Earthing systems, EV charging connection options and open PEN detection devices.
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- เผยแพร่เมื่อ 28 ก.ย. 2024
- Earthing systems and what options are available when installing an electric vehicle charging unit.
Does TN-S really exist?
TN-C-S broken PEN conductor problems and the 5 possible solutions given in BS7671.
Do the various devices available to detect fault conditions actually work?
Problems when using TT at a location which has a TN-C-S installation.
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Onlooker from the U.S. here. For some reason I'm fascinated by U.K. electrical and electrician videos (Thomas Nagy and David Savery are personal favorites). I'm amazed at how utterly paranoid you guys are about household electricity. OTOH, we use 120 and you guys use 230. Sure, if we get shocked it really hurts, but, mathematically, if you get shocked it really, really hurts. P.S. It would take an electrician here about an hour to fully install a Tesla charger here, and that includes the half-hour he takes padding the bill. If he even pulled out a Fluke to check his work, I'd be amazed.
Welllll....you might want to watch this video explaining why the USA is not 120V:
th-cam.com/video/jMmUoZh3Hq4/w-d-xo.html
Yes your ordinary outlets will be 120V....but car chargers will be 240V. That said it will still be safer as the potential to Earth is always 120V....but in 120V systems, compared to 240V, the likelihood of fires increases as you have to draw higher currents for the same power.
I can confirm the exact scenario you describe in your video (@ about 8 minute mark) happened to me today in work. I attended a property that was having a new service cable installed into the property by the dno. Originally the all the houses in the street had a tns pilc cable into each house.
A new SNE (separated neutral earth) cable was run into the property. With a split concentric cable. But, at the joint in the street, the main service was a relatively newly installed “repair cable” it was a concentric tncs with a COMBINED neutral earth!!!
The new service head has been labelled up sne (tns) even though it truly is tncs.
The dno engineer suggested the way to check would be to perform a continuity test between neural and earth at the head to ascertain a true tns situation (with a suitably low, but not too low reading!)
It certainly is food for thought!
Thanks John Excellent video, I’ve watched this twice, I’ve put off doing the car charging point course for 3 years, due to constant changing regulations. I was doing a bit research prior to taking the course this year. I was planning to install the Zappi for TN installs, however after watching this, I don’t think I’ll bother with the course, until some sort of solution is found.👍🏼
The Zappi is about as good as it gets for equipment.
The real solution is foundation earth electrodes, which are only practical for new construction.
John Ward as you say it’s only a solution on new builds & the chances of that happening are next to none in my opinion. So I think they need to come up with something else, PME has never been allowed with caravans, so why with cars? This video is excellent & so educational.
@@jwflame As the Government is ‘mandating’ EV’s in future, the potential risk will increase proportionately, surely it is then incumbent on the Government to declare a commensurate mandate to use 3 separate distribution conductors as the infrastructure is upgraded to cope with the required capacity. The PME 2-conductor system was clearly implemented driven by reduced costs. At the time the collective risk v benefit was probably acceptable. But with hot tubs, and EVs now increasing rapidly, this is no longer the case. I am astonished that DNOs are permitted to effect 2-conductor repairs on 3-cabled systems, thus knowingly degrading the safety of all affected consumers. This is then compounded by the fact that they don’t appear to be required to inform those consumers that, as a consequence of those repairs, not only has safety been compromised but it is actually being camouflaged because the potentially unsafe TN-C-S system is masquerading as a relatively safer TN-S system at the cutout. Is anything being done about this?
17:15 why didn't they just go the "whole hog" and put the tap on the 'top' and the outlet on the bottom, So it could drip on to the live connection ? 😁
That design is insane.
Just use an NVR, problem solved.
This whole thing seems so ridiculous. Somehow it was apparently perfectly fine to shock everyone in case of a broken Neutral before, whether they are touching metal parts in the kitchen, washroom or the outdoor tap, and any type of metal building materials that may or may not be earthed. And yet somehow, just because a car _may_ be outside, the exact same fault is supposed to be so much higher that NOW you need to improve things, *BUT only for the EV charger.* Getting shocked everywhere else is still perfectly acceptable. Personally, I typically wear shoes outdoors, whereas indoors, I am likely to touch metal parts while standing on a stone floor with bare feet.
I always assumed all countries would be installing earthing rods *_at a minimum_* next to each building for *Decades.*
Really, this regulation just seems to be designed to deter people from adopting EVs. They _could_ have mandated at any point that all buildings need to be upgraded to certain safety standards if improving safety was actually the goal.
As you say, it's an existing problem, which John fails to mention. A garden tap can go live in the event of a broken neutral. I suppose the regulators work on the basis that if the fault happens in the house, then all the metalwork will be bonded and there's no independent route to earth save whatever you are standing or sitting on. However, it won't help that garden tap issue (or anything else outdoors).
I suspect the regulators thing that the biggest issue with EVs are that they are massive chunk of metal, that might be parked in a street or an easily accessible driveway.
However, I'd note that even if a bullet-proof charger could be produced, there's nothing stopping somebody doing a "top-up" charge via a standard 13A socket.
Really, the only way to protect against this is to have something on the incoming supply that cuts it completely if a break in the neutral is detected. That way the entire property is protected. Of course it still had issues with possibly requiring an independent earth reference (although I have by doubts it that's all it's used for that it's quite the placement issue that John lists for that sort of role).
However, at a certain point, I wonder just how many improbable combinations of events have to happen to make this a real danger and just how many tens of billions of pounds have to be spent to save how many lives.
Until relatively recently, most homes in the UK had gas and water supplies in metal (usually steel) underground pipes, and as those were bonded to the main earth terminal of each building, that vast network of buried steel pipes acted as an earth electrode, so when the PEN conductor was broken, the voltage on exposed parts was kept low due to those connections via the gas and water services.
What's changed is that virtually all new installations use plastic (MDPE) pipes for gas and water, and older gas and water networks are being upgraded by replacing the buried steel pipes with plastic ones.
There was an attempt to get earth electrodes for TN systems into the wiring regulations (BS7671), however that only made it into a draft version and was removed from the final version.
Earth electrodes are permitted for TN systems and have been for decades, but as they are optional, they are rarely installed.
@@jwflame Strange you should mention gas utility pipes as yesterday evening on of my RCBOs (the downstairs ring) tripped accompanied by what sounded like load fireworks outside. A look outside, and there was a spectacular firework show dancing up the side of a neighbour's garage about 30 metres away. It was merrily blazing away and setting light to overhead trees.
It appears that a neighbour's carelessly disposed of barbecue coals had melted through a bin and then through the gas feed pipe. The crackles and bangs and sparks were, I suspect, due to fire affecting the incoming mains power. I reset the RCBO four times before it settled down when the fire was out. I was not the only one so affected as another neighbour had his RCD trip.
The power got turned off at the substation for a couple of hourse to allows the gas supply to be made safe and, very likely, the mains power.
So the question is, how could what appears to be an electrical problem on the supply side to another house cause RCBOs and RCDs to trip in a nearby properties?
I even got quoted in a local newspaper (via text scraped off the local town web forum site).
www.oxfordmail.co.uk/news/18516389.firefighters-tackle-blaze-chipping-norton-village/
@@TheEulerID Some RCBOs will trip on overvoltage and some other states. I've seen Wylex WSES RCCBs that like tripping when there is a power-cut too. Certainly with 'spikes' of power on/off, the capacative coupling of filter-capacitors to earth can cause RCD trip. Also note the capacacive-filtering of line-(N or E) capacitances, inrush to reservior capacitors etc, can in any case trip the overcurrent protection in MCBs/RCBOs, if you have lots of loads connected and the mains voltage 'comes on' at a high voltage point all of a sudden...
@@sbusweb I was guessing that some unusual surges had happened. The RCBOs I have also include a functional earth and those contain logic to detect some neutral line failures. Perhaps the voltage between earth and neutral went too high and t tripped. Perhaps some stray currents were flowing through the ground. Whilst it's a TN-C-S system, earth is bonded to metal gas and water pipes.
I have had an RCBO trip when the power came back on after a power cut once, and I put it down to some sort of capacitive load. Fortunately it's not the norm as I get at least half a dozen very short power cuts a year. Enough to put my computer and comms equipment on a UPS.
Interesting topic. Good video. In case of a PEN damage all internal appliances get high voltage on their chases - that can be very dangerous. Water heater, stove, laundry machine, to name a few.
Water heater will be fine - earthed via water feed :)
@@millomweb You'd be surprised. Water is not a good conductor of AC. Metal pipes are. Plastic pipes aren't.
@@Sculptoroid I know it's not a good conductor but it's better that steel threaded conduit that's gone rusty !
(A friend asked me to connect his cooker in his new (old) flat I wired the cooker in ok but the best earth I could find was his hot water cylinder - that was the best source of Earth for the flat.
I told him to get the place rewired.
The Tesla Gen 3 Wall Connector Manual has a link to this video. congratulations JW on your endorsement by Tesla.
As always sir a wonderfully crisp and clear presentation. On request would be at each point don’t assume people are following as exactly as you hoped and keep stating the obvious. I would also try to put links for people wanting to learn more not not links from standards and codes only but also reading elsewhere from a scientific electrical engineering perspective. That way people can learn at a much greater depth, hopefully pushing them to get more formal training.
Now that you’ve made a proper ground, you have a proper way for lightening to sneak in and fry your electronics. ⚡️
In NZ I we have a TN-C-S (MEN Multiple Earth Neutral), with grounding rod, in most of NZ the soil is clay loam (extremally wet clay loam lately), with a resistance well below 10ohm.
Thanks JW, very interesting topic.
In the long run , I think most new properties that are large enough to have a driveway and/or garage ARE going to have a 3 phase supply, if only to get the charging time down.
Highly unlikely - 7Kw is enough to charge most cars overnight for the vast majority of domestic users. In the UK, even small houses have driveways & garages, and 3-phase is very unusual.
@@mikeselectricstuff I know, it "is very unusual " now. But remember 7kw is only a 15mph charge for a Tesla . And if we are going to get CO2 levels down then gas cooking are water heating is going to go. So in a future 4 bedroom detached house with electric shower, cooker, water heating maybe 2 electric cars etc etc in that kind of house 100A single phase is going to start looking a bit weedy. Look at what Robert had to do when he got his second powerwall and a 22kw Zappi charger. Not 7kw 22wk. , yes uncommon now but , in years to come..... th-cam.com/video/gP51JjnWvLo/w-d-xo.html
Most EVs, Tesla included, are between 2 and 3 miles/kWh, so an 8 hour overnight charge at 7kW is between 112 and 168 miles of driving.
That also assumes the battery is totally depleted when you get home at 10pm and you have to leave the following morning at 6am, and will need to drive more than that distance immediately and can't possibly stop anywhere else to charge during the day.
There are probably a few individuals who do that, but electric cars are not suitable for them.
For the majority of people, charge time and driving range won't be an issue at all.
@@jwflame quite agree, but with powerwall(s) charging on economy 7 overnight. Etc. Do watch the video I linked above . And check out this one to see just how fast Tesla's can charge, when the "amps/kw(s)" available. th-cam.com/video/vOlOsqvCXBY/w-d-xo.html th-cam.com/video/vOlOsqvCXBY/w-d-xo.html
@@r.h.8754 And with a 300+ mile range and an 80% charge in 40 minutes (as in the above video) you could do it, no trouble. The limit would really be how far "you" could drive safely! I think HGV drivers are told 30 minutes break every 4 hours.
this video is most of the useful video I ever watched!!! Thank you/!!!!
Being a US based electrical engineer not associated with the power industry, this was extremely informative but left me with a lot of questions. Over here, I think we are all required to have the neutral bonded to an earth connection at the main panel, but I think the earth is generally the water inlet pipe, so not a separate electrode in most cases. One question is how much better it would be if the current on the earth connection is continuously monitored? Would high current on the earth connection provide an indication of many of the fault scenarios that you discuss?
Wrap the mesh around the gas and water pipe when digging up the drive, then stuff the earth rod through the bonnet of the car.
As far as I understood when a supply conductor is "broken" both or all three conductors covering a significant length go in the back of the people carrier.
Just a question- if my place has an neutral combined earth input from the supplier could I have other earth points coming direct from the property to earth I Dont have or require an EV system ,also no gas supply plastic water pipes and no nearby properties
,is it safe Can someone answer this please,,
Hi John,
Another highly informative video.
At 12:00 you said
“You can’t put an electrode near to any of these items [cables, gas or water]…in many cases you’re looking at distances of around 5 metres…”.
I can’t find this in the regs but would like to read more about it. Please could you tell us where it comes from? Thanks.
Most of it is in 'BS7430 Code of practice for protective earthing of electrical installations', some in Guidance Note 8, and distances from DNO cables can be found in various documents from the DNOs themselves such as Western Power, SP Energy Networks, a lot of which is partially of fully from the Energy Networks Association.
Some useful things here: www.spenergynetworks.co.uk/pages/documents.aspx
and here: www.westernpower.co.uk/documents/tech-info/design-standards/low-voltage
And...that's why i'm sticking with my diesel van lol :-D Great explanation as always JW... enjoyed that.
Why the concentration on external installations?
Is there not still significant a danger of shock from devices inside the house?
Ie. Builder cuts cable, lights go out, everyone goes to check the breakers, touches the “earthed” cabinet and gets shocked.
Would a Ground Fault interrupter positioned before Neutral-Earth is bonded work?
Inside you're not likely to be in contact with true earth. Outside is different.
John Wouldnt the metal mesh scenario be the same under fault conditions as the others where the metalwork makes your bonding and whatever in your house live,
The mesh is still connected to the live parts, but would have a much lower resistance and provide a path for the current, so the voltage at the mesh (and anything connected to it) will be significantly reduced.
John Ward Wouldnt that imply that a long run of metal water/gas pipes between a row of houses have an equally low resistance and then not be a problem? Secondly as many house supplies of water and gas are in plastic pipes is there a need for such a distance separation from earth electrodes?
@@alan2804 Yes, if the pipes are metal it will act in the same way as an earth mat or grid, and that's why broken PEN conductors were not such a problem in the past, as most houses had metal gas and water pipes.
For the last couple of decades, all new gas and water pipes underground have been plastic, and huge numbers of older metal ones are being replaced with plastic as areas are upgraded, so without installing an earth grid or mat there is nothing to provide a supplementary earth for most properties.
For a TT system there is no need to separate the electrode from plastic pipes, but it must still be well away from underground cables.
Just checked my N-E resistance - 1 ohm - which suggests N and E are connected locally.
Doesn't the regs specify suppliers need to provide a good earth ? That surely is the crux of the issue ? Ideally, routed separately from L & N.
Amazing the regs deal with crappy supplies by bodging a remedy at the end rather than ensuring the supply provides a sound CPC.
EV charging doesn't provide any new problems/issues. With TN-C-S, N+E failure would make any earthed metal-bodied devices live. Surely the simple solution is to have everything through a NVR contactor - so if L=N(=E), L would be immediately disconnected.
I dont get how EVs would be much different from a lot of other household equipment either. If your PEN is broken, you would get as much a shock from your car as you would from the washing machine and everything else that is normally earthed.
Also, I thought it was standard for every building to have at least an earth electrode locally anyway in a TN-CS system. In Germany this is mandatory, and all "modern" (probably starting in the 80s) even have their own earthing Bands routed along the outside walls of the building for very high surface area. On top of that, every building has 3-phase of course.
In Australia we also need a main earth electrode installed at the house for a TN-C-S system. I'm surprised this is not required in the UK.
Regarding the hazard inside, it is generally considered much less where all metalwork is equipotential and you are insulated from earth underfoot.
@@jay-em I agree. I'm surprised it's not done in the UK. In Republic of Ireland it is done, where both the DNO and customer's installation is fitted with earth electrodes connected to the neutral.
Earth electrodes at the house for a TN-C-S system is permitted in the UK, but it's not required so they are never installed.
@@jwflame Perhaps it should be required. It would provide more connections to earth. DNO's earth electrodes may only exist at substation and remote end of mains cable with perhaps a few intermediate electrode along the mains cable at various joints. Additional electrodes provided at customers' installations would enhance the earthing of the neutral/PEN conductor especially given that water and gas pipes are now laid in plastic so they're not acting as electrodes like they would have done when previously metallic.
A plastic water pipe would still take dangerous voltage as water itself is conductive. Unless I have missed something.
This is quite interesting over in the u.s. we are required to have a ground rod or actually 2 in most cases in the newer installations installed at each house. this is bonded with the neutral conductor at the point of entry to building essentially a main panel and everywhere else beyond that point it is a separate grounding conductor. I hope my terminology is relatively correct.
It's interesting that there are so many different grounding bonding options in the UK.
So we essentially use TN-C-S with earthride, everywhere and the utility is supposed to? Do multiple Earththinhs on their Network.
Brilliant video and explanation- nice one!
In the seventies it was fashionable to have piece of metal clad in plastic trailing on the floor with a little bit of metal touching earth therefore making an earth connection to combat static build up in the car, which now and again gave the occupants a shock , it did work ,In one of the scenarios above when the driver touched his car and was shocked, would it help if the car was earthed ? Ps sorry if I sound ignorant, I’m obviously not an Electrician
This was a GREAT video, thanks!
Why cant they use a free from earth transformer same principle as a shaver socket or reduced low voltage like on construction sites.
That is an option - the problem is a transformer large enough for an EV charger will be expensive and heavy - in the region of £500+ and 60-80kg.
Isolating transformers the smaller the better. I can imagine the large ones would defeat the purpose just by the large capacitance between the windings.
Great video John.
With many people needing EV Charge Points installed over the next years, and not all installers being as aware of the potential problems as yourself, this could become a major issue nationwide.
Re the earth mesh idea, wouldn't multiple earth rods, or a very long earth rod, (away from pipes, etc., of course) be an option?
I have seen copper pipes used as earth rods drilled into the ground by forcing mains pressure water through them, many years ago.
Not suitable for all types of substrates but where this works several pipes can be soldered together to go down very deep indeed.
Would that work?
What about using an isolation Transformer then you don't need to worry about DNO neutral breaking as the transformer effectively becomes a new source and this new supply is isolated from the incoming supply, thought you may have mentioned that method.
Good to see recognition of the fact that what appears to be a TNS supply is perhaps TNC-S due to 3 core mains cable (CNE) having been used to repair faults on 4 core (SNE) mains cables. DNOs should and usually do use 4 core Waveform type mains cables for repairing faults or altering 4 core PILC type mains cables that were commonly laid prior to the early '70s when PME networks became common place with the use of 3 core Consac, and later 3 core Waveform mains cables. However, as you've stated, three core CNE cable has been used to repair 4 core TNS mains in alot of instances which results in the customer's supply becoming a TNC-S supply. One problem with this is the customer's installation will not have the main equipotential bonding sized correctly in the case of supplies greater than 100A or older domestic installations. Many older domestic installation pre '81 (15th Edition) will have notably smaller main bonding conductors that won't necessarily be suitable for the return neutral current in the event of an open circuit fault on the mains CNE/PEN conductor.
Is this maybe a problem with DNO's responding to single dwelling increased supply main fuse sizes but not increasing the supply cable conductor sizes properly??
@@Mike_5 I see what you're suggesting, but no. The sizing of main equipotential bonding conductors is based upon the supply conductor's neutral CSA in PME/TN-C-S supplies whereas in TN-S supplies is based upon the CSA of the main earthing conductor. This is not an issue with modern installations up to 100A as the main equipotential bonding will be 10mm2 for both TN-S and TN-C-S but in larger rated supplies there could be a problem such as customers supplied using 95 or 185mm2 DNO service cables. If the installation designer has sized the main equipotential bonding on the basis he is dealing with a TN-S arrangement, but is inadvertently TN-C-S due to the DNO having used 3 core mains cable to repair a 4 core (TN-S) mains, then the bonding conductors could well be undersized. Although most large commercial and industrial customers are supplied directly from the DNO's sub-station where this shouldn't be an issue, very often a large 240mm2 mains cable in a high street may supply many 100A 16mm2 service cables but also a few larger service cables (95mm2 or 185mm2) to say a restaurant or bakery.
In a separate issue, older (TN-S) installations main bonding sizes are very often inadequate and aren't sized correctly for even modern TN-S requirements never mind TN-C-S. If the DNO's mains cable has become PME/TN-C-S and customer's haven't been made aware of a change to their earthing type. then the bonding will remain undersized. Remember that bonding in TN-C-S installations is larger than the equivalent TN-S installation as it will take the circuit's load return current downstream of an open circuit fault in the DNO's mains cable. If a DNO has changed the system earthing from TN-S to TN-C-S then I feel that they should inform the customers affected. The water supply companies will write to inform customers of the replacement of metallic water mains pipes with plastic as some very older electrical installations relied upon the incoming water pipe as their only means of earthing.
@@18in80 many thanks for the info it is very informative and comprehensive
The other issue is that on very large TN-S installations (factories and suchlike) it only takes a single NE insulation fault to actually render the entire installation the equivalent of TN-C-S anyway. In this sense, any loss of the incoming neutral will also cause mains potential on anything that is connected to earth, as per true TN-C-S. Another very good reason for thorough EICRs to be carried out.
Hi John,
As usual really enjoyed your look at this subject. As I am installing electrics in a new Garage next to the house with potential work ensuing on the house after the garage so I forwarded your video to the architect. Do we need to think about the specifications to add to any foundations to improve the earth for a particular situation? Even found this article as looked for articles in carbon Fiber concrete reinforcing (See details below). After all do not want to carryout foundation work and wish we had considered earthing, as we didn't consider it for the garage floor and foundations, the focus here at the time was insulation cold bridging and a Radon membrane. Now to consider earthing. I am old enough to remember the Tefal heads adverts, think I need that extension to look into the subject further. Especially after watching the "Fully Charged" Tesla Power wall installation. Where is it all going to end up? How much up front work do we need to put into work now to save much more expense later. Was going to put a single phase feed into the new big garage but should I put 3 phase in and even ask the "Hydro" to reroute my supply for the house from the 3 phase in the garage. Then need to consider a balanced 3 phase usage. Yep the Tefal head extension is required I reckon and just as well I have just retired to have the time to look into all this!!!!
Here is some bedtime reading for you.
Electrically Conductive Cement-Based Materials
January 2004 Advances in Cement Research 16(4):167-176
DOI: 10.1680/adcr.16.4.167.46658
Deborah ChungDeborah Chung
Foundation earthing isn't required yet, but is likely to be in the future. In terms of installing, if the concrete foundation will have metal reinforcement in it, then all that's required is to leave a small section of it accessible, so it can be connected to later.
For the cables, the most practical option is to install them in a duct, so the cables can be replaced later if required.
38:00 3 phase will be the only option in the future. There is a high possibility that gas or oil will not be available aboundantly... But appliances will be come all electric, such as EV chargers, Cooker-Ovens-Hob, Heat Pump, Combi Electric Boiler, Electric Shower, Electric Fireplace, Hot Tub and so on...
Thanks for a very informative video, having ploughed through the IET document on EVSE chargers and come to the conclusion that they seem to recomend a device that may be developed at some point for domestic users.... I am also concerned that the regs as currently exist with regards to domestic Solar PV and battery systems also seem equally vague, in the event of a power outage are all these systems being installed going to disconnect the house earth too and rely in a TT earth mat or earth rod? How often is this implemented? i.e operating in true island mode and how would you prevent cross connection with other nearby premises via water, gas, and other utilities/ extraneous conductive parts... P.S. in response to having struggled to find trained and competent tradesmen I have gone back to collage age 64 and am currently on Level 3 mpdule 5357 but hoping to add in the EV and microgeneration battery storage modules. P.P.S. I have a Zappi which seems to be about the best available and yes it sometimes tells me the voltage or earth resistance is out of range and disconnects..... Still trying to find Type B RCD's at a reasonable price too .
There's a few points here, if a PME supply is potentially dangerous, why is it the most common type of system in use and why are we still using it. Obviously cost.
Also what is the actual risk of someone touching that car while it's on charge and the system losses the neutral, very slim.
And why is it the electricians problem if the neutral is lost, that's the DNO's problem to properly maintain their system, I get fed up with more and more responsibility being put on the electrician, the electric companies are happy to take the money but not invest in the infrastructure, some of the supplies I come across are from the 60's and when I pull them up about it, they say it's fine. Apologies for the rant.
Did you say a TT system is better ?
What about a TN-C system where the first disconnect after meter , the neutral and the earthing circuit is tied up and is connected to an earth rod . Will this not be safer than a TT connection ?
Mr Genius JW...
Like aeroplanes I thought tyres on a car are conductive so doesn't that mean there is a point to real earth through the car's tyres which would make the voltage monitoring device effective?
Thank you for those infos, verry usefull!
Just wondering, if an earthing mesh is layed under a tarmac drive would that work as well .
Thanks John great video as usual. While watching I kept on thinking isolating transformer would be the answer. Just going through some of the comments I notice someone has had similar thought, and you have made a valid comment. Or for car manufacturers to produce a car that is double insulated so you would not need an earth connection.
The problem is the charging standards are now out there, so making a double-insulated car would require a new standard, which isn't going to happen.
@@mikeselectricstuff Personally I wouldnt trust a double-insulated Car to stay insulated at all after a few car mechanics have worked on it, or if water got in somewhere unexpectedly.
is it possible to use contactor as a main isolator on input side with coil 230 v ?
Yes, but only for contactors made to 60947-4-1 that are stated as being suitable for use as isolators.
Contactors to 61095 are not suitable for isolation.
So theoretically the only safe instalation is a no gas, TT property with spring fed water?
Apparently the batteries on board charge better with DC so couldn't the problem be mitigated by producing d.c. and funneling that outside to charge the vehicle
That's possible, and that's exactly how the fast charger devices available at some public locations work. The problem is that those devices are very expensive and typically require a 3 phase supply.
@@jwflame cheers John yeah I know I suppose it's a toss up between cost and ease of installation with the viable options to choose from as are particular to that site!
Thanks John!
Wouldn't the mesh type arrangement cause the same issue being close to underground cables/pipes?
Only if you want to use it as part of a TT system. If it's connected to the PME earth, then it doesn't matter because it's all part of the same earthing system.
The word (when) is a worry, for example when this fault occurs as if it is inevitable it will happen , I think if might be more appropriate , it’s similar to say ,when you get hit by lighting 😳
Thank you for the very informative video. Do you have any pointers on the design of the mesh please: 1) The size. 2) The material - I am thinking it will corrode and how best to connect a copper wire to it as two different metals will be involved and the joint buried. 3) A strange question to ask but could one use copper tubing that's been soldered as now connections would be copper to copper? I was thinking of using scarp 15/22mm tubing? Thank you.
Steel wire, welded into a 200x200mm grid. Some examples: www.specialistconstructionsupplies.co.uk/our-products/steel-reinforcement-mesh--rebar-for-concrete-slabs
Corrosion isn't an issue as it's completely encased in the concrete.
I suppose we'd have to consider whether the manufacturer of the mesh sees their product as suitable for use as a means of earthing and are there specific terminations (no doubt meeting various standards/approvals) from mesh to earthing conductors on this type of set up?
@@jwflame isn't the problem with having a steel mesh in the drive, that in many cases the electrical supply follows a similar path to the house (certainly the case in our semi)? The mesh will likely be laying about 50cm on top of the supply cable/gas supply. Certainly less than 5m away from it as you suggest would be safe?
Okay! TNCS = PME? 🤔🤔🤔! So did I thought. It was at least what I was taught in college. However, when I called UKPN to a customers property, I had identified the earth arrangements as PME. When their engineers were on site they said it was NOT a PME unless it's marked PME. Failing this, it is a TNCS.
PME is what's in the supply network, TN-C-S is the arrangement at the point it enters the property.
PME network will be TN-C-S at the property, but TN-C-S doesn't have to be PME, other network arrangements such as PNB are possible.
Hi John, what about isolation transformer?
Permitted and also included in BS7671 - cost and size of the transformer is the problem.
@@jwflame I had also though about wireless charging, but that's only convenient and not very efficient! Compared to direct connections!
It is a discussion opening topic,
Top work John
John Ward Hi John, I would think this must be the way forward. Maybe the cost of an isolation transformer is high right now, but it’s not as much as a new drive.
Love your videos, keep up the good work
Bill
@@jwflame many of the chargers can run from a 13a socket although the charge rate is slower. a 3kva transformer is £160 from RS. surely this will be enough to power a car charger.
Is it acceptable to ask your energy supply company to definitely tell you if you have TN-C-S or TN-S?
Yes, absolutely. They are the only ones which will know for certain.
@@jwflame Thanks John. My house in Wales is 100 years old and looks like it's got TN-S but, as you say, it may not be by now. I am experiencing a weird problem in that a light bulb glows slightly in the dark even when the switch is turned off.
@@edward_grabczewski David Savery did a video about this. It's probably not a wiring fault but a cheap LED bulb which continues to run on capacitive coupling between conductors on long cable runs. David demonstrated the effect with a mock-up in his workshop.
@@westinthewest Thanks for that. I've just watched both videos on the subject! Only problem is that if I remove the bulb and measure the voltage across the light socket terminals I get 20 VAC when the light switch is turned off. I wonder if it's because I've got two similar bulbs in sockets further down the corridor. I might try removing them and seeing if I still get this stray voltage. I'll also try measuring the voltage in LoZ mode on the Fluke 117 to rule out ghost voltages.
@@jwflame I changed to Tonik recently after being with ecotricity for a few years. I asked Tonik the following question:
"I need to know if my home is wired for TN-S or TN-C-S. I understand that homes that look like they're TN-S may in fact be TN-C-S owing to historical modifications in the cabling en-route from the substation. I need to know definitively (i.e. not a guess). "
and got the following reply (after one month):
"Thanks for getting in touch with us. We have a bit of a backlog, so please accept our apologies for the delay in replying.
Unfortunately, we're not familiar with the terminology you have used in your email, as none of this pertains to electricity meters. Should you be wanting this information for the substation wiring, it would have to be directed towards your Distribution Network Operator, which you can find out by using the link below.
www.energynetworks.org/info/faqs/who-is-my-network-operator.html
For wiring within your home, we suggest you contact a registered electrician.
"
So much for my electricity supplier. They don't even understand the question!
In a scenario where the charger is monitoring voltage on the CPC which relies on a person actually touching the car in a fault condition to disconnect, can the car be connected to CPC via the plug-in charger cable grounding the car body? This seems to me like the solution as the sensor device in the charger will see the fault without a person actually having to touch the vehicle to create the patch to earth? I don't know how the charging in the car actually works, would connecting the car body to ground whilst its charging mess up the vehicle electronics?
The car body is already connected to the CPC - that's where the dangerous voltage comes from if the PEN conductor to the installation is broken.
Car charging at home is basically just shoving 230V AC into the car connector - the conversion to DC and the rate of charge is all done by equipment within the vehicle. The other part is some basic control signals between the car and the wall unit to determine things like the total power available and only connect power when the car is present.
@@jwflame thank for the reply. Assume the charger had a CT sensor on the L, N and CPC. Under normal operation the CT sensor on the L & N would read current and the one on the CPC wouldn't (just like an RCD) as the neutral exists for the return flow. If you disconnect the neutral (broken PEN or even disconnect it at the fuse board) then the return path from the L is at least partially via the CPC (as some would return on the local neutral until the meter) so a CT sensor in the charger should be able to see current flowing on the CPC and disconnect? I suppose that would only work if the vehicle was actually pulling current to have a reading form the CT sensor on the L to begin with. if the vehicle was fully charged it would just sit there live until somebody touched it to pull the required current over the CPC to cause the charger to cut off. Is my logic correct?
Long time since I left uk, but I thought that if incoming services where non metallic then the earth bond wasn’t used any more am I wrong
Hi, I think JW deals with this. Although the water in more modern houses is likely to be plastic at the entry point, the gas pipes will probably be metal. And, the water pipes will still be metal and therefore earthed in older houses.
But, that still doesn't address my query regarding the super earthing grid he suggests that will also be running close to pipes instead of his problematical earthing rod.
It may come in as plastic, but if the installation is metallic and enters the ground at any point (like a copper water pipe laid under concrete to a kitchen island worktop for example) then that pipe needs bonded. Anything metallic that can introduce a potential within the equipotential zone formed by the installation must be bonded.
I can just imagine some numpties washing the electric car from the nearby outside tap, whilst the car is charging!
Most people are non technical and simply would not be aware - why would you be, the installation has almost certainly been installed by a "professional"!
A lay person may well think this is a good idea as it would save their time. Not to mention "killing two b1rds with one stone." Surely a better solution to the car charging solution would be to have a double wound transformer in the house with a rectifier, and nice hefty cables carrying DC outside to the car. A very expensive, but much safer solution.
That’s actually a strong point , mainly due to the absence of common sense these days
3 words, You cant fix stupid.
@@stevebeal73 high current DC has many safety issues of its own.
i wonder if uk is shifting towards 3 phase in residental? i mean, i'm glad to live in country where 230/400 3ph is pretty much always available and most times at decent current too.
of course, i realize that noone wanted to build what looks like electrically inferior system in year 2020, in countries like us/uk/... it's just legacy that tried to cut cost
Is this grid in new build regulations as ev chargers are now a requirement
This is a old problem that gives gas fitters & plumbers nightmares !
The only fix I can see for EV charging is a external switching power supply or a big isolation transformer in a box with a over current trip & a 2 wire leakage device on its output feeding the EV .
No earth after this unit so only 2 wires feed the car power directly .
2 more wires loop through as a safety device .
The external unit monitors this loop for voltage or a open as a indication of cable damage .
The enclosure must be double insulated & 110 % waterproof so it's not getting fitted outside !
A load management system tracking the generation frequency might be a good idea !
( So randomised time switching the charging current depending on the grid load )
This could be a control tone on the cable that the EV will use for setting its own charge current .
It checks & re-evaluates its charging current at random intervals then adjusts as needed relative to the grid frequency .
In the uk at 49.7 hz it must pause the charging cycle .
As we get more EV 's on the grid the smarter these things must be .
Fabulous video John, and one which I completely understood from beginning to end. But, what an issue, and will there EVER be a solution? Thank you for sharing with us.
On a slightly more...down to ground (pun inevitable) note, may I ask your opinion on whether, or rather how to go about 'grounding' a 240V electrical installation in a motorhome or caravan, because it seems to me that some of the issues raised in this and your other video, "TN-C-S Danger - Broken PEN Conductor (Combined Earth & Neutral)" are very much in question.
I realise that you are most likely a very busy guy, but your comments would be appreicated by me, and I'm sure many others.
Regards Mark in the UK
The solution will be foundation electrodes at every property, but that will take decades.
The law prohibits TN-C-S supplies being used for caravans, so they are almost always TT, with the whole of a typical caravan park being TT with the possible exception of any permanent buildings that might be TN-S or TN-C-S.
Caravans should not be plugged in at home either, as most homes have TN-C-S supplies, however plenty of people do.
9.4 of www.legislation.gov.uk/uksi/2002/2665/made
Why does a car even need the earth exporting to it? Its fed via an isolated supply a bit like a shaver socket.
It's not, the mains voltage goes into the car, the charger is simply there to act as a relay, turning it on and off basically. The power supply used to charge the batteries is inside the car itself.
Have you seen how big and expensive 7kw isolating transformer would be ?
@@mikeselectricstuff Thought it was DC converted electronically to charge the batteries, bit like a SMPS
Home car chargers just shove 230V into the car, the conversion and charge control is done inside the vehicle.
The fast DC chargers provide DC to the car, but those cost £1000s and require a high capacity 3 phase supply which no domestic property will have.
Was thinking of putting a TT stake in for my own EV motorcycle point but it would have to be within 2m of the plastic gas main and TNC-S supply so hard luck there for me.
What gets me though is the lovely metal kick stand on the bike reminds of the days when Cars had cables hanging down off the chassis to ground them out against air friction and static electricity.
So why isn't that a valid option to just plug the car directly into the ground, surely if the mass of the car is already in direct contact via exposed metal to the ground the likelihood of a person being the favored path is diminished.
Dear @John Ward
Good explanation. I can see one security risk you might not have seen in the first glance.
When looking at @35:42 and @13:33 with many houses on the same phase but with a broken combined N and PE wire for all those several houses, your house with a good ground connected Earth Mesh + Earth Rod might get a very big current on its PEN wire coming from the street. So from my point of view it would make sense to have a Fuse in this wire when it enters the house, to avoid to have a glowing wire in the basement in such a case of a broken PEN somewhere down the street. Regarding the amperage of the fuse I would suggest to have it 1.7 times the rating of the main phase fuses, in case you have a three phase installation in your house. The local earth mesh /rod must always be connected to all the PE wires of the house and water piping etc. in the house. The fuse should only break the incomming PEN against this fire risk.
Addendum: I just discussed this idea with another experienced guy and he mentioned that this PEN Fuse could blow when you are not at home and notice the troubles in the powergrid, and the grid might be already repaired when you come back home. So the Fuse should have a supervision electronics. In case of a broken PEN Fuse you might not notice it, as the Earth Rod/Mesh would still allow a medium load to run properly, e.g. you might only notice a flickering in the light when the fridge motor starts. Furthermore he recommends to cut all the power to the house whenever the voltage of any of the 3 Phases and the Neutral is outside of a certain acceptable range. You might need an independent little earth rod to measure these voltages to a proven reference ground point.
brilliant video but for an alternative reason... the lack of uk infrastructure investment and letting privatised electricity companies install 2 cable street infrastructure. this has meant the uk has a real problem with ev charger installation. as this guy says....if you do A.. you're Fckd.....if you do B you are still Fckd. shame on uk.
John that's not really a solution..... Yes sir I need to dig up your drive and install a mesh grid....
it probably cheaper to have 3 Phase put in
@@don1estelle In the long run that is probably going to be the way new builds go. At least for detached houses with off street parking.
The fundamental problem here is that TN-C-S is potentially dangerous anyway as a broken neutral can put near mains voltages on anything bonded to earth. So even if you don't have an EV, that garden tap can go to dangerous potentials compared to the ground you are standing on. That goes for any metalwork attached to the outside of a house which is bonded to the incoming earth. Of course, it's true for the inside of the property too, but presumably the regulators think it unlikely that there's an independent path to earth as, presumably, all internal metalwork ought to be bonded.
The broken supplier neutral problem will also apply to anything operated outside the house via an extension lead.
Really, if this is a significant systemic problem then it could only be "fixed" properly by electrical supply companies being required to install devices that cut off power and the point of entry to the property if dangerous voltages are detected on the neutral/earth supply.
So this is not a new problem caused by EVs, it's just that, presumably, the latter are just rather larger and more accessible hunks of metal.
In any event, I suspect we will see a lot of people just using 13A standard sockets and an extension lead to "top up" and EV on an ad-hoc basis.
PME Supply was in my opinion a cheap and nasty way out for the Supply company a auful lot of electricians didn't like the idea when PME came out
15:15 In most situations adjacent houses in the UK are connected to different phases to balance the load, so could the voltage between two cars could be 415v?
The car metalwork is connected to the neutral point, so it's unlikely you would get 400+ volts between them as that would require at least one of the vehicles to also have a fault between line and what was previously the neutral.
The combined neutral/earth to both houses would normally be the same conductor, so it depends on where the break is relative to the supply to each house.
Also depends on whether the 2 houses are using the same earthing system or not.
@@jwflame I see no reason to connect car chassis to AC neutral.
@@millomweb The car chassis probably isn't connected to AC neutral but it is connected to the CPC/earth which, in turn, is connected to neutral either at the cutout in a TNCS installation or, likely, somewhere in the street in a TNS installation.
@@speedmytube Do you know if the body is still used as the return path for the general 12V system in an EV? Seems odd to earth reference it if that's the case, connecting the output to the supply side of an otherwise isolated SMPS.
@@marcaxe yes it is
Hi John! I fully agree with you, that establishing a proper low resistance grounding is the only option to do it properly. Not only for EV-charging, but also for the general installation of the house. Thank you for giving me this insight into UK domestic installations.
I am from Germany and I was asking myself halfway through the video, why on earth (pun intended) you consider a TN-C-S network to be a problem. OK PEN faults can happen, but hey, the ground-connection of the "potential alignment rail" would bond the PE and the neutral close to earth potential. This rail is the central point of the house where all the metal parts as well as the PE are connected to and which is also connected to a low resistance grounding. I was aware, that single phase supply is typical in domestic installations in many parts of Europe, but I am mildly shocked, that low resitance grounding does not seem to be required by UK regulations.
In publicly accessible EV-Charging installations it is even required, that the foundation of the charger has a separate low resistance grounding in order to prevent potential differences that can occur between the far away grounding of the building (which is present on the PE) and the earth potential at the location of the charger (e.g. when a lightning strikes nearby).
Sometimes (over-)regulation sucks, but in this case I'm glad we have it.
Anyway - a good video. I learned something and I like your style of presentation. Subscription you have.
Best Regards
Andreas
Can you elaborate more about the standards there especially the "potential alignment rail" that is connected to a low resistance grounding?
@@IAmThe_RA Hi there! In Germany it is mandatory, that every building has a proper grounding with a low resistance to ground potential. This can be done in several ways (e.g. a ring of flat-iron around the foundation, a connection to the steel reinforcement of the concrete foundation, a pole that is driven deep into the ground).
The gounding resistance has to be measured in a standardized way and documented.
Now this grounding is connected inside the building to a terminal-rail called main-grounding-rail (formerly potential-alignment-rail), which is located close to the termination box of the electrical grid (the endpoint of the grid where the main fuses and the meter are located). All metal components of the structure, that can be touched (e.g. water- and gas-pipes, plumbing, handrails, roofing, rainwater-ducts, satellite dishes) must be connected to this main-grounding-rail. In larger structures you find additional grounding-rails, that are connected to the grounding to reduce the wiring effort.
This ensures, that every conductive piece that can be touched have ground potential, even if they bring in a different potential from elsewhere (e.g. a lightning strikes 500m away from the building and the water-pipe runs close to the strike and has elevated potential.
Now to the electrical installation: A three phase TN-C-S type grid comes with L1, L2, L3 and PEN (combined neutral and protective earth). The PEN is split at the termination point of the grid into neutral and PE of the installation. A fault of the PEN in the grid would mean absence of PE in the installation, with all negative consequences.
Therefore in Germany the PE must be connected as well to the main-grounding-rail of the building. That is why you locate it close to the termination point of the grid. This ensures, that the security mechanisms work properly, even if the grid does not provide earth potential through the PEN. On the contrary - when the grounding of the building should fail for whatever reason, the PEN still ensures at least a "close to earth potential" because the PEN is also connected to the main-grounding-rail of all neighboring buildings.
Hence the TN-C-S grid type is considered here superior to the TT grid type, where the earth potential of the electrical installation relies solely on the proper grounding of the building.
I hope this is what you where asking?
Best Regards
Andreas
@@andreasbentz6106 Thanks for you detailed elaboration 👍
Hi I was wondering what value is considered acceptable for the potential alignment rail? When tested what is the maximum value in your legislation?
@@hgn6716 Hi there! The answer is not as easy as providing a single valaue. The reason is, that the legislation requires "a proper function of the protective devices", hence the tripping value of the RCD in mA and the voltage of the measurement determine the required resistance value. Most measurements are taken at 50V and this means, that a 30mA RCD requires a maximum resistance of 1660 Ohm (which I consider a bad grounding), which is usually not a big problem. If you have a 300mA RCD at a construction site or an older building, this maximum drops to 166 Ohm which is sometimes hard to achieve, especially if the grounding is not properly done or has rotted away in older buildings. Also the hot summers with practically no water in the soil down to a level of 2-3m below ground were an issue.
In addition to the absolute value, you also need to observe the requirements for the measurement. The required procedure is a differential measurement called 3-wire measurement. You need a main ground probe at 20m distance to the potential alignment rail and an additional support probe also in 20m distance of the main probe (a triangle is OK). For Installations in rural areas, this is doable, but in urban areas you often have no chance to reach a proper distance for the probes. In these situations, other procedures are accepted.
If you want to see such a measurement, there is a video on youtube th-cam.com/video/NP2WahhBV_A/w-d-xo.html
But be warned, the guy is Bavarian and talks the local accent, which is very hard to understand even for native German speakers. So the automatic subtitles do not work. At 14:00 the actual preparation and measurement starts.
Cheers
Andreas
You can sometimes get very low readings from a single rod but it is so dependent on the underlying soil conditions, in lightning protection applications I've seen 6-9 ohms at a 3.6m x 16mm copper rod. In parts of London you might hit clay and you're laughing but 50-60 miles down the road in E Sussex you'll be into chalk and you've no chance. Foundation earthing is coming in an amendment soon that's fine for new houses but can it really be applied retrospectively to existing properties?
You could also "just" dig a trench around the house and add in a metal mesh band around the building. This also gives a pretty low resistance.
My girlfriend has a TT installation.... I like TTs
BANG 🤣
Massive can of worms. Another great video and explanation Sir John Ward
John Ward, for many years during my 43yrs of employment with BT (formerly GPO when I joined in 1972) earth testing was one of my duties as a Precision Testing Officer. In small telephone exchanges situated in the country earth testing was carried out every couple of years. I was involved also in testing what is termed "Earth Resistivity" testing to determine what size and type of earthing system was required. BT strived to get an 8ohm or better earth electrode system but this was very seldom achievable in rocky areas. Even with massive grid systems (we used solid copper bar) or multiple earth spikes bonded together or joined up and driven in the ground by a type of impact wrench it could prove impossible. Specialised Meggers and tables were used to determine the best earthing method. You are quite correct in stating that it is nigh on impossible to provide a low resistance earth with one or two spikes unless you are in very, very "good ground" with a low earth resistivity. Quite what the answer to this I am sure you have puzzled over. If some fancy (and probably very expensive!) bit of kit comes on the market to act as a safety cut out then I hope to hell it is a lot more effective than some of the new fangled "arc protection devices" you have tested over the last year!
I would’ve thought the best thing is an isolation transformer. You’re basically starting again.
Not cheap though, especially for high power applications.
People often forget that the ground impedance is only as low as the impedance of the other end of the circuit through ground.
Often due to space restrictions we test earth electrodes with a fault loop impedance tester which usually gives a value about 5-10 ohms higher than a three electrode test. Of course this is because the loop impedance includes the impedance of the DNOs earth.
Where there's a PME system that actually has multiple earths - rare as the regular electrodes along the cable simply don't exist - this should be low.
But you get a TT system fed from a post mounted transformer - which our local DNO aims for a 10 ohm earth electrode but in reality the geography makes that a pipe dream.
And ultimately we should be less interested in a race to low earth impedance, and more interested in the fundamental safety objectives - limit touch voltage and ensure protection operates within limits.
Back to the original topic. I'm sceptical about the importance of potential to local earth - I think extraneous conductive parts are far more an issue which on a drive limits us to next-doors car and maybe external plumbing.
I'd therefore be more interested in ensuring that two neighbours have a low resistance between their respective earth terminals - which if they were both PME on the same supply cable then this would be very low. If this is inspected periodically - and frankly if you've got an electric car you possibly should get your EICR when recommended even if the extent is limited to the charger.
I'm not convinced that at LV we get shocks capable of causing injury between a PME failure and the puddle on our concrete drive we're stood in with inappropriate footwear. I'd love to see evidence otherwise.
We’ve just moved house and plan to get a new driveway installed. So glad I watched this video before any work on it has started.
if you use rebar mat make sure its welded in the matrix X crosson pointd and not just "wired" get your welder to tag weld it all together and then have a couple of bits coming up at a suitable corner, remember tho it will rust externally so get an electrican to make a rust proof connection to the ground plane (which is what it is) Look up UFER GROUNDING SYSTEMS in wiki etc
Hi John, Dave here... old, cold and retired quite a few years ago. Whilst everyone was bonding the heck out of every thing, I kept telling them that safety through isolation was the 'better' method... however my very simple suggestion for an option 6 would be, 'EV charging should be via a class II psu'.
That option is in BS7671 as 722.413 Electrical separation.
Unlikely to be used due to the substantial cost and inconvenience of a large transformer for every charge point.
@@jwflame I hear what you say, but 'substantial cost and inconvenience' vs for example the >substantial cost of digging up / earth works (pun intended) and reinstating driveways, the building trade have nice yellow ones that could serve as a great conversational piece in any home. Also for less money than it costs to get Bob the builder out of bed
@@2013Davey , Bear in mind that fast EV chargers are roughly between 7 to 20 kVA. That's going to be a physically bulky and relatively expensive isolation transformer. Single-phase site transformers in the 10kVA continuous range are about £800 (and near 100kg) which buys you quite a bit of labour even in the leafier outer-London suburbs.
mm lots of Potential for Discussion! lol
I love watching your videos John - not in the profession but I just like to understand how things work - or try to at least!
I am in the process of having an EV charger installed (by BT Chargemaster) and have never been asked so many questions ahead of an installation visit! The latest questions include "send us photos of your water and gas bonding" which got me watching your videos on that subject which then led me to this one! I have TN-C-S
Given what you say should I cancel my installation for fear of being burned to a crisp, or just plan to wear thick rubber gloves and boots whenever plugging / unplugging my car to the charger?
As a layman I assumed that if the main supply was damaged to cut the neutral / earth then the supply would be automatically cut off by the utility company?
If that didn't work then one of the devices in my CU would do the job. If this is such a big risk why aren't houses in general protected? Why is charging a car such a special risk over and above something like a good old outside socket?
Anyway, someone better get all this sorted because we are all supposed to be driving electric vehicles asap !
29:10 are car tyres insulating these days? Are they not now conductive rubber, to dissipate static build up on the car.
Static voltage is high voltage and the mains voltage coming into your house is only low voltage
The version with the mesh grid under property. PEN broken. Doesn't this mean that the vehicle charger works normally, RCD won't trip because it has no reason, everything works and I have no way of knowing something is wrong? I presume only way is to measure loop impedance which will be significantly higher than normal 0.35 ohms or less in TN-C-S, am I right?
Thanks for a thorough summary John and for pointing out that those chargers designed using a CT on the PEN, are not compliant with the principle of reg. 415.1.2. That is going to give many EV Charger installers a problem, so I'm not sure it'll be welcome news to them! Zappi device anyone?
V2G is being quite widely seen as a way to give our future national supply more flexibility and reserve, as EV's take over in the next few years. The OVO V2G project with around 400 installations, has run into exactly the problems you describe and having discarded the Matt-e device, (DNO stability problems as well as single phase protection issues) they now insist on a separate earth electrode installation. They require this to be the regulation distance from incoming supplies but allow a test impedance up to 100 Ohms, which may be practical but obviously then reies on the CT/RCD style protection installed. I installed an 8 metre long 16mm diameter rod and 75Kg of conductive concrete (Furse/ABB product) to make my separate earth for this project, but it still tests at 30 Ohms in this rocky Peak district area.
People are left to self-assess an installation. Also a manual process to declare an EV installation to the DNO.
Would the same issues apply to heat pumps?
Are there many properties affected by looped supplies, or shared supply fuses?
My business is establishing a cross industry group to identify risks for EV charging ahead of the mass market migration to EVs, heatpumps, PV and battery storage.
Interesting to read issues related to V2G trials with WPD and OVO
zappi doesn’t just rely on a CT. It has many inbuilt safety features. myenergi.com/zappi-2-bs7671-and-protection-features/
@@jordeebrompton well it sounds convincing but it would be good to hear John's view.
@@jordeebrompton yes but it still relies on what is effectively an RCD device alone to protect against a fault current passing through the user. Has Myenergi confirmed compliance with 415.1.2? That is key.
Wow, sure that's food for thought, there must be a lot of unsatisfactory EV charging points around ⁉️. Thank you Mr JW.
Agreed mate. This is a total can of worm isn't it. So convoluted to achieve a compliant and safe installation. Times like this I wish I'd been a bricklayer. 😒
Daniells1982 would of earned more money
@@Mainly_Electrical Even labourers are on more than most sparkies.
andy530i disgusting mate most skilled trade paid peanuts really unless your the top dog
As transportation is being increasingly electrified, surely all new builds connected to a TN-C-S supply should be required to have a local, distributed earthing system installed such as a grid or copper wire around and below the perimeter of the concrete slab. Buildings where I live in Norway (with both TN & the older IT supplies) have this sort of arrangement and earthing arrangements for charging have been unproblematic, though many have dug up their driveways to install higher capacity cabling to their garage or carport.
In Ireland nearly all houses have TNCS and always have had a local earth electrode.
Interesting video some very well made points 🤔. I wonder how many have been killed or injured due to issues, are the issues truly understood in the industry. Would be interesting to do a video on already installed systems to see how many comply.
When you say you cannot use a TN-C-S for hottubs, How are people getting them installed? do you have to make a TT but then you are solely reliant on your RCD.
In Norway we have all three systems (TN, TT & IT). In regards of TN we get 3~ TN-C to the house, then we split the PEN to PE and N and get TN-S. We then have the following requirements: Surge protection, Earth lekage with Type B (Type A is not allowed with the exeption if the charger has its own dc lekage detection). I’m often pussled to see the difference in how different countrys do electrician work :P Like the one house you show about connecting to the PE from the supply line, but use a eart rod insted. Now allowed. We also have to drag a 25mm2 wire round the house and connect it to the PE bar. Acting as our earth rod. It’s not that common too only get 1 phase, but same principle with TN-C-S and earth wire in the ground. 1 phase systems is more common in old houses and often IT or TT systems and not TN. IT and TT we dont get neutral, we get 2 or 3 phases with 230v between them, and we do the same regarding the earth wire.
If you split PEN to PE an N this is not TN-S, it's TN-C-S . TN-S would be 5 cores incomming (L1, L2, L3, N and PE.
dd313car I know. I’ve never come across TN-S from the supply company. But we are not allowed to use tn-c from the main switch board in for example a big building and to the next. Here we nede to use tn-s.
Hi John thanks for the vid very well put . I have one thing that you did not touch on that I feel could be something that needs to be considered . Where you are adding an additional earth mat to the property that will help with the problem for Ev charging it also has an additional problem. In the event of a open pen conductor in the street your earth mat being of low resistance could actually be carrying a large amount of current from the whole street to earth so depending on the size of your earthing conductor to your earth bar and from it to the mat it could prove to be a fire risk . As has been found in the past . This in no way meant to detract from a excellent vid . Regards bill
Beeing happy that here in Germany, Austria and Switzerland most houses have such massive earthing systems since the 1970th😏. Additionally all installations where you will install a EV charging point have a 3phase supply.
So 3 phase for EVs, thus giving charging in the 20kw+ range not 7kw range and charge speeds of 50mph+ and not 15-20mph
Not necessarily. My property has main breaker of 3x32A. So I would use 3x20A for the charger. It gives me cca 14kW.
So more than the 7kw we would get in the UK on a single phase? At that rate you would charge at about 30mph and I assume those 32A fuses could be upgraded if the cables are up to it?
Here the normal type 2 charging point at home has 3x16A. The reason are the regulations of the power companies. Charging points >16A (single and three phase)need the agreement of the power company. In some cases you have to pay >2500euro for this. Max current for single phase applications is 20A@230V in all cases. Though single phase car chargers with 7kW are pretty useless here.
Technically it is not a problem to change a car whith 32A@3x400V (22kW) because most houses have a supply of 4x35 or 4x50mm2 Aluminium and a 3x50A Fuse in the cutout box.
@@patdbean Depending on my agreement with my supplier. When my neighbours wanted electric heating they had to wait. There was not enough capacity in local transformer. Our rules are very different from UK. But yes we can have 16,25,32,64 Amp B type breaker if local conditions allow.
Another great video that brings the regs into the real world. Looks like this issue is going to be a real head scratcher for some time yet.
I know the supply for me is TNS, because the cabling was stolen at the substation, so I got to see them put it back in. The cable they installed to replace the stolen cable was still a 4 wire SWA cable, replacing the original paper insulated steel tape armoured cable that was cut out.
However in areas with overhead supplies the cabling is TNCS, as the cabling to the poles has mostly been replaced with ABC over the years, replacing the original 4 conductor with aluminium 4 conductor, with the supply always being TNCS with the drop to the houses, only still overhead bare wire for properties that have not been transferred to non related owners for the last 30 years, otherwise it becomes a buried cable and external to property meter, being a TNS supply from pole to meter, and then a grounding rod by the meter. Old properties grandfathered in, as some have grounding to water pipes, or a ground rod, or nothing, depending on the age.
Did they remove the bodies before replacing the cable, or just dig them into the ground along with the new cable?
Extremely Great full for such informative VDO
20:30 If every house has extra electrode connected to pipe network then this will create ultimate ground mesh with massive contact area. I don't see how there is possible to create dangerous voltage potential there.
Very useful video, thank you
The issue you highlight for PME supply and car charging is founded on the problem on N supply line becoming broken to the house. Although this is serious - it is unlikely (but must be considered). The question I would like to ask is the problem that, depending on the effectiveness of the bonding of the supply neutral, and the current draw on the mains - there will be a voltage rise on PME earth (ie neutral) of between zero volts and 20 volts compared to true earth at your car which is not connected to ground via the tires.
It a person now plugs their car in in the rain while wearing flip-flops etc, you could get a potential difference of 10-20V between true-earth (the wet ground) and the car (connected to PME earth) once the charge is started. Surely this is a issue as 10-20 volts in a wet environment could be conductive. What is your opinion of this likely scenario.
(I have a PME house wiring with separate TT earth for my isolated earthed garage using 3 earth spikes - with plastic gas and plastic water piping and the mains incomer 30m away for my car charger earth rods.). Maybe borderline.
Next problem , many people use "granny-chargers" from a house supply which of course certain to be PME earthed.
Could you do a video on the standard safety equipment in a car charger supply - DC detect, earth/line/neutral solenoids, asymmetric signal detect on the pilot pin for earth failure and so on.
Many thanks.
JW, what's your opinion on earth grids embedded in concrete foundations and any resistance caused by the concrete to (true) earth/ground? Thanks for your educational videos.
Even my kids know you because I’m watching your video all the time.
Fascinating video John. Boats tend to have an isolation transformer at the point of entry, the supply is then used for socket outlets and charging onboard. Would this be an option here for the supply to the charging point?
John, your video is excellent. It is certainly making me push the boundaries of my technical knowledge and understanding. But in practical terms you seem to be saying the BP Chargemaster / Pod Point et al are going around installing 1000's of potentially unsafe EV charge points. Is this correct? Further, whilst the maths makes my head spin I simply can't reconcile what's in your video with text and schematic 'G1' on page 112 of the IET Code of Practice for EV Charging Equipment (3rd edition), which basically says, '3 properly spaced bog standard rods from the wholesaler, and jobs a good'un'
If PME with additional electrodes is used, the electrode resistance must be low enough to ensure the touch voltage is under 70V. The resistances are shown in Table G3 on page 111, which is the same as referred to in the video - typically in the range 2 to 5 ohms depending on the installation load (charger plus the rest of the building).
The main point is what's under that table - that it won't be possible to achieve such low resistances in many installations.
Page 112 is suggesting a minimum of 2 or 3 rods, which is one way of reducing the resistance, and is presumably intended for situations where a low resistance can be achieved. However if it can't be low enough due to the soil conditions, then that method of protection can't be used. Higher resistances will help lower the voltage, but it would still be above 70V when a fault occurs.
Regarding other installations - yes, some of them will be dangerous if the PEN conductor is broken, as previous versions of BS7671 suggested that protection against that problem was optional (so it wasn't fitted), and even the existing version has solutions which are inadequate, such as the voltage detection option which will only work in some cases, not all.
PEN faults are relatively uncommon compared to the number of properties (hundreds per year are reported) and electric vehicle charges are also relatively uncommon, so at the moment the chances of a PEN fault at an EV charger is small. However that situation will change, as EV charging points are likely to become a standard feature on a very large proportion of houses and other buildings.
Clearly there are a great many potential problems in this area, but how many instances have there been of open circuit PEN conductors? I would think that if this was anything other than an extremely rare occurance concerns would have been raised a long time ago.
400 reported incidents a year according to this article: myenergi.com/pen-protection/
Total number including unreported is unknown.
Well done John! That is the most comprehensive overview of the subject I’ve seen and illustrates the rather dry regs surrounding this confusing issue. I think it raises more questions and concerns but it does highlight the complexity! Hope the IET watch it! 👍
It's only a matter of when someone gets hurt from electric shock driving.these cars .
I have to ask if service pipes are metallic and under ground therefore grounded just like a earth electrode are they a form of a earth electrode in them self's
If you use the suggested method and a pen fault occurs the neighbouring houses will be using your earth connection for the return back to the transformer. The current imbalance will trip an rcd but that won’t disconnect the neutral so you could still have hundreds of amps coming into the house exceeding the current rating of the wiring and a safety risk. Could you please explain what currently protects against this and if there isn’t what you would recommend.
Current will be limited by the resistance of the earth grid/mat and the total load connected within the installations, and that current will be divided between all of the connections to Earth including bonding to metal pipes and similar.
This isn't an EV issue, why is it ok to have dangerous voltages on other equipment. if TNCS is so dangerous why is it so common and legal.
A very good point. TN-C-S is so limited in its use due to safety implications. Can't be used for caravan sites, swimming pools, private supplies in the public highway, petrol stations etc. Nor multiple individual premises that share a steel structure such as a row of shops with individual services and meters to each shop. I've always preferred TN-S and TN-S mains networks are still laid in some cases by DNOs with new TN-S services supplied to customers, though this is rare.
Just a thought JW, from experience of new house bashing in the 90's adjacent house are put on a different phase, so for example 3 new adjacent houses would be spread over 3 different phases. Therefore if a nutrual was lost according to your sketch then there could be a potential of 400v.
BTW good vid.
Hi Tony, out of interest did they keep Semi’s on the same Ph?
Not quite ..... If the 3 houses each had the same lode the "neutral" cable between them would find its own resting point at 0 volts! It is only when the loads are not balanced the neutral would be at a corresponding voltage, up to (if two houses have no load) 360V! Sill not good!
If you want to visulise it imagine it, picture a triangle measuring 415 units to a side. The center point of the triangle is the neutral /earth and each point is one phase. If you measure from point to center it is 240 units and if you extend the line from one point untill it intersects the side of the triangle you will get just over 360 units ;0)
@@djb774
I have seen in the past some old council houses, semi's, that shared the same over head cable, looped into one and out to next door. Back in the 80's, a hideous black twisted cable tacked along the underside of the eves.
Very much doubt that sort of thing is down now.
@@djb774 Not necessarily. About 50 years ago my next-door neighbour was dying and had electrical equipment powering his bed. His company's fuse blew, so they called the Electricity Board and I supplied the bed from my house. The first things that the man from the electricity board did was to check how I had connected the bed in case replacing the company's fuse would connect two phases together.
I should have said this was the then neighbour in the same pair of semis.
Very helpful explanation of different earthing systems and their hidden cans of worms as you call it.
It actually means that having a TT system and all plastic water and gas mains coming into the house is the safest option where no neighbour can make my plumbing and car live unless they willingly connect a wire to it?
With all plastic mains pipes under the sidewalk and to my house, does the minimum distance of 5 m between my earth electrode and mains still apply?