Circuit Breaker

A circuit can be damaged which will reduce its reliability. Therefore, electrical circuits need to be protected using circuit protection devices. These will help a lot in boosting the performance of electrical tools. Plenty of devices such as fuses,  chokes, decoupling capacitors Zener diodes, protection diodes, etc, can be utilized for the protection of circuits. Circuit breakers are also used for the same purpose in electrical systems.

A circuit breaker can be defined as a type of switching device that prevents damage to the electrical system by acting as a switch and that interrupts the current flow. This article will take a closer look at circuit breakers along with various types, we will study their advantages and disadvantages, examine their operational principles, and more.

What is a Circuit Breaker?

A circuit breaker is a switching mechanism that may be operated either manually or automatically to cut off the flow of electricity when it detects an abnormal current or fault in an electrical circuit, therefore reducing the overloading and short circuit situations.

Circuit breakers are often employed in household,  industrial, and commercial electrical setups so as to protect items from harm. They are crucial for preserving both the electrical infrastructure’s security and that of the connected devices.

• Circuit Breakers serves the same function as fuses but unlike fuses they are not destroyed/burn when activated or triggered .
• Unlike fuses, we do not need to replace them and can simply be reset once the fault has been recognized.
• When an overload occurs, a circuit breaker will open the circuit to prevent any type of harm .
• They contain a switch to return to the closed position once they have been flipped.

Working Principle of Circuit Breaker

A circuit breaker has mainly 2 contacts :

1. a moving contact
2. a fixed contact

Normally, the contacts are closed, thus allows current to pass throughout the circuit. A mechanism that releases accumulated potential energy separates the contacts in case of any  overload or short circuit. That mechanism may be magnetic, pneumatic, hydraulic, or spring-operated.

An arc, which is  strongly ionized and conducting plasma, is formed when contacts are  separated. The arc can damage the contacts and the surrounding equipment if not extinguished quickly.

Therefore, various methods like cooling, compressing, or replacing the ionized medium with fresh gas are used to quench the arc in circuit breakers. The voltage level and current rating of the circuit breaker determine the appropriate arc quenching medium to utilize.

Circuit breakers protect overload, short circuits, and overcurrent damage to the circuits. When a fault occurs in circuit , breakers cut off the current flow and then restart it once the issue is fixed. A circuit breaker may be reset and used again, unlike a fuse, which needs to be changed after just one use.

In a broader sense a circuit breaker mainly interrupts the flow of electricity by rapidly opening the circuit to identify a defect and monitoring the current in a circuit. Combining thermal and magnetic principles enables a dependable reaction to different kinds of failures, guarding against short circuits and over currents.

Working of Circuit Breaker

Types of Circuit Breakers

There are mainly four types of Circuit breakers

• Air Circuit Breaker
• Vacuum Circuit Breaker
• Oil Circuit Breaker
• SF6 Circuit Breaker

Air Circuit Breaker

The arc extinguishing medium of these breakers is high-pressure air blast , so they are also known as air blast circuit breakers. In case of an inaccurate flow, the blast valve opens the contact. By sweeping  ionized particles in the environment, the arc is prevented from restriking, raising the dielectric’s electricity in the medium.

There are three types of Air Circuit Breaker:

• Axial blast type
• Cross blast type
• Radial blast type

Vacuum Circuit Breaker

The arc quenching medium used  in this circuit breaker is a vacuum. The vacuums’ arc resistance is very low whereas the dielectric strength is very high . A container made of ceramic or metal encloses the contacts.It has been evacuated to extremely low pressure .

When the contacts open, the arc is initiated in the vacuum and quickly extinguished. Very low arc resistance and high dielectric strength of vacuum, makes the interruption process very fast and efficient.

These circuit breakers are appropriate for low and medium-voltage applications, such as commercial and industrial circuits. Their arc energy and noise level are low ,while reliability and durability are high.

Oil Circuit Breakers

Oil is utilized as the arc extinguishing medium ,in this circuit breakers. The arc strikes once the contacts are opened in the oil, hence, evaporating the surrounding oil as hydrogen gas. The arc is surrounded by a hydrogen gas bubble. This hydrogen gas has a high thermal conductivity which cools the arc and deionize the medium.

The surrounding oil becomes turbulent, leading the arcing products out of the way. When the system experiences a fault, the circuit breaker’s contacts open under the insulating oil, creating an arc that cools the surrounding oil and releases heat. There are two categories of oil circuit breakers.

There are two types of oil circuit breakers:

• Bulk oil circuit breakers
• Low oil circuit breakers

SF6 Circuit Breakers

Sulfur hexafluoride gas (SF6) is used by SF6CBs. Due to this gas’ superior insulating qualities, SF6CB devices are incredibly efficient.

Moreover, SF6 is a far more efficient cooling medium than air since it quickly recombines after extinguishing the arc. Since the gas utilized has good dielectric qualities and is non-flammable, SF6CBs are particularly effective devices in medium and high voltage systems as a result of these characteristics.

Advantages and Disadvantages of a Circuit Breaker

Some of the Advantages and Disadvantages of a Circuit Breaker are given Below

Advantages of a Circuit Breaker

• It prevents/halts the excessive flow of current which can cause damage.
• Circuit Breakers is in a form of a switch , therefore can be reset anytime .
• They are very reliable.
• Provide selective protection as well as isolation of different parts of the power system.
• Interrupt high fault currents without producing harmful gases or flames.
• Minimizes the possibility of fault-related fire dangers and power disruptions.

Disadvantages of Circuit Breakers

• Installation and repair are expensive in comparison to fuse.
• Fuse reacts faster than a circuit breaker.
• For proper operation, they needs regular maintenance and testing.
• They might result in transients or voltage spikes while switching.

Applications of Circuit Breaker

Some Applications of Circuit Breakers are :

• They are used for switching of loads in commercial complexes, industries, and buildings, hotels etc.
• They are also used , for protection against short circuits, faults, overloads etc. in rail vehicles, such as trains, trams, metros, etc.
• Circuit breakers are used to protect distribution transformers ,induction motors etc., They also offer demand response and load management for power system loads.

How to test a Circuit Breaker ?

If a circuit continuously keeps tripping whenever you use gadgets, it could be the time to replace your breakers . Checking the voltage levels with a digital multimeter makes it simple to determine if breakers have the issue.

Follow these steps :

• Unplug/turn off all devices connected to the breaker.
• Take out the panel from the breaker box .
• Turn on your digital multimeter.
• Hold the red probe against the screw on the breaker you’re testing.
• Put the black probe against the neutral bar.
• Compare the meter reading to the breaker requirements.
• If you have a single pole breaker, verify that the reading on it is around 120. The breaker needs to be replaced, if reading is 0. In case of a double pole breaker, make sure that the reading is between 220-250 V. The voltage of a faulty double pole breaker is 120 V, means it uses only half of its power.

How to Replace a Circuit Breaker ?

After testing the Circuit Breaker , we need to replace the circuit Breaker if it’s found to be faulty.

To replace the faulty Circuit Breaker follow the following steps

• Find a replacement breaker with the same voltage.
• Turn off the individual breaker you need to replace.
• Now, take out the wires by loosening the terminal screws.
• Remove the old breaker.
• Push the new breaker in by slide its clips into position.
• Tight the terminal screw using needle-nose pliers to hold the wires.
• Then, turn on the breaker and attach the panel again to the breaker box.

Conclusion

Circuit breakers acts as the essential safety devices, that interrupts/stops the flow of current in case of overload or faults. Their innovation has revolutionized the electrical systems, offering protection against damage, fire hazards, and even enhancing efficiency. As the technology evolves, circuit breakers continue to adapt, remaining indispensable in safeguarding our modern-day electrical infrastructure.

FAQs on a Circuit Breaker

Differentiate between a fuse and the circuit breaker ?

The basic differences between them is that a fuse is a piece of metal that melts when an overload occurs , while a circuit breaker has an internal switch that trips in case of excessive current flow in the circuit .

How does a circuit breaker trip?

The circuit breaker trips when excessive amount of electricity /current load flows through a circuit . The flow of electricity is cut off to keep the circuits/appliances safe from overheating or damage.

Explain the advantages of an Air Circuit breaker.

The advantages of an air circuit breaker are

• There is no risk of fire.
• As the dielectric strength increases faster, it leads to contacts having less gap in between.
• There is no need for arcing products
• The arcing time and energy are small, so frequent operations can be done.
• The interrupting current has no effect.

What are the signs of a bad breaker?

Following are the typical signs of a bad breaker:

• Burned parts and ragged wires in the circuit breaker.
• The obvious signs of wear and tear.
• The burning smell of the electrical panel.