I’m an 18th edition apprentice and 3 lecturers have tried explaining this to me. Thanks for the clearest explanation I’ve had. Finally this makes sense. Thank you John Ward.
I only have experience where I can say for certain. 1. Only phase and neutral conductors are supplied. 2. No earth rods are installed at the transformers. 3. No earth rods or bonding to re-bar in the concrete is carried out. 4. Therefor this is a substandard TT system. 5. Sometimes earth and neutral are joined together making things worse. Go watch my Facebook video Samui English Electrician
What a legend. I'm doing my level2 electrical installation and types of earthing arrangements is part of the installation methods unit. the diagrams used by the college were usless so thanks for this...
Hi John, your videos are fantastic. I am currently doing a 2 1/2 week course in domestic installations - my instructor no doubt knows his stuff but dear god he does not know how to teach or communicate. I have highlighted the most important things for me to learn this weekend and you have addressed two of them in the last half an hour. Thanks!! :) *subscribed*
In Germany you could find TN-C (older buildings) or TN-C-S (modern buildings) are the most common systems. But sometimes you could find TT, which depends on your supplier. The buildings with TN are fitted with an additional earthing rod for the cable failure you described at 10:48 min. Formerly they used the incoming water pipe, but now the most water pipes are made of plastic and the earthing rod is placed in the ground plate of the house (newer ones) or got a separate rod. And the most building connections are three-phase-current. The three lives L1, L2 and L3 all have 230V measured against N (or PE), but 400V against each other, so you've got two voltages in your system.
Fascinating overview of how the UK system approaches electrical safety. I am in the US and I can now see the advantages to our system of having a center tapped neutral on the distribution transformer secondary. The earth (grounding) conductor is connected to the neutral at the entrance to the structure and there is an earthing rod driven at the structure.
What can I say John, except you have an excellent way of passing on the concepts in a simple and concise way. Call me a sado but I so much look forward to your articles.....
Here in Norway the customer must provide an earth rod regardless of what system is being used. Even TN-C-S-systems must be connected to earth where the PEN is split to N and earth. So whatever happens to the earthing from the power company, there will be a local, good earth point.
Robert Szasz No, only the electricity supplier is permitted to do such things. Therefore you are stuck with whatever earthing system they provide, or ignore theirs and use an earth rod / TT system.
+sjokomelk Same in Finland, I think we are almost 100% TN-CS. If you have IT-system, wont that mean that an Edison-screw light socket has its threads live too? Or do you use bayonette mounts?
In Australia we have a MEN (multiple earthed neutral) system where the star point of the transformer is earthed and each house is supplied with active(s) and a neutral. At the main switchboard an earth stake is connected to the main earth terminal and a link is main to the neutral terminal. This means that any A-E faults will flow through the houses earth wires then go back on the neutral. If there is a fault with the neutral as well and it is broken then the current will flow through the earth stake to the transformer, providing the best of bot options 1 and 3 from the video.
That's the TN-C-S system. In Germany is this the most common system too. But only in houses build or modernized after 1973. Before this date TN-C was the common system, with no separate wire for N and PE. You've got only one wire for this, the PEN.
Now the PEN is in Germany allowed only if it is minimum 10mm² copper or 16mm² aluminum. But only for new installations, the old ones made before 1973 succumb to the right of continuance. But only if they are not unsafe, making massive changes (extensions for example) and if they no longer conform with the regulations that were valid during the time of installation. A change of a wall socket, lamp or a switch does not affect the right of continuance.
TN-C-S is also the standard for system grounding in the US and Canada and has been for quite some years, except it is common for the main distribution board to have its own ground rod connected to the ground bussbar. The only other difference is that the supply transformer has a 240V center tapped secondary which is grounded and the end taps providing the 2 120V hots.
I knew JW was the place to come for this information. Looks to me that in the 'absence' of an earth, the neutral simply needs to be connected to the earthing cable inside the house at the board.
Thank you so much I'm doing my 2391 and I'm dyslexic so need as much help as possible and your teaching is amazing for me very clear and to the point thanks again 👍
these videos are so helpful. I've nearly completed my City & Guilds Level 3 Electrical Installation Diploma and this content is really helping with my wider understanding and prep for exams. I like your style of explanation, thank you.
In Denmark the TT system is exclusively used. RCD are required on all installations which supply up to 20A, including old ones that was made before the invention of the RCD. It is the consumers responsibility to make sure a device has ground a connection, and it is only mandatory make the ground connection on domestic appliances.
A Malaysia we follow UK specs most of the time (down to voltage and socket type), though most households here use TT earthing. TN systems are virtually unheard of.
Great explanation!! In the USA we have 2 hot wires 120/240 and 1 ground/neutral the grounds and neutrals are bonded inside the main panel. The nec requires 2 ground rods for each electrical panel inside the house.
It's 2 rods if you have more than 25 ohms only with 1 rod. Wrong on each panel board. I for the main, none for others as they are sub's using se-r. Unless it's an outbuilding. Still uses the se-r, but also requires the rod.
Just wanted to say a huge thanx to you. Very concise and descriptive and made what seems to be (sometimes) difficult to understand, understandable. Great speech and great use of visual aids. Thanx again😁👍
We have been "PME'd" here but my neighbour (same phase) is TT. My neighbour's system tripped (the voltage type you mentioned)but her fault also tripped an RCD in our property. Looking at you diagram, i think i can see how this has happened. Thanks you for such a clear explanation.
Great video! Here in Denmark we pretty much only use the TT system. I'm not sure why... but i guess it's because the electric company like the idea that they won't have to be responsable of the PE connection.
Here in Italy we also use TT for houseolds, only industrial use TN, I thik that's because earthing, in that case, is on the customer so if earth conductor fails, the power company has no responsability.
How on earth (no pun intended) can you get proper Earth conduction in Italy with a TT system, especially when for example you live in a rocky terrain? You guys have to drill 30M deep rods or something? :P
Very good. Here in Australia we use the TN-CS system but the main earthing point is connected to an earthing electrode via the main earthing conductor and to the main neutral bar on the consumer side via a link which must be the same CSA as the incoming neutral. We call this the MEN link, and the system the MEN system (Multiple Earthed Neutral) as the neutral is earthed via the MEN link and in various points back to the TX star point. The consumer main neutral therefore functions as a PEN conductor. As JW mentioned, we do occasionally get instances of open or high impedance consumer main neutrals and shocks have occurred. RCDs clearly won't open as there's no current imbalance between A and N on the consumer side. There are also hazards if consumer mains are connected with incorrect polarity but RCDs (if installed!) will open if current flows to earth in these cases. Things are easier when you have only the one system! :o)
MEN is the standard here in Australia. It's a TN-CS system, with a separated neutral/earth bar arrangement, and a earth rod in the ground. We have to find resistance as low as we can get - typically 1-10 ohms. Some sites (Centre of the country - sandy country) can see earthing rods 10-15M in depth. We equipotentially bond everything to stop balance issues.
In Australia, the Multiple Earthed Neutral (MEN) earthing system is used and is described in Section 5 of AS 3000. For an LV customer, it is a TN-C system from the transformer in the street to the premises, (the neutral is earthed multiple times along this segment), and a TN-S system inside the installation, from the Main Switchboard downwards. Looked at as a whole, it is a TN-C-S system. So, normally there will be a link in between the neutral and earth bus bars behind the switchboard, as well as at the local transformer.
I've seen a few You Tube informative videos but this beats those hands down in presentation skills, clarity, knowledge and video quality. You should branch out into "How to make a You Tube video"!
As an ex cable jointer I actually have had a shock from the N/E conductor of a 1ph concentric service cable! The shift electrician had attended a property and said there was no incoming supply. Labour team had been told to open an excavation over the service so I could cut and test. As soon as I removed the PVC sheath, I got a rattle. The cable had been damaged nearer the service joint and strands cut, water got in and the cable blew open circuit to the joint and phase to N/E towards the house! We weren’t issued with the much hated neon testers in those days. 😊
There is a label on the cutout here that says "This installation is connected to a PME system" - so that confirms mine. A house we lived in before had a plate on the cutout saying "PME system" too. However, we also lived in one house where the supply came in from the poles, and that was TT. Our ELCB was a Chilton voltage-operated one.
Re supplying outside marquees etc from a TNC-S system - the danger would only arise if that supply came from BEFORE the "C-S2 split. Provided the supply to the marquee etc. is from AFTER the C-S split all would be fine- just like stuff in your house.
Thanks for another very informative video. Could I ask a question on TT earthing systems. Is it allowed in the UK to connect the earth rod to the neutral at the customer end, and what would be the result or problem if this is done on a TT supply. I believe that doing this would only help by tieng the two together and thus reduce any problem of poor earth rod resistance.
SSE are now installing more and more TN-S systems on new connections work. TN-S is now always used when connecting up metal clad buildings or connecting to the old PILC cables. Funny how everything seams to go full circle. As a cable jointer I personally think that TN-S is a better system. Really good vid by the way.
Here in Germany we use TN-Net, TT-Net and IT-Net. The TN is splittet into TN-S, TN-C and TN-S-C. We use normal 3 L Phase, some old houses have only one L Phase. The power cable come in house direct into a big fuse for every phase - at this point the 'Saved Earth' and 'Neutral' go to two difference lines. This place is the exchange point between the power company and my home power net. After this I must install the Watt-Meter from my power company. After this we can install every RCD how we want use ... Most older installation haven't one. For Thailand I not know the situation, we use there an own transformator ...
There is another type of Earthing that you could of included. It is called PNB. Normally used for one domestic supply only to a single phase 11kv - 230 transformer where the earth for the transformer is via the neutral block on a 100 amp cut out connected by a 32mm covered copper wire to earth electrode/pin in the ground. Although historic, lots still exist and are in use in Dorset/Wiltshire/Hampshire and Somerset.
Thanks John , This is exciting ,I am starting to understand , may be its the white board but youve just broke a barrier . Before i know it I'll be wiring a plug !! Seriously, the other experts who try to explain should come down to our level and see what its like , its no fun down here ,but you obviously know a few thickos and kow whats required
What I'm struggling with at the moment is on TNCS how come the Neutral voltage isn't going straight to Earth at the property? With the E and N joined at the property surely the return would go straight to earth rather than back to the Transformer. It would be like you're sticking the N into the ground. Or have I missed the point?
If you like this topic , watch a video entitled "EW rice interviews Elihu Thomson " he's the engineer that came up with earthing " and maybe some others around the same time . Go to around 10.27 in the video and he states it was his invention for safety . I like the term you English use "Earthing " ,better than what we in the States use " Grounding " great video ps Mike Holt has good videos on this topic.
great video, very clearly and well explained. However 2 points. Most of Northern Ireland (rural areas) are still in TT. My house built in 2006 was done in TT. Also when you say neutral is the same potential as earth. Must be remembered that in an AC system half the voltage is carried in the neutral and the lifter you get when you accidentally touch between neutral and earth is worse than live to neutral (or at least always feels much worse!) Overall, well done.
We use TN-CS in the US but we additionally attach a bare wire from a ground rod at the electric meter to the earth terminal in the fuse box. We also run a bare copper from the rod to the nearest hose bibb, I think for discharging lightning. The plumbing would provide a path thru to the utility's piping system which used to be metal. It's probably changed since plastic supply pipes were introduced. Wait, many pipes from the 60's were asbestos-cement which i wouldn't think was conductive so I'm not sure of the system. They may have terminated with a ground rod at the water meter in that case.
Had a case where a screw shorted light switch switched line to earth. No RCD. Only symptom was the combi boiler kept tripping out on flame failure. Only when the Utility room light was on (not obvious at the time...) On inspection the live was 140v above ground at the boiler- flame failure detector required more! The earth spike was underneath patio paving, and may have been quite dry... On bright days there was no fault to find!
Here in the land of convicts and sea front properties the neutral wire often corrodes off in the outside connection box, we almost exclusively use M.E.N same as your TT supply but each customer has a removable link between the neutral and earth in the consumer unit for testing, this provides a limited path to the transformer when the incomming neutral fails.
Every house i wired, always drove earth rods. 3 core going out to the cutout, and youd be connected into the earth block, which is basically the neutral block there. Theres an inspection box for the earth rod, which is normally placed under the meter cabinet externally.
At 10:46 in that instance, where you show the break, the appliance would cease to operate as there is no return path (neither N nor E). The more dangerous situation is where the Neutral circuit is broken downstream (towards the transformer) of the closest earth rod, in which case appliances will continue to operate using the E path as return, thereby putting metal appliance and metal pipe surfaces at, or near, line potential.
JW, could you expand further as to the earthing of a portable generator please? I use a 1kw Honda invertor generator on board our boat, generally for battery charging only. It represents a particular problem as afloat there is no possibility of an earth connection. The boat has a 240v shore power circuit on board which is generally connected to the mains supply in the marina when in the home berth. But when away cruising I plug the generator in to the shorepower inlet socket. Other boat users have suggested that the generator to boat shorepower connection cable should connect neutral to earth, infntbkniw what the thinking is behind this suggestion. Your videos are very useful indeed - keep them coming. Many thanks, Rob
In the U.S. we drive a ground rod and attach it to the neutral point of the transformer, but it looks like you guys attach the ground rod to one of the ends of the transformer. We also have corner grounded Delta systems here too. Soooo I guess you can ground a transformer anywhere in the coil you want to and it will still have the same benefit for lightning, static, etc.? 😵💫
One point you didn't mention. If you are far enough away from the transformer, the voltage drop on the lines can be significant. Where I used to live voltage available sometimes dropped below 200v. That meant the Neutral was no longer zero, and could be anything up to 20 volts above earth. Even in my last house there was enough voltage on the Neutral to trip the RCD.
Quite a few years on! Well presented, but it would be useful to observe that it's usual to require cross bonding between Earth and copper piping within houses - e.g in my place (which has TN-C-S) the water and gas pipes are cross bonded, with the underground pipes being plastic, so that all the exposed copper etc is connected to Earth. Plumbing alterations should take account of this, if there are any electrical disconnections in the installation.
That is an important subject, and John deals with it in a separate video on bonding. However, bonding is not earthing; bonding is to avoid a voltage potential between metallic parts in a building. It's related of course in that it will be bonded to earth in effect, but there is also equipotential bonding.
Very well explained, one query, for PME System you said that if the neutral (neutral and earth) breaks, it will be dangerous situation because no earth is available. My question is, if a neutral breaks, there will be no supply left because to complete a simple circuit we will need to have a connection of both Live and Neutral. so there will be no current flowing through and have no danger as there would be no supply. can anyone please explain?
The electrical supply is explained wonderfully. My thought is: if we do without grounding, the power supply will be similar to safety Tafo. Wouldn't that be much safer? Unless someone touches the L and N lines directly. Grounding causes more problems is my opinion.🤔
It's safer but only until some fault to Earth occurs somewhere - it's then an uncontrolled earth referenced system. Isolated supplies have their uses, but only in strictly controlled and monitored environments.
Great Video John, thanks a lot!, may I ask please - For TNS system, since both Earth and Neutral cables are connected to each other in the transformer side, why does i cannot measure continuity between both cables in my Electrical panel Distribution Board?! This kinda freak me out kindly help! thanks
drich modina There should be continuity between N &E - if not, either the earth is defective, or you are measuring in the wrong place, such as after the main switch when it is off.
***** i measured it in our 63A 3 phase with 1 phase branch distrubution board. I also thought that if i measure continuity between earth and neutral there. Most likely the RCD will trips. Please please teach me where to measure it properly and why does the RCD dont trip if the two cables have continuity. Thanks a lot in advance!
Suppose I have a three-phase motor fed from a panel that has 3 phases and one grounded neutral. I then decide to ground the mass of the equipment through an earth rod (TT) in instead of using the grounded neutral from the panel. What would the drawbacks be if I decided to interconnect this earth road with the neutral from the panel (that comes from a grounded wye LV side three-phase transformer)?
It sounds like you're describing a grounding conductor off the equipment shell bonded to the neutral coming in from the utility. This is fine. If you're talking about having two separate ground references on the same equipment, this is not fine.
In France, TT is the default system for everything; in new construction they typically use a earthing "ring" with wires buried all around the concrete foundation instead of rods; RCDs are mandatory. Here in Canada IT is used in Healthcare facilities; these systems are subject to very strict rules.
Might sound daft but why do TN-S cables have a higher resistance than a TN-C-S. Surely the resistance should be very similar or do they use lower quality cable for the earth or is it just longer run?
+Scott Clewlow TN-S is usually supplied on PILC cable, which has 2 copper conductors for line & neutral, the earth is the outer lead covering with a steel tape over it, so resistance is higher. TN-C-S typically supplied on concentric, which is all copper for the line and combined neutral & earth.
Hi john I'm currently doing C&G 2365 and have been asked to give drawn examples of Tns, tncs, tt and IT supply and earthing systems. I have no problem with the former three but the IT system is proving problematic to gather info on. Do you know when or where people get trained in this type of install? My 2365 textbook states. IT and TNC systems are not included in this course so there is no information included on these type of installations. Thanks. Phil.
+phil Harvey IT is where the supply is isolated from earth, such as an isolating transformer. Neither side of the supply is connected to earth, or it is connected to earth through a high impedance. It is typically used for medical installations such as operating theatres. TNC is a system where the neutral and protective conductor (earth) are combined into a single conductor within the installation, so only 2 wires to each item. It is specifically prohibited other than in a few very specific instances, so in reality is never used in the UK. The supply is the same as TNC-S, except that there is no split to separate earth and neutral where the supply enters the building, it continues for the whole installation with the combined neutral and protective conductor. There is some information on both in BS7671.
Hi, on a tt system what is to stop someone simply linking their main earth to the neutral instead of installing a rod and putting up with high earth loop impedance? Just curious Thanks
Actually the old TNS cables have their lead sheath covered by a steel spiral wrap which is then covered with a fabric insulation which is coated with a tar like substance, I know as I've got one of those old cables supplying my old house, so therefore the lead sheath is not actually in direct contact with the ground so it has to rely on it's lead sheath for earth continuity. And there's loads of those old cables still in use where I live and further afield in the surrounding area. And I've also seen a modern concentric cable with separate neutral and earth conductors, the earth is formed by usually seven bare copper strands fitted around one half of the live phase insulation with again seven separately insulated copper strands fitted around the other half of the phase insulation to form the neutral with of course an overall insulating sheath on the outside. So some TNS installations with more modern cables do exist, probably where an existing service cable has failed and has had to be replaced, like the one next door to me. Old dead water supply pipes are in direct ground contact and have to be earthed at the consumer's property so they can effectively form a local earth electrode if connected, and of course the same applies to some older gas supply pipes too, like mine which is iron and that is also connected to my incoming earth conductor.
It occurs to me that, whenever I watch a video on TN-CS system, there is a need for an earth rod supplement within the property wiring to avoid the PEN fault you describe! Is there a reason WHY such a supplementary earth rod arrangement(TT) should NOT be installed on a TN-CS system? I would logically assume that the TN-CS would be considerably lower in impedance to the TT supplement but the TT would protect to some degree rather than none, in the case of a PEN fault you describe?
Hell Mr. John, if you please could you or someone else answer me in two queries? What was the benefit (at TN-S system) of the old cables with lead shield to come directly in contact with the earth? Maybe in the case where the cable were being cut accidently the property will still had earth connection (the earth itself will connect the two pieces of the broken cable)? Also, at TN-CS system what is the reason of multiple connections (at 10:48 min) between Neutral and Ground; maybe if the cable were being cut at some point the houses that are connected after the cutting point will still have Earth Ground connection and from now on because the only return path for the current to return will be the Ground earth the result will be a breaker or fuse or RCD to triggered immediately. So in practical this a way of detection a cut cable and to avoid a house to stay without Ground Earth (PE); because of the triggering of the breakers the properties don't have electricity and consequently the electric company must necessarily to repair the break cable? Am I right in my hypothesis or I misunderstood/missing something?
A very interesting video, in my hobby (amateur radio) we tend to have grounding arrangements that attach to the shield of coaxial cable at the base of the aerial. This cable then generally connects to the equipment chassis within the house which is also connected via the standard mains lead to the standard domestic mains earth. In my set up the "ground mat" under the lawn is also bonded to the water piping of the house. It is a slight concern that in the event of a live-earth short in any part of the house a proportion of the fault current will flow through the equipment chassis to the " other ground". For various lightning protection reasons it can be very bad news to isolate the two grounding systems.. ie to provide a seperate safety earth only for the radio gear. This situation must be very widespread, presumably the answer is to make the bonding path as low resistance as feasible to minimise the current flow through the other path? We have an RCCB so presumably my question is more of a hypothetical one? Thanks for the video, most educational!
In the event of a broken neutral for a TN-CS earthing system , and there is a line fault fault , will the system not automatically turns into a TT-system ?
Hi JW very interesting I’m on the PME system For a couple of years now I’ve had the odd LED in the kitchen flicker .... but a couple of days before Christmas Day the lamp in the living room was flickering badly it’s connected along with my mother’s riser chair through a UPS and it was making funny noises so plugged the chair and lamp back into the wall socket and changed the lamp... Then on Christmas Day (2018) dinner out of the way we were watching tv when the RCD tripped switch it back on everything was fine for about 30 mins and it done it again this happed a few times through the night...( I had called my sparky and was coming out Boxing Day to have a look ) about 8am my UPS for my hard drives etc started going between battery and mains and very loud humming noises of the transformer inside the UPS Anyway sparky came out tested everything and put it down to a faulty RCD put another one in (not new) everything tested ok .... tried the old one in a test circuit and it tripped ! But as I was switching thing back on in the house came back out to speak to the electrician when I noticed a neighbour had an electrician in as well I told mines and he called him they were having the same problem as well so we called Scottish utilities they came out and was a fault underground .... I have since had the RCD that was put in go faulty again it wasn’t new plus was in when having problems ..... so new one installed so far so good But next week having a new unit installed with the new robc and a power surge on the supply into the house .... Great channel 👍
Could you please explain the difference between TN-C and TN-C-S? I already understand the latter, since the US uses it with a slight variation: the neutral is grounded not only at the transformer (a single-point-earthed-neutral TN-C-S system, but also at the house of each customer (a multi-point-earthed-neutral TN-C-S system). But I don’t see the difference between the two types of earthing systems. Both ground the neutral at the transformer. Both connect the neutral wire to normally-noncurrent-carrying conductive (metallic) parts at each customer, meaning the neutral and ground wires are combined before the customer but separated when entering each customer house.
TN-C has the ground and neutral combined within the house, so there is no separate ground wire. Ground connections for each outlet are just a small link between the neutral and ground connections. Rarely used anywhere and not permitted in the UK and plenty of other countries.
In bulgaria we use shuko plugs and we rearly have separate earthing wire.In the wall socket we just put a bridge(copper wire) between earth and neutral and it works nearly all the time.
I have TN C-S properly installed is it allowed to earth the body of the motor or the control panel earthing point as add protection I can pond it to a sticking out construction steel that I conected to the building foundation which happened to be near them
For a commercial building, where the transformer is a private property, will the earth cable from the transformer be connected to the main earthing terminal inside the main distribution board for a tns system? please clarify. Here in pakistan the mdbs are generally earthed by two earth rods...
Muhammad Farooq Fun fact : In Italy, Spain, Greece, Serbia, Croatia, Albania, Bulgaria and Romania, if you want to make a contract with the pieces of shit known as enel, you would need to buy yourself a transformer and then give it to them for free (as part of the contract you make with them). And most of the time they will be the only option... because they are a regional monopoly... 100% unregulated free market and capitalism go so well together !
Doesn't supplementary bonding of water & gas pipes to earth, lessen the chance of any shock occurring even if a PME supply cable or earthing rod was damaged. I know most modern houses use PVC supply pipes which would negate this benefit. But on older homes does this help?
How do power company face the issue of earthing the transformer to avoid a fault on high voltage to be 'distributed' trough the PEN to all the customers attached? TNC could have been ok 50 years ago when RCD weren't available and MCB/fuses were only protections available for ground-fault. But today with RCD I think is better to have PE as far as possible from the high-voltage 'center grounding' of the transformer. l'd just prefer to avoid the risk of getting few kV on my desk lamps casing.
Yes, N&E are connected at the point they enter the building. You should also get continuity on TN-S, as although the wires are separate, they are still joined at the transformer.
There is a minor error here. Most lead supply cables are covered in bitumen. The lead sheath is only visible where the termination has been made at the cutout. So the lead sheath rarely functions as an electrode. Also, in very old services the lead sheath can crack due to loading stress on the ground above, so a periodic loop impedence test is especially important on TN-S supplied installations.
Hi, i have a 1900s house with a lead cable , 3 cutouts (only one in use) and a green earth cable running to a small side box( i think the whole assembly is tar filled)..my house is wired in pvc coated twin and earth...mostly grey, some white...everything works fine. my question is...there is a green earthing wire in the kitchen not attached to anything and one in the bathroom also...should i clamp them to a cold water pipe or just remove them, many thanks colin...
we have a Wooden Electricity pole outside our house and down the side of the wooden pole runs a thick black wire (the black seems to be just plastic insulation and where the insulation has brocked away you can see the Thick wire which is silver and not copper coloured), and its tapped to what looks like the Neutral wire on the pole and then the wire just goes either into the ground oif the property, or goes to the meter box on side of wall of property. - This is all put on the electricity supply board not on the consumer side of things. So does this mean the house/premises still has to have one or more earth rods even with this earth wire tapped to neutral line from the wooden pole? - or have the electrical supply board supplied to required earth protection to the house? - the house/property is in the republic of Ireland by the way, just in case the electrical supply is distributed differently to the UK.
I’m an 18th edition apprentice and 3 lecturers have tried explaining this to me. Thanks for the clearest explanation I’ve had. Finally this makes sense. Thank you John Ward.
just wanted to say thank you for providing one of the most concise and clear explanations of earthing structures
Cìâ
nhta çcucu derasunaaq
On cum ma fut
I only have experience where I can say for certain.
1. Only phase and neutral conductors are supplied.
2. No earth rods are installed at the transformers.
3. No earth rods or bonding to re-bar in the concrete is carried out.
4. Therefor this is a substandard TT system.
5. Sometimes earth and neutral are joined together making things worse.
Go watch my Facebook video Samui English Electrician
As they say...a drunk could understand that John...couldn’t be clearer...excellent. Thanks.
What a legend.
I'm doing my level2 electrical installation and types of earthing arrangements is part of the installation methods unit. the diagrams used by the college were usless so thanks for this...
Hi John, your videos are fantastic. I am currently doing a 2 1/2 week course in domestic installations - my instructor no doubt knows his stuff but dear god he does not know how to teach or communicate.
I have highlighted the most important things for me to learn this weekend and you have addressed two of them in the last half an hour.
Thanks!! :)
*subscribed*
In Germany you could find TN-C (older buildings) or TN-C-S (modern buildings) are the most common systems. But sometimes you could find TT, which depends on your supplier. The buildings with TN are fitted with an additional earthing rod for the cable failure you described at 10:48 min. Formerly they used the incoming water pipe, but now the most water pipes are made of plastic and the earthing rod is placed in the ground plate of the house (newer ones) or got a separate rod. And the most building connections are three-phase-current. The three lives L1, L2 and L3 all have 230V measured against N (or PE), but 400V against each other, so you've got two voltages in your system.
In Finland TN-C was also common earlier but after 1989 it was allowed only with a 10 square mm PEN-wire.
@@okaro6595 Same thing here, PEN only permitted if it's at least 10mm² copper or 16mm² aluminium.
Fascinating overview of how the UK system approaches electrical safety. I am in the US and I can now see the advantages to our system of having a center tapped neutral on the distribution transformer secondary. The earth (grounding) conductor is connected to the neutral at the entrance to the structure and there is an earthing rod driven at the structure.
Thanks for explaining the types of Earthing systems , Everyday is a electrical learning day!
What can I say John, except you have an excellent way of passing on the concepts in a simple and concise way. Call me a sado but I so much look forward to your articles.....
Your videos are so thorough and articulate the subject very well.
Here in Norway the customer must provide an earth rod regardless of what system is being used. Even TN-C-S-systems must be connected to earth where the PEN is split to N and earth. So whatever happens to the earthing from the power company, there will be a local, good earth point.
sjokomelk That is also permitted in the UK - however it is not required, so is almost never done in reality.
***** in a T-T system can you bond the earth and neutral at the premises demarcation?
Robert Szasz No, only the electricity supplier is permitted to do such things. Therefore you are stuck with whatever earthing system they provide, or ignore theirs and use an earth rod / TT system.
***** Although sometimes you can call the DNO out for them to convert a TT system into a TN-C-S one, albeit at a cost.
+sjokomelk
Same in Finland, I think we are almost 100% TN-CS.
If you have IT-system, wont that mean that an Edison-screw light socket has its threads live too? Or do you use bayonette mounts?
Currently studying 17th edition and the earthing had me baffled but your video has cleared that up, great vid thanks
did you make it?
This is a fantastically straightforward and clear explanation of earthing. Thanks a lot, JW
In Australia we have a MEN (multiple earthed neutral) system where the star point of the transformer is earthed and each house is supplied with active(s) and a neutral. At the main switchboard an earth stake is connected to the main earth terminal and a link is main to the neutral terminal. This means that any A-E faults will flow through the houses earth wires then go back on the neutral. If there is a fault with the neutral as well and it is broken then the current will flow through the earth stake to the transformer, providing the best of bot options 1 and 3 from the video.
The best system
That's the TN-C-S system. In Germany is this the most common system too. But only in houses build or modernized after 1973. Before this date TN-C was the common system, with no separate wire for N and PE. You've got only one wire for this, the PEN.
There are some pen systems in Australia but it's not very common and only in particular circumstances
Now the PEN is in Germany allowed only if it is minimum 10mm² copper or 16mm² aluminum. But only for new installations, the old ones made before 1973 succumb to the right of continuance. But only if they are not unsafe, making massive changes (extensions for example) and if they no longer conform with the regulations that were valid during the time of installation. A change of a wall socket, lamp or a switch does not affect the right of continuance.
TN-C-S is also the standard for system grounding in the US and Canada and has been for quite some years, except it is common for the main distribution board to have its own ground rod connected to the ground bussbar. The only other difference is that the supply transformer has a 240V center tapped secondary which is grounded and the end taps providing the 2 120V hots.
I think termed as single phase 2 hot wires?
@@johnburns4017 It's more commonly called split phase.
Thank you Mr. Ward even though i reside in the states your vlogs help me immensely.
I knew JW was the place to come for this information. Looks to me that in the 'absence' of an earth, the neutral simply needs to be connected to the earthing cable inside the house at the board.
Thank you so much I'm doing my 2391 and I'm dyslexic so need as much help as possible and your teaching is amazing for me very clear and to the point thanks again 👍
when he said hello I'm JW.. you most certainly are John Wick with this... You my friend deserves a seat at the High Table. 👏👏👏👏
these videos are so helpful. I've nearly completed my City & Guilds Level 3 Electrical Installation Diploma and this content is really helping with my wider understanding and prep for exams. I like your style of explanation, thank you.
In Denmark the TT system is exclusively used. RCD are required on all installations which supply up to 20A, including old ones that was made before the invention of the RCD. It is the consumers responsibility to make sure a device has ground a connection, and it is only mandatory make the ground connection on domestic appliances.
I live in the UK. Our earthing system is TT. Our house was built in the late 1960s.
A Malaysia we follow UK specs most of the time (down to voltage and socket type), though most households here use TT earthing. TN systems are virtually unheard of.
Great explanation!! In the USA we have 2 hot wires 120/240 and 1 ground/neutral the grounds and neutrals are bonded inside the main panel. The nec requires 2 ground rods for each electrical panel inside the house.
It's 2 rods if you have more than 25 ohms only with 1 rod. Wrong on each panel board. I for the main, none for others as they are sub's using se-r. Unless it's an outbuilding. Still uses the se-r, but also requires the rod.
In main land Europe it is more common with 3 phases + neutral configured in a star system. 400V between phases and 230 between phase and neutral.
Just wanted to say a huge thanx to you. Very concise and descriptive and made what seems to be (sometimes) difficult to understand, understandable.
Great speech and great use of visual aids.
Thanx again😁👍
A clear presentation style going straight to the key points- a very refreshing change from some of the other vids I have seen! A thumbs up from me!
I commend you on the simple and clear demonstration of the variable systems. Well done.
Excellent video, for the first time really understand the three different earthing systems. Please keep up the good work!
We have been "PME'd" here but my neighbour (same phase) is TT. My neighbour's system tripped (the voltage type you mentioned)but her fault also tripped an RCD in our property. Looking at you diagram, i think i can see how this has happened. Thanks you for such a clear explanation.
Clearest presentation I’ve seen on this topic.
I love it. It's like Hugh laurie swallowed the 17th edition. You rock
now it's doctor Ward ;)
Probably the best explanation I have seen. Thank you.
Great video! Here in Denmark we pretty much only use the TT system. I'm not sure why... but i guess it's because the electric company like the idea that they won't have to be responsable of the PE connection.
Here in Italy we also use TT for houseolds, only industrial use TN, I thik that's because earthing, in that case, is on the customer so if earth conductor fails, the power company has no responsability.
How on earth (no pun intended) can you get proper Earth conduction in Italy with a TT system, especially when for example you live in a rocky terrain? You guys have to drill 30M deep rods or something? :P
Very good. Here in Australia we use the TN-CS system but the main earthing point is connected to an earthing electrode via the main earthing conductor and to the main neutral bar on the consumer side via a link which must be the same CSA as the incoming neutral. We call this the MEN link, and the system the MEN system (Multiple Earthed Neutral) as the neutral is earthed via the MEN link and in various points back to the TX star point. The consumer main neutral therefore functions as a PEN conductor. As JW mentioned, we do occasionally get instances of open or high impedance consumer main neutrals and shocks have occurred. RCDs clearly won't open as there's no current imbalance between A and N on the consumer side. There are also hazards if consumer mains are connected with incorrect polarity but RCDs (if installed!) will open if current flows to earth in these cases.
Things are easier when you have only the one system! :o)
These videos are great. Very hard to get this information presented in an understandable manner
MEN is the standard here in Australia. It's a TN-CS system, with a separated neutral/earth bar arrangement, and a earth rod in the ground. We have to find resistance as low as we can get - typically 1-10 ohms. Some sites (Centre of the country - sandy country) can see earthing rods 10-15M in depth. We equipotentially bond everything to stop balance issues.
In Australia, the Multiple Earthed Neutral (MEN) earthing system is used and is described in Section 5 of AS 3000. For an LV customer, it is a TN-C system from the transformer in the street to the premises, (the neutral is earthed multiple times along this segment), and a TN-S system inside the installation, from the Main Switchboard downwards. Looked at as a whole, it is a TN-C-S system. So, normally there will be a link in between the neutral and earth bus bars behind the switchboard, as well as at the local transformer.
The explanation at the beginning, about the transformer grounding cleared up so many questions for me, thank you
I've seen a few You Tube informative videos but this beats those hands down in presentation skills, clarity, knowledge and video quality. You should branch out into "How to make a You Tube video"!
Bless you dude, I thoroughly enjoy watching your tutorials. They're very easy to digest. 😉
Thank you.. your videos are helping me massively with retraining as a sparky.
I really appreciate you doing this for others to learn from :)
As an ex cable jointer I actually have had a shock from the N/E conductor of a 1ph concentric service cable!
The shift electrician had attended a property and said there was no incoming supply. Labour team had been told to open an excavation over the service so I could cut and test. As soon as I removed the PVC sheath, I got a rattle.
The cable had been damaged nearer the service joint and strands cut, water got in and the cable blew open circuit to the joint and phase to N/E towards the house! We weren’t issued with the much hated neon testers in those days. 😊
Should have said the phase wasn’t open circuit, just the ne.
Thank you. I've been searching answers about this for long time and now got them from you. I enjoyed your video.
There is a label on the cutout here that says "This installation is connected to a PME system" - so that confirms mine. A house we lived in before had a plate on the cutout saying "PME system" too. However, we also lived in one house where the supply came in from the poles, and that was TT. Our ELCB was a Chilton voltage-operated one.
John, many thanks again for an very clear exposition. Well done.
Re supplying outside marquees etc from a TNC-S system - the danger would only arise if that supply came from BEFORE the "C-S2 split. Provided the supply to the marquee etc. is from AFTER the C-S split all would be fine- just like stuff in your house.
Thanks for another very informative video. Could I ask a question on TT earthing systems. Is it allowed in the UK to connect the earth rod to the neutral at the customer end, and what would be the result or problem if this is done on a TT supply. I believe that doing this would only help by tieng the two together and thus reduce any problem of poor earth rod resistance.
SSE are now installing more and more TN-S systems on new connections work. TN-S is now always used when connecting up metal clad buildings or connecting to the old PILC cables. Funny how everything seams to go full circle. As a cable jointer I personally think that TN-S is a better system. Really good vid by the way.
Here in Germany we use TN-Net, TT-Net and IT-Net. The TN is splittet into TN-S, TN-C and TN-S-C. We use normal 3 L Phase, some old houses have only one L Phase. The power cable come in house direct into a big fuse for every phase - at this point the 'Saved Earth' and 'Neutral' go to two difference lines. This place is the exchange point between the power company and my home power net. After this I must install the Watt-Meter from my power company. After this we can install every RCD how we want use ... Most older installation haven't one. For Thailand I not know the situation, we use there an own transformator ...
Is it allowed to make TN-S-C ?
Thank you very much for a brilliant explanation.
There is another type of Earthing that you could of included. It is called PNB. Normally used for one domestic supply only to a single phase 11kv - 230 transformer where the earth for the transformer is via the neutral block on a 100 amp cut out connected by a 32mm covered copper wire to earth electrode/pin in the ground. Although historic, lots still exist and are in use in Dorset/Wiltshire/Hampshire and Somerset.
Thanks John , This is exciting ,I am starting to understand , may be its the white board but youve just broke a barrier . Before i know it I'll be wiring a plug !! Seriously, the other experts who try to explain should come down to our level and see what its like , its no fun down here ,but you obviously know a few thickos and kow whats required
What I'm struggling with at the moment is on TNCS how come the Neutral voltage isn't going straight to Earth at the property? With the E and N joined at the property surely the return would go straight to earth rather than back to the Transformer. It would be like you're sticking the N into the ground. Or have I missed the point?
Another great video. Comprehensive, clear and concise.
If you like this topic , watch a video entitled "EW rice interviews Elihu Thomson " he's the engineer that came up with earthing " and maybe some others around the same time . Go to around 10.27 in the video and he states it was his invention for safety . I like the term you English use "Earthing " ,better than what we in the States use " Grounding " great video ps Mike Holt has good videos on this topic.
great video, very clearly and well explained. However 2 points. Most of Northern Ireland (rural areas) are still in TT. My house built in 2006 was done in TT. Also when you say neutral is the same potential as earth. Must be remembered that in an AC system half the voltage is carried in the neutral and the lifter you get when you accidentally touch between neutral and earth is worse than live to neutral (or at least always feels much worse!) Overall, well done.
We use TN-CS in the US but we additionally attach a bare wire from a ground rod at the electric meter to the earth terminal in the fuse box. We also run a bare copper from the rod to the nearest hose bibb, I think for discharging lightning. The plumbing would provide a path thru to the utility's piping system which used to be metal. It's probably changed since plastic supply pipes were introduced. Wait, many pipes from the 60's were asbestos-cement which i wouldn't think was conductive so I'm not sure of the system. They may have terminated with a ground rod at the water meter in that case.
Had a case where a screw shorted light switch switched line to earth. No RCD. Only symptom was the combi boiler kept tripping out on flame failure. Only when the Utility room light was on (not obvious at the time...) On inspection the live was 140v above ground at the boiler- flame failure detector required more! The earth spike was underneath patio paving, and may have been quite dry... On bright days there was no fault to find!
Just found your channel. Many thanks for these videos. Extremely helpful.
Here in the land of convicts and sea front properties the neutral wire often corrodes off in the outside connection box, we almost exclusively use M.E.N same as your TT supply but each customer has a removable link between the neutral and earth in the consumer unit for testing, this provides a limited path to the transformer when the incomming neutral fails.
Thanks for your detailed explanation. Something useful for those of us in Nigeria
Every house i wired, always drove earth rods. 3 core going out to the cutout, and youd be connected into the earth block, which is basically the neutral block there. Theres an inspection box for the earth rod, which is normally placed under the meter cabinet externally.
At 10:46 in that instance, where you show the break, the appliance would cease to operate as there is no return path (neither N nor E). The more dangerous situation is where the Neutral circuit is broken downstream (towards the transformer) of the closest earth rod, in which case appliances will continue to operate using the E path as return, thereby putting metal appliance and metal pipe surfaces at, or near, line potential.
JW, could you expand further as to the earthing of a portable generator please? I use a 1kw Honda invertor generator on board our boat, generally for battery charging only. It represents a particular problem as afloat there is no possibility of an earth connection. The boat has a 240v shore power circuit on board which is generally connected to the mains supply in the marina when in the home berth. But when away cruising I plug the generator in to the shorepower inlet socket. Other boat users have suggested that the generator to boat shorepower connection cable should connect neutral to earth, infntbkniw what the thinking is behind this suggestion.
Your videos are very useful indeed - keep them coming.
Many thanks,
Rob
In the U.S. we drive a ground rod and attach it to the neutral point of the transformer, but it looks like you guys attach the ground rod to one of the ends of the transformer. We also have corner grounded Delta systems here too. Soooo I guess you can ground a transformer anywhere in the coil you want to and it will still have the same benefit for lightning, static, etc.? 😵💫
One point you didn't mention. If you are far enough away from the transformer, the voltage drop on the lines can be significant. Where I used to live voltage available sometimes dropped below 200v. That meant the Neutral was no longer zero, and could be anything up to 20 volts above earth. Even in my last house there was enough voltage on the Neutral to trip the RCD.
How does neutral gain 20v? (versus dropping)
Quite a few years on! Well presented, but it would be useful to observe that it's usual to require cross bonding between Earth and copper piping within houses - e.g in my place (which has TN-C-S) the water and gas pipes are cross bonded, with the underground pipes being plastic, so that all the exposed copper etc is connected to Earth. Plumbing alterations should take account of this, if there are any electrical disconnections in the installation.
That is an important subject, and John deals with it in a separate video on bonding. However, bonding is not earthing; bonding is to avoid a voltage potential between metallic parts in a building. It's related of course in that it will be bonded to earth in effect, but there is also equipotential bonding.
As usual always very good and clear. I wish all explanations were this good. Thank you.
😢
Very well explained, one query, for PME System you said that if the neutral (neutral and earth) breaks, it will be dangerous situation because no earth is available. My question is, if a neutral breaks, there will be no supply left because to complete a simple circuit we will need to have a connection of both Live and Neutral. so there will be no current flowing through and have no danger as there would be no supply. can anyone please explain?
The electrical supply is explained wonderfully. My thought is: if we do without grounding, the power supply will be similar to safety Tafo. Wouldn't that be much safer? Unless someone touches the L and N lines directly. Grounding causes more problems is my opinion.🤔
It's safer but only until some fault to Earth occurs somewhere - it's then an uncontrolled earth referenced system.
Isolated supplies have their uses, but only in strictly controlled and monitored environments.
@@jwflame You are extremely competent and know what you are talking about. What has become so rare today. Thanks!
Brilliant and very clear instructional video. Thank you John (liked and subscribed.)
I now want to see an electricity sub station's Earth rod (s). How do they calculate the size / effectiveness?
And how reliable in a real life scenario for the furthest installation in line.😒
Usually lots and lots of 8mmx30mm copper tape buried around the entire sub station it's all designed by the engineers of the sub and presumed loads
Very clear and concise information! Unfortunately you left out the IT system.
Left out because it's rarely used anywhere.
Great Video John, thanks a lot!, may I ask please - For TNS system, since both Earth and Neutral cables are connected to each other in the transformer side, why does i cannot measure continuity between both cables in my Electrical panel Distribution Board?! This kinda freak me out kindly help! thanks
drich modina There should be continuity between N &E - if not, either the earth is defective, or you are measuring in the wrong place, such as after the main switch when it is off.
***** i measured it in our 63A 3 phase with 1 phase branch distrubution board. I also thought that if i measure continuity between earth and neutral there. Most likely the RCD will trips. Please please teach me where to measure it properly and why does the RCD dont trip if the two cables have continuity. Thanks a lot in advance!
Very clear and concise presentation, thank you
Suppose I have a three-phase motor fed from a panel that has 3 phases and one grounded neutral. I then decide to ground the mass of the equipment through an earth rod (TT) in instead of using the grounded neutral from the panel. What would the drawbacks be if I decided to interconnect this earth road with the neutral from the panel (that comes from a grounded wye LV side three-phase transformer)?
It sounds like you're describing a grounding conductor off the equipment shell bonded to the neutral coming in from the utility. This is fine. If you're talking about having two separate ground references on the same equipment, this is not fine.
In France, TT is the default system for everything; in new construction they typically use a earthing "ring" with wires buried all around the concrete foundation instead of rods; RCDs are mandatory. Here in Canada IT is used in Healthcare facilities; these systems are subject to very strict rules.
+w0ffe I think IT is only used in Operation Rooms. Most non OR's are usually TN-S.
Might sound daft but why do TN-S cables have a higher resistance than a TN-C-S. Surely the resistance should be very similar or do they use lower quality cable for the earth or is it just longer run?
+Scott Clewlow TN-S is usually supplied on PILC cable, which has 2 copper conductors for line & neutral, the earth is the outer lead covering with a steel tape over it, so resistance is higher.
TN-C-S typically supplied on concentric, which is all copper for the line and combined neutral & earth.
Man, this is great- I subscribed and liked the video. Thank you very much!
Clarity at last! Many thanks.
Hi john I'm currently doing C&G 2365 and have been asked to give drawn examples of Tns, tncs, tt and IT supply and earthing systems. I have no problem with the former three but the IT system is proving problematic to gather info on. Do you know when or where people get trained in this type of install? My 2365 textbook states. IT and TNC systems are not included in this course so there is no information included on these type of installations. Thanks. Phil.
+phil Harvey IT is where the supply is isolated from earth, such as an isolating transformer. Neither side of the supply is connected to earth, or it is connected to earth through a high impedance. It is typically used for medical installations such as operating theatres.
TNC is a system where the neutral and protective conductor (earth) are combined into a single conductor within the installation, so only 2 wires to each item. It is specifically prohibited other than in a few very specific instances, so in reality is never used in the UK. The supply is the same as TNC-S, except that there is no split to separate earth and neutral where the supply enters the building, it continues for the whole installation with the combined neutral and protective conductor.
There is some information on both in BS7671.
+John Ward nice one john. I would guess that training for IT installs is trained by the energy supply company.
Hi, on a tt system what is to stop someone simply linking their main earth to the neutral instead of installing a rod and putting up with high earth loop impedance? Just curious
Thanks
Hi Mr Ward. Please explain why other countries (Singapore for instance) would consider TNC S dangerous and, in effect, not allowed. Thank you
Actually the old TNS cables have their lead sheath covered by a steel spiral wrap which is then covered with a fabric insulation which is coated with a tar like substance, I know as I've got one of those old cables supplying my old house, so therefore the lead sheath is not actually in direct contact with the ground so it has to rely on it's lead sheath for earth continuity. And there's loads of those old cables still in use where I live and further afield in the surrounding area. And I've also seen a modern concentric cable with separate neutral and earth conductors, the earth is formed by usually seven bare copper strands fitted around one half of the live phase insulation with again seven separately insulated copper strands fitted around the other half of the phase insulation to form the neutral with of course an overall insulating sheath on the outside. So some TNS installations with more modern cables do exist, probably where an existing service cable has failed and has had to be replaced, like the one next door to me. Old dead water supply pipes are in direct ground contact and have to be earthed at the consumer's property so they can effectively form a local earth electrode if connected, and of course the same applies to some older gas supply pipes too, like mine which is iron and that is also connected to my incoming earth conductor.
nice info about GND-earthing
It occurs to me that, whenever I watch a video on TN-CS system, there is a need for an earth rod supplement within the property wiring to avoid the PEN fault you describe! Is there a reason WHY such a supplementary earth rod arrangement(TT) should NOT be installed on a TN-CS system? I would logically assume that the TN-CS would be considerably lower in impedance to the TT supplement but the TT would protect to some degree rather than none, in the case of a PEN fault you describe?
Hell Mr. John, if you please could you or someone else answer me in two queries? What was the benefit (at TN-S system) of the old cables with lead shield to come directly in contact with the earth? Maybe in the case where the cable were being cut accidently the property will still had earth connection (the earth itself will connect the two pieces of the broken cable)? Also, at TN-CS system what is the reason of multiple connections (at 10:48 min) between Neutral and Ground; maybe if the cable were being cut at some point the houses that are connected after the cutting point will still have Earth Ground connection and from now on because the only return path for the current to return will be the Ground earth the result will be a breaker or fuse or RCD to triggered immediately. So in practical this a way of detection a cut cable and to avoid a house to stay without Ground Earth (PE); because of the triggering of the breakers the properties don't have electricity and consequently the electric company must necessarily to repair the break cable? Am I right in my hypothesis or I misunderstood/missing something?
You are clear and concise greatly appreciated
A very interesting video, in my hobby (amateur radio) we tend to have grounding arrangements that attach to the shield of coaxial cable at the base of the aerial. This cable then generally connects to the equipment chassis within the house which is also connected via the standard mains lead to the standard domestic mains earth.
In my set up the "ground mat" under the lawn is also bonded to the water piping of the house. It is a slight concern that in the event of a live-earth short in any part of the house a proportion of the fault current will flow through the equipment chassis to the " other ground".
For various lightning protection reasons it can be very bad news to isolate the two grounding systems.. ie to provide a seperate safety earth only for the radio gear.
This situation must be very widespread, presumably the answer is to make the bonding path as low resistance as feasible to minimise the current flow through the other path? We have an RCCB so presumably my question is more of a hypothetical one?
Thanks for the video, most educational!
In the event of a broken neutral for a TN-CS earthing system , and there is a line fault fault , will the system not automatically turns into a TT-system ?
Hi JW very interesting I’m on the PME system
For a couple of years now I’ve had the odd LED in the kitchen flicker .... but a couple of days before Christmas Day the lamp in the living room was flickering badly it’s connected along with my mother’s riser chair through a UPS and it was making funny noises so plugged the chair and lamp back into the wall socket and changed the lamp...
Then on Christmas Day (2018) dinner out of the way we were watching tv when the RCD tripped switch it back on everything was fine for about 30 mins and it done it again this happed a few times through the night...( I had called my sparky and was coming out Boxing Day to have a look ) about 8am my UPS for my hard drives etc started going between battery and mains and very loud humming noises of the transformer inside the UPS
Anyway sparky came out tested everything and put it down to a faulty RCD put another one in (not new) everything tested ok .... tried the old one in a test circuit and it tripped !
But as I was switching thing back on in the house came back out to speak to the electrician when I noticed a neighbour had an electrician in as well I told mines and he called him they were having the same problem as well so we called Scottish utilities they came out and was a fault underground ....
I have since had the RCD that was put in go faulty again it wasn’t new plus was in when having problems ..... so new one installed so far so good
But next week having a new unit installed with the new robc and a power surge on the supply into the house ....
Great channel 👍
Could you please explain the difference between TN-C and TN-C-S?
I already understand the latter, since the US uses it with a slight variation: the neutral is grounded not only at the transformer (a single-point-earthed-neutral TN-C-S system, but also at the house of each customer (a multi-point-earthed-neutral TN-C-S system).
But I don’t see the difference between the two types of earthing systems. Both ground the neutral at the transformer. Both connect the neutral wire to normally-noncurrent-carrying conductive (metallic) parts at each customer, meaning the neutral and ground wires are combined before the customer but separated when entering each customer house.
TN-C has the ground and neutral combined within the house, so there is no separate ground wire. Ground connections for each outlet are just a small link between the neutral and ground connections. Rarely used anywhere and not permitted in the UK and plenty of other countries.
In bulgaria we use shuko plugs and we rearly have separate earthing wire.In the wall socket we just put a bridge(copper wire) between earth and neutral and it works nearly all the time.
That arrangement (TN-C) is prohibited in the UK.
Didn't know that.Thanks for answer.
I have TN C-S properly installed is it allowed to earth the body of the motor or the control panel earthing point as add protection I can pond it to a sticking out construction steel that I conected to the building foundation which happened to be near them
For a commercial building, where the transformer is a private property, will the earth cable from the transformer be connected to the main earthing terminal inside the main distribution board for a tns system? please clarify. Here in pakistan the mdbs are generally earthed by two earth rods...
Muhammad Farooq Fun fact :
In Italy, Spain, Greece, Serbia, Croatia, Albania, Bulgaria and Romania, if you want to make a contract with the pieces of shit known as enel, you would need to buy yourself a transformer and then give it to them for free (as part of the contract you make with them). And most of the time they will be the only option... because they are a regional monopoly... 100% unregulated free market and capitalism go so well together !
Doesn't supplementary bonding of water & gas pipes to earth, lessen the chance of any shock occurring even if a PME supply cable or earthing rod was damaged. I know most modern houses use PVC supply pipes which would negate this benefit. But on older homes does this help?
How do power company face the issue of earthing the transformer to avoid a fault on high voltage to be 'distributed' trough the PEN to all the customers attached? TNC could have been ok 50 years ago when RCD weren't available and MCB/fuses were only protections available for ground-fault. But today with RCD I think is better to have PE as far as possible from the high-voltage 'center grounding' of the transformer. l'd just prefer to avoid the risk of getting few kV on my desk lamps casing.
JW, should I have continuity between my neutral and Earth in a TNCS supply if testing with a standard multimeter from a socket?
Yes, N&E are connected at the point they enter the building. You should also get continuity on TN-S, as although the wires are separate, they are still joined at the transformer.
There is a minor error here. Most lead supply cables are covered in bitumen. The lead sheath is only visible where the termination has been made at the cutout. So the lead sheath rarely functions as an electrode. Also, in very old services the lead sheath can crack due to loading stress on the ground above, so a periodic loop impedence test is especially important on TN-S supplied installations.
To make the TN-C-S system safer we use extra ground rod connected at the point where Earth and Neutral wire is separated in Estonia.
Hi, i have a 1900s house with a lead cable , 3 cutouts (only one in use) and a green earth cable running to a small side box( i think the whole assembly is tar filled)..my house is wired in pvc coated twin and earth...mostly grey, some white...everything works fine. my question is...there is a green earthing wire in the kitchen not attached to anything and one in the bathroom also...should i clamp them to a cold water pipe or just remove them, many thanks colin...
we have a Wooden Electricity pole outside our house and down the side of the wooden pole runs a thick black wire (the black seems to be just plastic insulation and where the insulation has brocked away you can see the Thick wire which is silver and not copper coloured), and its tapped to what looks like the Neutral wire on the pole and then the wire just goes either into the ground oif the property, or goes to the meter box on side of wall of property. - This is all put on the electricity supply board not on the consumer side of things. So does this mean the house/premises still has to have one or more earth rods even with this earth wire tapped to neutral line from the wooden pole? - or have the electrical supply board supplied to required earth protection to the house? - the house/property is in the republic of Ireland by the way, just in case the electrical supply is distributed differently to the UK.