An Introduction to the Various Types of Circuit Breakers

In one of our earlier blogs, we discussed circuit breakers and what they do. So, to reiterate what we said, circuit breakers are basically electrical components that stop the flow of electricity within a circuit for the purpose of safety.

For instance, if there’s an overload, the circuit breaker will literally “break” the circuit to prevent electrical fires and other electrical issues.

Now, circuit breakers aren’t all the same. In fact, you have a few options in the market and that’s what we are here to look at. So, let’s explore.

Oil Circuit Breaker

Oil circuit breakers have mineral oil as the quenching medium, which offers high insulation capabilities. The fixed and moving contacts in these type of circuit breakers are immersed in the oil. So, when the current is separated, the carriers come into contact, which sets off the arc.

This vaporizes the oil, which is then decomposed with hydrogen gas to form a hydrogen bubble around the arc. This bubble prevents the arc from re-striking.

Oil circuit breakers are old and quite common.

Air Circuit Breaker

As the name indicates, these circuit breakers work with air. They come with an arc that serves as the quenching medium at atmospheric pressure. Though oil circuit breakers are the most common, air circuit breakers have an advantage over them. You see, oil circuit breakers cannot be used at 15V or more because the oil can catch fire.

This is where air circuit breakers shine.

SF6 Circuit Breaker

In SF6 circuit breakers, you have the current carrying contacts operating in sulphur hexafluoride gas or SF6 gas. The gas offers excellent insulation and high electro-negativity. As a result, it also boasts a high affinity for absorbing free electrons. To put it simply, when a free electron collides with the gas molecule, it gets absorbed.

This results in the creation of negative ions that are heavier than the free electron. So, the mobility of charged particles inside the gas is lower, which means conduction is minimal. Plus, the gas boasts high heat transfer properties due to reduced viscosity.

On the whole, the gas acts as a far more effective quenching medium than the arc in an air circuit breaker. This makes SF5 circuit breakers perfect for use with high voltage electrical systems (33KV to 800KV).

Vacuum Circuit Breaker

Here, vacuum is used as the quenching medium. These circuit breakers possess a dielectric recovery character and are very effective at interruption. They can interrupt high-frequency current even when the arc is unstable.