从用户端角度确定低压成套开关设备额定电流

Determination of Rated Current of Low-Voltage Switchgear from Customers Perspective

GB 7251.1—2013中规定"一条电路的额定电流可低于安装在这条电路中(根据各自的器件标准)的额定电流",但是低于多少标准值并未给出。结合日常检验工作案例,分析了过度降容法确定低压成套开关设备和控制设备额定电流存在的弊端,从用户端的角度提出确定低压成套开关设备和控制设备额定电流应采用"额定分散系数×调整系数×断路器的额定电流"的方法,从而保证了低压成套开关设备和控制设备过载保护功能的有效实施。

GB7251.1-2013 mentioned “the rated current of a circuit may be lower than the rated currents of the devices (according to the respective device standard) installed in this circuit”, but the standard doesn’t give limits how much lower it can be.Combining with the routine testing work case, this paper analyzed the disadvantages of excessive reducing capacity method to determine the rated currents of low-voltage switchgear and control gear assemblies and proposed to adopt “rated diversity factor×modify factor×rated current of circuit-breakers” method from the customers perspective to determine the rated currents of low-voltage switchgear and control gear assemblies, so as to ensure the over-load protection function of the low-voltage switchgear and controlgear assemblies implemented effectively.