The Different Types of Circuit Breakers and Their Applications

It is important to acknowledge the dangers associated with improper use and mishandling of electricity and electrical equipment, which may at times lead to serious injury or death. When dealing with electricity it is important to be qualified and to ensure safety is a priority.

Circuit breakers are important in all electrical systems ensuring the safe use of electricity by protecting the system and all the devices from damage from overload and short circuits. Circuit breakers are also important to the users, in case of electrical faults that could cause harm to the user.

Circuit breakers are thus an essential component in any electrical system, from small residential systems to large industrial setups and commercial installations. These circuit breakers ensure the systems are safe, and reliable and can automatically protect the electrical system and equipment against electrical faults such as overloads, shorts and ground faults.

What is a circuit breaker?

Essentially, circuit breakers are safety devices designed to protect electrical systems and equipment from damage due to electrical faults from overloads or shorts. As such, circuit breakers help prevent fires, electrical shocks, and other hazards associated with electrical faults.

Circuit breakers work by automatically detecting faults and interrupting the flow of electricity if a short or overload is detected. This helps prevent further damage by preventing any overheating and further damage that could cause fire or any more damage. Once the circuit breaker is tripped, that is breaks the flow, it can only be restored through a manual reset.

Circuit breakers are of several types and classes depending on their unique applications and characteristics. The choice of the circuit breaker to be used in any system depends solely on the specific application, the electrical system being deployed, and also the types of faults to be expected. Some of the most common circuit breakers include air circuit breakers, miniature circuit breakers, molded case circuit breakers, ground fault circuit interrupters, residual current circuit breakers, earth leakage circuit breakers, and high voltage circuit breakers.

How Circuit Breakers Work?

The mode of operation of circuit breakers is very basic but also important to understand before installing or choosing one for a particular reason. As stated earlier the choice of a circuit breaker will be very heavily dependent on the application and system.

The cables and other system elements present resistance to electrical current as it travels through a circuit. A fire or other hazard may result from excessive current flowing through the circuit, which can overheat the wires and other components. Circuit breakers, as the name suggests, are made to recognize when a circuit's current is too high and instantly break the flow of electricity to stop harm.

When installed in the system, the circuit breaker is meant to continually monitor the current flowing through the circuit and detect any overload. All circuit breakers have a current rating for the maximum load that they can bear. Once the current flow exceeds the rated current, the circuit breakers trip, or break the circuit thus cutting off the flow of current.  In turn, this prevents the wires and components in the systems from overheating and further damage.

Classification of circuit breakers

The classification of circuit breakers can be based on several factors such as application, mode of operation, voltage levels, the medium for arch quenching, interrupting rating, how they are made, and other factors. The widest classification is based on the electrical system type and can be either alternating current (AC) circuit breakers or direct current (DC) circuit breakers. Both of these operate similarly.

Further, in a more general classification circuit breakers can be based on the voltage levels in which they operate. Here is a classification from the highest to the lowest:

1. High Voltage Circuit Breakers: Electrical power transmission and distribution systems carry voltages above 72kV AC, normal circuit breakers cannot be used. Hence high voltage and ultra-high voltage circuit breakers are designed to interrupt high-current faults. These circuit breakers control and protect the electrical power transmission lines. HV circuit breakers are operated using solenoids.

2. Medium Voltage Circuit Breakers: These are used in power distribution systems for voltages between 1000V and 72kV AC and can interrupt medium current faults. Unlike the high voltage circuit breakers and the low voltage circuit breakers, medium voltage circuit breakers can be operated manually and also controlled electrically using solenoids.

3. Low Voltage Circuit Breakers: These are used in low voltage power distribution systems for voltages up to 1000V AC and can interrupt low current faults. Low-voltage circuit breakers can be found in small-scale industrial settings and enterprises.

4. Miniature Circuit Breakers: These are used in residential, commercial, and light industrial applications for voltages less than 1000V AC and can interrupt low current faults. Mostly miniature circuit breakers are used in 120/240/415V electrical systems.

This classification is only based on the operating voltage levels, and thus it is important to understand that the type of circuit breaker used in each instant in a circuit has its application. All circuit breakers serve different applications, characteristics, and construction.

Common types of circuit breakers

There are several types of circuit breakers, each with its unique applications and characteristics. Here are some of the most common types of circuit breakers and their applications:

Low Voltage Circuit Breakers

1. Air Circuit Breakers (ACBs)

ACBs are designed to handle large currents and are often used in low-voltage power distribution systems. ACBs operate within 800 to 10000 amps and voltages less than 450V. They can also be used as backup protection for motors, generators, and other high-powered electrical equipment. The ACBs are slowly replacing the oil circuit breakers.

2. Miniature Circuit Breakers (MCBs)

MCBs are typically used in residential and commercial applications to protect against overloads and short circuits. They are designed to trip at lower currents and are often more sensitive than other types of circuit breakers.

3. Molded Case Circuit Breakers (MCCBs)

MCCBs are similar to ACBs in that they are designed to handle larger currents. However, they are typically used in more demanding industrial applications, such as manufacturing plants and data centers.

4. Ground Fault Circuit Interrupters (GFCIs)

GFCIs are designed to protect against electrical shock in wet or damp environments, such as bathrooms, kitchens, and outdoor areas. They monitor the current flowing through a circuit and will trip if a ground fault is detected.

5. Residual Current Circuit Breakers (RCCBs)

RCCBs are similar to GFCIs in that they protect against electrical shock. However, they are designed to monitor the imbalance of current between the live and neutral conductors of a circuit, rather than detecting a ground fault.

6. Earth Leakage Circuit Breakers (ELCBs)

ELCBs are another type of circuit breaker designed to protect against electrical shock. They detect and interrupt current leakage to the earth, which can occur when an appliance or device becomes damaged or faulty.

Medium and High Voltage Circuit Breakers

7. Vacuum Circuit Breakers

A vacuum is used as the arc quenching medium in a vacuum circuit breaker, also known as a VCB. The vacuum is significantly more effective than any other medium for quenching arcs because of its extremely high dielectric strength. It can rapidly regain its dielectric power. A very tiny distance between the contacts of a VCB is necessary to prevent restriking due to its high dielectric strength. The vacuum pressure employed in VCB is between 107 and 105 torrs (1 torr = 1mm of Hg). It is appropriate for medium-voltage switching between 22 kV and 66 kV.

8. Sulphur Hexafluoride gas (SF6) Circuit Breaker

Sulphur hexafluoride gas circuit breakers are primarily utilized in medium-voltage applications. It is also known as SF6 circuit breakers. Because of its high efficiency at quenching arcs, SF6 gas is employed in this breaker for this purpose. The gas is nonflammable and good at insulating and absorbing electrons, i.e., electronegative.

While being extremely effective in quenching arcs, SF6 breakers, use SF6 gas which is expensive, toxic, and greenhouse gas. Thus, these breakers are still not widely used because they pose a risk to both humans and the environment.

9. Oil Circuit Breakers

Oil circuit breakers are the kind of circuit breakers that employ oil as a dielectric or insulating material to quench the arc. One of the first high-voltage circuit breakers primarily uses transformer oil. These circuit breakers employ oil, which has far superior insulating qualities than air. Once the contacts split, oil is poured over the CB contacts to quench the arc. The oil serves as a heat sink for the heat produced by the arc.

10. High Voltage Circuit Breakers (HVCBs)

HVCBs are used in high-voltage power transmission systems, such as those used to transmit electricity across long distances. They are designed to handle extremely high currents and are critical components in ensuring the reliability and safety of the power grid.

In order to maintain the security and effectiveness of your electrical system, it's critical to select the appropriate type of circuit breaker.