I agree. I’ve been wondering about earthing arrangements for an EV charger. Other videos have glossed over the problem and focused on impractical solutions. Thanks for posting

Radu, the UK was part of the EU when this video was made. You should explain you are talking about a local grounding system for each house, that must be provided by the home owner to the distribution operator...

@@silviuguseila2552 Yes, my thoughts too. A dedicated building grounding system with a defined maximum impedance is being discussed here. My understanding is that in this case, a fault like this will cause a high fault current due to the low impedance of the foundation earth electrode which would trip a breaker and make it safe. This happens in the UK too by virtue of bonding of extraneous conductive parts such as gas and water services to the main earth terminal, but since the impedance of those pipes can be high, reliable disconnection will not occur.

This happened in our home when I was young. It was a TT system, but the Neutral connection failed. As you said, all the light loads that were on a different phase to the heavy loads in the house blew up as the heavy loads presented a much lower voltage drop across them.

Hungary is the same electrical system. (3x400/230V) PEN fault = neutral potential increases (N potential

same thing would probably happen here in the US, id like to see him explain it and draw it out though because i wonder if the earth/ground wire issue in the video happens on our split phase system. We have come close to losing the neutral as it was being chewed on by animals for 50 years and when you used the microwave the lights on the other phase got brighter (gained about 10-15v) and everything on the same phase lost the same.

also as far as i know we never have an earth/ground wire that comes from the pole here.

kibi15 The same thing once happened to me. I’m retired now, but used to work in a large college. One day I was seeing all sorts of strange adults, fluorescent lamps flickering or dim or over-bright, various other things not working properly or overheating etc. I reported it to security who told me not to worry about it, as EDF were working in the substation. They were indeed working in there, they had rollers laid out and were pulling through new HV cables, two bundles each of three single core cables, each about the size of a rubber fire hose. New cables not connected to anything, and old ones not disturbed in any way. Whatever the fault was it was not related to this work. Returned to security to to report it again. Was told that it was just the Voltage being a bit low, and not to worry about it. The installation was overloaded, hence the new HV cables and transformer being installed, so the Voltage did tend to be a bit on the low side. At this point I grabbed an AVO, and measured the Voltage on a number of random sockets in various rooms, some were under Voltage and some over, by a considerable amount. I guessed that the different Voltages were on different phases, and thinking about it thought that it sounded like a neutral problem with the neutral point wandering about, closer or further from different phases depending on the load being drawn from each. Then measured between neutral and earth, and found various, considerable, Voltages. The installation was way out of balance at that time with L2 being the most heavily loaded, with L1 next and L3 least. I returned to security again, told them that something was seriously wrong, and it needed urgent attention. I received the incredible reply that they would give the keys to the LV intake room so I could go down to investigate. I told them in no uncertain terms that I was a humble I.T. technician, certainly not qualified in any to do anything about it, that they needed an electrician to deal with it, and I had no reason to think that the fault was in the intake room anyway. Unfortunately, the college no longer had an electrician, the one they used to have gad left and it was decided not to replace him to save money, but to just call in a local electrician required, which was most days in a building that size. Local electrician was out on another job somewhere, but came in later in the day, came to see me, to ask why I had reported a problem; he’d just been told by security what the Voltage was a bit low, and there was nothing he could do about that. When I came in the following morning the electrician was there. He told me to go with him and in a large panel in a corridor behind the library where the fault actually was.

I know I co-wrote EMC 07 for the RSGB on the Subject, rsgb.org/main/files/2019/12/UK-Earthing-Systems-And-RF-Earthing_Rev1.4.pdf

Always! 👍🏼

This is interesting, so the copper cable around the outside of the central aluminum cable started to deteriorate. I would like to see what that looks like

Tncs shouldn't be allowed

You plumbers don’t know what a real tinkle is 😝

@@mohammedkhan5344 we (Iceland) ground the PE wire here (after the breakup). So there would be a difference. The PE lead is connected to the plumbing as well as the rebar of the building. So you need 2 or more failures for this to become a deadly fault.

In Poland we have recommendation to ground the point of splitting PEN wire to PE and N. I cannot relate to your case, but I think it is worth carrying a voltage detector with you. It looks like thick pen or marker and is an equipment of every professional electrician.

@@Hammy135 your.proud that you a.shock??? You must be a terrible.electrician

The problem is, the earth stake does not have low enough impedence to carry the full neutral current, so it, and everything bonded to it can carry hazardous touch potential. Near to the earth stake, you can also have a hazardous step potential.

Isn't the MENS the same TN-CS?

PEN fault protection device

From? Southeastern Serbia, you mean. Serbian code requires TT for residential since many years ago, have you been under a rock?

In Poland for example you have to have a local electrode no matter what type of connection you have on the supplier side. That protects you against all possibilities. The earth electrode should be connected to building foundation metal reinforcement therefore the resistance is very low. Obviously this is a requirement for all the new buildings and there is thousands of private dwellings where there is no local point of earthing.

Exactly as we do in Israe

@ProfessionalAmateur Unfortunately, everything is based on the distribution network and the "star point" of the transformer. (this is a fundamental problem in TN electrical networks). The ground electrode is "only" in reserve)

@ProfessionalAmateur Yes! Unfortunately, our standards are not hard enough in this matter.

That's how it is here in Ireland

That seems on first sight to be a good idea. As J.W also explains in a later video about earthing for E.V. charge points, such a supplemental earth is no where near adequate to ground currents that would otherwise make their way through low impedance paths. A TT. rod (at the cable head) has too high a Ze to handle large fault currents. Additionally the neutral break may take in a number of properties all feeding to the now floating P.E system. The only way out is through that metal case. Others mention 3 phase property. But we should remember that the DNO balances the phases by property via alternate single phase supplies. So you may be lucky and have a V drop rather than a V rise. Do the regs protect us against conductor loss or live earth. Not yet...

@@alistercarmichael4990 you are right, maybe to provide condition/requirement with lowering TT impedance 20 ohm sth, it would be greatly safe and would be safer than TT only system.

could you explain the effects of using PME in TN-C-S systems ? how does it reduce the effects of electric shock in the case of a broken neutral. I read that PME is required in the case of a TN-C-S system

The outer wires being damaged leaving the inner connected is fairly unlikely. It's more likely that failures occur at joints between cables, there are large numbers of joints, every property has at least one outside. There can be multiple types of cables in use, particularly on older networks where repairs and partial replacements have been done over the years/decades.

Ah yes that makes sense. Thanks for the prompt response on such an old video!

Voltage monitoring only detects the broken PEN conductor in some situations, it doesn't work in all of them.

The spike does reduce the risk but does not remove it.It still is high impedance so significant current can go through the person.

If the point at which the PEN became open circuit was further away from the installation, and between this point and the installation there was an earthed electrode, then what would happen in this case? Would the electrode then provide an alternative path back to the source earth? If so, the Line current that that returns from the appliance and back through the installation Neutral, would that then return to earth potential once it reaches the first connection to earth. If this happens, then this would prevent the current returning through the earthed parts of the system?

@@ianrainford8910 "If the point at which the PEN became open circuit was further away from the installation" = The norm said each electrical connection (branching distribution system) must be connected to the equipotential local networks air distirbutie if every 100m must be connected to a local earth connection. ( away ?? ) The next question I dont anderstand but I think you forget a thnik : each earthing of an electric conductor increases the current that is controlled by the MCB so when a short circuit arises, MCB protection will interrupt the affected conductor within max. 5 sec. (in reality, this happens under 0.2 Seconds if the ground outlet was properly designed

The advantage is the cable is significantly cheaper, as it only has 2 conductors. Usually a single centre core for line with the combined neutral/earth as separate wires surrounding it.

An RCD is used to protect against faults that happen after it. It cannot protect against faults that happen before it.

I am from a country where the TN-C-S system is quite common so let me provide some insight on why they might use this system while a better alternative, the TN-S system, is available. My country used to be a part of the Soviet Union, and during the Soviet era residential buildings weren’t as electrified as they are today so they didn’t even bother to provide a proper earthing system. Hell, in some older buildings that didn’t undergo the modernization of electrical systems one can find socket outlets without PE contacts. Now, when people use a lot more electrical equipment at their homes than before, the need in proper earthing arose, and the newer editions of our national electrical codes require to use the TN-S system when possible. They do provide the TN-S system in new buildings but due to poor financing they don’t do so in older buildings as installing a five wire all the way from the buildings to their respective transformer substations is quite costly. Instead, they split the PEN wire in building’s main distribution board into the N and PE wires (the point of split is also earthed to prevent dangerous touch voltages in case of the PEN wire failure) thus providing the TN-C-S system. It is worse than the TN-S system for sure but at least better than the TN-C system.

RCDs weren't as available and inexpensive as they are now and live to a grounded chassis fault on TN is a dead short so normal breakers react.

+Sparky Projects So you're telling me you can have hot water without a water heater? :)

Claro las duchas electricas tienen una resistencia,esta calento la carcasa de la ducha

I didn't know that. Do you have a reference number for it in BS7671?

steve quinsee, you need to supply your should with a TT system. Live and neutral, but don't connect to the MET at the source (house), you install an earth rod at the shed and use this as the earth for the supply in the shed.

A supplementary electrode is permitted and has been for decades. Most other countries have been installing them as a standard item for ever. It's now a recommendation in the UK that all installations have one.

@@jwflame John do you mean earth rod when you say _supplementary electrode._

Or install an Earth Rod so that theres no chance of the water or gas pipes being seperated from earth if plumbers sk work. Just have an Earth rod driven far enough so that if the Neutral is broken then the Earth rod will direct the current flow via Earth.

Bonding other Extraneous Conductive Parts is already a requirement in any case, regardless of TN-C-S or not!.

@unknown 3226 yes thats why all housesin Australia have a earth rod because most houses are supllied via overhead cables. Can easily get a broken Neatral. I see it on a weekly basis while working. Its dangerous the methods used in Australia. Even with a earth rod the current will flow everywhere and all the Earthed appliances will get touch voltage. 1.3mtres is earth rod requirement in oz. But it needs to be driven 3 or 4 metres to get the best result when i test the rod

Yes - but a single rod won't do very much. To have any real effect, the electrode would need a very low impedance, typically under 10 ohms. Only likely to be achieved with a large metallic grid or mesh.

@@jwflame I just installed 1 earthing rod 1,5m long 40cm deep under ground surface and measured it afterwards, it showed up 13,2 ohms. I think If I had chosen a 2m long rod the 10ohm value would be in reach easily. Then I installed another 2 rods and connected all three of them with a metallic sheet 4mm thick by 40mm wide and after I covered the whole system back I got a measurement of 3.1 ohms. The rods were 1.5m long placed 3 meters between them in a straight line in a 60cm deep ditch.

Because than if have an earth fault, from live to earth, the current will go to the neutral (via earth and via itself) and you'll get the full current (that flows in live) and the RCD will NOT trip. For exsample: an applience draws 3 Amps, then you get a shock from it, the current will flow through you (230 mA) and the neutral (2770 mA) and the RCD gets back the full 3 Amps.

Yes, it's always been permitted. In the latest 18th edition amendment 2 it's now recommended that one is installed.

An isolated system would be safer, but only while it remained isolated. Any fault anywhere causing either conductor to be connected to ground would go unnoticed but result in the whole system being ground referenced, making it the same as a normal system but without any proper control over which conductor is neutral or safety devices such as RCDs.

Thanks for your reply. Meanwhile, I've also heard grounding protects you against capacitive coupling. So when it comes for example to high voltage it is possible that objects become charged and when you touch one wire the circuit can be completed through capacitive coupling (if you are standing too close to the other wire, I don't mean through lightning arcs). As far as I know this is one of the (possible) reasons why for example the neon-lamp mains tester lights up even if you're standing on an isolated plastic floor (that can hold up more than 1000 Volts and should not conduct below that value).

As well as preventing a build up of high voltages of static protective multiple earthing of the Netutral on the supply on TN-C-S also helps protect the consumer to some extent from lightning surges especially rural locations on overhead supply susceptible to strikes on the lines

So this would be immediately after the link to earth between the cut-out & domestic meter.

Gordon Watt No, the problem only occurs if the break is before the link, so that both N and E are disconnected from the supply network, but N&E for the installation remain connected together.

@@jwflame If the point at which the PEN became open circuit was further away from the installation, and between this point and the installation there was an earthed electrode, then what would happen in this case? Would the electrode then provide an alternative path back to the source earth? If so, the Line current that that returns from the appliance and back through the installation Neutral, would that then return to earth potential once it reaches the first connection to earth. If this happens, then this would prevent the current returning through the earthed parts of the system?

An earth rod would divert some of the current in the event of a fault, and reduce the voltage on exposed metal parts. However unless the impedance was extremely low, the effect would be insignificant.

Yes it would act as another path to 0v potential so it would keep the whole thing grounded. It would also decrease your Ze reading and help with earth loop impedance as it's a parallel path.

What impedance value would be needed for an Earth electrode so that the installation is ok in any Neutral fault? In Australia we wack the rod in and never test it, sortajust hope for the best.....I know in the UK its tested until suitible results, whats a good result?

If also independent earthing rod present with an impedance below 20 ohm sth, then it greatly improves the safety and save life probably.

​ @Mark H Google AS/NZS 3000 Earth fault loop impedance , NZ and Aus is using TNCS system with Earth rod installed and yes you will need very low Imp for Earth Loop to be working

+peto22 Which country is that? Norway? I know in Norway they have 3-wire Delta 220 Volts transformers in rural area's and at some places where they converted 3-wire Delta 220 Volts to 4-wire Wye 127/220 Volts the neutral is still not used because there are no mayor wiring standards in Europe for 127 Volts. So - In a 3-Wire Delta 220 Volts System everything s connected Phase to Phase because there is no neutral - In a 4-Wire Wye 127/220 Volts System everything in Europe is still connected Phase to Phase because Europe does not have 127 Volt appliances in general and multiple voltages will lead to confusion among users. - In a 4-Wire Wye 230/400 Volts System most appliances are connected Phase to Neutral and only 3-phase appliances and 400 Volt engines are connected Phase to Phase. 127 Volts appliances cannot be used without a transformer.

I live in Finland. We have 3x400/230v Wye. Delta isn't used under 1kv for electricity supply. 20/0,4kv transformers are Delta-Wye and larger ones Delta-Delta.

The same in France, TT-System grounding everywhere although residential houses without farming or other business are single phase 40A. They alternate between phases between the houses. But if you want more you always get triphase starting with 3x20A with increments until 3x80A. If you want more you need a business connection. In the Netherlands old systems are the same (TT-System) however since 99% of the old houses has gas heating and cooking most people only need 1x25A. New houses are usually TN-C-S grounding 1x25A or 3x25A. Almost everywhere 230/400 Volt Wye although some old streets in Amsterdam still had 127/220 Volt Delta which they have problems upgrading because if they forget one house it would cause a fire. That's one of the disadvantages of underground cables. Once you burried them, you cannot easily see what is connected.

+Risto Q Nothing, you should at least supply your own ground. In case a neutral fault happens, everything rises to the same potential limiting electrocution risk. To prevent the Protective Earth from rising even with a broken neutral, you should switch to TT grounding. But this requires an earth rod with a very low impedance (aka more expensive).

It is very rare that there is no electric equipment on. An RCD does not protect against this so forget the RCD in this context. Do not even think of putting an RCD on the PEN wire.

As far as I can see right now there is no benefit to the consumer. The benefit to the power distributor is not having to provide a conductor back to the substation.

TN-C has several problems. The PEN wire is longer so there is more chance for it to break. It causes stray currents that can cause interference on data cables. It is not compatible with RCDs so if RCDs are required you need to use them on the sockets. Also it seems to be dangerous when unqualified and in many places illegal DIYs get their hands on it. In Finland there has been three fatalities since 1980 and some five accidents since 2005 because people have connected the earth to the line and not the neutral. I saw no accident because of spontaneously broken PEN-wires, some were caused by illegal DIYs and there was a fatality involving electricians outside.

Such devices are mentioned in the new 18th edition regulations, specifically for electric vehicle charging. They do not appear to exist yet.

You can install one, but it won't do very much unless it has a very low impedance of only a few ohms, which in reality is very difficult to achieve.

So i install an Earth rod in Australia on a TNCS supply for no real safety reason???

@@jwflame Hi John, first let me thank you for your very good programmes, I have found them very informative. I now live in rural Thailand and severed neutral overhead cables are very common, I know of at least 3 in our local area. The last was about 2 weeks ago, late afternoon our appliances stopped working and the lights started flickering, the voltage fluctuated between about 120/180. I walked into the main part of the village and every thing was normal street lights and our in-laws supply all good in fact the only street light not working was directly outside our house, my wife did not want to phone the electric utility because she thought the problem was in our house. Our house is at the end of a branch line, so at first light I walked the line and found the break at our next door neighbours extremely overgrown tree/man eating bush. My wife phoned the utility and they responded very quickly. This will happen again because of the many overgrown trees between our house and the nearest transformer.

@@jwflame Part 2 of an extremely long winded post. Our property has NO protective earth or ground rod and despite the Thai electrical regs closely following that of Australia with regards to the MEN link most other properties in the village are similar with just two prong plugs and sockets. The village is wired for MEN with neutral to earth links about every 4th pole. I am going to install a solar system, so wanting to do it correctly and not trusting local Thai electricians, I have been researching the subject. My conclusion was to first rewire the house to Thai regs with regards to the MEN link/earth rod and earth wiring. The regs call for a 2.4M ground rod to be installed no testing required (the cost of my own meggar test equipment rules out me testing the ground rod myself). I now have a quandary do I go the MEN link way and potentially turn a single earth fault into a whole house earth fault or ? Any suggestions would be greatly appreciated.

copelandaa It probably would, as it would trip with a voltage difference between the installation earth and an electrode / rod in the ground.

@@jwflame So best have an ELCB and RCD fitted in series? To be sure?

@@johnburns4017 I am not an electrician, but I think it would be not in series. An RCD would be just like that, but you would put a current or voltage sensing ELCB to sense the current from PEN-N to PE just at the place of split, before the PE is put into main PE block (with any auxilary earthing), and trip the main circuit breaker (disconnecting both L and N). So if there is any reasonable current going via L->N->PE will trip the main supply. The advantage would also be that if the resistance to ground is high, it will still trip. It might also be possible to fit an additional ELCB from the main PE block to the earth, to also trip the main circuit breaker, to measure the current to ground directly. The problem is that in many buildings there might be other earthing devices, and might not be enough. But probably doesn't hurt. It can probably be done even in TN-S system.

mazmaz1981 no because the fault exists BEFORE the RCD. The RCD will only measure in front of itself and not behind (I.e between RCD and load) so even though the PEN Neutral is broken, the RCD wouldn't see it. Think of it like someone standing behind you, you can't see them unless you turned around, same here. I think if there was an RCD at the substation then that would trip as it would read the imbalance (read 0 volts returned on neutral) - Pretty sure I've understood that right

TNS is a good system, but it requires a separate earth conductor all the way back to the transformer - if it's combined with the neutral at any point after the transformer it's not TNS. An earth rod can be used with TNCS to reduce the dangerous voltage if a break occurs, but to have any effect it must have a very low resistance, 5 ohms or less typically, which usually means very large buried metal grids or using the reinforcement in the concrete foundations of a building. A single rod won't do very much.

+johnsilentster Yes you should never connect one device to a seperate earth while the rest of the installation is TN-C-S. You have two options: - convert you whole installation to TT by installing your own ground rod and RCD's on every circuit - convert your shack to TT by installing a seperate fusebox with its own ground rod and RCD's on every circuit Even when you do it yourself always show your plan to a qualified and certified electrian up front and let it check your work and certifiy your installation! Some electricians might not want to certify TT systems.

Oh I just saw that you explain this at 5:55...:)

metersocket00 Not generally - only for those locations where there is no earth connection provided by the supplier (TT) which is a minority of installations. TN-C-S and TN-S installations rarely have an earth rod. They are not required or specified for such installations, although regulations do not prohibit installing one. Metallic service pipes entering the building such as for gas or water are connected to the main earth for the installation, and these are typically buried underground. However on newer buildings or those which have upgraded water/gas connections, the pipes underground are normally plastic.

Stupidly we don't link our incoming neutral to ground via a rod...

In TN-S systems we use the sheathing of the distributors incoming SWA, which to me looks like it goes underground.