Types of electrical circuit breakers 1
Types of electrical circuit breakers
Circuit breakers are essential elements of the electrical distribution system, playing a vital role in protecting electrical circuits and appliances from overcurrent and short circuits. These devices are extremely important to ensure the safety of individuals and property, and contribute to achieving the sustainability and efficiency of electrical systems.
A wide range of circuit breakers are available in the market today, and they come in different sizes and designs to meet different needs. The use of these breakers ranges from small household applications to large industrial systems. Whether you are considering protecting a small electrical circuit in your home or managing a large industrial electrical grid, a good understanding of the types of circuit breakers and their functions is essential.
Electrical breakers are diverse in their designs and functions, including main and detail electrical breakers, fuses, and circuit breakers that serve different purposes. The choice of breaker type depends on the nature and planned use of the electrical circuit.
In this article, we’ll explore the types of circuit breakers in more detail, including a breakdown of each type’s functions and the criteria to consider when choosing the right circuit breakers for your specific electrical application.
What should a circuit breaker do?
The main purpose of circuit breakers is to open the circuit safely. To ensure this goal is achieved, the circuit breaker must perform several vital functions:
- Withstanding fault current for short periods:The circuit breaker must be able to withstand fault current for short periods, which allows other circuit breakers to intervene and solve the problem.
- BREAKING A CIRCUIT SAFELY: A circuit breaker must be able to break a circuit in a safe and efficient manner when a fault current is detected, using stored mechanical energy, such as a spring or compressed air.
- Quickly extinguishing the arc:The circuit breaker must have the ability to quickly and effectively extinguish the electric arc that arises between the contacts, to avoid damage resulting from the heat of the arc.
- Withstanding voltage after disconnection:The circuit breaker must be able to withstand the voltage after disconnection, to ensure that there is no negative impact on the contacts or other electrical devices.
- Preventing re-tripping:A circuit breaker must prevent re-tripping, which is an essential part of its function to protect electrical systems and equipment.
When fulfilling these functions effectively, a circuit breaker can contribute to maintaining the integrity of electrical circuits and ensuring their safe and efficient operation.
Arc extinction media deal with electrical challenges effectively and play a vital role in ensuring safety and protection in electrical systems. Here’s a paraphrase of the information:
Arc extinction modes:
When an electric arc attempts to create a circuit, it becomes crucial to suppress it to avoid dangers. There are several methods used for arc extinction, including:
- Air:
- Arc Cooling: It helps in cooling the arc to maintain air resistance and reduce current.
- Air Blowing: Used in circuit breakers where the arc is quenched using a blast of compressed air, enhancing the dielectric strength of the air.
- broom:
- The technique of using a broom to suppress the arc and improve air insulation.
- Insulating oil:
- Used in some breakers to effectively cool and extinguish the arc.
- Insulating gas (such as SF6):
- It is used as an insulating medium to improve insulation and arc suppression properties.
Methods used for arc extinction:
- Arc cooling:
- It relies on arc cooling to increase air resistance and reduce current.
- Air blowing:
- A blast of compressed air is used to quench the arc and improve air insulation.
- Increase arc length:
- The length of the arc is increased to increase the effort required to maintain the arc, eventually leading to its extinction.
- Reduce the cross section of the arc:
- It is used to reduce the arc cross-section and increase its resistance.
- Arc deflection:
- A magnetic field is used to deflect and cool the arc.
- Division or division of the arc:
- The arc is divided into small arcs to reduce the current and extinguish the arc.
- Zero current cooling:
- It is used in alternating current to avoid current surge at zero point.
- Using a capacitor charged in parallel:
- It is used in DC circuit breakers to introduce artificial zero current to extinguish the arc.
These media and methods reflect the extent of technological development in the field of electrical circuit breakers and how to improve their performance and safety.
Types of circuit breakers based on the type of current:
Electrical circuit breakers vary based on the type of current they operate on. They are classified into two main types: AC circuit breakers and DC circuit breakers.
- AC circuit breakers:
- Alternating current refers to a current that changes direction regularly, where the voltage and current can reach zero several times per second.
- AC circuit breakers provide frequent opportunities for arc suppression at zero points, which increases their efficiency.
- Choosing AC circuit breakers requires careful consideration of high voltages which can require special techniques to effectively suppress the arc.
- DC circuit breakers:
- DC current is a constant voltage and current in one direction.
- The challenges of arc suppression in DC circuit breakers are different due to the lack of zero arc points.
- These breakers use special techniques such as using capacitors charged in parallel to introduce artificial zero current and extinguish the arc.
High voltage circuit breakers:
High voltage circuit breakers are divided into two main parts:
- Oil circuit breakers:
- It relies on insulating oil to improve insulation and arc cooling properties.
- It is used at high voltages and is considered effective in quenching the arc.
- Electrical circuit breakers without oil:
- Do not rely on oil to extinguish the arc, but rather use other means such as air, vacuum, and insulating gases.
- They offer environmentally friendly alternatives that are more suitable for modern applications.
Classification of circuit breakers depends on the type of current and voltage level, which is vital for achieving better efficiency and safety in electrical power systems.
Minimum Oil Circuit Breaker (MOCB):
This type of oil circuit breaker uses less oil as compared to BOCB. MOCB are used in applications that require fast arc suppression efficiency but with smaller amounts of oil.
MOCB are based on the same general principle of using oil to quench the arc and cool the contacts. The contacts are immersed in oil, and when the contact is broken, a thermal arc is created, and gas is generated that replaces the oil inside the tank. The air at the top of the tank acts as a cushion to decompose the gas.
Bulk Oil Circuit Breaker (BOCB):
BOCB uses large amounts of oil and is based on the same basic principle. It varies with respect to the design of the tank and the way the oil is stored and cooled. It uses a large iron tank that holds a large amount of oil, and this design provides better control of oil flow and cooling.
These systems are ideal for applications that require effective arc suppression and efficient contact cooling in conditions where voltage is subject to large fluctuations.
Oil circuit breaker technology remains in use in some applications as oil is an effective insulator and able to withstand harsh environmental conditions.
Single Break BOCB:
In this type of oil circuit breaker, one fixed contact and one moving contact are used. When a current fault occurs, the moving contact moves backward, generating an arc that is suppressed by the compressed gas inside the oil. Only one separator is provided between contacts.
Double Break BOCB:
In a dual BOCB splitter, two types of fixed contacts and one moving contact are used. Fixed contacts are fixed to the tank at both ends connected to the live conductors, while the movable contact can move up and down using an insulating rod.
Under normal operating conditions, the moving contact is pushed up to make contact at both ends with the fixed contacts. When a fault occurs, the moving contacts are pulled down to break the contacts and generate arcs at both ends. In this way, the arc is divided into two parts that have less strength and can be easily cooled and quenched inside the oil.
Advantages:
- The oil has high dielectric strength.
- The oil isolates the live contacts from the grounded parts.
- The production of hydrogen gas helps in cooling the arc.
- Oil pressure helps displace gas and improve insulation properties.
- Reduces the effect of current chopping when disconnecting.
cons:
- The oil is flammable and can pose a fire hazard.
- The arc may damage the contacts.
- Repeated use can cause carbonation in the oil, reducing its barrier effectiveness.
- Requires regular maintenance to check contacts and oil.
- Oil requires a large amount, which increases the cost.
- Large cabinets take a lot of space and weigh a lot.
In terms of venting, MOCB is divided into two types.
Axial Ventilation MOCB: In axial ventilation MOCB, the openings of the arc chamber are designed in such a way that when the moving contacts slide down to break the circuit. A hole allows cold oil to move from the lower hole sweeping the arc in the axial direction through the upper hole.
Axial venting generates very high pressure and therefore has very high deionization capabilities and thus high oil dielectric strength. It is used for low current at high voltages.
Radial Venting MOCB: During radial venting MOCB, the openings are designed radially along the arc chamber. Therefore, the arc is swept radially through multiple vents.
The radial opening has low pressure and therefore the oil has low dielectric strength. Therefore, MOCB is used for radial relief of high current at low voltages.
A combination of axial and radial ventilation is used within a single MOCB to efficiently break low and high voltages.
Advantages
- Requires less oil.
- Less oil means lower risk of fire.
- It has light weight.
- It has a small size and takes up little space
- It is cheaper than BOCB.
- It is easy to maintain and the oil can be easily replaced.
- Best for installation in places that are not used frequently.
cons
- Less oil is more affected by the amount of carbonation of the contacts.
- Oil quickly loses its insulating power.
- Requires more frequent maintenance.
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