Relationship between low-voltage circuit breaker clearance, creepage distance and low-voltage system - News - Global IC Trade Starts Here.

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I. Overview Due to the relatively underdeveloped state of China's electrical industry, there are many issues regarding low-voltage circuit breakers, such as limited variety, insufficient specifications, and performance gaps. Additionally, the lack of comprehensive design standards and user confusion about the products have led to improper usage in engineering applications. This has resulted in operational difficulties, increased failures, and long-term safety risks. This article aims to highlight these common issues and encourage greater attention from both manufacturers and users. II. How to Choose a Low-Voltage Circuit Breaker The selection of a low-voltage circuit breaker should primarily consider its ultimate short-circuit breaking capacity and rated short-circuit breaking capacity. Standards like IEC 947-2 and GB 4048.2 provide clear guidelines on these parameters. It is also important to evaluate the clearance and creepage distance, which depend on the insulation level of the low-voltage system. Proper insulation coordination ensures that transient overvoltages do not exceed the specified impulse withstand voltage. Key considerations include: (1) The rated insulation voltage of the device must be equal to or higher than the supply voltage. (2) The rated impulse withstand voltage of the device should meet or exceed that of the power system. (3) Any transient overvoltage generated by the device must be below the system's rated impulse withstand voltage. III. Causes of Circuit Breaker Accidents According to long-term field data, the main causes of circuit breaker accidents include: (1) Operational failure (2) Insulation failure (3) Poor opening/closing performance (4) Poor electrical conductivity These issues can generally be attributed to technical or human factors. Technical reasons may involve product defects or improper operation, while human factors relate to mistakes made during installation, maintenance, or operation. A detailed analysis follows: **Technical Reasons** 1. Operational Failure: This occurs when the circuit breaker fails to operate correctly, leading to delayed fault removal and potential grid instability. Common causes include mechanism defects, mechanical damage, and power supply issues. 2. Insulation Failure: Internal insulation problems, such as water ingress or oil degradation, can lead to serious damage. External insulation issues, like flashover due to pollution or lightning, can also cause accidents. 3. Poor Opening/Closing Performance: Mechanical defects or insufficient oil levels often result in failure to interrupt current effectively. 4. Poor Conductivity: Faults such as loose contacts, broken connections, or poor contact pressure can reduce electrical efficiency and increase the risk of failure. **Human Factors** 1. Manufacturing Quality: Poor design, substandard parts, or incorrect assembly can lead to early failures. For example, inadequate testing of outdoor devices for weather resistance can result in water damage. 2. Improper Use: Incorrect installation, adjustment, or maintenance can significantly affect performance. Issues like missing screws, improper sealing, or lack of oil in oil circuit breakers are common causes of accidents. In conclusion, ensuring safe and efficient operation of low-voltage circuit breakers requires a combination of proper design, high-quality manufacturing, and correct usage. Both manufacturers and users must work together to address these challenges.