Cheers John. I was doing a c2 remedial job in the summer, I was there for high Zs on the main switchboard outgoing ways. All the 60amp plus circuits were too high, done a Zs test to find 3.5 ohms. This was much higher than the original test that had failed them six months ago. Done another Zs at the cablehead to find the same reading. Contacted Scottish power who came out and done some tests of their own which yielded the same results. When they disconnected the earth from the cable head there was no earth to the incoming mains. They then disconnected us from the grid and put us on a temp genny over the weekend and fixed the broken PEN on Monday. Nothing in the building was blew up, god only knows how long it was like that for. The building is a large portal frame industrial unit, with the steelwork being the earth electrode. The loads are mainly lights and three phase motors. The phases are well balanced around 20a per phase lighting, so with phases balanced and a decent load there was no damage. The electricity board had another spark come in and check the other dis boards for signs of burning before they would connect the genny. After all that had been done it was an easy fix, I just done another Zs and typed up the cert. That’s my story. All the best John.
So you were using the PEN as a ground electrode and using the poor resistance of the Scottish granite as the neutral back to the power transformer. Must have been making that transformer ground pad rather warm, because you can bet half of it had rotted away already. I remember seeing substations near rail lines, where the earth mats had melted away, because of a broken track link that meant the earthing mat, across the road, was now the return path for the traction current, bypassing that broken jumper link in a set of crossovers. All the overhead towers, with their concrete foundations, are tied to the rail, so the stray path was very broad. Stick a rod into the ground 3m apart, and measure the voltage, and you could see the voltage rise up as the train passed the break, and stay at around 30VDC till it changed over to another transformer rectifier supply. Also that DC meant steel would rust away like crazy, always starting at one end, and moving along the rebar till it was gone. One end shiny steel, other end black rust.
Your right about the DC systems I have done a lot of work on 12 and 24Vdv control systems at low current and if the terminations get wet or a cables damaged in a duct the DC just eats the metal away with electrolysis.
@@SeanBZA Overhead electric railways in the UK are 25 kV AC - the DC railways are the 3rd rail systems in the South and the Undergrounds' 4 rail systems. In the AC traction environment nearly everything is tied back to the traction return and the Railway substation. The railway want to keep the return currents, as far as possible, in the return conductors and rail and use differing systems to achieve this. One reason is to keep induced voltages out of conductive communications and signalling cables and to stop electric shock conditions occurring along the track (fences etc.)
@@barrieshepherd7694 Yes, but by me they use 3kV DC, because the regen braking can feed power into other units, plus lower voltage makes for a slightly safer operation. There are a lot of rail power standards, and a lot of locomotives can support a few supply options in the same car, and many can also switch between them as well. That 3kV DC supply was fed to the coaches, where it ran a motor generator set to provide power for accessories on cars with power, and was used directly to power lighting, using a series connection of flourescent tubes and dropper resistor to provide light, and also for the winter heating using large ceramic resistor blocks. Doors operating using pneumatic lines, along with braking.
We had a PEN fault some years ago when a tree fell on the overhead cable, but only disconnected the neutral. Called SSE Power to tell them we were getting variable voltage, but sometimes 300 volts. Someone comes out, check it at the substation (which is in our front garden) and says its 240 volts and its fine. I told him to check at the house because he was using the neutral at the substation, which he reluctantly did. His face when he checked at our meter as he measured over 300 volts..
John you are somehow the best at this in your English school master way which is highly regarded. You also explained the 400v across 3 phase lines thing so well and made it seem so obvious. Thanks for the excellent channel
Thank you for this explanation. This happened to the village where my parents lived, I never understood why some houses only had minor damage, but some had major, including melting things and fires
Yes had loss of neutral when the copper thieves came and took the ground and neutral wiring in the substation , and also stripped the cable to get the neutral conductor to the point it went into concrete in the substation. Second time they attempted to steal the copper in the 11kV Reyrolle switch, which meant another 4 days without power. I saw the imbalance because the UPS was doing bucking, and measuring the AC showed it was close to 270VAC. Went to the meter room (3 phase incoming, split into the 3 phase rails and then meters, plus the one 3 phase meter for the mobile phone tower on premise) and saw 270VAC, 350VAC and 140VAC as phase voltages. Turned off the main switch, and called the electrical supplier about loss of neutral. Second time the upstream 11kV fuses blew, disconnecting the supply. One thing I have done, and suggested to all my neighbours, is to install surge arrestor plugs, a few of them, and make sure the RCD is working, though you used to get a CBI RCD with an extra earth wire, which had in it as well a trio of MOV devices, so it would pass current through the core in imbalance if you had either loss of neutral, neutral rising above 100V from ground, or incoming voltage rising above 300VAC. The surge arrestors at least will trip the breaker (no pesky 3/13A fused plugs here, just a 20A breaker per spur, not the UK 32A breaker and ring main), and thus protect the equipment to a great deal, though it is often terminal for the surge arrestor, so buy a new one. Otherwise you install distribution board surge arrestors, but those are often a higher voltage unit, more suited for the issue of MV supply dropping onto the LV supply. Yes a lot of the street had issues, neighbours on the high side blew out geysers, TV sets, and the coffee shop on the corner lost almost all equipment, as they were, despite being a very high load normally, unfortunately on the lowest loaded phase, so got the high voltage. Blew up the POS, the digital oven controls, the AC, the fridges and all other electronic devices. I just had 3 lights burn out, along with one MOV going short circuit.
7:15 there would be current flowing in the PEN in your diagram, as it has to flow between the different installations to get to the other phases. I think you mean the sum of all the current would be zero, so there would be nothing that needs to flow back to the transformer.
US does not have this issue because residential uses a single phase transformer for a group of homes. This single phase transformer normally powers four or more houses. The transformer is a split phase 120/240 on the secondary. A similar issue can happen when one residence looses its neutral. The condition does not spread to others. Sometimes an underground junction box is used instead of a transformer to tie a group of homes together and the condition could happen as you described when the neutral is lost from the junction box to the transformer.
Our bungalow, built in the 60's is exactly this. We had a dodgy local substation phase for a few months and quite oftens, every-third house lost power.
We are experiencing something similar to this in my street. Low voltage during times of high load for the last two years. The DNO are finally addressing the problem and although they claim it's an earth problem (in laymans terms), I suspect they mean a fault on the CNE.
Excellent info as always John. I used to work for an electricity meter manufacturer and we often fitted a small phase failure indicator in our induction disc three phase instrument transformer operated meters that basically worked on the principle you describe here. The main concern was losing a phase in terms of potentially lost revenue 😎👍.
In Germany, residential buildings are usually connected to three-phase current. Three phases and PEN. There is also the foundation earth elektrode that is connected to PEN. Then N and PE are separated. Lights and sockets are then connected to 230V. The electric stove is supplied with 400V three-phase current. But the oven is one 230V device. Two hotplates are connected to 230V in the second phase. Two hotplates are connected to 230V on the third phase. This only requires 2.5 mm² wires, 3x 16A. But you definitely need the N conductor because otherwise the voltage will shift. However, the PEN must never be brocken! Therefore the PEN must be at least 16mm². Or separate N and PE connected after the electricity meter. Old installations with common thin PEN have not been permitted for years. Car chargers are also connected in three phases. Mostly 11kW Requires an N conductor because the car rectifies the three 230V phases to DC.
Stoves get the three phases but they are in a star connection so the actual 400 V is not used, instead the hotplates get 230 V. This works better in systems that hae various power settings. Also it is possible to run it with single phase by connecting the three inputs together. This typically means you are limited in the total power.
@@temp26j724-i Load balancing is mandatory when you have to deal with a residential feed with 3 phase+Neutral. If you have a subscription for 9Kw you only have 3 per phase, so if your stoove is a 9Kw one you must spread the load on all phases. Usually the oven is 3KW on one phase, a small 1Kw and a big 2kw burner for the second phase and again small and big for the third. Note, in some place in Belgium, it's 220V phase to phase with 110 Phase to neutral. So it's wired phase to phase, in this case the neutral lost have no impact as 110V is not even available on any plug.
Good video along with a great explanation. Some years ago my property along with a few of my neighbours suffered from a negative line fault. Basically anything that was plugged in blew up.
I first read this as "Diverted NEURAL current..." and was confused. I spend a full minute reading the title and trying to see how three phase power fit with anything neural. 😅 Great video though!
Interesting comment you made about 3 phase/400v gear being uncommon in residential or even a lot of commercial buildings. When I lived in Australia, 3 phase to a residential premises wasn't uncommon (it wasn't the norm, but it could be easily be requested if the street had 3 phases (not all do)), and in fact I stayed in a home where various circuits were split across at least two of the phases. The residence also had a ducted reverse cycle air conditioning unit that cooled/heated the whole house, which required all 3 phases to operate.
🙏 thanks for sharing with us. I purchased a Dual Display 40A 63A 230V Din Rail Adjustable digital Over Under Voltage device but I did better than that by creating my own micro-grid providing me with 10kVA from two clean sine wave inverters and 37kw of self built battery storage so my energy should be a lot cleaner and safer than that of the grid. However, since i've adopted an automatic contactor relay which detects a potential loss of generation and reconnects the building to the grid, I have also used a contactor relay that separates the two neutral/earth sources in order to avoid problems especially in the unlikely event of lightning which might create a gradient of very high voltages across the ground that could be very different between the two earth electrodes which are more than 30m apart. Do you find this the correct procedure ?
I suppose the TNCS systems seemed like a good idea when fuse protection was all that was available, and you needed a very low resistance earth path to actually blow the fuse. These days with RCDs/RCBOs surely TT should make a comeback?
It could - but with TT in a modern installation you are relying on electronic devices (RCD/RCBO) to disconnect. With high current earth faults and circuit breakers it's a mechanical device operated by a magnet.
I would have thought that with smart meters a voltage monitoring function could be could be built in to quickly detect faults. In event of a out of spec input voltage it could automatically flag a warning and possibly even disconnect as well. In addition a remote voltage monitoring facility could be useful to identify problems in an area. Problem now is many appliances use switch mode power supplies such as lights TVs, computer etc so unless the input voltage goes below the minimum operating voltage (often below 100V in many devices) or exceeds the maximum voltage rating of the devices then many people would not notice as the device works normally. Many could tolerate for some time a considerable over voltage before failing.
Up to a point - however with a long duration of overvoltage the SPD will conduct continuously, heat up and fail. It might cause the fuse or circuit breaker upstream to open, but whether that would protect anything depends on how long it would take, and whether it was for the whole installation or just for the SPD. There are dedicated overvoltage devices available which would disconnect such as www.dehn-international.com/store/p/en-DE/F440777/spd-pop-mcb-pop-mcb-pop
Hi John, really interesting watching your videos. I was quite interested in the earth rod recommendations (I think in amendment 2 part 4). Like you say many other country's have this anyway. I wonder what your opinion is though, if say you have a TN-CS system and you go to the trouble of installing an earth rod (and have 30mA RCD on all circuits as it is almost always required), then why not just change it to a TT (earth only connected to the rod)? If there is a neutral fault on the incomer and it rises to live potential, then st least everything in the house remains at earth potential. And - if it is better to use the DSOs neutral as the earth (together with a earth rod), why not in a TT system connect the earth to the incoming neutral?
To convert to a TT system can often be done, but in many installations it's a lot more difficult than just shoving an earth rod in, and it may not be possible at all. See th-cam.com/video/S5OtLg6voZY/w-d-xo.html for further details. If you connect the earth electrode in a TT installation to the incoming neutral, it's not a TT system any more.
Dead right to bring this up, especially now with so many electric cars in use, this situation could potentially result in a car body on charge becoming very LIVE and deadly. And another thing that concerns me a bit is that there's likely to be some folk seriously overloading old 1920's or 30's vintage service cables where they already have lots of big electrical loads like an electric cooker, tumble dryer, shower etc. and then they add a dirty great BIG, say 20Kw EV charger, that could potentially burn out someone's neutral and create a deadly situation. And some folk think they know about electrics... This is why proper training or at least some serious theoretical study is so essential. Perhaps the government should make surge protection a necessity in domestic installations now.
here where i am, we have a TN-C-S system: the distribution side is 400/230 V TN-C aerial conductors and the consumer side TN-C-S system (single or 3 phases, depending on the needs). by the norms, the electricity provider needs to ground (connect it to earth) the PEN conductor as often as possible and on the consumer side, where the PEN separation is done (PEN to PE and N), we have to bring an earthing connection (or electrode rod connection how u call it) that is needed to have a resistance (impedance) under 4 ohm if is only used as shock protection or under 1 ohm if is combined with the lightning protection. does a low value for the earthing system resistance make any difference in this case (broken PEN)? or what is the reason for this values? oh, i forgot! and we also are forbidden to put any protection or separation device on the PEN (or PE) conductor - it need to be uninterrupted from the case of the appliance all the way to the transformer.
Can you do another video explaining what would happen if you had a big 3 phase generator (say 80Kva) and the power / current draw was really badly balanced over the phases
So would an AFDD detect this (or at least the over voltage symptom) as it has over voltage protection? I guess the disadvantage is that it won't disconnect the PEN?
@@jwflame Many thanks John. It's not something that they talk much about with AFDDs, over voltage protection is just a passing statement. I am pretty sure that we had this type of fault at our house earlier this year, but got an undervoltage. It started with a power cut, but then, a few minutes later, I noticed that some neon lights were glowing faintly and a mini dehumidifier, fed from a AC to DC adapter, was running, but it made a funny sound like the motor was going really slowly. I then switched off all the AFDD RCBO, except the kitchen, which had already tripped, and a lighting circuit, so I knew when the power was back on. When power came back on, I reset the breakers, and I think the kitchen one showed self test fault, although it was hard to tell with the pattern of flashing. The SPD was unaffected. Neighbors reported similar effects to their lights. About two weeks later my fridge freezer stopped working. So I wonder if it was damaged by an undervoltage caused by what I think was a lost neutral. Apparently undervoltage can be just as damaging to some appliances, such as those with motor. I have brought a Sollatek FridgeGuardiS to protect my new fridge freezer, you just plug through it like you would a smart plug. Obviously only protects one plug but easier than getting an electrician to install something at the consumer unit.
I was thinking a Ze test would flag up a broken PEN conductor, as if the PEN conductor was open you would be measuring the resistance of the other loads on other phases even if the phases were perfectly balanced the loads in most case would be higher than the 0.35 TNCS limit
It would in many cases, but not all - all depends on what else is connected and particularly any additional earth connections to the PEN via metallic service pipes, metal framed buildings and similar.
Can you have a 230v 3 phase delta supply into a premises. If not, why do most motors provide for a delta connection. I know it's convenient for inverter supplied equipment, but even old motors before inverters often have the facility
When it's about 3 phase for a premise, the secondary of transformer is ALWAYS a start "Y" in order to provide neutral for protection A 3 phase "traditional" squirrel cage motor mention the voltage on his plate. like 220/380. then you wire it accordingly to the tension you feed it with. So if you have 3 phase 220V you must wire it delta "Δ" if you wire it star "Y" it will not be able to deliver all it's power and will surely burn. This under voltage was used to provide a "gentle" start, but it last less than 1 or 2 seconds. If your voltage is 380 the coupling will be Y. And for a plate showing 380/660 the coupling for 380 is Δ ! When you use an inverter, the inverter supply the voltage to the motor but never higher than the input. Inverter convert main AC to DC then recreate AC. The input of an inverter may be mono or tri. If inverter is a single phase one, the input voltage is 220 and so is the output, so the motor coupling will be Δ for a 220/380 motor (this cannot run a 380/660V motor)
@@Phantom-mk4kp Im sure you are asking if DNO would provide PolyPhase (3ø 400V) supply into properties. Yes they will subject to conditions. What JW meant is Residential properties typically gets only 1ø as the need does not arise (apparently though) for application to DNO for PolyPhase supplies into Domestic properties...
@@temp26j724-i No I knew 3ph was available, in fact I answered my own question after reading it back and thinking about it, delta or star is not so much a supply characteristic but how it's implemented at the load
Why on earth (no pun intended) did the DNOs decide to start installing PME supplies? Was it a cost-cutting measure? Seems so stupid to me. Why not just have a good old-fashoned TN-S supply and not have any of these problems? You even have to treat TN-S as TN-C-S now as it has probably been combined in-line anyway or will be at some point.
3 phase can be connected either way, depends on what it is being connected to. The 3 phase supply is the same regardless of how it's used, and obtained from a Y / star connected transformer with a neutral.
I suppose a delta‑only system (no neutral to loads, the transformer common connected only for protective earth) would have been more failsafe; perhaps that's one of the reasons Δ3×220 was historically common in much of Europe. Italy once implemented a similar system, but using the 127V phase-neutral for incandescent lamps (which work more efficiently at the lower voltage); no great catastrophe if the neutral broke there. But then most of Europe moved to 220/380 (now 230/400) to reduce transmission losses, and unwilling to change the appliances to 380V, they stuck the 220V appliances between a phase and neutral. If we had to do it over from scratch, I'd prefer Δ3×400 or thereabouts; small appliances would be slightly more expensive but still not overly difficult to make (most cords are already rated for 500V line-line), and the grid could be TN‑S at lower cost than current 230/400 TN‑C‑S (by using a smaller PE core in place of the large CNE). Smaller grids could use balanced single-phase (400V line-line again, 200V line-earth). I suppose power companies could still have cut corners by corner-grounding the system and combining the grounded phase with protective earth, though… Not that we can do much else about the current situation.
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So good to see you back again! We have all missed you and your unique and pertinent explanations...please post more!
agree :) there is a JW video and a ElectroBOOM one in my notifications, and i came here first.
Great to see you back John.
Cheers John. I was doing a c2 remedial job in the summer, I was there for high Zs on the main switchboard outgoing ways. All the 60amp plus circuits were too high, done a Zs test to find 3.5 ohms. This was much higher than the original test that had failed them six months ago. Done another Zs at the cablehead to find the same reading. Contacted Scottish power who came out and done some tests of their own which yielded the same results. When they disconnected the earth from the cable head there was no earth to the incoming mains. They then disconnected us from the grid and put us on a temp genny over the weekend and fixed the broken PEN on Monday. Nothing in the building was blew up, god only knows how long it was like that for. The building is a large portal frame industrial unit, with the steelwork being the earth electrode. The loads are mainly lights and three phase motors. The phases are well balanced around 20a per phase lighting, so with phases balanced and a decent load there was no damage. The electricity board had another spark come in and check the other dis boards for signs of burning before they would connect the genny. After all that had been done it was an easy fix, I just done another Zs and typed up the cert. That’s my story. All the best John.
So you were using the PEN as a ground electrode and using the poor resistance of the Scottish granite as the neutral back to the power transformer. Must have been making that transformer ground pad rather warm, because you can bet half of it had rotted away already. I remember seeing substations near rail lines, where the earth mats had melted away, because of a broken track link that meant the earthing mat, across the road, was now the return path for the traction current, bypassing that broken jumper link in a set of crossovers. All the overhead towers, with their concrete foundations, are tied to the rail, so the stray path was very broad. Stick a rod into the ground 3m apart, and measure the voltage, and you could see the voltage rise up as the train passed the break, and stay at around 30VDC till it changed over to another transformer rectifier supply. Also that DC meant steel would rust away like crazy, always starting at one end, and moving along the rebar till it was gone. One end shiny steel, other end black rust.
@@SeanBZA that was about the size of mate. Sure, funny things can happen with loss of neutral and your railway line scenario is a cracker.
Your right about the DC systems I have done a lot of work on 12 and 24Vdv control systems at low current and if the terminations get wet or a cables damaged in a duct the DC just eats the metal away with electrolysis.
@@SeanBZA Overhead electric railways in the UK are 25 kV AC - the DC railways are the 3rd rail systems in the South and the Undergrounds' 4 rail systems.
In the AC traction environment nearly everything is tied back to the traction return and the Railway substation. The railway want to keep the return currents, as far as possible, in the return conductors and rail and use differing systems to achieve this. One reason is to keep induced voltages out of conductive communications and signalling cables and to stop electric shock conditions occurring along the track (fences etc.)
@@barrieshepherd7694 Yes, but by me they use 3kV DC, because the regen braking can feed power into other units, plus lower voltage makes for a slightly safer operation. There are a lot of rail power standards, and a lot of locomotives can support a few supply options in the same car, and many can also switch between them as well. That 3kV DC supply was fed to the coaches, where it ran a motor generator set to provide power for accessories on cars with power, and was used directly to power lighting, using a series connection of flourescent tubes and dropper resistor to provide light, and also for the winter heating using large ceramic resistor blocks. Doors operating using pneumatic lines, along with braking.
We had a PEN fault some years ago when a tree fell on the overhead cable, but only disconnected the neutral. Called SSE Power to tell them we were getting variable voltage, but sometimes 300 volts. Someone comes out, check it at the substation (which is in our front garden) and says its 240 volts and its fine. I told him to check at the house because he was using the neutral at the substation, which he reluctantly did. His face when he checked at our meter as he measured over 300 volts..
Had a similar thing with WPD a few years ago, shortly after they arrived the sub db in the garage burst into flames
ABSOLUTELY SO GLAD, that you are BACK!
Thank You!
Love this kind of content.
Glad to see you back JW.
Welcome back John. I was the one who emailed you. Glad to see a return!!
Great to see you back JW. Been a long time👍
John you are somehow the best at this in your English school master way which is highly regarded. You also explained the 400v across 3 phase lines thing so well and made it seem so obvious. Thanks for the excellent channel
Thank you for this explanation. This happened to the village where my parents lived, I never understood why some houses only had minor damage, but some had major, including melting things and fires
Yes had loss of neutral when the copper thieves came and took the ground and neutral wiring in the substation , and also stripped the cable to get the neutral conductor to the point it went into concrete in the substation.
Second time they attempted to steal the copper in the 11kV Reyrolle switch, which meant another 4 days without power. I saw the imbalance because the UPS was doing bucking, and measuring the AC showed it was close to 270VAC. Went to the meter room (3 phase incoming, split into the 3 phase rails and then meters, plus the one 3 phase meter for the mobile phone tower on premise) and saw 270VAC, 350VAC and 140VAC as phase voltages. Turned off the main switch, and called the electrical supplier about loss of neutral. Second time the upstream 11kV fuses blew, disconnecting the supply.
One thing I have done, and suggested to all my neighbours, is to install surge arrestor plugs, a few of them, and make sure the RCD is working, though you used to get a CBI RCD with an extra earth wire, which had in it as well a trio of MOV devices, so it would pass current through the core in imbalance if you had either loss of neutral, neutral rising above 100V from ground, or incoming voltage rising above 300VAC. The surge arrestors at least will trip the breaker (no pesky 3/13A fused plugs here, just a 20A breaker per spur, not the UK 32A breaker and ring main), and thus protect the equipment to a great deal, though it is often terminal for the surge arrestor, so buy a new one. Otherwise you install distribution board surge arrestors, but those are often a higher voltage unit, more suited for the issue of MV supply dropping onto the LV supply.
Yes a lot of the street had issues, neighbours on the high side blew out geysers, TV sets, and the coffee shop on the corner lost almost all equipment, as they were, despite being a very high load normally, unfortunately on the lowest loaded phase, so got the high voltage. Blew up the POS, the digital oven controls, the AC, the fridges and all other electronic devices. I just had 3 lights burn out, along with one MOV going short circuit.
Thank you so much for all your videos ! Great to see you again !
Love the collection of old engineering books John. Recognise a few of those from my own bookshelf!
Good to see you back…
THE legend!
Agreed! The go to is back…and I Spy a Horowitz and Hill on the bookshelf John, respect fella 👏👍❤️
@@adrianshingler9783 The best book of all time!
Welcome back John! Love the videos
Back again!👍
Nice to see another great video on TH-cam and your good self, JW👍
Good to see your back John
As always an excellent presentation
Great to see J.W.
Good to see you again John, pray may you continue...
7:15 there would be current flowing in the PEN in your diagram, as it has to flow between the different installations to get to the other phases.
I think you mean the sum of all the current would be zero, so there would be nothing that needs to flow back to the transformer.
Nice to have you back John! Any chance you can blow something up on the next video? Please!!! 🔥 🤞👍
Great to hear from you again JW! 🎉
Good to see you are back great video as always.
Nice to see you again!
US does not have this issue because residential uses a single phase transformer for a group of homes. This single phase transformer normally powers four or more houses. The transformer is a split phase 120/240 on the secondary. A similar issue can happen when one residence looses its neutral. The condition does not spread to others. Sometimes an underground junction box is used instead of a transformer to tie a group of homes together and the condition could happen as you described when the neutral is lost from the junction box to the transformer.
Our bungalow, built in the 60's is exactly this. We had a dodgy local substation phase for a few months and quite oftens, every-third house lost power.
Welcome back!
We had the very old supply cable coming into the house, covered in gutter percher, it had a small lead tag with a B on it, meaning it was the B phase.
We are experiencing something similar to this in my street. Low voltage during times of high load for the last two years. The DNO are finally addressing the problem and although they claim it's an earth problem (in laymans terms), I suspect they mean a fault on the CNE.
Please upload more videos, Thank you.
Very valuable knowledge for students.
Very happy to see you post again! Top notch!
Greetings John, good job.
Excellent info as always John. I used to work for an electricity meter manufacturer and we often fitted a small phase failure indicator in our induction disc three phase instrument transformer operated meters that basically worked on the principle you describe here. The main concern was losing a phase in terms of potentially lost revenue 😎👍.
Thanks John. A great video and your usual crystal clear explanation.
thanks again John.
Thanks John. Very informative.
Thank you John.
Brilliant explanation as always John 👌👌👌
Good content in a concise manner.
Yup, clear, concise and accurate. Thanks JW
Thank you!
Welcome back. Great to see you again.
Cheers John.
Great video John - as always …👌
In Germany, residential buildings are usually connected to three-phase current.
Three phases and PEN. There is also the foundation earth elektrode that is connected to PEN.
Then N and PE are separated. Lights and sockets are then connected to 230V.
The electric stove is supplied with 400V three-phase current.
But the oven is one 230V device. Two hotplates are connected to 230V in the second phase. Two hotplates are connected to 230V on the third phase. This only requires 2.5 mm² wires, 3x 16A.
But you definitely need the N conductor because otherwise the voltage will shift.
However, the PEN must never be brocken!
Therefore the PEN must be at least 16mm².
Or separate N and PE connected after the electricity meter.
Old installations with common thin PEN have not been permitted for years.
Car chargers are also connected in three phases. Mostly 11kW
Requires an N conductor because the car rectifies the three 230V phases to DC.
Agreed.
Internal PEN interruptions(break/anomaly) are not as Catastrophic as External(LV Network) CNE interruptions though.💥😮
Stoves get the three phases but they are in a star connection so the actual 400 V is not used, instead the hotplates get 230 V. This works better in systems that hae various power settings. Also it is possible to run it with single phase by connecting the three inputs together. This typically means you are limited in the total power.
@@okaro6595I understand its somewhat for Load Balancing within that premises supplied 3Phases?
@@temp26j724-i Load balancing is mandatory when you have to deal with a residential feed with 3 phase+Neutral. If you have a subscription for 9Kw you only have 3 per phase, so if your stoove is a 9Kw one you must spread the load on all phases. Usually the oven is 3KW on one phase, a small 1Kw and a big 2kw burner for the second phase and again small and big for the third. Note, in some place in Belgium, it's 220V phase to phase with 110 Phase to neutral. So it's wired phase to phase, in this case the neutral lost have no impact as 110V is not even available on any plug.
He lives!
Good video along with a great explanation. Some years ago my property along with a few of my neighbours suffered from a negative line fault. Basically anything that was plugged in blew up.
Excellent content as always, welcome back.
Been waiting for this =] Great video as always.
I first read this as "Diverted NEURAL current..." and was confused. I spend a full minute reading the title and trying to see how three phase power fit with anything neural. 😅 Great video though!
Interesting comment you made about 3 phase/400v gear being uncommon in residential or even a lot of commercial buildings. When I lived in Australia, 3 phase to a residential premises wasn't uncommon (it wasn't the norm, but it could be easily be requested if the street had 3 phases (not all do)), and in fact I stayed in a home where various circuits were split across at least two of the phases. The residence also had a ducted reverse cycle air conditioning unit that cooled/heated the whole house, which required all 3 phases to operate.
Every house but one that I've lived in Australia has had 3 phase.
The king is back
🙏 thanks for sharing with us. I purchased a Dual Display 40A 63A 230V Din Rail Adjustable digital Over Under Voltage device but I did better than that by creating my own micro-grid providing me with 10kVA from two clean sine wave inverters and 37kw of self built battery storage so my energy should be a lot cleaner and safer than that of the grid. However, since i've adopted an automatic contactor relay which detects a potential loss of generation and reconnects the building to the grid, I have also used a contactor relay that separates the two neutral/earth sources in order to avoid problems especially in the unlikely event of lightning which might create a gradient of very high voltages across the ground that could be very different between the two earth electrodes which are more than 30m apart. Do you find this the correct procedure ?
I suppose the TNCS systems seemed like a good idea when fuse protection was all that was available, and you needed a very low resistance earth path to actually blow the fuse. These days with RCDs/RCBOs surely TT should make a comeback?
It could - but with TT in a modern installation you are relying on electronic devices (RCD/RCBO) to disconnect.
With high current earth faults and circuit breakers it's a mechanical device operated by a magnet.
I would have thought that with smart meters a voltage monitoring function could be could be built in to quickly detect faults.
In event of a out of spec input voltage it could automatically flag a warning and possibly even disconnect as well. In addition a remote voltage monitoring facility could be useful to identify problems in an area.
Problem now is many appliances use switch mode power supplies such as lights TVs, computer etc so unless the input voltage goes below the minimum operating voltage (often below 100V in many devices) or exceeds the maximum voltage rating of the devices then many people would not notice as the device works normally. Many could tolerate for some time a considerable over voltage before failing.
Super, thanks! Would an installed surge device give any protection against those persistent over-voltage situations caused by broken CNE?
Up to a point - however with a long duration of overvoltage the SPD will conduct continuously, heat up and fail. It might cause the fuse or circuit breaker upstream to open, but whether that would protect anything depends on how long it would take, and whether it was for the whole installation or just for the SPD.
There are dedicated overvoltage devices available which would disconnect such as www.dehn-international.com/store/p/en-DE/F440777/spd-pop-mcb-pop-mcb-pop
Hi John,
really interesting watching your videos. I was quite interested in the earth rod recommendations (I think in amendment 2 part 4). Like you say many other country's have this anyway. I wonder what your opinion is though, if say you have a TN-CS system and you go to the trouble of installing an earth rod (and have 30mA RCD on all circuits as it is almost always required), then why not just change it to a TT (earth only connected to the rod)? If there is a neutral fault on the incomer and it rises to live potential, then st least everything in the house remains at earth potential. And - if it is better to use the DSOs neutral as the earth (together with a earth rod), why not in a TT system connect the earth to the incoming neutral?
To convert to a TT system can often be done, but in many installations it's a lot more difficult than just shoving an earth rod in, and it may not be possible at all. See th-cam.com/video/S5OtLg6voZY/w-d-xo.html for further details.
If you connect the earth electrode in a TT installation to the incoming neutral, it's not a TT system any more.
@@jwflame Thanks John, just watched your other video, that explains a lot.
Dead right to bring this up, especially now with so many electric cars in use, this situation could potentially result in a car body on charge becoming very LIVE and deadly. And another thing that concerns me a bit is that there's likely to be some folk seriously overloading old 1920's or 30's vintage service cables where they already have lots of big electrical loads like an electric cooker, tumble dryer, shower etc. and then they add a dirty great BIG, say 20Kw EV charger, that could potentially burn out someone's neutral and create a deadly situation. And some folk think they know about electrics... This is why proper training or at least some serious theoretical study is so essential. Perhaps the government should make surge protection a necessity in domestic installations now.
here where i am, we have a TN-C-S system: the distribution side is 400/230 V TN-C aerial conductors and the consumer side TN-C-S system (single or 3 phases, depending on the needs).
by the norms, the electricity provider needs to ground (connect it to earth) the PEN conductor as often as possible and on the consumer side, where the PEN separation is done (PEN to PE and N), we have to bring an earthing connection (or electrode rod connection how u call it) that is needed to have a resistance (impedance) under 4 ohm if is only used as shock protection or under 1 ohm if is combined with the lightning protection. does a low value for the earthing system resistance make any difference in this case (broken PEN)? or what is the reason for this values?
oh, i forgot! and we also are forbidden to put any protection or separation device on the PEN (or PE) conductor - it need to be uninterrupted from the case of the appliance all the way to the transformer.
Can you do another video explaining what would happen if you had a big 3 phase generator (say 80Kva) and the power / current draw was really badly balanced over the phases
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Would the power company reimburse any damages if this happened to domestic properties?
They will, but how long that takes and what people actually get is another matter.
This would/should be caught by the G99 protection via vector shift at network operator side.
So would an AFDD detect this (or at least the over voltage symptom) as it has over voltage protection? I guess the disadvantage is that it won't disconnect the PEN?
AFDDs should detect this and disconnect the circuit, which could protect equipment connected depending on the disconnection time.
@@jwflame Many thanks John. It's not something that they talk much about with AFDDs, over voltage protection is just a passing statement.
I am pretty sure that we had this type of fault at our house earlier this year, but got an undervoltage. It started with a power cut, but then, a few minutes later, I noticed that some neon lights were glowing faintly and a mini dehumidifier, fed from a AC to DC adapter, was running, but it made a funny sound like the motor was going really slowly. I then switched off all the AFDD RCBO, except the kitchen, which had already tripped, and a lighting circuit, so I knew when the power was back on. When power came back on, I reset the breakers, and I think the kitchen one showed self test fault, although it was hard to tell with the pattern of flashing. The SPD was unaffected. Neighbors reported similar effects to their lights.
About two weeks later my fridge freezer stopped working. So I wonder if it was damaged by an undervoltage caused by what I think was a lost neutral. Apparently undervoltage can be just as damaging to some appliances, such as those with motor.
I have brought a Sollatek FridgeGuardiS to protect my new fridge freezer, you just plug through it like you would a smart plug. Obviously only protects one plug but easier than getting an electrician to install something at the consumer unit.
I was thinking a Ze test would flag up a broken PEN conductor, as if the PEN conductor was open you would be measuring the resistance of the other loads on other phases even if the phases were perfectly balanced the loads in most case would be higher than the 0.35 TNCS limit
It would in many cases, but not all - all depends on what else is connected and particularly any additional earth connections to the PEN via metallic service pipes, metal framed buildings and similar.
Can you have a 230v 3 phase delta supply into a premises. If not, why do most motors provide for a delta connection. I know it's convenient for inverter supplied equipment, but even old motors before inverters often have the facility
230V 3phase Delta Supply?🤔
@@temp26j724-i Only thing that comes close is a USA 120/240 system, where 3P+N delta would be 208.
When it's about 3 phase for a premise, the secondary of transformer is ALWAYS a start "Y" in order to provide neutral for protection
A 3 phase "traditional" squirrel cage motor mention the voltage on his plate. like 220/380. then you wire it accordingly to the tension you feed it with.
So if you have 3 phase 220V you must wire it delta "Δ" if you wire it star "Y" it will not be able to deliver all it's power and will surely burn.
This under voltage was used to provide a "gentle" start, but it last less than 1 or 2 seconds.
If your voltage is 380 the coupling will be Y.
And for a plate showing 380/660 the coupling for 380 is Δ !
When you use an inverter, the inverter supply the voltage to the motor but never higher than the input.
Inverter convert main AC to DC then recreate AC. The input of an inverter may be mono or tri. If inverter is a single phase one, the input voltage is 220 and so is the output, so the motor coupling will be Δ for a 220/380 motor (this cannot run a 380/660V motor)
@@Phantom-mk4kp Im sure you are asking if DNO would provide PolyPhase (3ø 400V) supply into properties.
Yes they will subject to conditions.
What JW meant is Residential properties typically gets only 1ø as the need does not arise (apparently though) for application to DNO for PolyPhase supplies into Domestic properties...
@@temp26j724-i No I knew 3ph was available, in fact I answered my own question after reading it back and thinking about it, delta or star is not so much a supply characteristic but how it's implemented at the load
Why on earth (no pun intended) did the DNOs decide to start installing PME supplies? Was it a cost-cutting measure? Seems so stupid to me. Why not just have a good old-fashoned TN-S supply and not have any of these problems? You even have to treat TN-S as TN-C-S now as it has probably been combined in-line anyway or will be at some point.
100% because it was cheaper.
¿ Do you have delta 3 phase in the UK? In the US we have both wye and delta.
3 phase can be connected either way, depends on what it is being connected to.
The 3 phase supply is the same regardless of how it's used, and obtained from a Y / star connected transformer with a neutral.
I suppose a delta‑only system (no neutral to loads, the transformer common connected only for protective earth) would have been more failsafe; perhaps that's one of the reasons Δ3×220 was historically common in much of Europe. Italy once implemented a similar system, but using the 127V phase-neutral for incandescent lamps (which work more efficiently at the lower voltage); no great catastrophe if the neutral broke there.
But then most of Europe moved to 220/380 (now 230/400) to reduce transmission losses, and unwilling to change the appliances to 380V, they stuck the 220V appliances between a phase and neutral.
If we had to do it over from scratch, I'd prefer Δ3×400 or thereabouts; small appliances would be slightly more expensive but still not overly difficult to make (most cords are already rated for 500V line-line), and the grid could be TN‑S at lower cost than current 230/400 TN‑C‑S (by using a smaller PE core in place of the large CNE). Smaller grids could use balanced single-phase (400V line-line again, 200V line-earth).
I suppose power companies could still have cut corners by corner-grounding the system and combining the grounded phase with protective earth, though… Not that we can do much else about the current situation.
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"There are no domestic items using 400V" - what about bigger induction hobs/ovens, those have three phase mains connections
Not in the UK.
UK homes don't have 3 phase and cooking appliances are single phase.
My inverter is supposed to throw a fault in such a situation
Oooh is this the kind of fault Nick Bundy saw earlier this year: th-cam.com/video/siHx-zaY1uE/w-d-xo.html
Yes
Decrease the repetition - all good, all clear
Though you died.
Great to see you back John