Power Cord Types: A Brief History & Introduction
European CEE 7/7
The CEE 7/7 has two male round prongs and a female. With this standard, the grounding is done in two different ways:
- On the plug side there may be a female receptacle prong.
- Or there may be a ground strap on the top and bottom that achieves grounding (a third pin on the cord itself).
This CEE 7/7 is used by approximately 104 countries around the world. It’s popular and practical — going up to 16 amps instead of just two-and-a-half amps, but it’s also kind of big and bulky.
European CEE 7/16
The CEE 7/16 has no grounding. It consists of just two round pins. Some of the reasons behind its popularity are that it’s very small, and very applicable to small electrical products that do not require grounding. The CEE 7/16 is used far and wide, in 113 countries all over the world, from Afghanistan to Vietnam.
UK BS 1363
The BS 1363 plug socket, in my opinion, is the best design around. And the reason I say that is because it’s the safest. The ground pin on BS 1363 cords is longer than the live neutral pins, so it always goes into the plug socket first. This really helps to prevent shock. On top of that, both the live and the neutral pins are insulated up to a certain point.
The only real downside is that BS 1363 cords are kind of bulky and heavy. It’s used in approximately 98 countries worldwide.
The NEMA 1-15 became embedded early on, and virtually every electronic device uses either a polarized or unpolarized version of the 1-15. They remain enduringly popular because they are easy to acquire, abundantly available, and cheap because they’re manufactured in large quantities. The NEMA 1-15 is in use in 43 countries globally.
Behind the 1-15, the three-pronged NEMA 5-15 (15 amp) is perhaps the second most common type of NEMA power cord.
IEC C13 to C14
The IEC C13 to C14 power cord in the United States can be rated up to 15 amps at 125 volts, and in most cases this still is fully sufficient for most devices, hence the popularity.
You will find the IEC C13 to C14 power cord on the back of every computer, monitor and lots of other devices such as overhead projectors.
IEC C19 to C20
In fact, computing power doubles approximately every two years (following Moore's Law), a trend that consistently fuels the need for higher-density data centers, and hardware that requires more power and to be able to extract more efficiency out of a limited data center space.
To respond to this challenge, the C13 to C14 is slowly starting to be phased out in favor of the more powerful IEC C19 to C20.
Today, it’s not uncommon to find servers that are 20 amps instead of 15 amps. EV charging stations are often 32 amps or higher. You can see the transition happening almost in real time in the data center world, in the evolution of the PDU strips.
When PDU strips first came out, they were almost entirely made up of C13 to C14 connectors. Then it became more common to see a PDU strip of 80/20 C13 to C14 and C19 to C20. Today, PDU strips in data centers are far more likely to be a 50/50 split to accommodate C19 to C20 power cord types.
Different power cords used across the world
CEE power cord types
Denmark has its own standard. Italy has its own standard (which is also used in Chile). Switzerland has its own standard too, which is very similar to Italy’s but with the center prong staggered up.
Countries far and wide outside of Europe also use these types of power cords for electronics, from Azerbaijan to Madagascar to Togo.
You’ll find CEE 7/7 power cords and plug sockets everywhere in day-to-day life where they’re used. For example, if you plug a device into the wall in one of these countries, or use an extension cord, it’s likely to be a CEE 7/7 one.
UK BS power cords
NEMA power cords
IEC power cords
That’s because router switches, hubs, server racks, they all usually require an intelligent PDU power strip to function in a data center, and each of these PDUs may have up to 32 devices safely plugged into them at any one time.
NEMA medical-grade power cords
Medical grade power cords look identical to their non-medical counterparts, except they have a bright green dot on them to show they have been rigorously tested. The connectors on hospital grade power cords have to be soldered and not crimped. They have to be of a durability that large and heavy items (such as crash carts) can be maneuvered over them, without a risk of damage between the wire and the terminals.
It’s probably easier to think of them as ‘heavy-duty’ cords. You will also find them in warehouses and other industrial industries.
Good to know:
There are people that market their products as medical grade for, say, Europe or the UK, but it's just made up marketing. There's no written standard that they're conforming to with their tests.
Instead, for industrial, hospital, or higher power requirements typically pin and sleeve are used, such as IEC 60309 pin and sleeve products. This can involve some huge connectors, from 3-5 pin, with an amperage range from 16-128 amps.
A history of power cord types
You might be wondering why we even bother with all these different standards when we have the IEC (International Electrotechnical Commission) standard. To put it simply, the answer is because the world is a complex place and everybody has their own ways of doing things.
A brief history of the IEC standard
The first International Electric Conference was held in 1881, in Paris, France (source). A culmination of these efforts led to the formation of the IEC in 1906, but throughout its history, it has notably failed in its targets of universalisation.
In 1986 the IEC proposed a particular plug and cord designed “to provide a standard for a safe, compact and practical… plugs and socket-outlets that could be accepted by many countries as their national standard, even if not in the near future (source).”
The problem is, only Brazil adopted the IEC’s ambitious design. It is literally the only country in the world that uses the NBR 14136 and NBR 6147.
The trouble with trying to create a one-world standard is that it takes enormous planning and for everyone to agree to implement. Just imagine the cost of having to bring every building up to new standards across the world. Instead, the history of power cords is a bit of a haphazard one, with countries setting up their standards on what was easiest for them to adopt at the time.
It’s why a hodgepodge of countries use the United State’s NEMA standard, and why Italy and Chile share a common power cord type. In my opinion, there probably won’t ever be a true international standard. Or at least, not for a very long time.
A brief history of the NEMA standard
The first centralized power station came online in New York City in 1882 (source) and regulation quickly began through the American Institute of Electrical Engineers, an organization that was established in 1884 (source).
Rather than make the transition to IEC, the decision was made to double-down on those standards and better regulate them. The result was the establishment of the National Electrical Manufacturers Association (NEMA) in 1926 (source).
That being said, where possible, NEMA standards have been developed to be used alongside IEC standards. A key example of this would be in data center PDUs (as mentioned above).
NEMA, a very thorough organizationNEMA has a lot of specifications that define how plugs and receptacles should be used, ranging from two-and-a-half amps up to 60 amps. This thoroughness sets NEMA apart from much of the rest of the world.
Most countries around the world have their own standards up to a point — usually only up to 16 amps — and after that default to IEC 6309 pin and sleeve standards instead (for example, for high-powered commercial industrial applications).
Everybody takes this approach, except for America and other NEMA standard countries — because they don't have any definitions. They don't have any NEMA definitions of what you use in 20 amps, 30 amps, 40 amps, 50 amp situations.
So everybody worldwide uses pin and sleeve except for NEMA counties. In America, we have all these NEMA standards, for example straight blade standards, and twist and lock standards. For two-a-half-amp, 15 amp, 20, 30, 40, 50 amp, and so on. So there's tons of NEMA standards. And, most of the definitions are found in NEMA’s UL specifications (which in turn are mostly based on NEC standards). NEMA came up with these standards, but they based it on the NEC standard.
A brief history of the United Kingdom’s BS 1363 standard
It was developed to address a previous lack of standardization, as well as some safety fears with prior designs — and formally mandated by the UK Government in 1958 (source).
Here is an example of the UK Government traveling in its own direction, and consciously choosing to develop a standard specific to its own electrical systems and needs, irrespective of IEC recommendations.
A brief history of the European CEE standardsThe European CEE 7 standards were proposed in 1951 originally, and last modified in 1983 (source). Unsurprisingly, there are lots of different standards that vary from nation-to-nation across Europe. To the extent that, as a result, there has been no attempt by the EU to enforce a universal standard across its member states.
That being said, the European Committee for Electrotechnical Standardization (CENELEC), which was founded in 1973 has encouraged the adoption of the CEE 7 standard. In fact, its mission statement is to “help facilitate trade between countries, create new markets, cut compliance costs and support the development of a Single European Market” (source). The result is that most countries across Europe use CEE 7 today.
A part of this movement towards CEE 7 was through compromise. Germany and France initially had different standards — CEE 7/4 and CEE 7/5 — and they decided to make a hybrid of the two, one that would work for both of them (CEE 7/7).
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