Types of Electrical Circuit Breakers

The current demand for electricity in Sydney is quite high. At the same time, houses cannot handle these huge power demands resulting in electrical faults.

The best option to halt any electrical related mishaps in your home is to control the heart of the electrical system – the circuit breaker.

Circuit breaker automatically shuts off the switch when there is overcurrent or electrical fault. It functions to isolate the faulty point under abnormal conditions that protect your power system. Widespread in use for almost a century, the device is one of the most critical fire safety tools in modern homes, buildings and appliances.

Under normal conditions, the circuit breaker has two metal contacts intact, allowing the passage of current to your electrical system. During the circuit breaking process, the contacts separate and arc forms between the gaps instantaneously.

Even though the contacts separate when you turn off your circuit breaker, the formed arc provides a low resistance path for the current. It builds up heat in the device and delays the circuit interruption. That’s why the efficiency of circuit breakers depends on how it can extinguish or interrupt the arc immediately.

Moreover, interrupting the arc depends on the medium between the two contacts such as oil, air, sulphur hexafluoride (SF6) and vacuum. Knowing how arc reacts to these media can help you determine what circuit breakers would most likely prevent electrical fire, shock or electrocution.

Also, these media differ significantly on what type of circuit breaker you’re using. Thus it’s essential to know the types of electric circuit breakers to avoid future electrical mishaps in your home.

That said, here are the different types of electrical circuit breakers:

Types of Circuit Breaker 

Based on Voltage Range

The first logical classification of the circuit breaker depends on the voltage range intended for circuit breakers usage. Here are the different voltage ranges:

  1. Low voltage CB (less than 1kV)
  2. Medium voltage CB (1-52kV) 
  3. High voltage CB (66-220kV)
  4. Extra high voltage CB (300-765kV) 
  5. Ultra-high voltage CB (above 765kV)

The low voltage circuit breaker is the most common among these. It’s usually installed in your homes, markets, business, and small-case industries. On the other hand, both medium and high voltage CBs are common in transmission class breakers. While the two last highest intended voltages are used in power plants and other wide-scale projects.

Installation Location

Aside from the voltage range, the difference in parts of the circuit breakers makes it preferably installed in two locations. Here are the two types of circuit breaker based on site:

Indoor Type 

These circuit breakers are designed to use in weather-resistant enclosures in buildings, homes and the likes. It typically includes low, medium and high voltage gas insulated switchgear with a metal-clad enclosure.

Outdoor Type

These types don’t usually need a roof due to their design and can withstand wear and tear. Outdoor CB has an external insulating medium that makes it more suitable outdoors than its counterpart.

Both types have almost the same operations, interrupting mechanism, and internal structures such as current-carrying parts. They only differ in installation location due to the main difference in enclosures and packaging structures.

External Design

The external design differs only for outdoor type circuit breakers. Its basis is the physical structure design that is subdivided in two ways:

Dead Tank

These breakers are at the ground potential that encloses all interrupting and insulating media. In other words, the tank is shorted at a ground position or dead potential.

Live Tank

These breakers have tanks enclosing the interrupter and insulating medium. It is above the ground with insulation in between, thus having higher potential than the ground.

Medium Used for Arc Quenching

The most significant classification of circuit breakers is determining its interruption medium used for arc quenching. The common media used are air, oil, vacuum and SF6 (Sulfur hexafluoride). Currently, other different interruption techniques use magnetic, thermal and other modes but revolving around the same shared medium.

Oil Circuit Breakers

In oil circuit breakers, the oil serves as an arc extinguishing medium. It means that when the contacts open in oil, the arc forms producing heat and the surrounding oil evaporates as hydrogen gas. 

The oil acts as an insulator between the two conducting parts of the circuit breaker. One of the reasons why mineral oil is a better medium than air is due to its excellent cooling properties. Oil circuit breakers fall into two categories:

  • Bulk Oil Circuit Breaker- It uses transformer oil as the arc extinction medium of the circuit breaker. The rating range of this lies from 25MVA at 2.5KV to 5000 MVA at 230KV.
  • Minimum Oil Circuit Breaker- From its name, it requires less oil that acts as interrupting media. The oil in this breaker disrupts the arc formation, and it doesn’t insulate the live parts of the earth. 

Under the oil-less breaker, there are four main types of oil circuit breakers namely: air circuit breaker, air blast circuit breaker, Sulphur hexafluoride circuit breaker and the vacuum circuit breaker.

Air Circuit Breakers

The air circuit breakers are suitable for high current interruption at low voltage. It uses air at atmospheric pressure as an interrupting medium. Examples of these breakers include:

  • Plain Air Break Circuit Breaker
  • Arc-Chute Circuit Breaker
  • Magnetic Blow-out Type Circuit Breaker

Air Blast Circuit Breakers

It is the second air-based medium in circuit breakers. But the main course of this type uses a blast of air to blow out the arc. The air interrupts the arc in axial, cross and radial blast. 

In the axial air blast, the air flows in the same direction as the arc. Meanwhile, the cross and radial blast flows perpendicularly and radially, respectively.

Sulphur Hexafluoride Circuit Breakers

In this type of breaker, it uses sulphur hexafluoride gas to interrupt the arc. The compound has a very high insulating and disrupting property, making it superior to oil or air.

Vacuum Circuit Breaker

The vacuum has the highest insulating strength that outpowers any medium in terms of interrupting arcs. The whole construction of this material is very simple compared to other circuit breakers. 

Aside from its ability to interrupt very high current, such a type is less bulky, cheaper in cost, needs negligible maintenance and has a long life.


Once a power system is established, it’s crucial to control and protect it from faults. During electrical failures, the arcs of the circuit breakers produce heat that can damage anything in your system or cause any accidents. Controlling your circuit breakers efficiently depend mainly on effective extinguishing of the arcs. 

Knowingly, the different media in the circuit breaker interrupt the arcs. Meanwhile, the various circuit breakers have their specific medium; thus, it’s essential to know the types of electric circuit breakers. Overall, circuit breakers differ mainly on voltage, installation location, external design and interrupting mechanism.

Sutherland Shire Electrician can help you on what’s the best circuit breaker for your home. We can help you with your electrical requirements with the guarantee of quality work from our level 2 electricians. We aim to make you happy with our reliable 5-star service.

Call us at (02) 8378 2825 today, and we are always ready to help.

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