Overload and Short Circuit Protection for Low-voltage Electrical Installations

Ge Dalin（Medium & Low Voltage Group，Infrastructure and City Business，Siemens Ltd.，China，Shanghai 200082，China）

 

    Abstract The overload and short circuit current protection of power supply device of low-voltage electrical installations is analyzed. Selection of circuit -breaker or fuse for protecting from potential overload and short circuit of distributing line lies in the coordination between the tripping characteristic curve and the cable thermal resistibility of protection device，so as to ensure the operating safety and reliability of distributing line. Besides, the principle and related formula of overload and short circuit protection of distributing line are analyzed based on the understanding on related standards in IEC 60364.

    Key words   Power supply device Fault current   Distributing line Cable thermal resistibility Formula of overload protection Formula of short circuit protection

 

    摘 要 分析低压电气装置电源设备可提供的过负荷电流和短路电流。选择断路器或熔断器保护配电线路可能出现的过负荷和短路故障，其实质是保护电器的脱扣特性曲线与电缆热耐受能力的协调配合，确保配电线路安全可靠地运行。同时依据作者对 IEC 60364 有关标准的理解，分析配电线路过负荷保护和短路保护的原理和相关公式。

    关键词 电源设备 故障电流 配电线路 电缆热耐受能力 过负荷保护公式 短路保护公式