The Evolution of the Circuit Breaker: 1940-Present

Man Studying Plans - Retro Clipart IllustrationThe circuit breaker is arguably one of the most useful innovations in the field of electrical wiring. Its primary function is to protect an electrical circuit from being damaged in the event of a short circuit or an overload of current. It is unique in the sense that you can reset the circuit breaker to have it working again. Prior to this, using a fuse was the norm. The problem with the fuse was that it would have to be replaced every time a short circuit happened.

The very first circuit breaker was devised in 1879 by Thomas Edison, when he came up with the idea of protecting circuit wiring used for lighting from the common problems of current overloads and short circuits. Of course, we now know that his system suffered from the fatal flaw of using fuses that would need to be constantly replaced.

Many other inventors up to the 1940s would present their version of the circuit breaker and progress was made. Looking back at their designs, it is fascinating to see how many of them were representative of the ones that are now commonly used. It was not until the 1940s that circuit breakers were able to see mainstream use in homes, factories and buildings.

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Our Need for Circuit Breakers

In the 21st century, circuit breakers are used virtually everywhere. Homes, buildings, and entire cities are able to provide its inhabitants with electricity. People no longer have to worry about losing power because of a single short circuit, and they are designed to handle high voltages and currents. With a rise in the world population and a greater demand for power, there was no choice but to design breakers that would allow for this. But how did we get to the point where circuit breakers have become so reliable and powerful?

Circuit breakers are used in

To answer this question, you need to travel all the back to the 1940s. At that time, circuit breakers were still a hot item when it came to managing and using electricity. Many people were still experimenting with different ways to create the most efficient circuit breakers possible while allowing for them handle higher levels of current. In the context of a single family home, the standard was a 30-amp fuse panel that provided 120 volts. Two plug fuses were installed to protect the branch circuits, and you had one large switch that would disconnect the power.

In the late 50s, 60-amp circuit breakers were the norm, and they were able to provide twice the voltage of the previous models. This was due to the fact that you now had four plug fuse blocks and two cartridge fuse blocks. As a result, four separate branch circuits were now available. This was the first time that you could label the location that each branch circuit was feeding power to.

Electrical ground wires connected to a metal plate junction.

Compared to today’s standards, there was a very limited amount of power that these panels could provide. Your normal living standards would lead to non-stop overloading and short-circuiting in a home in the 50s, even equipped with the best circuit breakers they could get their hands on!

Things got better in the 60s when the circuit breaker came in the form of an electrical panel that provided several rows of circuit breakers. You could provide up to 200-amp services while having expandable circuit spaces (12-24 of them). What does this mean? It means that these homes can provide lighting to several places in the home and provide electrical power to the outlets. This was also the time period where fuse-based circuit breakers were being shipped out due to the fact that they had to be changed whenever a fuse got blown.

You will not be able to have anything less than a 100-amp panel installed in today’s world. That’s how far we have come in providing everyone with circuit breakers that can provide high levels of electrical power on a daily basis.

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The Technology Used

Woman electric wiring technician at Douglas Aircraft Company, Long Beach, California. During World War 2, Oct. 1942.Now that we understand how powerful circuit breakers have become, another question that comes up in the evolution of circuit breakers is the technology that was used to make them better. After the second World War, there were heavy reconstruction efforts to restore order. One of the areas of particular interest was designing circuit breakers that could efficiently interrupt high levels of current.

The main challenge people faced was that when you interrupt the current, the air temperature near the circuit breaker instantly rises and an electric arc is formed. This arc acquires thermal energy that is proportional to the size of the current that is being halted. According to measured data, “electric arcs have enormous energy: Their temperature can exceed 50,000oC and pressures up to 100 MPa can be contained within a volume of less than a liter.” Imagine the effect that this arc would have in a power plant!

The circuit breakers made before the 1940s were primarily oil-filled and could only handle low levels of voltage and current. Oil was used because it was shown to be a good electrical insulator. The main weakness of these circuit breakers was that a large volume of oil was required to quench the arc and contain it. This made it largely impractical from a size standpoint. Moreover, if the arc could not be quenched, and pressure was allowed to build up, you faced a serious risk of a flammable explosion.

electrical shield, old switchboardWith that in mind, there was a shift toward developing compressed air circuit breakers. The mechanism for canceling out the arc works as follows: The pressure difference between the ambient air outside and the inside of the breaker creates convection that cools the arc down. After some tweaking and fixing, engineers were able to come up with a valve design that could release compressed air from the chamber in a safe and effective manner.

This gave compressed air circuit breakers the advantage of easier maintenance, but compressed air circuit breakers were far from perfect – the reliance on air meant that they were far larger than oil circuit breakers and required more complex machinery.

For almost 3 decades, there was a relentless amount of competition between air circuit breaker companies and oil circuit breaker companies. It was hard to see which one of them would emerge as the victor in this technology race.

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Which Tech Was the Victor?

The irony of the situation is that both types of circuit breakers would eventually be phased out for a superior technology: Circuit breakers powered by sulfur hexafluoride (SF6), an inert gas that possessed superior insulating properties to either available solution. SF6 technology was phased out in the 60s and would eventually replace the previous circuit breakers (oil and compressed air) by the start of the 90s.

a 3d render of a sulfur hexafluoride

The SF6 circuit breaker works as follows: When the arc is formed in a circuit breaker, a high pressure flow of cold SF6 gas is released and interacts with the arc to extinguish it. Sounds simple, right?

It certainly was – it was superior than the other circuit breaker models on all fronts. The noise level was minimal, there was no fear of explosions due to the high flammability of the breaker’s liquid, maintenance was easy, and the operation was clean. Predictably, this led to sales of oil breakers and compressed air breakers tanking and eventually being phased out as a thing of the past. Sure enough, SF6 breakers were developed to have far greater breaker capacity than any model before it.

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  New type Trip Switch Fuse box. All switches are ON position. Electricity, power, fuse related.A New Breaker Comes Along

Alongside SF6 technology was yet another viable competitive: the vacuum circuit breaker. This breaker operates on the principle of quenching the arc in the “vacuum interrupter,” a closed chamber within the breaker. When the contacts separate, a metal vapor arc discharge is initiated, and the arc is extinguished in the blink of an eye. This is possible because of the high dielectric strength that exists between the separated contacts. For context, this dielectric strength is up to four times greater than SF6 gas!

One of the main advantages that vacuum breakers have is that they require less operating energy than SF6 breakers. No additional extinguishing medium is required, and it has a far greater capacity for the number of times it can experience circuit overload before some form of retrofitting needs to be done.

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Head to Head

Right now, we have two superior technologies that are competing head to head. Even with the advantages listed in the previous paragraph, they are minute to the point where many experts agree that neither one is better than the other. Some companies will prefer to use one type of circuit breaker over the other for reasons that include personal preference, company traditions and rules, and so on.

Where does this leave the future of circuit breakers? Are we going to see a fusion of vacuum and SF6 circuit breaker technologies? Will a new third party rise from the ground and leave both of them in the dust? What can we expect?

Electrical and Instrument working on direct current power distribution system

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Time for an Upgrade? Not Quite Yet

Two male arms reaching for each other, with a smoking electric current connecting their fingers in empty space background conceptThe major game-changer in this field would be the ability to prevent arc formation from happening in the first place, instead of having to manage it. This would require re-thinking basic electrical principles and our understanding of how circuits are designed in the first place.

However, we may eventually see the rise of circuit breakers that are entirely electronic in design. They would not have to rely on any kind of gas or external material in order to perform their job. We are already seeing prototypes of this kind of breaker in high-voltage, direct-current (HVDC) systems.

The only problem we have right now is that the technology is not up to par. It would cost too much money and the design would be far more complex than what we currently have with the vacuum and SF6breakers. You will have to wait a few decades until this kind of technology will be made available to the public.

No matter which technology you choose to use for your business or your building, always make sure that you are choosing a trusted, qualified and reliable supplier that has a large inventory, and professionals who can help answer any questions or queries that you might have. You need to choose the circuit breaker that best fits your requirements and needs.