there for measuring EFLI when in island mode. I am just wondering have you obtained the inverter impedance when using calculation of ZS in island mode instead of measuring it? Verifying EFLI in island mode I find really challenging when using calculation as manufacturers can't provide me impedance values for the inverter. I have never fully trusted the values from my test instruments as they seem inconsistent. Hence I have always ensured I have my consumer unit in island mode protected by an RCD, similar to your video.
Most won't provide a value however the EESS cop as shown in the video has a rule of thumb calculation you can use. 1.2 x inverter rated output. Thanks !
Many thanks for the reply Mark. I have rewatched your video. Not sure I am missing something here. As I can't joint the dots to see how the how using the inverter rated current x 1.2 provides the earth fault loop impedance in island mode. I completely get that it estimates as a rule of thumb the fault currently and I acknowledge in reality the low fault current probably won't operate properly won't operate the overcurrent protective devices effectively in the event of a fault when running in island mode, hence RCD. It's the fact that the CoP asked us to obtain these values of impedances for island mode operation. I hope this makes sense to you. 😊
@clintstamper7573 if you have fault current and operating voltage you also have a value of Ze. That is why the rule of thumb shown in eess version 3 exists. To help in that situation
That totally makes sense, tbh I wasn't sure if we were allowed to apply that calculation as they inverters to me are non linear loads. I would love the CoP to give more emphasis on this. Your the first person I have spoken to say this. Many thanks Mark I do really appreciate your time, I am sure many others do too👍
@clintstamper7573 I think the IET webinar around the DPC for amd4 went over it mate. Also I'm sure I've heard Graham Kenyon discuss it. Either on our podcast (the renewables podcast) or possibly an efixx live. So much content I can't remember lol. That is why the EESS says its a rough rule of thumb. It won't be accurate but it's something. The results I obtained in this little test sort of make that true enough.
Great video. I was confused with the earthing arrangements when I did my last solar course. I did not see the point in referencing the installation to the mass of earth in off grid mode as that’s not where the electricity came from (In terms of the transformer).? Electricity always wants to go home. So why the need for an earth rod? Some inverters are almost like a shave point/centre tapped transformer or site transformer so the rod would not do anything in off grid unless there was one at the generating set and one somewhere else? I get the TN-S link that is now becoming a thing within these inverters to give ADS, however just don’t get the fact that the regs/manufactures instructions say that a earth rod is still required? Is the earth rod just to give reference so RCD’s will still trip if people come in contact with the lines? And if that’s the case why don’t shaver sockets have reference?
Exactly the reason for the rods to give that return path on faults outside of the wiring system. With shaver sockets it's a single point of utilisation in a specific circumstance and unlikely to be feeding equipment outdoors or class I in nature etc.
Does the inverter provide your short circuit protection. It will current limit and cut off supply, in most case a short circuit will never achieve the current required for the mcb to trip ie x5 for type b, so short circuit discrimination is not provided in island mode. The overload discrimination on an all in one is worth some thought ie 32amp ring main an over load of 40amp can the inverter supply this amount of current for long enough to trip mcb ??
This is within the video and the 1.2 x rule of thumb will rarely give enough fault current for disconnection on short circuit. Which is why those values are so important for our design process for both fault and additional protection. The entire purpose of the video alongside some fun lol
Cheers, I personally would like to see a simple statement from IET or at least someone like you who through your videos has gained respect Short cct protection on and off grid Overload on and off grid Fault protection on and off grid Earth off grid My eps would not trip rcd off grid the earth pin on socket was not connected to inverter the fact yours tripped seems strange ??? Surely must be a path from socket earth to inverter
@christophersanderson8688 this is a setup issue the rcd test should operate off grid. Your earth electrode in island mode should be connected to the EPS consumer unit or directly to a single socket if that's all you have. It's all in the eess cop
Mind blowing topic - which I will watch this vid, probably a few times in a few days when I get the chance (weekend) I just wonder if the relay switching will tick every single box 101% when things like Garo's PME/PEN EV devices can fail or falsely trip etc... Also. if you have 6 to 10 earth rods, ConduDisc etc... for Island/TT/Off-Grid setup side of things, do you really need to disconnect the main DNO earthing arrangement during island/off-grid, when the all metal gas/water mains are also earthed (proper earthed, not plastic pipes to property) Example: you are on a genuine TNS system, with additional earth rods etc, metal gas/water bonding, then operate a "mostly off-grid" setup, but with grid connection to sync & charge battery overnight from grid on poor solar days/winter... Would you really need to disconnect/reconnect the DNO earth if/when in Island/100% Off-Grid mode & not grid sync'd/supply/top-up batteries ??? This subject seems to be a "Yes you should, but there are exceptions when no you don't" Along with the but it is all still linked with gas/water bonding side of things, when you're a stones throw away from sub-station and then there is always the very slight but still possible risk of said earthing relay failing & be stuck open/closed with running on TT or DNO/TT/Sup Earthing arrangement anyway Surely, (Don't call me Shirley), there must be some sort of method that simplifies & satisfies the safety of owner/dno engineers that main earthing & TT arrangement can co-exist for all instances of grid/island/off-grid operation modes/setups TL-DR, mind blowing topic, cheers for delving into this side of stuff for Island/Off-Grid setups
You can maintain the DNO earth while off grid. My own system has all the earth inputs connected into the MET. They serve different purposes in the different modes
@@electrician247 Phew, like I said I just skipped a few bits and thought OMG, WTF etc... Yup, similar setup, 50% grid tied inverter(for export mostly) & 50% off grid inverter for house, running with with DNO earth & back garden full of earth rods (most double length) etc... I thought, hang on, I gotta disconnect DNO - nah don't like that idea too much Like I said, should have watched complete vid before jumping the gun - cheers for reply sir
I thought you had to disconnect the DNO earth all together as are you not providing a path back to the install with earth points close to each other? Ive gone fully TT and got the DNO to mark the connection as such. Water and Gas have been changed to plastic and DNO earth not connected. I've only got one point to earth now, day after installing TT i got 2.15 Ohms but i went OTT with the TT install
You can maintain the DNO earth in your islanding system but it must be supplemented with electrodes. I've views around this I've shared in other videos.
Great video Mark. Very informative. Thanks for taking the time. Really helpful for others in the industry. 👍🏻
Mark fantastic video. Mark in any island mode hybrid inverter or generator, I was under understanding that we can join a tncs system to earth rods. New homes have dual connections. If you have any pen fault devices connected, say an ev charger, it will not work in any island mode unless it's connected to the earth rod because of the change over to the island. Earth can never be put on a switch like a change over. This subject is very interesting.
That is correct Gino. We either swap the grid mode earth to TT and ditch the dno earth entirely or maintain them all as a collective of earth's for varied uses depending on grid or off grid modes. Thanks
@@electrician247 cheers 🍻
Brilliant content thanks very much for sharing this ! , Bruno is doing a marvelous job love him 🤩 Great to see that Polar include the N/E bond relay for island mode , is there anything in the regs which states that any EPS/UPS downstream overcurrent protection device should be of a lower value than the maximum inverter output current ? EG if the inverter is rated at 16A maximum we shouldn't be using 32A Mcb's to protect EPS/ups ring final circuits . Currently It looks like we're more reliant on the internal electronics for current protection rather than any MCB's which rely on a high PFC for quick disconnection . Thanks again this is all very helpful
Excellent mark fills in some of the gaps in knowledge between the 2 operating modes. I do agree that some grey areas might still exist particularly when using less common battery & inverter systems and the floating non referenced earth they might output on island mode & whether the RCD/RCBO will operated under all Enviromental conditions:) and any generated reference point from the electronics of the inverter.
Another thing you could do as well as use an appropriate RCD /RCBO is
Limit any items you run on essential circuits as 1 item of class 1 equipment & make sure other items are of class 2 construction.😀
Or lable your island mode essential sockets as * please use with only one class1 item* 😀
Here is everything you wanted to experiment with on the EESS course, but didn't get to have a go :-) Really useful Thanks
Thanks for taking the time to make the video it's very interesting.
Thanks and no problem. Throughly enjoyed myself
Very interesting look at testing/demo.
Great video Mark,
Looks like a great piece of test kit there for measuring EFLI when in island mode. I am just wondering have you obtained the inverter impedance when using calculation of ZS in island mode instead of measuring it? Verifying EFLI in island mode I find really challenging when using calculation as manufacturers can't provide me impedance values for the inverter. I have never fully trusted the values from my test instruments as they seem inconsistent. Hence I have always ensured I have my consumer unit in island mode protected by an RCD, similar to your video.
Most won't provide a value however the EESS cop as shown in the video has a rule of thumb calculation you can use. 1.2 x inverter rated output.
Thanks !
Many thanks for the reply Mark. I have rewatched your video. Not sure I am missing something here. As I can't joint the dots to see how the how using the inverter rated current x 1.2 provides the earth fault loop impedance in island mode. I completely get that it estimates as a rule of thumb the fault currently and I acknowledge in reality the low fault current probably won't operate properly won't operate the overcurrent protective devices effectively in the event of a fault when running in island mode, hence RCD. It's the fact that the CoP asked us to obtain these values of impedances for island mode operation. I hope this makes sense to you. 😊
@clintstamper7573 if you have fault current and operating voltage you also have a value of Ze. That is why the rule of thumb shown in eess version 3 exists. To help in that situation
That totally makes sense, tbh I wasn't sure if we were allowed to apply that calculation as they inverters to me are non linear loads. I would love the CoP to give more emphasis on this. Your the first person I have spoken to say this. Many thanks Mark I do really appreciate your time, I am sure many others do too👍
@clintstamper7573 I think the IET webinar around the DPC for amd4 went over it mate. Also I'm sure I've heard Graham Kenyon discuss it. Either on our podcast (the renewables podcast) or possibly an efixx live. So much content I can't remember lol.
That is why the EESS says its a rough rule of thumb. It won't be accurate but it's something. The results I obtained in this little test sort of make that true enough.
Great video. I was confused with the earthing arrangements when I did my last solar course. I did not see the point in referencing the installation to the mass of earth in off grid mode as that’s not where the electricity came from (In terms of the transformer).? Electricity always wants to go home. So why the need for an earth rod? Some inverters are almost like a shave point/centre tapped transformer or site transformer so the rod would not do anything in off grid unless there was one at the generating set and one somewhere else? I get the TN-S link that is now becoming a thing within these inverters to give ADS, however just don’t get the fact that the regs/manufactures instructions say that a earth rod is still required? Is the earth rod just to give reference so RCD’s will still trip if people come in contact with the lines? And if that’s the case why don’t shaver sockets have reference?
Exactly the reason for the rods to give that return path on faults outside of the wiring system. With shaver sockets it's a single point of utilisation in a specific circumstance and unlikely to be feeding equipment outdoors or class I in nature etc.
Does the inverter provide your short circuit protection. It will current limit and cut off supply, in most case a short circuit will never achieve the current required for the mcb to trip ie x5 for type b, so short circuit discrimination is not provided in island mode. The overload discrimination on an all in one is worth some thought ie 32amp ring main an over load of 40amp can the inverter supply this amount of current for long enough to trip mcb ??
This is within the video and the 1.2 x rule of thumb will rarely give enough fault current for disconnection on short circuit. Which is why those values are so important for our design process for both fault and additional protection. The entire purpose of the video alongside some fun lol
Cheers, I personally would like to see a simple statement from IET or at least someone like you who through your videos has gained respect
Short cct protection on and off grid
Overload on and off grid
Fault protection on and off grid
Earth off grid
My eps would not trip rcd off grid the earth pin on socket was not connected to inverter the fact yours tripped seems strange ??? Surely must be a path from socket earth to inverter
@christophersanderson8688 this is a setup issue the rcd test should operate off grid. Your earth electrode in island mode should be connected to the EPS consumer unit or directly to a single socket if that's all you have. It's all in the eess cop
Mind blowing topic - which I will watch this vid, probably a few times in a few days when I get the chance (weekend)
I just wonder if the relay switching will tick every single box 101% when things like Garo's PME/PEN EV devices can fail or falsely trip etc...
Also. if you have 6 to 10 earth rods, ConduDisc etc... for Island/TT/Off-Grid setup side of things, do you really need to disconnect the main DNO earthing arrangement during island/off-grid, when the all metal gas/water mains are also earthed (proper earthed, not plastic pipes to property)
Example: you are on a genuine TNS system, with additional earth rods etc, metal gas/water bonding, then operate a "mostly off-grid" setup, but with grid connection to sync & charge battery overnight from grid on poor solar days/winter...
Would you really need to disconnect/reconnect the DNO earth if/when in Island/100% Off-Grid mode & not grid sync'd/supply/top-up batteries ???
This subject seems to be a "Yes you should, but there are exceptions when no you don't"
Along with the but it is all still linked with gas/water bonding side of things, when you're a stones throw away from sub-station
and then there is always the very slight but still possible risk of said earthing relay failing & be stuck open/closed with running on TT or DNO/TT/Sup Earthing arrangement anyway
Surely, (Don't call me Shirley), there must be some sort of method that simplifies & satisfies the safety of owner/dno engineers that main earthing & TT arrangement can co-exist for all instances of grid/island/off-grid operation modes/setups
TL-DR, mind blowing topic, cheers for delving into this side of stuff for Island/Off-Grid setups
You can maintain the DNO earth while off grid. My own system has all the earth inputs connected into the MET. They serve different purposes in the different modes
@@electrician247 Phew, like I said I just skipped a few bits and thought OMG, WTF etc...
Yup, similar setup, 50% grid tied inverter(for export mostly) & 50% off grid inverter for house, running with with DNO earth & back garden full of earth rods (most double length) etc...
I thought, hang on, I gotta disconnect DNO - nah don't like that idea too much
Like I said, should have watched complete vid before jumping the gun - cheers for reply sir
I thought you had to disconnect the DNO earth all together as are you not providing a path back to the install with earth points close to each other? Ive gone fully TT and got the DNO to mark the connection as such. Water and Gas have been changed to plastic and DNO earth not connected. I've only got one point to earth now, day after installing TT i got 2.15 Ohms but i went OTT with the TT install
You can maintain the DNO earth in your islanding system but it must be supplemented with electrodes. I've views around this I've shared in other videos.
hi you disconnect earth from the grid but the earth rods are still connect yes??
All earth's to inverter disconnected, dno, rods the lot.