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Circuit Breaker: Smart "Valve" in the World of Electric Current

Industrial News

Circuit Breaker: Smart "Valve" in the World of Electric Current

2025-01-17

In the complex power system network, circuit breakers play an irreplaceable key role. Their main responsibility is to accurately control the on and off of the circuit. In daily operation, they connect or cut off the current in an orderly manner according to various instructions to ensure the orderliness of power distribution. For example, in the power supply network of the city, when night falls and the demand for electricity rises sharply, the circuit breaker will reasonably distribute the current to various areas according to the instructions of the power dispatching center to ensure that every household and every factory can obtain a stable power supply. Once the power system encounters a fault, such as a short circuit, overload or other emergency situations, the circuit breaker quickly activates the protection mechanism. It cuts off the circuit at an extremely fast speed to prevent the spread of the fault current, just like closing the dam gate in time when a flood comes, effectively preventing the collapse of the entire power system that may be caused by local faults, thereby minimizing the scope and time of power outages, and ensuring the continuity of industrial production and the convenience of residents' lives.

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1. Structural analysis of circuit breakers

Contact system

The contact system is the key part of the circuit breaker for current in and out. The selection of contact material is crucial. Metal materials with good conductivity, high temperature resistance and wear resistance, such as copper alloy, are usually used. Its design structure directly affects the conductivity and service life of the circuit breaker. High-quality contact design can ensure that the contact resistance remains at a low level when the current passes through, reducing power loss and heating. At the same time, a reasonable contact opening and closing method can reduce the possibility of arc generation, and when the arc occurs, the shape and spacing of the contacts can cooperate with the arc extinguishing system to better extinguish the arc.

Arc extinguishing system

The arc extinguishing system is the core technical highlight of the circuit breaker. When the circuit is disconnected, a strong arc will be generated between the contacts. This is due to the ionized gas discharge phenomenon caused by the current trying to maintain the original path. The arc extinguishing system extinguishes the arc through a variety of ingenious designs. For example, some circuit breakers use a method of stretching the arc, using special arc-extinguishing grids to divide the arc into multiple small segments, so that the arc is stretched, cooled, and finally extinguished under the action of the magnetic field; some use arc blowing technology, using gas or oil flow to quickly blow through the arc, take away the heat generated by the arc, and cause it to extinguish. The efficient operation of the arc extinguishing system is the key guarantee for the circuit breaker to safely and reliably cut off the circuit.

Operating mechanism

The operating mechanism is responsible for executing the opening and closing action instructions of the circuit breaker. It needs to have a high degree of reliability and mechanical stability. Common operating mechanisms include electromagnetic and spring types. The electromagnetic operating mechanism uses electromagnetic force to achieve rapid closing and disconnection of the contacts, with a fast response speed, and is often used in occasions with high requirements for action speed; the spring operating mechanism releases energy through the pre-stored spring to drive the contact action. Its structure is relatively simple and reliable, and it is widely used in medium and low voltage circuit breakers. The precise action of the operating mechanism ensures that the circuit breaker can complete the circuit on and off operation as required under various working conditions.

Trip device

The trip device is the "intelligent brain" of the circuit breaker. It monitors various parameters in the circuit in real time, such as current size, voltage level, etc. When an abnormal situation is detected in the circuit, such as overload current exceeding the set threshold, short-circuit current suddenly increasing, or voltage seriously unbalanced, the trip device will immediately trigger the operating mechanism to quickly trip the circuit breaker and cut off the circuit. Modern trip devices often have multiple protection function settings, and can be flexibly adjusted according to different application scenarios and power system requirements to achieve accurate protection of power equipment.

2. Types and application scenarios of circuit breakers

Types and applications of low-voltage circuit breakers

Air circuit breaker: Using air as the arc extinguishing medium, it has the advantages of simple structure and low cost. Widely used in the distribution box of family residences, it can effectively protect the family circuit from damage caused by overload, short circuit and other faults. For example, when multiple high-power electrical appliances are used at the same time in the home, causing current overload, the air circuit breaker will trip quickly to avoid dangers such as overheating of wires and fire. At the same time, in some small commercial places, such as small shops and restaurants on the street, air circuit breakers can also meet their basic power protection needs and ensure power safety in daily business activities.

Molded case circuit breaker: Its shell is made of plastic material and has good insulation and protection performance. It is widely used in the field of industrial control, such as power distribution of production line equipment and motor control in factories. It can operate stably in relatively harsh industrial environments and effectively protect industrial equipment from electrical faults. For example, in large machine tool equipment in factories, molded case circuit breakers can monitor and protect the start-up and operation process of motors. Once the motor has overload, stall and other faults, the molded case circuit breaker can cut off the power supply in time to prevent the motor from burning, reducing equipment maintenance costs and production downtime.

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Types and applications of high-voltage circuit breakers

Oil circuit breaker: It once occupied an important position in the high-voltage power system. It uses insulating oil as arc extinguishing and insulating medium. It played a key role in the early construction of substations and was able to effectively control the on-off and fault protection of high-voltage transmission lines. However, due to the safety hazards of insulating oil such as flammability and explosion, and the high maintenance cost, with the development of technology, its application has gradually been replaced by new circuit breakers.

Vacuum circuit breaker: Using vacuum environment as arc extinguishing medium, it has significant advantages such as fast arc extinguishing speed, small size and easy maintenance. It has been widely used in medium and high voltage distribution networks, such as regional substations in cities and high-voltage distribution systems in industrial parks. It can quickly and reliably cut off high-voltage circuits and ensure stable transmission of electricity. For example, in the city's 10kV-35kV distribution network, vacuum circuit breakers frequently perform line separation and combination operations, effectively isolate faulty lines, ensure normal power supply in non-faulty areas, and improve the reliability and stability of urban power supply.

SF6 circuit breaker: Using the excellent insulation and arc extinguishing performance of SF6 gas, it is suitable for large-scale power projects such as ultra-high voltage and ultra-high voltage. It plays a vital role in long-distance and large-capacity transmission lines, such as transmission projects of large hydropower stations and ultra-high voltage transmission networks across provinces and regions. It can withstand extremely high voltage levels and performs well when cutting off huge currents, effectively ensuring the safety and efficiency of long-distance power transmission. For example, in my country's "West-to-East Power Transmission" UHV transmission project, SF6 circuit breakers are one of the key equipment to ensure the stable transmission of electricity from the western energy base to the eastern coastal areas.

3. Intelligent development trend of circuit breakers

With the rapid development of science and technology, intelligence has become an important direction for the development of circuit breakers. Intelligent circuit breakers are built with advanced sensors and microprocessors. Sensors can collect various data in the circuit in real time, including detailed information such as current, voltage, power factor, harmonic content, etc. The microprocessor quickly analyzes and processes these data. Through the communication module, the intelligent circuit breaker can upload its own working status, fault information and other data to the power monitoring system. Power workers can remotely understand the operation of the circuit breaker in real time at the monitoring center, and realize the refined management of the power system. For example, in a large-scale smart grid, operation and maintenance personnel can predict possible fault hazards in advance based on the data uploaded by the intelligent circuit breaker, arrange maintenance and overhaul work in time, and avoid faults. At the same time, the intelligent circuit breaker also has a self-diagnosis function, which can automatically detect the health status of its internal mechanical parts and electrical components. Once an abnormality is found, it will immediately issue a warning signal to notify the staff to deal with it, which greatly improves the reliability and safety of the power system and reduces operation and maintenance costs, laying a solid foundation for building a more intelligent, efficient and stable power network.