Circuit Breaker 101: All You Need to Know

A circuit breaker is an automatic power-off switch that protects an electrical circuit from overcurrent. Overcurrent or excessive current can come from circuit overloads, short circuits, arc faults, or ground faults. Circuit breakers use heat or magnetic fields generated by electrical current to cut off the circuit.

Modern homes, buildings, and appliances rely heavily on circuit breakers for fire safety. While the basic function of a circuit breaker is the same as a fuse, the advantage of a circuit breaker is that it does not need to be replaced in the event of an overcurrent, saving money and allowing for quick repairs.

In this article, we will look at the different types of circuit breakers and the applications they are best suited for. They differ based on the voltage level they handle, how they are constructed, the type of interruption they provide, and the type of structural properties they have.

1. What is a circuit breaker?

A circuit breaker is generally understood as an electrical safety device that protects an electrical circuit from electrical anomalies and damage caused by overcharging, voltage fluctuations, and short circuits. The main function of a circuit breaker is to interrupt the flow of current to the connected electrical equipment when a dangerously high voltage is detected, thereby protecting it from any lasting electrical damage. Circuit breakers used to protect against short circuits are also beneficial in avoiding the risk of overloads and electrical fires.

To put it more clearly, a circuit breaker does the same thing as a fuse. Circuit breakers can be reset either manually or automatically, unlike fuses, which should be replaced after overloads.

2. Why circuit breakers are important?

What would happen without a circuit breaker? Given the way a circuit breaker does its job silently in the background, it’s easy to underestimate its actual usefulness.

However, circuit breakers play a vital safety role and their primary function is to provide safety and protection by interrupting the potential dangers that may arise from electrical faults. Here are the reasons why they are important:

Safety First: Circuit breakers prevent electrical overloads that could cause events such as fire, equipment damage, or personal injury. When the system detects an anomaly, it automatically shuts down to protect itself and continue to operate safely, protecting it from harm and keeping it running.
Overload Protection: Sometimes, an electrical system draws more current than it should. Circuit breakers protect the system from this overload by cutting off the excess current, which helps prevent potential fires caused by overheating.
Life of equipment: Power surges and short circuits can significantly shorten the life of your equipment. Circuit breakers help protect expensive equipment by interrupting power during such events.

3. Types of circuit breakers

There are many types of circuit breakers, depending on voltage, installation, external design, location, and breaking mechanism. The following will introduce the types of circuit breakers according to different classification standards.

1). According to voltage level:

Low Voltage Circuit Breakers (LV): Used in circuits operating at low voltages (up to 1,000V) in residential, commercial, and industrial applications. LV circuit breakers are designed for easy maintenance. They are usually easily disassembled for repairs without the user having to disassemble the switchgear. Some components are automatic, allowing operators to open and close them remotely. These circuit breakers can also be used in DC applications. Because the internal arc of DC does not stop and start like AC, a different type of circuit breaker must be used within the equipment.
- Miniature Circuit Breakers (MCBs): Miniature circuit breakers cannot handle currents above 100 amps, making them suitable for many home and commercial applications. Once installed, they are simple to use, but not very adjustable – for example, you usually cannot adjust their trip settings. They operate by thermal or thermomagnetic properties.
- Molded Case Circuit Breakers (MCCB): These breakers can handle currents up to 2,500 amps, making them a more reliable choice for high-power residential and industrial uses. The higher the ampere rating, the trip load can usually be adjusted.
Medium voltage circuit breakers (MV): Used in systems with voltages between 1,000V and 72,500V, for both indoor and outdoor use. Indoor applications have long used air to interrupt the arc, but for voltages below 40,500 volts, they are increasingly switching to vacuum circuit breakers. Current transformers detect the current flowing through the circuit and trip it using an electronically controlled switch. Protection relays monitor the current for dangerous anomalies.
- Vacuum Circuit Breakers (VCB): Vacuum break circuit breakers take advantage of the fact that there are no particles in a vacuum to ionize, so an arc cannot form. They confine the arc in a so-called “bottle”. These breakers have a longer life expectancy than air break circuit breakers.
- Air Circuit Breakers (ACB): These circuit breakers are usually electronically controlled, but some are microprocessor controlled. They are highly configurable, allowing manual setting of delays and trip levels. Air circuit breakers are common in industrial plants and are used to distribute power from a main station.
High Voltage Circuit Breakers (HV): Used in power transmission systems with voltages above 72,500V. These circuit breakers use solenoids operated by protective relays and current transformers. They usually have complex safety nets to prevent overcurrent, which can take many forms. These circuit breakers use a variety of different methods to interrupt the arc: large amounts of oil, trace amounts of oil, air flow, vacuum, sulfur hexafluoride, and carbon dioxide. For example, there are SF6 circuit breaker and oil circuit breaker.

2). According to the operating mechanism:

Air Circuit Breaker (ACB): uses air as the arc extinguishing medium.
Vacuum Circuit Breaker (VCB): uses a vacuum to extinguish the arc.
SF6 circuit breaker: it extinguishes the arc using sulfur hexafluoride gas. Widely used in high voltage applications due to its excellent insulation properties.
Oil circuit breaker: uses oil as the arc extinguishing medium. Commonly used in medium and high voltage applications, but is being phased out due to environmental concerns.

3). According to the installation environment:

Indoor circuit breakers: Designed to be installed inside a building or enclosed space. Typically used in switchgear rooms and control panels.
Outdoor circuit breakers: designed to withstand environmental conditions such as rain, wind, and extreme temperatures. Typically found in substations and outdoor power distribution systems.

4). According to the operating mechanism:

Manual circuit breaker: manually operated by a person to connect or close the circuit.
Automatic circuit breaker: automatically trips when a fault occurs and can usually be reset manually or automatically.

5). According to the number of poles:

Single-pole circuit breakers: protect one live wire and are used in low-voltage applications, typically residential.
Double-pole circuit breakers: protect two live wires and are used in 240V applications such as large appliances.
Three-pole circuit breaker: protects three live wires and is used in three-phase systems commonly found in industrial environments.
Four-pole circuit breaker: protects three-phase systems with a neutral connection, ensuring full protection.

4. What might trigger a circuit breaker?

Just as we introduced the importance of circuit breakers in the previous article, we can also indirectly understand the main reasons for circuit breaker tripping and power outages:

1). Circuit Overload

Circuit overloading simply means that the voltage of the current running through a single circuit in your home or office is too high and is more than the circuit is designed to carry. For example, a single outlet could be overloaded by using multiple extension cords and multiple appliances at the same time. This problem is also more likely to occur if the appliances plugged in require a lot of electricity. If your circuit breaker is activated, this is a good sign that it is doing its best to prevent electrical hazards from causing risks. You can solve this type of problem by separating appliances used on different outlets instead of running multiple appliances on a single circuit. This will reduce the voltage level, making it safer and more controllable for your wiring and electrical output.

2). Short Circuit

A short circuit is caused by incorrect wiring in your home or office or a faulty appliance, switch, plug, outlet, or wire, and just like a circuit overload, causes an electrical current that is too strong for a single circuit to handle. It occurs due to the live (hot) wire coming into contact with the neutral wire and/or another hot wire. When this happens, the charge from each wire combines together, resulting in an unsafe voltage that exceeds the circuit’s load capacity. A sign that a short circuit has occurred is if the circuit breakers are continuously tripping in the same area of the house. Additionally, if you notice a faint burning smell coming from any electrical output, it is important to contact a certified electrician immediately and never try to do anything on your own. This way, they can safely fix your electrical problem and prevent potentially harmful electrical hazards from occurring.

3). Ground Fault

Ground faults are similar to short circuits, but are different because they occur when a live (hot) wire comes into contact with a protective metal box wall or ground wire. This electrical hazard is especially dangerous in wet areas such as bathrooms, kitchens, or outside outlets, so state authorities require that residences be equipped with ground fault circuit interrupters (GFCIs) that should be used in conjunction with safety switches and outlets. If you discover a ground fault in your home, it is vital to have a qualified electrician assess this type of problem, as it can easily cause electrocution, electrocution (especially in wet areas), and even fire. Ground faults are not the easiest electrical faults to spot symptoms of, but if you experience the following; you feel a slight electric shock when you touch a metal surface, if your TV/computer screen displays strobing wires, if you hear a humming/buzzing noise coming from your TV or stereo, or if your GFCI trips frequently, these are signs that you need to seek professional help so that the problem can be properly resolved as soon as possible.

5. When to replace electrical circuit breakers?

Circuit breakers are an essential part of any electrical circuit and help prevent accidents and surprises. Circuit breakers need to be replaced when they show signs of failure or wear. Common indicators include frequent tripping for no apparent reason, physical damage such as burns or corrosion, and circuit breakers that are hot to the touch. Additionally, if an appliance or light connected to the circuit is experiencing power issues, it could be a sign of a faulty circuit breaker. Upgrading the electrical system or adding new, high-demand appliances may also require replacing circuit breakers to handle the increased load. Regular maintenance checks by a professional electrician can help determine if a circuit breaker needs to be replaced to ensure safe and efficient electrical performance.

6. How do I replace an electrical circuit breaker?

It is recommended to seek the help or assistance of a professional electrician for anything related to circuit breakers. Replacing an electrical circuit breaker requires precision and experience. Replacing an electrical circuit breaker involves the following steps:

Power Off: Turn off the main power for safety.
Remove the Panel Cover: Unscrew and remove the electrical panel cover to gain access to the circuit breakers.
Identify Circuit Breakers: Locate faulty circuit breakers that need to be replaced.
Disconnect Wires: Carefully disconnect the wires connected to the faulty circuit breaker.
Remove the circuit breaker: Gently pull the old circuit breaker out of its socket.
Install a new circuit breaker: Insert the new circuit breaker into the slot and reconnect the wires.
Replace the panel cover: Screw the panel cover back on.
Restore power: Turn the main power back on and test the new circuit breaker.

7. Conclusion

Circuit breakers are important devices for protecting electrical and personal safety. They interrupt abnormal currents and return to normal after the fault is corrected. They are also easier to maintain than fuses, saving maintenance costs. A full understanding of the types and usage scenarios of circuit breakers can help us better select and maintain this vital electrical component and protect the safety of household electricity. Don’t forget that when dealing with electrical problems, it is a safer choice to seek the help of a professional electrician.