In the modern power system, the circuit breaker plays a pivotal role, which is not only an indispensable component to protect the circuit, but also has a profound impact on the reliability and safety of the entire electrical system. Next, INFINITECH will take you through and discuss some common questions about circuit breakers.

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> Circuit breaker definition, working principle, type and how to choose the right circuit breaker specifications

> Circuit breaker installation and wiring methods

> Routine maintenance points and common fault types of circuit breakers

> Safety precautions and application example Guide

> New technical features and advantages of intelligent circuit breakers

> How to choose circuit breakers

Circuit breaker, also known as breaker, is a key protection device used in electrical lines. Its main function is to be able to close, carry and break the current under normal working conditions, and in the event of abnormal conditions (such as overload, short circuit or undervoltage) can automatically cut off the circuit within a specified time, in order to protect other electrical equipment and lines in the circuit from damage. The circuit breaker induces current changes through its internal release device (including thermal release device, electromagnetic release device, etc.). When the current exceeds the preset safety value, the release device acts to prompt the mechanical system of the circuit breaker to quickly break the contact and disconnect the circuit.

Circuit breaker working principle

The working principle of the circuit breaker revolves around its core task - when the circuit is overloaded or short-circuited, the current increases sharply, the heat generated makes the bimetal sheet bend, or the electromagnet draws, and the mechanical structure is driven to quickly disconnect the circuit and achieve protection. The leakage circuit breaker has a built-in zero sequence current transformer, which monitors the change of leakage current in the circuit and acts immediately once it exceeds the set value. Its internal structure and working mechanism can be divided into the following parts:

Internal structure:

1. Contact system: including a fixed contact and an active contact, closed under normal conditions to form a current path.

2. Arc extinguishing device: quickly extinguish the arc when the circuit is broken to prevent contact damage, common arc extinguishing chamber, arc extinguishing grid and so on.

3. Operating mechanism: Control the opening and closing of the circuit breaker, can be manually operated or can be electric, electromagnetic or electronic control.

4. Trip device: induction circuit state, when overload, short circuit or leakage is detected, the circuit breaker is triggered to trip, mainly including thermal trip device (overload protection), electromagnetic trip device (short circuit protection) and leakage protection module.

5. Housing and insulation: Protects the internal components and provides the necessary insulation and mechanical protection.

Working mechanism:

• Overload protection: The thermal release uses the thermal expansion principle of the bimetal sheet. When the normal current flows through, the heat generated causes the bimetal sheet to bend slightly, but not enough to trigger tripping. When the current is overloaded, the bimetal sheet heats up faster, the bending degree increases, and finally triggers the trip mechanism to disconnect the circuit.

• Short-circuit protection: there is an electromagnet in the electromagnetic trip device, when the circuit is short-circuited, the large current instantly generates a strong magnetic field, attracts the armature action, and quickly pushes the mechanism to disconnect the contact. This process is extremely fast, usually done within milliseconds, to reduce damage to the equipment from the arc.

• Leakage protection (for leakage circuit breakers) : The built-in leakage protection module monitors the difference between incoming and outgoing currents in the circuit. Once an imbalance is found (that is, there is current leaking to the ground wire), when the set threshold is reached, the leakage protection mechanism will immediately act to cut off the circuit.

Automatic circuit cutting process:

1. Detection: The trip device continuously monitors current changes in the circuit.

2. Judgment: When the current exceeds the set safety threshold (overload or short circuit) or leakage is detected, the corresponding trip device is activated.

3. Execution: The trip device sends a signal to the operating mechanism, triggering mechanical motion to quickly separate the active contacts and interrupt the current.

4. Arc extinguishing: At the same time, the arc extinguishing device intervenes to ensure that the arc is extinguished in a short time to avoid contact damage and electrical fire.

5. Reset: After the fault is rectified, the circuit is reset manually or automatically (depending on the circuit breaker design) to return to the normal working state.

Type and selection of circuit breakers

As a key component of circuit protection, circuit breakers have various types and are suitable for different electrical environments and protection needs. Here are some common circuit breaker types and their application scenarios, and how to choose the right circuit breaker specification for your circuit needs:

Circuit breaker types and their application scenarios:

1. Air switches (air circuit breakers) : Suitable for residential, commercial and industrial power distribution systems to provide overload and short circuit protection. They use air as the extinguishing medium and quickly break the circuit in case of failure.

2. Smart Circuit breakers: In addition to basic overload and short circuit protection, intelligent monitoring, remote control and data analysis functions are integrated for modern building and industrial systems that require fine management and automated control.

3. Leakage circuit breaker (RCD or GFCI) : designed to prevent electric shock accidents, when detected leakage current immediately action, widely used in family bathroom, kitchen, swimming pool and other humid environment, as well as hospitals, schools and other places with high safety requirements.

4. Miniature circuit breakers: Compact and suitable for panel mounting, they are often used for circuit branch protection in residential and light commercial applications.

How to choose the right circuit breaker specification:

• Rated current (In) : The rated current of the circuit breaker should be selected based on the expected maximum load current of the protected circuit. It is generally recommended that the rated current of the circuit breaker is at least equal to or slightly greater than the rated current of the load, but not more than 2 times the load current. For devices such as motors with large starting currents, a circuit breaker with a higher rate may need to be selected.

• Rated voltage: Ensure that the rated voltage of the circuit breaker matches the voltage level of the circuit to ensure safety and performance.

• Short-circuit resistance (Icw) : Select the short-circuit breaking ability of the circuit breaker according to the maximum short-circuit current that may occur in the circuit to ensure that the circuit breaker can effectively cut off the short-circuit current to avoid electrical fire and equipment damage.

• Trip characteristics: Select an appropriate trip curve (such as B, C, and D) based on the load type to meet different overload characteristics and protection requirements.

• Use environment: Consider the environmental conditions in which the circuit breaker will be installed, such as temperature, humidity, pollution level and altitude, and choose a circuit breaker that is suitable for the specific environment.

• Additional functions: Select whether additional functions are required according to actual needs, such as leakage protection, overvoltage protection, remote control interface, etc.

Installation and wiring methods

Circuit breaker installation and wiring is a key step to ensure the safe operation of the electrical system, the following are some basic principles and methods:

Correct installation position:

1. Main switch and branch: the leakage circuit breaker can be installed at the main switch or on each branch. Installed at the main switch to provide comprehensive protection, but once tripping, it is difficult to find the leakage power supply; Shunt installation is more accurate and easy to troubleshoot, but multiple circuit breakers are required.

2. Indoor and outdoor: Choose the right location according to the application environment, indoor is usually installed in the control cabinet, distribution box, and outdoor needs to be installed in the waterproof and dustproof outdoor electrical cabinet.

Vertical or horizontal installation requirements:

• Basic principles: It is recommended that the circuit breaker be installed vertically. Ensure that the tilt of the circuit breaker is no more than 5°. The upper end connects to the power input cable, and the lower end connects to the power output cable.

• Special cases: Some circuit breakers (such as plastic-case breakers for thermo-electromagnetic trips) allow horizontal or horizontal installation, but fully electromagnetic trips (oil cup trips) should be installed vertically. Universal (frame type) circuit breakers must be installed vertically for structural reasons.

Wiring steps:

1. Power off: Before starting any wiring work, make sure to cut off the power from the source, using a test pen or voltmeter to confirm that there is no power.

2. Installation and fixing: The circuit breaker is fixed to the DIN rail or other support structure of the electrical box in accordance with the specified position.

3. Connect the power cable: Usually, the terminal above or marked "L", "LINE" or "Power" is connected to the incoming cable (power side) and secured by screws.

4. Connect the LOAD cable: Connect the bottom terminal or the terminal marked LOAD or Outgoing terminal to the power cable on the load side.

5. Neutral line and ground line: If the circuit breaker has special neutral line and ground line terminals (such as N and PE), connect them correctly.

6. Check the wiring: After the wiring is complete, carefully check whether each wire is firm and correct to avoid short circuit and grounding errors.

7. Test and power-on: After all the wiring is completed and confirmed, the power can be gradually restored, and the function of the circuit breaker is normal by using the circuit tester or the load test.

Use with other components of the circuit:

• Fuse: When the circuit breaker is used in conjunction with the fuse, the fuse should be installed on the power side to provide initial short circuit protection. The circuit breaker acts as the second level of protection, responding to overload and residual current.

• Interlocking and interlocking: In complex circuits protected by multiple circuit breakers, interlocking or interlocking mechanisms may be required to ensure the order of operation or to prevent misoperation between parallel circuits.

Each specific project or application may have its own specific requirements, so it is best to refer to the manufacturer's specific instruction manual and local electrical codes when installing and wiring.

Maintenance and troubleshooting

The maintenance and fault handling of circuit breaker is an important part to ensure the stable operation of electrical system. Here are a few key points:

Routine maintenance points:

1. Cleaning check: Periodically clean the dust outside the circuit breaker and keep the ventilation hole unblocked to prevent dust from affecting heat dissipation or reducing insulation.

2. Fastening check: Check whether the terminal is loose and ensure that all screws are firmly connected.

3. Appearance inspection: Observe whether the circuit breaker shell has damage, cracks, especially for outdoor installation of circuit breakers, to check the waterproof sealing.

4. Operation check: Manually operate the circuit breaker regularly (open and close several times) to confirm that the operating mechanism is smooth without stuck.

5. Record trip history: record the trip times and reasons of the circuit breaker, analyze whether there is frequent trip, timely adjustment or replacement.

Common fault types and diagnosis:

1. Contact problem:

   • Fault performance: contact ablation, wear resulting in poor contact, resulting in overheating or tripping.

   • Handling measures: Check the condition of the contacts, and replace the contacts or the entire circuit breaker if necessary.

2. Arc extinguishing system failure:

   • Failure: The arc extinguishing chamber is damaged, and the circuit breaker cannot effectively extinguish the arc, which may lead to explosion or serious damage.

   • Treatment measures: Professional maintenance or replacement of the arc extinguishing chamber components to ensure that the arc extinguishing system is intact.

3. Mechanical component failure:

   • Fault performance: operating mechanism stuck, spring failure, etc., affecting the normal closing of the circuit breaker.

   • Treatment measures: check and lubricate the operating mechanism, replace the damaged mechanical parts.

4. Electrical parameters abnormal:

   • Fault performance: rated current, short circuit capacity and other parameters do not match the actual circuit, frequent tripping.

   • Treatment measures: re-evaluate the circuit requirements, adjust or replace the appropriate circuit breaker.

Fault diagnosis method:

• Observation method: First observe whether there is obvious physical damage outside the circuit breaker.

• Test method: Use electrical testing instruments (such as megohm meter, clamp ammeter) to detect whether the insulation resistance and current of the line are normal.

• Replacement method: If conditions permit, replace the suspected faulty circuit breaker with a good circuit breaker of the same model to determine whether it is the problem of the circuit breaker itself.

• Professional testing: For complex faults, detailed inspection and maintenance should be carried out by professional electricians or factory technicians.

Precautions for safe use

Safe use of circuit breakers is an important part of electrical installation and maintenance, the following are some key safe use precautions:

Check items before installation:

1. Product inspection: Ensure that the circuit breaker has a certificate, certification mark, and does not exceed the expiration date. Check whether the package is in good condition and free of physical damage.

2. Parameter check: Check whether the rated current, voltage level, and trip characteristics of the circuit breaker match the circuit requirements.

3. Environmental assessment: Check whether the installation position meets environmental requirements, such as temperature, humidity, and ventilation, to ensure that the circuit breaker works properly.

4. Cable preparation: Ensure that all cables and connectors meet standards and are prepared in advance to prevent chaos on site.

Special installation requirements of leakage circuit breaker:

1. Independent circuit: Ensure that the leakage protector protects an independent circuit and must not be electrically connected to other lines.

2. Neutral line treatment: Correctly distinguish the working neutral line and the protection neutral line, the working neutral line should pass through the zero sequence current transformer of the leakage protector, and the protection neutral line should not be connected to the leakage protector.

3. Installation location: In areas with high humidity, high temperature or high risk of electric shock, the leakage protector must be installed separately and cannot be shared.

4. Avoid parallel connection: When the capacity of a leakage protector is insufficient, it should not be used in parallel, and a larger capacity device should be directly selected.

5. Reliable grounding: For leakage protectors with operating currents greater than 15mA, the protective equipment housing must be reliably grounded.

Operation safety specifications:

1. Power off operation: Before any installation or maintenance work, be sure to disconnect the power supply and use a test pen or meter to verify that there is no power.

2. Personal protection: Wear appropriate personal protective equipment, such as insulating gloves, protective glasses, hard hats, etc.

3. Check tools: Use qualified insulation tools to ensure that the tools are dry and intact.

4. Follow the manual: strictly follow the circuit breaker installation and operation manual, especially the special requirements of special models.

5. Clear identification: Ensure that all circuit breakers and circuits are clearly labeled for easy identification and operation.

6. Test and verification: After installation, first carry out functional testing, such as using the test button to verify whether the leakage protection function is normal, to ensure that everything is correct before officially put into use.

Following the above safety precautions can significantly reduce the probability of electrical accidents and ensure the safety of personnel and equipment.

Application examples and design guidelines

In residential, commercial, and industrial environments, circuit breaker configuration and design considerations vary. Here are some basic application examples and design guidelines:

Residential environment:

• The main circuit breaker: the leakage circuit breaker with overload and short circuit protection is usually selected as the main switch, and the rated current is estimated according to the total household electricity consumption, generally between 63A and 100A.

• Branch circuit: According to the room function and electrical load, configure different rated current micro circuit breakers, such as kitchen and bathroom should be installed leakage protection, lighting circuit can use ordinary micro circuit breakers.

• Design layout: Ensure that the circuit breaker is installed in an easily accessible location, such as the distribution box, and the layout is clear to distinguish the individual circuits and perform maintenance.

Business environment:

• Main switchboard: Large commercial buildings will have more complex distribution systems, and the main circuit breaker usually has a higher current capacity and may be equipped with a power management system.

• Sub-regional configuration: according to the functional area of the business district (such as office, catering, lighting, etc.) divided into different circuits, using frame circuit breakers or plastic-case circuit breakers, each area may have independent leakage protection.

• Emergency power supply: special circuit for emergency lighting, fire fighting system and other important loads, and standby power circuit breaker for automatic switching.

Industrial environment:

• High voltage and low voltage: both high and low voltage systems in the industry, high voltage circuit breakers need to consider insulation levels, arc extinguishing capacity, low voltage systems emphasize breaking capacity and selective protection.

• Multilevel protection: A multilevel protection policy is adopted. The upper-level circuit breaker is responsible for the overall protection, and the lower-level circuit breaker is specific to the device or circuit to minimize the impact of a fault.

• Dedicated circuit breakers: For heavy duty, frequently started equipment, such as large motors, choose a dedicated circuit breaker that can withstand high starting currents and may be equipped with a thermal magnetic or electronic trip.

• Automation and communication: Industrial circuit breakers often have intelligent control and communication functions, integrated into the SCADA system to achieve remote monitoring and fault warning.

General considerations in electrical design:

• Selective coordination: Ensure that the protection characteristics of all levels of circuit breakers are coordinated with each other, and the trip time of the upper level circuit breaker should be longer than that of the next level to avoid power failure of the whole system.

• Short-circuit current calculation: Select the breaking capacity of the circuit breaker according to the maximum short-circuit current of the system to ensure that the circuit can be safely disconnected under the worst conditions.

• Environmental adaptability: Consider the protection level of the circuit breaker (IP code), temperature and humidity adaptation range, especially in outdoor or harsh environments.

• Future development: Reserve a certain margin, taking into account possible future load growth and technology upgrades, to avoid frequent replacement of circuit breakers.

The design should follow the local electrical codes and industry standards, combined with the actual needs of flexible application, to ensure that the system is safe, reliable and efficient.

New technology and intelligent circuit breakers

By integrating sensors and communication modules, intelligent circuit breakers realize real-time monitoring of current, voltage, power factor and other parameters, and can be remotely controlled, integrated with the Internet of Things (IoT) platform, and provide users with value-added services such as energy management, fault warning, and remote maintenance. These technological advances not only enhance the intelligence level of the system, but also greatly enhance the flexibility and efficiency of the power system.

Intelligent circuit breaker features and advantages:

1. Comprehensive monitoring: Intelligent circuit breakers can monitor the voltage, current, power, electric energy, leakage, temperature and other key electrical parameters of the circuit in real time, providing a comprehensive electrical health diagnosis.

2. Advanced protection functions: In addition to basic overload and short circuit protection, intelligent circuit breakers can also achieve more accurate leakage protection, over/under voltage protection, temperature protection, and have adaptive learning and predictive maintenance capabilities.

3. Warning and automatic response: Before the occurrence of abnormal conditions, the intelligent circuit breaker can warn in advance, and automatically disconnect the circuit when necessary, effectively preventing electrical fire and equipment damage.

4. Remote control and management: Users can remotely control the switching status of circuit breakers through smart phones, computers and other terminal devices, using apps or web platforms, and view and analyze electrical data.

5. Timing control and scene setting: Support automatic control of circuit switches according to time arrangements or specific scenes to improve energy efficiency.

6. Cluster control and intelligent linkage: Integrated with other smart devices, you can control the switch of multiple devices with one click through scenario Settings, improving life and work efficiency.

7. Data analysis and optimization: The large amount of data collected can be used to analyze the usage habits of electrical systems to help users optimize energy consumption and reduce costs.

Integration with the Internet of Things (IoT) :

• Highly integrated and interconnected: Intelligent circuit breakers can directly connect lighting, switches, household appliances, charging piles and other terminal devices, and upload data to the cloud through 4G/5G, Wi-Fi, Bluetooth and other communication technologies.

• Private cloud and Public Cloud platform: With iot platforms, enterprises or individual users can build private clouds for secure data storage and analysis, or take advantage of public cloud services and enjoy flexible remote management capabilities.

• Standardized communication protocols: Internet of Things communication protocols such as MQTT, CoAP, HTTP are adopted to ensure stable and efficient data exchange between devices.

• Data security and privacy protection: In the process of data transmission and storage, encryption technology is used to ensure the security and privacy of user data.

How to choose circuit breakers

When purchasing circuit breakers, comprehensive consideration of price, brand reputation, after-sales service and user evaluation is crucial. International brands such as Schneider, ABB and Siemens are known for their high quality and advanced technology, while Chinese brands such as Chint and Drissie are also gradually emerging to provide cost-effective products. Users should make wise choices based on actual needs and budgets, combined with market feedback.