This video is outstanding! You begin by listing what will be covered, and use imaging and written diagrams so we can follow along easily. Very well done tutorial.
I have tried to get an explanation for years but was always left guessing or not quiet trusting the explanation. This has finally solidified and makes everything tangible. Thank you so much for this.
Excellent video! I am embarrassed by some of uninformed (ignorant) comments by other Americans. You very clearly noted your invitation for experts in the North American grid system to fill in gaps. That is a far better approach than possibly providing erroneous information on this important and potentially lethal topic. Thank you.
Thank you for the highly informative video. It's amazing that 3 phase power is supplied to ordinary residences in Germany. Obviously, that drives up the cost of building and maintaining public power facilities, but it is probably less expensive in the long run because homeowners can then use 3 phase motors, which are less expensive, more efficient and simpler than A/C motors that are designed on operate on single phase power. In the USA, it is extremely unusual for 3 phase power to be available at an ordinary residence. It is normally available only in commercial and industrial areas. It is also provided to large farms that need to operate very large motors that run pumps and load silos.
Do the washing machines, clothes dryers, dishwashers, furnaces, and other motorized appliances in Germany actually have 3 phase motors in them? And if that is the case, what sort of outlet is used to bring 3 phase power to them?
You are correct about the "split phase" systems coming into American homes. Once it hits the home, you have the split phase 240VAC and a Neutral return line. At the power distribution panel (breaker box) of the home, there is a neutral buss bar which connects directly to the ground (earth) electrode. The split phase 240VAC is then connected to two breaker rails inside the panel. I forgot to include the electrical KWH metre, that comes before the breaker rails so the power company can monitor how much power you are using. Anyhow, for your 120VAC wall sockets they go from phase to neutral with a separate earth line going all the way back to the breaker panel and connecting to the neutral/earth buss bar. For your larger appliances (Dryer, Hot Water heater, HVAC system, Ovens) and so on, these are hooked to the split phase breakers which span between both breaker bars inside the panel. These as well have an earth wire. I can explain this much easier with a schematic if you wish. Hope this helps mate!
Excellent video. Fantastic explanation. In the USA in some states ( Mid-West e.g. Kansas, Oklahoma ) the primary distribution Voltage (7.2 or 14.4 kV) if often 4 wire Y configuration. with one Earthed High Voltage conductor. It may be because of the thunderstorms encountered in those areas. Also SWER systems can be employed without an isolation transformer. The House Voltages are 120 - 0 - 120 Volts. or 240 Volts 60 Hz between the outer two. Look forward to part 2.
Hey thank you for the info. I could imagine that there are a number of different systems to be found in different parts of the US ( just as you described, when talking about typical climatic conditions in the Mid-West) I have read about the SWER ( Single Wire Earth Return) system, but I thought it was only used in Australia. Good to know that it can be found in parts of the US too. In Germany we don't use it at all . Our country has a very well developed infrastructure and virtually every household has 3-phase AC. But that's mainly because the country is much smaller than the US. Supplying every household in your vast country with 3-phase AC would be an undertaking of epic proportions.
The Post Apocalyptic Inventor No worries. The SWER systems are used in Australia and New Zealand for remote locations. Voltages are often 11 or 19.5 kV single phase, In that part of the world they are fed from a 3 wire system and require an isolation transformer, otherwise the feeder would trip out on Earth fault. In The USA set ups vary from State to State, In Texas there are SWER systems 20 to 30 miles long with lightning arrestors on each 3 rd or 4th pole in case of lightning storms to protect the transformers from Voltage surges.
Great video, thanks! You are correct we use SWER systems here in Australia. It is very common, even just a short distance from the major cities (like Melbourne) in the rural areas. As it supplies farm houses, they generally have small workshops, also. It makes it hard as they often require 3 phase power for heavy machinery, so quite often they will require their own 3-phase generator for these loads. Phase converters are also sometimes used. It also sometimes causes an unexpected problem for pilots of helicopters and light planes (like myself)! As the power poles are spaced quite far apart compared to a normal transmission line, it is almost impossible so see where the wire is, many light planes and helicopters who are landing on a farm airstrips or making an emergency landing in a field, have struck the SWER lines and crashed.
Standard US household wiring is this: 110 - 120 volts: Black - Hot White - Neutral Green - Earth 220 - 240 volts have a couple different color codes: 30 amps Red - Hot 1 Black - Hot 2 White - Neutral No ground 50 amps Red - Hot 1 Black - Hot 2 White - Neutral Green or bare - Earth In some occasions the black may be blue in 220 - 240 volts wiring. I know some people say the US needs to change over to 230 volts and though it looks good on paper the reality is the residential grid cannot support it because it was build designed around what we have now, The sheer cost and man power to change out every transformer and fly new line would be amazingly expensive and not financially responsible in a country that is going down the economic toilet. There would be massive increases to power bills nation wide to cover the cost of the upgrade. It is best to leave it as it is, It's not broken so no need to fix it.
Fantastic video. I found several things very fascinating about how you, Germans, treat your power system. Here in the U.S.A. residential clients do use a split phase system with a center tapped transformer. The primary winding is connected to 2 legs of the 3 phase lines, which are usually about 5kVrms in residential neighborhoods. The 2 legs of power distributed throughout the home have opposite polarities and add to 240Vrms when connected together and 120Vrms with respect to ground. Typically high current loads use a connector with both power legs and a ground, sometimes they also include the neutral. Commercial clients will usually have a 3-phase star/wye transformer secondary with voltages of 120Vrms with respect to ground and 208Vrms from line-to-line. Industrial factories or workshops will sometimes have voltages of 208/410Vrms. Also, you may occasionally see a High-leg delta secondary with voltages of 120, 208, 120 with respect to ground. This uses one grounded center tapped transformer in the typical Delta configuration. The neutral conductor should only be bonded to the safety ground at one location, usually right after the service entrance. I found it interesting that your system actually uses a ground point at the pole as well, since this could cause unwanted telluric currents to run along the neutral line between the two ground points. Additionally, to be UL listed all isolation transformers must be grounded on the secondary wiring. I also found it intriguing that all of your circuits are GFI protected. Here only outdoor outlets and ones installed near water must have this protection. They also must trip at 6mA. Do you encounter any nuisance trips with single phase motors? Again, thank you for the video and cheers from across the pond!
+Joshua Mudge Also all electrical installations which are located in open places such as lights and sockets are supplied from transformers 240/240 for greater safety of people.
Hi. Very well presented and explained. I live in France and here there is a mix of single and 3 phase supplies to houses. Though most of the new builds have single or mono phase. The incoming supply (unlike the UK) does not include an earth, this is provided by an earth rod located near the "fuse box".
Here in the U.S. most homes have 2 phases going into the home. Only high-load devices like furnaces and clothes dryers use 2 120v phases together for 240v. Everything else is connected to one 120v phase and a neutral. There is also a ground conductor in outlets and light fixtures which is connected with the neutral conductor at the panel. Most homes have circuit breakers, fuses are in older houses. Newer homes might be built with whole-house GFCI(our term for RCD) systems but I don't know if that's common. Most existing ones don't. They are usually found only on a few circuits, such as the one feeding a bathroom.
Thanks for the great video! Regarding power in the US: residential service transformers take just 1 high voltage phase, with a center-tapped secondary as you described. The other end of the primary is earthed for the return. This is why -- particularly at the end of a pole line in rural areas -- you will see poles with just a single high voltage wire at the top. An interesting facet of this system: the center tap of the secondary and the "low" side of the primary are bonded to the same earth ground. If that ground is broken or is insufficient that can lead to stray current coming into the house on the neutral...! FYI, In the US we call an RCD a "GFCI" or "GFI" -- ground-fault circuit interrupter.
+jruser I had the experience of just that, a high wind took out a tree in the neighborhood and as I stood in my home the lights went out and a very strong 60Hz hum was heard coming from the basement. I figured it had to have been the neutral ground receiving that "high line" voltage flowing through the water main out to the street. This area is served by one wire and the system neutral as you described. The event didn't last long but the sound emulated what you might have imagined as the wires came together, sparking and humming. When I say this was loud it was VERY loud. To this day I can measure about 2 amps flowing between my load center box ground and the water main ground. This will be present even with no loads running. I never opened the connection to measure the voltage. There is a ground rod connection just below the power meter as well, so that should not be an issue.
I've seen two of your videos and very much enjoy them! Keep up the amazing videos! If I knew more about our transformers here in the US I would let you know. Fantastic video!
Probably the best video I've seen on UA-cam, certainly the best in a long time. You've cleared up a load of questions I had about how the electrical grid works. Do most houses in Germany really have three phase power? In the UK it's very rare to have a three phase supply, most have only a single phase coming to the house. I have three phase but I've wired the house to a single phase. I asked an engineer from power company about balancing the load on the phases and he said they don't care for the sort of current draws a house is likely to put on the system.
CNCtrl Yes basically every house in Germany has three phases available. Most people don't have 3-phase sockets in their houses though. But household equipment like electric water heaters, ovens and storage heaters are almost always powered by 3-phase AC here in Germany.
The Post Apocalyptic Inventor Interesting, what size of fuse do you have on each phase? A modern family house in the UK would typically have a 100A fuse but 80A and even 60A fuses were common in the past. The biggest draw I can think of for a typical house would be an electric shower at around 40A so there's still a lot of headroom on a 100A fuse.
The two 300 VA transformers I will use (identical) are 240 V primary with two 10 V secondaries . I will check out your upcoming video . Thanks for your help PAI , greetings from Sydney , Australia !
PERFECT! Just the stuff I was trying to know more about lately :) because I bought Rigol osciloscope I got into Isolation transformers :) Danke schoen from Slovakia.
I haven't read all the comments, so if someone has already answered this please excuse me. For your North American diagram where it enters the house -- Power enters "distribution panel" of a house as three wires off of the "distribution transformer" you have labeled in your diagram, and the two hot lines are 120V, 180 degree phase offset due to the center tapping. If high power devices are used (ex. electric range, clothes dryer, restaurant ice cream machine, welding equipment, etc.), they usually require 220-240V and are connected across the two hot lines. Otherwise, the circuits of the house are typically split roughly equally among the two phases. To be strictly legal, a third ground wire connects all equipment chassis together, and to earth AND neutral at the distribution box, however, in practice, a LARGE quantity of homes are grandfathered as two wire without even regard for polarity of live vs. neutral. Grounding is sometimes overlooked and chassis are connected together. It can be quite interesting in the event of a fault... GFCI outlets, or GFI (ground-fault circuit interrupters) are required in wet locations such as bathrooms or outdoor outlet installations.
Crystal clear explanation. Truly useful, well planned, complete and captivating explanation. You are a gifted teacher. Living in Greenland means we share in the inherited "Danish" system which is European in character. One question. All water services in the house are connected to earth and as far as I can see this earth consists of a connection to a bare copper multistrand wire cast into the concrete and connected mechanically to the steel reinforcing in the concrete. This is then connected to the equipotential earthing bus bar in the fuse box cabinet to which all yellow-green lines are connected, one from each cable leading to a socket. I'm a bit confused on how PE and N are connected. Where can I see that the Neutral and PE are separated "inside the house" as you state? Is there some isolation created between the two? Again, great video. I'm impressed, and looking very much forward to the next in this series. Thanks from a complete beginner.
N and PE are basically the same. If you use copper wire with high currents for a long period of time i can occur that the connection e.g. at an insulating screw point is getting loose (due to thermal stress etc.). So as you can see if you would use the same wire for N and PE it can happen that someday you have no connection to N/PE, but to your Phase! (Which might be pretty dangerous for humans in most cases if undetected).. To prevent this, you use two separate wires for N and PE, the N wire is the "stressed" one. The PE is the "backup", which is normally unloaded, and because of this, theoretically excluded from the connection faults as described before. I hope this will help you to understand the meaning of PE and why it´s basically the same, but not the same ;)
In old installations the split with done inside the socket to save on copper wire! A problem with that is: any current through a wire will cause a voltage drop. Since there can be quite alot of current flowing through the neutral wire (imagine using water cooker for example), the neutral is no longer at the same level as it is in the breaker box, but a few volts higher. If N and PE are the same wire, that means your "Earth" level varies with the load. That's especially annoying if you connect different devices like a computer and a stereo for example, that are connected to outlets at opposite sides of the room. You can check the voltage drop yourself btw., if you have a (safe) multimeter. Get a high power device (in essence anything that's heating something) and plug it into an outlet that has a second outlet immediately adjacent or use a three way adapter cable. Measure the voltages to between the wires and to PE in one socket while you turn on and off the load in the socket. You should see the voltage drop.
hola que tal saludos desde Mexico, solo para felicitarte por tus videos, son muy buenos sobre todo tus explicaciones, diagramas y dibujos, todo es muy bueno
I have just discovered your videos, and have spent this evening watching many of them. They are fascinating and very educational, thank you. In this video about the Power Grid, you describe all 3 phases going into the home. Is this standard procedure in Germany? I ask because I do not think this is standard in the UK, where I am. As far as I know, UK homes only have one phase to each household. Of course, larger offices, factories etc may have all three phases, especially if they have 415 Volt equipment. I do not know of any 415 volt equipment for a typical UK house. Of course, the UK has some historic quirks with electrical wiring, but it surprised me to hear that maybe Germany has all 3 phases at every home. Thanks, Ian
SheddyIan Hello. It's nice to hear that you liked my videos so much :) Yes in Germany the power grid is a 3-phase system from the power plant all the way to the single houses. 3 phase power is available in virtually every home. Electric ovens and water heaters are 3 phase loads, which you will find in many households in Germany. People like me, (who like to use power tools), often have special 3-phase outlets in their garage, basement or home workshop as well. Like in the UK normal living rooms only have single phase AC and consumer products are almost always designed for that in Germany as well. People without a home workshop or any special use for heavy power tools etc. do often not have any of these 3-phase outlets, but they could easily be added, because the 3 phases of the low voltage grid lead into their house and are available inside the breaker box (= home distribution board). Even if a house does not have any 3-phase loads at all, the single phase electric outlets, the lighting and other loads are connected to the 3 phases and the neutral in such a way, that each of the phases is loaded about equally. We do that to avoid asymmetrical load conditions in the power grid. Germany has a very well developed infra structure and it indeed seems to be the case, that in many countries, 3-phase AC is much less available than here. To find out more about the situation in the UK, you could for example open your breaker box and check, if the 3 phases lead into your house or not. Furthermore I recommend you to check an electricians training book from the UK. Please tell me, if you find out more. I would be interested in knowing more about the situation in your country.
The Post Apocalyptic Inventor Hi, I am sorry to be so slow replying, I have been asking around for some information. I know that in the house I currently live in there is only one phase coming in to the fuse board. (My house and wiring is old enough to only have fuses, not breakers!). I have also spoken to a retired electrician, and he tells me that he does not know of any houses that have 3 phase, only factories or commercial properties with a larger load. Load splitting between the 3 phases is done at street level, so on a typical street, house 1 might be 1st phase, house 2 might be 2nd phase and house 3 might be 3rd phase, house 4 being 1st phase etc. Electric water heating in the UK is usually done with a storage tank, which has a 13 Amp immersion heater installed on a time switch to run for a few hours each day to heat the water, sometimes taking advantage of a cheaper overnight tariff to heat the water for the next day. Although many British homes use gas to heat either a hot water storage tank or to provide instant hot water with no storage. Electric ovens and electric instant hot water showers also just use one phase, and are usually rated at 45 Amps or so. On a side note, British electrical wiring is different to other countries, in that we usually use the ring-main system for electrical outlets. The cable leaves the distribution board, and is connected to each outlet in a daisy chain before returning back to the distribution board again. In this way, a smaller cable can be used (2.5mm) and yet still provide 30 or 32 Amps of maximum current to each circuit. (Each outlet being rated at 13 Amps). Lighting circuits are wired radially, using 1mm or 1.5mm squared cable. I hope this is of interest Ian
SheddyIan Very interesting information. I live in Denmark and our wiring is identical to the german 3-phase system. With 3 phases at hand in the house, all installation wiring can be made with 1,5 square millimeter cable. Even an electric cooker can run on a 13A group. The only place i have a (5 x) 2,5 mm cable is to my garage, because i work with a 250A Esab mig welder, demanding a 16A fuse group. The supply from the cable box in the street is a 4 strand 16 sq. mm cable, fused with 63A. The ground fault relay (hfi in danish) is mandatory.
How does current flow from the neon test light through the body to ground when the body is touching the non conductive poly-carbonate handle of the test light?
+Sam Cummins Well normally it only should light up, when the metal tip at the end of the tester is touched, as I demonstrated in the video. I also have never seen any of these testers light up, when only the plastic handle is touched. If the neon test light would still light up without the metal tip being touched, it again could possibly be explained by capacitive coupling, with the poly-carbonate acting as a dielectric. But with a typical mains tester as shown in this video, when being applied to a 230V line, this actually shouldn't happen. What kind of tester are you using?
Great video, especially the part about the RCD. I did a video about isolation transformers myself some time ago,but compared to yours, mine is utter crap. :)
What a coindicence, I've been tinkering with isolation transformers recently as I make off-line switching power supplies, mainly just so that I can safely probe the primary side of the converter with a ground referenced oscilloscope without damaging anything. I made my own isolation transformer with a cheap old 3.3kVA (at 25% duty cycle; 1.5kVA continuous) centre-tapped earth 240V-115V (suprisingly not a 2:1 ratio) building site transformer. I was trying to rewind it to have 2 secondaries, 115V and 230V but that didn't work out. In the end I just cut the earth centre tap so earth passes straight through to the output without going to the transformer. I hadn't considered how it would make the RCBO ineffective. I've accidentally touched a live wire that was supposed to be off before and all that happened was the RCBO tripped and my arm was thrown away. I still haven't found the screwdriver tip I was holding. I've also tapped off a 380V DC PFC bus capacitor in a ATX power supply for testing SMPS that will later have PFC preregulators added and debug the 2 separately. I know almost nothing about house wiring, but it seems in USA they have 2 phases and a neutral to their house, 120V is phase-neutral, 240V for big appliances is phase-phase. In UK we seem to have 3 phase 400V up to a street and then only 1 phase 230V into the house, with different houses getting different phases to approximately balance the load, but it may vary in different areas. We also have a ring mains system in the house which means all wiring connections are accessible behind plug sockets but its really difficult to know where a wire goes after it disappears into the wall. I disconnected a wire that should have cut off power in my living room but it was being pulled up to live through the transformer primary of my microwave in the kitchen. It's also why all our mains plugs have 5A or 13A fuses in the actual plug as well as in the device.
***** But having high voltage lines increases efficiency. I'm sure there is a reason for having any small transformers than larger ones. Again--Likely because you can more easily transport high amounts of power at high voltage with less loss than you can at low voltage. This is why we use dangerous AC voltages in the first place and not something safe like 12 volts.
+Kris S If using low voltage, eg 12V then you will need biger wire gauge. If there has toaster 2000 watts with low voltage 12 volt is 2000/12 = 166Amper. For 240volt is 2000/240 = 8,33amper. In the first case it needs cables 2GA for second 8GA. the problem in the US is the low voltage 115volt.
telosfd Exactly. Low voltage = more heat and bigger wires. 120v is the standard and changing that now wouldn't be easy--Plus, the danger goes up with the voltage, so a balance is needed. Otherwise we would just run our houses off of the mains 600,000 volt lines that go through the countryside.
+Devranjan Das its probably mostly used to ground the core of the transformers, if you have ever seen someone making arks from the core of a microwave transformer, the ark is jumping from the core to a ground wire.
diething1 Well my friend. I'm sorry to tell you, but there is no easy way to accomplish what you're asking for. My advice is to start with the simple things. Maybe you should start by buying an electronics book for hobbyists. Something from the 70s or 80s. back then things were simpler than they are today and learning electronics started with resistors, capacitors and transistors.( Not with microcontrollers and FPGAs like today :D). Back then many people who weren't professionals wanted to understand electronics and there was a big market for books and magazines, teaching the basics of electronics. The stuff from back than is still good and often not very expensive. (You could even check the local libraries). Books like that can give you a feeling, of waht kind of basic components exist and what they do. Once you understand the basics you can work your way up to a more professional understanding. As an addition to the practical knowledge taught among hobbyists, you have to learn how to apply basic mathematics to electric circuits. Principles you must look up and learn to understand in any case: Ohm's Law, Kirchhoffs's Voltage Law, Kirchhoffs Current Law, component equations for capacitors and inductors. Once you know these things, I would recommend to buy an electricians training book. It will help you to understand the basics of AC-Systems, without the need for higher mathematics. If you want to get an even deeper and more general view of electronics you would have to study electrical engineering. You could again try that by reading books, but that alone won't work. You would have to spend a lot of time learning mathematics and how to apply it in the field. That can only be done by actually doing a ton of calculations. It can only be learned by practicing. That is very hard, if you have no instructor. If you wanted to do that on your own you needed several very good books, having both training exercises and solutions with explanations. But books like that are as rare as anything. Studying at university might provide you with a lot of exercises and instructors, but the things you learn there are very theoretical in nature and most people need many years to finish their studies. Still many leave university with a feeling of ignorance. There is no easy way.
American pole transformers has only one high voltage input with one fuse, but there's no protective device at the output of the transformer. Correction - some transformers have 1 high voltage input, called CSP type.
We here in U.K do not get 3 phase into our houses, there is 3 phase out in the street and then every house gets it's own phase, thus, if there is a fault at the substation and 1 phase goes down, you might lose half the street lights, and one third of the street (not all the houses together, but say every third or forth house, or alternate houses across the street) will lose power! Saying that though we are in a 1950s house and all 3 phases do come in and are fused "on the supply side" and only one phase is "tapped" hope this is of help to you explaining how it works in the U.K?
Sometimes when I turn on my stereo power amp it trips the RCD, do you know why that happens, and what I could do to prevent it? Thanks for your interesting vids.
yeah, watched that vid after the first and felt a little stupid for asking the question, however, if that is the cause, is there a cheap and simple way to deal with it, preferebly without having to open up the amp and mod it internaly?
+dunkelheit843 If it trips the RCD then try to use a power cord without a neutral wire in it and see what happenes. Don't touch the chassis though if it's made of bare metal. If it works, there may be a badly designed emi filter in the amp. If it's not actually the RCD that is tripping but rather a normal fuse in the fuse box (make sure), then I bet that is a very powerful amp with no inrush limiting implemented. Also, I'm sorry if that is a cool sounding amp and it gives such headaches.
thanks for the advices, it's defenetly tripping the RCD. However I've got it plugged in via a remote controlled powerswitch (nexa brand) and I've noticed it only happens when I turn in on using this device, however if I use the powerswitch built into the amp I haven't gotten it to trip the RCD, so there's something wrong rather with this combination of amp and remote operated powerswitch.
Just some small corrections. The two phase power entering a US home is 240v with reference to ground as each voltage is 180 degrees out of phase with each other. Your diagram showed 120 Volts in relation to ground measured across both phases. You probably meant that each phase measured by itself in relation to ground is 120 volts.
roomba The arrows in my drawing are simply pointing to the two conductors and are supposed to mean that the two points the arrows point at have a voltage of 120 V with reference to earth ground, not that there is 120V between the two conductors. In that case I would have drawn a voltage arrow between them instead. I'm not an expert for the American system, as I said in the video. But from what I have read, I find your statement somewhat confusing, so help me out if you can: The distribution transformer is just a single phase transformer with a grounded center tap at the secondary. The voltage between each end of the transformer secondary and the center tap (earth ground) is 120V AC. With reference to earth ground the voltages at the two ends ( or "phases") are 180 degrees out of phase because they are to opposing ends of a secondary winding. Between the two ends you would then measure 240 V AC, but that voltage only exists between the two "phases". But the way I see it, there would only be 120V AC with reference to earth ground at any given point on the secondary side. Am I missing something ?
Resistance of human body. Right. But it is not so easy. Actually there is big influence of capacity of skin and body and also if you are insulated from ground you can still recieve electric shock, because you still can have capacitive coupling with ground. And also this values will change after some time from begining of shock and current will go up. If you using this neon light testing screwdriver, you also can stand on insulatin surface, but neon still glow. Because of capacitive coupling between your body and ground.
xxJerry19xx Yeah capacitive coupling can be a tricky thing. These kinds of testers are actually not used by any professional I know and you shouldn't trust them, but it's a good way of showing people what it means to have an earthed referenced grid.
Hi PAI . Have you built a variac into your isolation transformer ? (shown in the video) . Hope to see more details of the transformer . Great work on the vids mate , your English sounds very cultured to my ear . Regards .
Im thinking of building the same (transformer) . Should it be wired as Mains then Isolation then Variac or a different layout ? Also the 300 VA transformers I will use (from salt chlorinators) have 2 secondary windings (4 wires) that were connected as 10v 0v 10v (to SCRs). Should I connect these secondaries to the other 10v 0v 10v ? Regards and thanks , Steve .
Steve Smith You have to connect the isolation transformer to teh mains and after that you attach the variac to it. I will talk a lot about the details of my isolation transformer in the next video. The video is now to 75 percent ready and it will gon online withing the next week. It will help you to get some orientation. I don't quiet understand what kdnn of transformer you are using ? Is it a "1 to 1" transformer that delivers 230 V at the output ? ( Or 115V if you live in the US or Canada). Are the 10V-Secondaries additional secondaries or are they the only secondary windings ? If they are just additonal windings you can either leave them alone, you can connect them in parallel (polarity is important !), or you can connect them in series to get +10V /-10V or 20 V
Of course the RCD is not just a breaker box and I didn't say that. I said that it measures the sum of the currents passing through. I simply spared an explanation of how an RCD works in detail, because that is not the topic of this video, which is already 25 minutes long.
+David divad Wood and concrete are conductive! They are very bad conductors, but they are not ideal insulators as well. If high voltages are present the currents that will flow, can still be high enough to harm you. Furthermore: Alternating currents can flow through your body due to ''capacitive coupling'', as I mentioned in the video. A layer of material with low conductivity between your body and an electrode will act like the "dialectric" inside a capacitor.
+David divad It depends on the voltage between the ground and the "live" wire. If it is a high voltage line and you jump in the air to reach it, then your body will provide a path of higher conductivity than the air that normally separates the wire from the ground. If the voltage is high enough, the free space between your feet and the ground (while you are jumping), will possibly be arced over by the current and you will be fried. If we a talking about a 115 or 230 V wire however, it is very probable that nothing serious will happen to you, since the voltage is to low, to ionize the air between your feet and the ground. I still highly recommend though, that you do NOT try that in real life!
+David divad yes, upstairs in a dry wood frame new building. all day long . with grounding system not tied in or just don't touch both.. handle the live, can't tell. the handle the bare grounded conductors.. Clearly not idea.. but just like the bird on the wire.. like was just explained..
Thank you for the great video content. Outstanding. As to some of the comments, I would like to add some actual facts about the state of US regulatory law. In the US, GFCI and AFCI standards are written by committees of practicing electricians. They farm all the hard work out to an NGO called United Laboratories or UL (CAS in Canadia I believe). Their sole focus on GFCI and AFCI safety is the PE connection to the enclosure. Absolutely not to the real problem of Human safety. By contract UL can only test and rule on the topics and devices they are given. Look at this document: www.screenlightandgrip.com/html/481_GFCI_Workshop.html - It is informative and fun - about the E safety systems used in the movie Titanic. In particular, review the figure under section UL943. If that does not get the point across, grab the neutral and hot phase of a GFCI/AFCI circuit. Have someone notify next of kin. The EU system of RCDs is a pain (I worked in Amsterdam for years trying to get 3P motors with phase shift problems to work, I know). But, they are so far ahead of the US and Canadia, it is crazy. If you have no experience with 3P power, don't confuse people with comments about the US GFCI/AFCI system. 3P is another world. A pocket calculator and Ohm's law don't stand up to Dr. Maxwell. Look at RCDs as part of Maxwell's world - not Edison or Ohm. At any rate, great video. Thank you.
+Charles Phillips I think it has to do with Germany using old reactor designs similar to the Chernobyl reactor design and the ones in Japan. Why wait for a disaster to happen when you can prevent it? Maybe they will update them and get them back online.
Where did you get your electrical training? The American medium voltage grid does not carry a neutral conductor. The neutral is created at the center tap of the transformer secondary which is then grounded.
I'd never never never ever use one of these damn neon screwdrivers... just use ohms law to find out what happens to you if the voltage of the circuit you are testing is suddenly more than 240V... These things are just deathtraps.
This video is outstanding! You begin by listing what will be covered, and use imaging and written diagrams so we can follow along easily. Very well done tutorial.
The most detailed electritian lesson in 25 min. Truly perfect, bravo.
I have tried to get an explanation for years but was always left guessing or not quiet trusting the explanation. This has finally solidified and makes everything tangible. Thank you so much for this.
Excellent video! I am embarrassed by some of uninformed (ignorant) comments by other Americans. You very clearly noted your invitation for experts in the North American grid system to fill in gaps. That is a far better approach than possibly providing erroneous information on this important and potentially lethal topic. Thank you.
Thank you for the highly informative video. It's amazing that 3 phase power is supplied to ordinary residences in Germany. Obviously, that drives up the cost of building and maintaining public power facilities, but it is probably less expensive in the long run because homeowners can then use 3 phase motors, which are less expensive, more efficient and simpler than A/C motors that are designed on operate on single phase power.
In the USA, it is extremely unusual for 3 phase power to be available at an ordinary residence. It is normally available only in commercial and industrial areas. It is also provided to large farms that need to operate very large motors that run pumps and load silos.
Do the washing machines, clothes dryers, dishwashers, furnaces, and other motorized appliances in Germany actually have 3 phase motors in them? And if that is the case, what sort of outlet is used to bring 3 phase power to them?
What a wonderfully clear exposition!
Robert Spector Thank you sir :)
Finally someone who shows the awesomeness of our power grid.
Fantastic...THANKYOU ....from a very appreciative 3rd year EE student.
You are correct about the "split phase" systems coming into American homes. Once it hits the home, you have the split phase 240VAC and a Neutral return line. At the power distribution panel (breaker box) of the home, there is a neutral buss bar which connects directly to the ground (earth) electrode. The split phase 240VAC is then connected to two breaker rails inside the panel. I forgot to include the electrical KWH metre, that comes before the breaker rails so the power company can monitor how much power you are using. Anyhow, for your 120VAC wall sockets they go from phase to neutral with a separate earth line going all the way back to the breaker panel and connecting to the neutral/earth buss bar. For your larger appliances (Dryer, Hot Water heater, HVAC system, Ovens) and so on, these are hooked to the split phase breakers which span between both breaker bars inside the panel. These as well have an earth wire. I can explain this much easier with a schematic if you wish. Hope this helps mate!
Excellent video. Fantastic explanation.
In the USA in some states ( Mid-West e.g. Kansas, Oklahoma ) the primary distribution Voltage (7.2 or 14.4 kV) if often 4 wire Y configuration. with one Earthed High Voltage conductor. It may be because of the thunderstorms encountered in those areas. Also SWER systems can be employed without an isolation transformer. The House Voltages are 120 - 0 - 120 Volts. or 240 Volts 60 Hz between the outer two. Look forward to part 2.
Hey thank you for the info. I could imagine that there are a number of different systems to be found in different parts of the US ( just as you described, when talking about typical climatic conditions in the Mid-West) I have read about the SWER ( Single Wire Earth Return) system, but I thought it was only used in Australia. Good to know that it can be found in parts of the US too. In Germany we don't use it at all . Our country has a very well developed infrastructure and virtually every household has 3-phase AC. But that's mainly because the country is much smaller than the US. Supplying every household in your vast country with 3-phase AC would be an undertaking of epic proportions.
The Post Apocalyptic Inventor
No worries. The SWER systems are used in Australia and New Zealand for remote locations. Voltages are often 11 or 19.5 kV single phase, In that part of the world they are fed from a 3 wire system and require an isolation transformer, otherwise the feeder would trip out on Earth fault.
In The USA set ups vary from State to State, In Texas there are SWER systems 20 to 30 miles long with lightning arrestors on each 3 rd or 4th pole in case of lightning storms to protect the transformers from Voltage surges.
Great video, thanks!
You are correct we use SWER systems here in Australia. It is very common, even just a short distance from the major cities (like Melbourne) in the rural areas. As it supplies farm houses, they generally have small workshops, also. It makes it hard as they often require 3 phase power for heavy machinery, so quite often they will require their own 3-phase generator for these loads. Phase converters are also sometimes used.
It also sometimes causes an unexpected problem for pilots of helicopters and light planes (like myself)! As the power poles are spaced quite far apart compared to a normal transmission line, it is almost impossible so see where the wire is, many light planes and helicopters who are landing on a farm airstrips or making an emergency landing in a field, have struck the SWER lines and crashed.
Excellent as always. Please keep it up!
Standard US household wiring is this:
110 - 120 volts:
Black - Hot
White - Neutral
Green - Earth
220 - 240 volts have a couple different color codes:
30 amps
Red - Hot 1
Black - Hot 2
White - Neutral
No ground
50 amps
Red - Hot 1
Black - Hot 2
White - Neutral
Green or bare - Earth
In some occasions the black may be blue in 220 - 240 volts wiring.
I know some people say the US needs to change over to 230 volts and though it looks good on paper the reality is the residential grid cannot support it because it was build designed around what we have now, The sheer cost and man power to change out every transformer and fly new line would be amazingly expensive and not financially responsible in a country that is going down the economic toilet. There would be massive increases to power bills nation wide to cover the cost of the upgrade. It is best to leave it as it is, It's not broken so no need to fix it.
Fantastic video. I found several things very fascinating about how you, Germans, treat your power system.
Here in the U.S.A. residential clients do use a split phase system with a center tapped transformer. The primary winding is connected to 2 legs of the 3 phase lines, which are usually about 5kVrms in residential neighborhoods. The 2 legs of power distributed throughout the home have opposite polarities and add to 240Vrms when connected together and 120Vrms with respect to ground. Typically high current loads use a connector with both power legs and a ground, sometimes they also include the neutral.
Commercial clients will usually have a 3-phase star/wye transformer secondary with voltages of 120Vrms with respect to ground and 208Vrms from line-to-line. Industrial factories or workshops will sometimes have voltages of 208/410Vrms. Also, you may occasionally see a High-leg delta secondary with voltages of 120, 208, 120 with respect to ground. This uses one grounded center tapped transformer in the typical Delta configuration.
The neutral conductor should only be bonded to the safety ground at one location, usually right after the service entrance. I found it interesting that your system actually uses a ground point at the pole as well, since this could cause unwanted telluric currents to run along the neutral line between the two ground points. Additionally, to be UL listed all isolation transformers must be grounded on the secondary wiring.
I also found it intriguing that all of your circuits are GFI protected. Here only outdoor outlets and ones installed near water must have this protection. They also must trip at 6mA. Do you encounter any nuisance trips with single phase motors?
Again, thank you for the video and cheers from across the pond!
+Joshua Mudge Also all electrical installations which are located in open places such as lights and sockets are supplied from transformers 240/240 for greater safety of people.
+stephen dwyer You should learn to construct a sentence. I'm trying very hard to see your point through your incoherent rambling.
whats that supposed to mean?
+stephen dwyer Ramblings of a madman....
+stephen dwyer do they also have dots or periods where you come from?
Hi. Very well presented and explained. I live in France and here there is a mix of single and 3 phase supplies to houses. Though most of the new builds have single or mono phase. The incoming supply (unlike the UK) does not include an earth, this is provided by an earth rod located near the "fuse box".
Here in the U.S. most homes have 2 phases going into the home. Only high-load devices like furnaces and clothes dryers use 2 120v phases together for 240v. Everything else is connected to one 120v phase and a neutral. There is also a ground conductor in outlets and light fixtures which is connected with the neutral conductor at the panel.
Most homes have circuit breakers, fuses are in older houses. Newer homes might be built with whole-house GFCI(our term for RCD) systems but I don't know if that's common. Most existing ones don't. They are usually found only on a few circuits, such as the one feeding a bathroom.
Thanks for the great video!
Regarding power in the US: residential service transformers take just 1 high voltage phase, with a center-tapped secondary as you described. The other end of the primary is earthed for the return. This is why -- particularly at the end of a pole line in rural areas -- you will see poles with just a single high voltage wire at the top.
An interesting facet of this system: the center tap of the secondary and the "low" side of the primary are bonded to the same earth ground. If that ground is broken or is insufficient that can lead to stray current coming into the house on the neutral...!
FYI, In the US we call an RCD a "GFCI" or "GFI" -- ground-fault circuit interrupter.
+jruser I had the experience of just that, a high wind took out a tree in the neighborhood and as I stood in my home the lights went out and a very strong 60Hz hum was heard coming from the basement. I figured it had to have been the neutral ground receiving that "high line" voltage flowing through the water main out to the street. This area is served by one wire and the system neutral as you described. The event didn't last long but the sound emulated what you might have imagined as the wires came together, sparking and humming. When I say this was loud it was VERY loud. To this day I can measure about 2 amps flowing between my load center box ground and the water main ground. This will be present even with no loads running. I never opened the connection to measure the voltage. There is a ground rod connection just below the power meter as well, so that should not be an issue.
Outstanding video. First class. I have seen so many explanations of this and none of them are this good.
Really great work my friend. Spot on, looking forward to part 2
Very, very good explanation. Keep up the good work!
This is an excellent explanation of hazards related to earthing. Looking forward to your future videos!
I've seen two of your videos and very much enjoy them! Keep up the amazing videos! If I knew more about our transformers here in the US I would let you know. Fantastic video!
Very nice explanation. Helped me in understanding the isolation aspects. Thank You.
I'm eagerly waiting for the second part!
thanks for the great video.
Probably the best video I've seen on UA-cam, certainly the best in a long time. You've cleared up a load of questions I had about how the electrical grid works. Do most houses in Germany really have three phase power? In the UK it's very rare to have a three phase supply, most have only a single phase coming to the house. I have three phase but I've wired the house to a single phase. I asked an engineer from power company about balancing the load on the phases and he said they don't care for the sort of current draws a house is likely to put on the system.
CNCtrl Yes basically every house in Germany has three phases available. Most people don't have 3-phase sockets in their houses though. But household equipment like electric water heaters, ovens and storage heaters are almost always powered by 3-phase AC here in Germany.
The Post Apocalyptic Inventor Interesting, what size of fuse do you have on each phase? A modern family house in the UK would typically have a 100A fuse but 80A and even 60A fuses were common in the past. The biggest draw I can think of for a typical house would be an electric shower at around 40A so there's still a lot of headroom on a 100A fuse.
The two 300 VA transformers I will use (identical) are 240 V primary with two 10 V secondaries . I will check out your upcoming video . Thanks for your help PAI , greetings from Sydney , Australia !
PERFECT! Just the stuff I was trying to know more about lately :) because I bought Rigol osciloscope I got into Isolation transformers :) Danke schoen from Slovakia.
Just a hint: *NEVER EVER* connect the scope to the isolation transformer. *ALWAYS* connect the device under test to it!
Could you please elaborate why not to connect osciloscope to isolat trans? I always thought thats the way to do it... thanks
Another exceptionnaly informative video... Thanks!! Can't wait for the follow-up...
I haven't read all the comments, so if someone has already answered this please excuse me. For your North American diagram where it enters the house --
Power enters "distribution panel" of a house as three wires off of the "distribution transformer" you have labeled in your diagram, and the two hot lines are 120V, 180 degree phase offset due to the center tapping.
If high power devices are used (ex. electric range, clothes dryer, restaurant ice cream machine, welding equipment, etc.), they usually require 220-240V and are connected across the two hot lines.
Otherwise, the circuits of the house are typically split roughly equally among the two phases.
To be strictly legal, a third ground wire connects all equipment chassis together, and to earth AND neutral at the distribution box, however, in practice, a LARGE quantity of homes are grandfathered as two wire without even regard for polarity of live vs. neutral. Grounding is sometimes overlooked and chassis are connected together. It can be quite interesting in the event of a fault...
GFCI outlets, or GFI (ground-fault circuit interrupters) are required in wet locations such as bathrooms or outdoor outlet installations.
Thanks for the info PAI! Some unanswered questions are... well... answered now. :)
Crystal clear explanation. Truly useful, well planned, complete and captivating explanation. You are a gifted teacher. Living in Greenland means we share in the inherited "Danish" system which is European in character.
One question. All water services in the house are connected to earth and as far as I can see this earth consists of a connection to a bare copper multistrand wire cast into the concrete and connected mechanically to the steel reinforcing in the concrete. This is then connected to the equipotential earthing bus bar in the fuse box cabinet to which all yellow-green lines are connected, one from each cable leading to a socket. I'm a bit confused on how PE and N are connected. Where can I see that the Neutral and PE are separated "inside the house" as you state? Is there some isolation created between the two?
Again, great video. I'm impressed, and looking very much forward to the next in this series. Thanks from a complete beginner.
N and PE are basically the same. If you use copper wire with high currents for a long period of time i can occur that the connection e.g. at an insulating screw point is getting loose (due to thermal stress etc.). So as you can see if you would use the same wire for N and PE it can happen that someday you have no connection to N/PE, but to your Phase! (Which might be pretty dangerous for humans in most cases if undetected)..
To prevent this, you use two separate wires for N and PE, the N wire is the "stressed" one. The PE is the "backup", which is normally unloaded, and because of this, theoretically excluded from the connection faults as described before.
I hope this will help you to understand the meaning of PE and why it´s basically the same, but not the same ;)
Thanks! Very nice explanation and I think I've got it now. I appreciate you taking the time to help me understand.
You're welcome!
In old installations the split with done inside the socket to save on copper wire!
A problem with that is: any current through a wire will cause a voltage drop. Since there can be quite alot of current flowing through the neutral wire (imagine using water cooker for example), the neutral is no longer at the same level as it is in the breaker box, but a few volts higher. If N and PE are the same wire, that means your "Earth" level varies with the load. That's especially annoying if you connect different devices like a computer and a stereo for example, that are connected to outlets at opposite sides of the room.
You can check the voltage drop yourself btw., if you have a (safe) multimeter. Get a high power device (in essence anything that's heating something) and plug it into an outlet that has a second outlet immediately adjacent or use a three way adapter cable. Measure the voltages to between the wires and to PE in one socket while you turn on and off the load in the socket. You should see the voltage drop.
Thankyou Gerolf great video. Happy Christmas!!
Thank you sir.
Very informative!
So far best channel to me!
Danke
hola que tal saludos desde Mexico, solo para felicitarte por tus videos, son muy buenos sobre todo tus explicaciones, diagramas y dibujos, todo es muy bueno
Great explanation and illustration!
Thanks a lot! I always was looking for such a video and you made it very good.
I have just discovered your videos, and have spent this evening watching many of them. They are fascinating and very educational, thank you.
In this video about the Power Grid, you describe all 3 phases going into the home. Is this standard procedure in Germany? I ask because I do not think this is standard in the UK, where I am.
As far as I know, UK homes only have one phase to each household. Of course, larger offices, factories etc may have all three phases, especially if they have 415 Volt equipment. I do not know of any 415 volt equipment for a typical UK house.
Of course, the UK has some historic quirks with electrical wiring, but it surprised me to hear that maybe Germany has all 3 phases at every home.
Thanks,
Ian
SheddyIan Hello. It's nice to hear that you liked my videos so much :)
Yes in Germany the power grid is a 3-phase system from the power plant all the way to the single houses. 3 phase power is available in virtually every home. Electric ovens and water heaters are 3 phase loads, which you will find in many households in Germany. People like me, (who like to use power tools), often have special 3-phase outlets in their garage, basement or home workshop as well. Like in the UK normal living rooms only have single phase AC and consumer products are almost always designed for that in Germany as well.
People without a home workshop or any special use for heavy power tools etc. do often not have any of these 3-phase outlets, but they could easily be added, because the 3 phases of the low voltage grid lead into their house and are available inside the breaker box (= home distribution board).
Even if a house does not have any 3-phase loads at all, the single phase electric outlets, the lighting and other loads are connected to the 3 phases and the neutral in such a way, that each of the phases is loaded about equally. We do that to avoid asymmetrical load conditions in the power grid.
Germany has a very well developed infra structure and it indeed seems to be the case, that in many countries, 3-phase AC is much less available than here. To find out more about the situation in the UK, you could for example open your breaker box and check, if the 3 phases lead into your house or not. Furthermore I recommend you to check an electricians training book from the UK. Please tell me, if you find out more. I would be interested in knowing more about the situation in your country.
The Post Apocalyptic Inventor Hi, I am sorry to be so slow replying, I have been asking around for some information.
I know that in the house I currently live in there is only one phase coming in to the fuse board. (My house and wiring is old enough to only have fuses, not breakers!). I have also spoken to a retired electrician, and he tells me that he does not know of any houses that have 3 phase, only factories or commercial properties with a larger load.
Load splitting between the 3 phases is done at street level, so on a typical street, house 1 might be 1st phase, house 2 might be 2nd phase and house 3 might be 3rd phase, house 4 being 1st phase etc.
Electric water heating in the UK is usually done with a storage tank, which has a 13 Amp immersion heater installed on a time switch to run for a few hours each day to heat the water, sometimes taking advantage of a cheaper overnight tariff to heat the water for the next day. Although many British homes use gas to heat either a hot water storage tank or to provide instant hot water with no storage.
Electric ovens and electric instant hot water showers also just use one phase, and are usually rated at 45 Amps or so.
On a side note, British electrical wiring is different to other countries, in that we usually use the ring-main system for electrical outlets.
The cable leaves the distribution board, and is connected to each outlet in a daisy chain before returning back to the distribution board again. In this way, a smaller cable can be used (2.5mm) and yet still provide 30 or 32 Amps of maximum current to each circuit. (Each outlet being rated at 13 Amps).
Lighting circuits are wired radially, using 1mm or 1.5mm squared cable.
I hope this is of interest
Ian
SheddyIan Very interesting information. I live in Denmark and our wiring is identical to the german 3-phase system. With 3 phases at hand in the house, all installation wiring can be made with 1,5 square millimeter cable. Even an electric cooker can run on a 13A group. The only place i have a (5 x) 2,5 mm cable is to my garage, because i work with a 250A Esab mig welder, demanding a 16A fuse group. The supply from the cable box in the street is a 4 strand 16 sq. mm cable, fused with 63A. The ground fault relay (hfi in danish) is mandatory.
absolutely wonderful video....really congratz.
How does current flow from the neon test light through the body to ground when the body is touching the non conductive poly-carbonate handle of the test light?
+Sam Cummins Well normally it only should light up, when the metal tip at the end of the tester is touched, as I demonstrated in the video. I also have never seen any of these testers light up, when only the plastic handle is touched. If the neon test light would still light up without the metal tip being touched, it again could possibly be explained by capacitive coupling, with the poly-carbonate acting as a dielectric. But with a typical mains tester as shown in this video, when being applied to a 230V line, this actually shouldn't happen. What kind of tester are you using?
great video! thank you Nikola(Tesla)!
God damn this is a good video! Pure YT gold!
Great video, especially the part about the RCD. I did a video about isolation transformers myself some time ago,but compared to yours, mine is utter crap. :)
Thank you Professor, fantastic.
Most wonderful, crystal clear and ever so interesting. Yet again, a great teaching video. !SKNAHT ... Opps, I got it backwards =>THANKS!
i love this site ;it is simply simpe
What a coindicence, I've been tinkering with isolation transformers recently as I make off-line switching power supplies, mainly just so that I can safely probe the primary side of the converter with a ground referenced oscilloscope without damaging anything. I made my own isolation transformer with a cheap old 3.3kVA (at 25% duty cycle; 1.5kVA continuous) centre-tapped earth 240V-115V (suprisingly not a 2:1 ratio) building site transformer. I was trying to rewind it to have 2 secondaries, 115V and 230V but that didn't work out. In the end I just cut the earth centre tap so earth passes straight through to the output without going to the transformer. I hadn't considered how it would make the RCBO ineffective. I've accidentally touched a live wire that was supposed to be off before and all that happened was the RCBO tripped and my arm was thrown away. I still haven't found the screwdriver tip I was holding. I've also tapped off a 380V DC PFC bus capacitor in a ATX power supply for testing SMPS that will later have PFC preregulators added and debug the 2 separately.
I know almost nothing about house wiring, but it seems in USA they have 2 phases and a neutral to their house, 120V is phase-neutral, 240V for big appliances is phase-phase. In UK we seem to have 3 phase 400V up to a street and then only 1 phase 230V into the house, with different houses getting different phases to approximately balance the load, but it may vary in different areas. We also have a ring mains system in the house which means all wiring connections are accessible behind plug sockets but its really difficult to know where a wire goes after it disappears into the wall. I disconnected a wire that should have cut off power in my living room but it was being pulled up to live through the transformer primary of my microwave in the kitchen. It's also why all our mains plugs have 5A or 13A fuses in the actual plug as well as in the device.
Smartest guy on Earth :)
Haha The European electrical grid is so much more safe than here in america!
***** But having high voltage lines increases efficiency. I'm sure there is a reason for having any small transformers than larger ones. Again--Likely because you can more easily transport high amounts of power at high voltage with less loss than you can at low voltage.
This is why we use dangerous AC voltages in the first place and not something safe like 12 volts.
+Kris S If using low voltage, eg 12V then you will need biger wire gauge. If there has toaster 2000 watts with low voltage 12 volt is 2000/12 = 166Amper. For 240volt is 2000/240 = 8,33amper. In the first case it needs cables 2GA for second 8GA. the problem in the US is the low voltage 115volt.
telosfd Exactly. Low voltage = more heat and bigger wires. 120v is the standard and changing that now wouldn't be easy--Plus, the danger goes up with the voltage, so a balance is needed.
Otherwise we would just run our houses off of the mains 600,000 volt lines that go through the countryside.
I think RCD works on peek current also, so if you have 230 RMS peek voltage is 325 V and resistance to turn on RCD would be around 10K ohm...
Petar Bažant Thank you. Good point. I made an annotation at that point in the video.
Very nice video. What I didn't understand is why create the earthing conductor in the first place to get rid of it using an isolation transformer?
Now, that's a very good question. Why is a ground provided in the supply side? If it was not there no shock hazard (to ground) would exist. Hmm...
+Devranjan Das its probably mostly used to ground the core of the transformers, if you have ever seen someone making arks from the core of a microwave transformer, the ark is jumping from the core to a ground wire.
Great explanation! What about the next SMPS tutorial? When will that be released? Thanks!
What are some sources to know more about electricity, terms involving electricity, and any prerequisites needed to deeply understand electricity?
diething1 Well my friend. I'm sorry to tell you, but there is no easy way to accomplish what you're asking for. My advice is to start with the simple things. Maybe you should start by buying an electronics book for hobbyists. Something from the 70s or 80s. back then things were simpler than they are today and learning electronics started with resistors, capacitors and transistors.( Not with microcontrollers and FPGAs like today :D). Back then many people who weren't professionals wanted to understand electronics and there was a big market for books and magazines, teaching the basics of electronics. The stuff from back than is still good and often not very expensive. (You could even check the local libraries).
Books like that can give you a feeling, of waht kind of basic components exist and what they do.
Once you understand the basics you can work your way up to a more professional understanding. As an addition to the practical knowledge taught among hobbyists, you have to learn how to apply basic mathematics to electric circuits. Principles you must look up and learn to understand in any case:
Ohm's Law, Kirchhoffs's Voltage Law, Kirchhoffs Current Law, component equations for capacitors and inductors.
Once you know these things, I would recommend to buy an electricians training book. It will help you to understand the basics of AC-Systems, without the need for higher mathematics.
If you want to get an even deeper and more general view of electronics you would have to study electrical engineering. You could again try that by reading books, but that alone won't work. You would have to spend a lot of time learning mathematics and how to apply it in the field. That can only be done by actually doing a ton of calculations. It can only be learned by practicing. That is very hard, if you have no instructor. If you wanted to do that on your own you needed several very good books, having both training exercises and solutions with explanations. But books like that are as rare as anything. Studying at university might provide you with a lot of exercises and instructors, but the things you learn there are very theoretical in nature and most people need many years to finish their studies. Still many leave university with a feeling of ignorance. There is no easy way.
Great video!
American pole transformers has only one high voltage input with one fuse, but there's no protective device at the output of the transformer.
Correction - some transformers have 1 high voltage input, called CSP type.
+DjResR allot of usa transformers I see on youtube videos are single phase where there are 3 phase lines i see 2 and 3 phase ones.
We here in U.K do not get 3 phase into our houses, there is 3 phase out in the street and then every house gets it's own phase, thus, if there is a fault at the substation and 1 phase goes down, you might lose half the street lights, and one third of the street (not all the houses together, but say every third or forth house, or alternate houses across the street) will lose power! Saying that though we are in a 1950s house and all 3 phases do come in and are fused "on the supply side" and only one phase is "tapped" hope this is of help to you explaining how it works in the U.K?
Clive Clarke-Watson Hey thanks for the information. I knew that a similar system is in use in the US, but I wasn't sure about the UK.
Glad to be of help!
Sometimes when I turn on my stereo power amp it trips the RCD, do you know why that happens, and what I could do to prevent it? Thanks for your interesting vids.
dunkelheit843 It is most probably due to the "remanance" of the transformer of your amp. I explained that in the followup video to this episode.
yeah, watched that vid after the first and felt a little stupid for asking the question, however, if that is the cause, is there a cheap and simple way to deal with it, preferebly without having to open up the amp and mod it internaly?
+dunkelheit843 If it trips the RCD then try to use a power cord without a neutral wire in it and see what happenes. Don't touch the chassis though if it's made of bare metal. If it works, there may be a badly designed emi filter in the amp. If it's not actually the RCD that is tripping but rather a normal fuse in the fuse box (make sure), then I bet that is a very powerful amp with no inrush limiting implemented. Also, I'm sorry if that is a cool sounding amp and it gives such headaches.
thanks for the advices, it's defenetly tripping the RCD. However I've got it plugged in via a remote controlled powerswitch (nexa brand) and I've noticed it only happens when I turn in on using this device, however if I use the powerswitch built into the amp I haven't gotten it to trip the RCD, so there's something wrong rather with this combination of amp and remote operated powerswitch.
great vid!!
My home in Italy has no connection between the PE and the N, should I change it?
Just some small corrections. The two phase power entering a US home is 240v with reference to ground as each voltage is 180 degrees out of phase with each other. Your diagram showed 120 Volts in relation to ground measured across both phases. You probably meant that each phase measured by itself in relation to ground is 120 volts.
roomba The arrows in my drawing are simply pointing to the two conductors and are supposed to mean that the two points the arrows point at have a voltage of 120 V with reference to earth ground, not that there is 120V between the two conductors. In that case I would have drawn a voltage arrow between them instead.
I'm not an expert for the American system, as I said in the video. But from what I have read, I find your statement somewhat confusing, so help me out if you can:
The distribution transformer is just a single phase transformer with a grounded center tap at the secondary. The voltage between each end of the transformer secondary and the center tap (earth ground) is 120V AC. With reference to earth ground the voltages at the two ends ( or "phases") are 180 degrees out of phase because they are to opposing ends of a secondary winding.
Between the two ends you would then measure 240 V AC, but that voltage only exists between the two "phases". But the way I see it, there would only be 120V AC with reference to earth ground at any given point on the secondary side. Am I missing something ?
Yes, that is correct. Please read the last part of my comment in which I give you the benefit of the doubt.
The Transformers are used in the US are mostly called High-Leg Delta
en.wikipedia.org/wiki/High-leg_delta
Resistance of human body. Right. But it is not so easy. Actually there is big influence of capacity of skin and body and also if you are insulated from ground you can still recieve electric shock, because you still can have capacitive coupling with ground. And also this values will change after some time from begining of shock and current will go up. If you using this neon light testing screwdriver, you also can stand on insulatin surface, but neon still glow. Because of capacitive coupling between your body and ground.
xxJerry19xx Yeah capacitive coupling can be a tricky thing. These kinds of testers are actually not used by any professional I know and you shouldn't trust them, but it's a good way of showing people what it means to have an earthed referenced grid.
Australia has the same system as Europe.
Merry Christmas.
Hi PAI . Have you built a variac into your isolation transformer ? (shown in the video) . Hope to see more details of the transformer . Great work on the vids mate , your English sounds very cultured to my ear . Regards .
Steve Smith Yes I used a variac and I'm working on the followup right now. I will explain how variacs work as well. So I guess you will like it :)
Im thinking of building the same (transformer) . Should it be wired as Mains then Isolation then Variac or a different layout ? Also the 300 VA transformers I will use (from salt chlorinators) have 2 secondary windings (4 wires) that were connected as 10v 0v 10v (to SCRs). Should I connect these secondaries to the other 10v 0v 10v ? Regards and thanks , Steve .
Steve Smith You have to connect the isolation transformer to teh mains and after that you attach the variac to it. I will talk a lot about the details of my isolation transformer in the next video. The video is now to 75 percent ready and it will gon online withing the next week. It will help you to get some orientation. I don't quiet understand what kdnn of transformer you are using ? Is it a "1 to 1" transformer that delivers 230 V at the output ? ( Or 115V if you live in the US or Canada). Are the 10V-Secondaries additional secondaries or are they the only secondary windings ? If they are just additonal windings you can either leave them alone, you can connect them in parallel (polarity is important !), or you can connect them in series to get +10V /-10V or 20 V
Thanks so much dear...
Excellent
Very informative
The RCD may be called a GFI (Ground Fault Interrupter) in the USA.
It is not just a breaker box.
Of course the RCD is not just a breaker box and I didn't say that. I said that it measures the sum of the currents passing through. I simply spared an explanation of how an RCD works in detail, because that is not the topic of this video, which is already 25 minutes long.
The Post Apocalyptic Inventor
Sometimes I am too cryptic, sorry.
GFI = RCD ? in usa was the message.
Ah ok. It`s all right then. Thanks for the information and sharing my video :)
I cant understand it..wood and concrete is not conductive so how i`m completing a circuit while standing on wooden floor ?
+David divad Wood and concrete are conductive! They are very bad conductors, but they are not ideal insulators as well. If high voltages are present the currents that will flow, can still be high enough to harm you. Furthermore: Alternating currents can flow through your body due to ''capacitive coupling'', as I mentioned in the video. A layer of material with low conductivity between your body and an electrode will act like the "dialectric" inside a capacitor.
So lets say if id jump in air and while i`m in air i could touch hot wire without getting shocked ?
+David divad It depends on the voltage between the ground and the "live" wire.
If it is a high voltage line and you jump in the air to reach it, then your body will provide a path of higher conductivity than the air that normally separates the wire from the ground. If the voltage is high enough, the free space between your feet and the ground (while you are jumping), will possibly be arced over by the current and you will be fried.
If we a talking about a 115 or 230 V wire however, it is very probable that nothing serious will happen to you, since the voltage is to low, to ionize the air between your feet and the ground.
I still highly recommend though, that you do NOT try that in real life!
Nah i`m not that stupid to try that, thank you for answer!
+David divad
yes, upstairs in a dry wood frame new building. all day long .
with grounding system not tied in or just don't touch both..
handle the live, can't tell.
the handle the bare grounded conductors..
Clearly not idea.. but just like the bird on the wire..
like was just explained..
Putting a circuit breaker at the isolation transformer's output? :P
#mustwatch for Electronics stud....
Thank you for the great video content. Outstanding. As to some of the comments, I would like to add some actual facts about the state of US regulatory law.
In the US, GFCI and AFCI standards are written by committees of practicing electricians. They farm all the hard work out to an NGO called United Laboratories or UL (CAS in Canadia I believe). Their sole focus on GFCI and AFCI safety is the PE connection to the enclosure. Absolutely not to the real problem of Human safety. By contract UL can only test and rule on the topics and devices they are given.
Look at this document:
www.screenlightandgrip.com/html/481_GFCI_Workshop.html - It is informative and fun - about the E safety systems used in the movie Titanic.
In particular, review the figure under section UL943. If that does not get the point across, grab the neutral and hot phase of a GFCI/AFCI circuit. Have someone notify next of kin.
The EU system of RCDs is a pain (I worked in Amsterdam for years trying to get 3P motors with phase shift problems to work, I know). But, they are so far ahead of the US and Canadia, it is crazy.
If you have no experience with 3P power, don't confuse people with comments about the US GFCI/AFCI system. 3P is another world. A pocket calculator and Ohm's law don't stand up to Dr. Maxwell. Look at RCDs as part of Maxwell's world - not Edison or Ohm.
At any rate, great video. Thank you.
Today I learned german power poles are pretty.
Georgious country side footage. Jealous all I have is a desert.
It's a shame Germany is shutting down it's nuclear power plants. I don't think Germany is in any danger of a Tsunami.
+Charles Phillips I think it has to do with Germany using old reactor designs similar to the Chernobyl reactor design and the ones in Japan. Why wait for a disaster to happen when you can prevent it?
Maybe they will update them and get them back online.
Do you draw these pictures yourself? Got a Surface?
TheAmmoniacal I draw all pictures myself. I basically do it the old way: with pencil and paper. After that I edit the pictures on my pc.
Where did you get your electrical training? The American medium voltage grid does not carry a neutral conductor. The neutral is created at the center tap of the transformer secondary which is then grounded.
I'd never never never ever use one of these damn neon screwdrivers...
just use ohms law to find out what happens to you if the voltage of the circuit you are testing is suddenly more than 240V...
These things are just deathtraps.
5mA death? that doesnt make sence