Layouts, configurations, and applications
Distribution systems around the world have evolved into different forms. The two main designs are North American and European. For both forms, hardware is much the same: conductors, cables, insulators, surge arresters, regulators, and transformers are very similar. Both systems are radial, and voltages and power carrying capabilities are similar.
The main differences are in layouts, configurations, and applications. Figure 1 compares the two systems. Relative to North American designs, European systems have larger transformers and more customers per trans-former. Most European transformers are three-phase and on the order of 300 to 1000 kVA, much larger than typical North American 25- or 50-kVA single-phase units.
Secondary voltages have motivated many of the differences in distribution systems.
North America has standardized on a 120/240-V secondary system; on these, voltage drop constrains how far utilities can run secondaries, typically no more than 250 ft. In European designs, higher secondary voltages allow secondaries to stretch to almost 1 mi.
European secondaries are largely three-phase and most European countries have a standard secondary voltage of 220, 230, or 240 V, twice the North American standard.
Although it is rare, some European utilities supply rural areas with single-phase taps made of two phases with single-phase transformers connected phase to phase.
In the European design, secondaries are used much like primary laterals in the North American design. In European designs, the primary is not tapped frequently, and primary-level fuses are not used as much. Euro-pean utilities also do not use reclosing as religiously as North American utilities.
Some of the differences in designs center around the differences in loads and infrastructure. In Europe, the roads and buildings were already in place when the electrical system was developed, so the design had to “fit in.” Secondary is often attached to buildings.
In North America, many of the roads and electrical circuits were developed at the same time. Also, in Europe houses are packed together more and are smaller than houses in America. Each type of system has its advantages.
Some of the major differences between systems are the following:
Cost
The European system is generally more expensive than the North American system, but there are so many variables that it is hard to compare them on a one-to-one basis. For the types of loads and layouts in Europe, the European system fits quite well.
European primary equipment is generally more expensive, especially for areas that can be served by single-phase circuits.
Flexibility
The North American system has a more flexible primary design, and the European system has a more flexible secondary design. For urban systems, the European system can take advantage of the flexible secondary; for example, transformers can be sited more conveniently. For rural systems and areas where load is spread out, the North American primary system is more flexible.
The North American primary is slightly better suited for picking up new load and for circuit upgrades and extensions.
Safety
The multigrounded neutral of the North American primary system provides many safety benefits. Protection can more reliably clear faults, and the neutral acts as a physical barrier, as well as helping to prevent dangerous touch voltages during faults.
The European system has the advantage that high-impedance faults are easier to detect.
Reliability
Generally, North American designs result in fewer customer interruptions. Nguyen et al. (2000) simulated the performance of the two designs for a hypothetical area and found that the average frequency of interruptions was over 35% higher on the European system.
Power quality
Generally, European systems have fewer voltage sags and momentary interruptions. On a European system, less primary exposure should translate into fewer momentary interruptions compared to a North American system that uses fuse saving.
The three-wire European system helps protect against sags from line-to-ground faults.
A squirrel across a bushing (from line to ground) causes a relatively high impedance fault path that does not sag the voltage much compared to a bolted fault on a well-grounded system. Even if a phase conductor faults to a low-impedance return path (such as a well-grounded secondary neutral), the delta-wye customer transformers provide better immunity to voltage sags, especially if the substation transformer is grounded through a resistor or reactor.
Aesthetics
Having less primary, the European system has an aesthetic advantage: the secondary is easier to underground or to blend in. For underground systems, fewer transformer locations and longer secondary reach make siting easier.
Theft
The flexibility of the European secondary system makes power much easier to steal. Developing countries especially have this problem. Secondaries are often strung along or on top of buildings; this easy access does not require great skill to attach to.
Outside of Europe and North America, both systems are used, and usage typically follows colonial patterns with European practices being more widely used. Some regions of the world have mixed distribution systems, using bits of North American and bits of European practices.
Westinghouse engineers contended that both 240/480-V three-wire single-phase and 265/460-V four-wire three-phase secondaries provide cost advantages over a similar 120/240-V three-wire secondary (Lawrence and Griscom, 1956; Lokay and Zimmerman, 1956). Higher secondary voltages do not force higher utilization voltages; a small transformer at each house converts 240 or 265 V to 120 V for lighting and standard outlet use (air conditioners and major appliances can be served directly without the extra transformation).
More recently, Bergeron et al. (2000) outline a vision of a distribution system where primary-level distribution voltage is stepped down to an extensive 600-V, three-phase secondary system. At each house, an electronic transformer converts 600 V to 120/240 V.
Reference // El. power distribution equipment and systems – T.A.Short
Related electrical guides & articles
There is no problem at all. 230V was agreed as the EU standard, but equipment has to be designed to have tolerances of + and – 10% (207V to 253V). That allows equipment to cope with EU mainland 220V +10% -6% (207V to 242V) and UK 240V +6% -10% (216V to 253V) supplies, without countries changing their actual supply voltages. Countries did not actually change their supplies to 230V.
I am an electrical contractor and I have a client that has purchased a european piece of equipment. It is a 3.3kw device that specifically says 230 volt. Any reason it cannot be connected to our 240 volt
It depends on what kind of equipment you are talking about. There is a possibility it can get damaged, since its operation is not under the recommended specifications by the manufacturer.
I know I always wondered about , if we were smart here in north America(canada for my self) there is no reason that an electrical system designed in the 1890 ‘s or whatnot should still be used in the 2020 and beyond, I worked across the pond andin a few countries and now I am retired but my analysis is the We should keep the 60 Hz , but slowly phase in 240?415 volts 3phase ,4 wire and standardize it, and let the world obviously standardize their 230/400 volt 3 phase 4 wire 50 HZ. We can make appliances from 1 -1500 watts dual voltage easy, we just need to come up with a new receptacle/plug format all agreed on design. We should keep the 1500 watts max on common circuits , rest being 240 volts , 20 amp and up as the case may be. Single phase should be just 240 volts for us one live and one neutral, commercial/Ind. just use the 240/415 volts system and not bother with Industrial voltages such as 277/ 480 and 347/600, they are just a pain anyway having to use dry core transformers extra switches, conduit and the like, fewer plug configurations/ pin and sleeve connecting equipment and so on. In summary (this just a brief view , backed up with facts, for myself), and electrical system such as this would likely only need half the number of circuits now (in residential units) less labor etc. an electrical system we now have is more than 125 years old here in canada and true in the usa as well, a very different era, and should be looked at, oh and another thing common circuit breakers as another as standard, unlike here in north America, would be a help. Unless I am mistaken Tesla himself recommended initially that voltage of 220-240 to ground be used after a lot of careful calculations and 60HZ.
In the Figure one comparison, there is an error in the EU grid. The fist transformar coverts a Delta into Star. And the second transformer converts the Delta into Star, how can this be if the system is in Delta, please correct me if I am wrong, thanks in advance.
This article should include American 120/208 3phase and 277/480v 3 phase. Not common in homes, but is widely used everywhere else.
120v in the american system was largely done for compatibility with early DC systems. It’s just a shame we dont use 240v single phase as the standard appliance voltage.
American system is cheaper and easier to expand on. The only real advantage to the Euro Model is the lower cost of wiring needed in building homes.
“European primary equipment is generally more expensive, especially for areas that can be served by single-phase circuits.”
europe is building to last,
us is building to rebuild every time new house is built.
Ok i have to hook up european power,well 15 double outlets the outlets came in today!! Well it says L and N and Earth?? I have 2 120v hots and a nuetral and a ground. Now the ? is do i use the 2 hots for L or do i use 1 hot on Ĺ and 1 hot on N and forget the neutral and use ground to earth can you please help me????
Has anyone answered your ? yet on wiring the 15 outets? I too am facing the same issue.
This article has little basis in science or reality. It appears to be a propaganda sales job on the nasty business of Europeans running 240V to every appliance and lamp in a home. The bit about a 120V secondary only running 250′, but 240V can run a mile is easily proven false. I could point out ten more completely bogus statements.
I’d remove this trash off your otherwise fine website.
You are right about the Europeans, I’m living in Europe and many people, even on the electric forums, say that propaganda about 200-250v, but here in that article either way is shown that American system is better and cheaper, first of all because of the closeness of medium voltage (kilovolts) everywhere, which makes American system able to modificate. That standard in Europe 230/400v proposed for global standard by International Electrotechnical Commission is actually ….. primitive a little, in the U.S. it’s used only for high wattage stuff and not even for all. In America are specialized parameters of energy for specific appliances, You use generators, transformers, frequency converters, much more often the direct current, and much more the voltage over 1000v and in Europe it all is not common (everything is simplified to send only that 3ph 400v on too long distances and minimalized, the old wires are very thin so easy to damage and then You have open 200v, but from the other side if You have big sizes of conductor it’s actually waste of money), many NEMA plugs configurations which makes unable to plug 120v connector to 240v receptacle f.exmpl., Regards
Please point out the ten more completely bogus statements CJ Cooney
I wonder how a three phase system is configured in North American Layout. Can anyone shed a light on this.
Thanks.
The indicated North American Layout will cause a great source unbalance and there will be a need from time to time to check neutral current unbalance.
European layout allows the system neutral to be kind of ungrounded unless the current trought the grounding resistor is large. In this case the ungrounded advantage vanishes.
In some European countries Petersen Coils Grounding are used. This is expensive but allows limiting the neutral fault current.
North American Layout allows large ground short circuit currents thus simplifying relay settings and coordination but the equipment will be strenghtened.