Abstract: The requirement of the grounding resistance value for a control system is seldom discussed in the literature. Many domestic manufacturers of control system often use to 4Ω as the requirement of grounding resistance value. Through the analysis, we can get the following conclusions: A. Action current of circuit breaker or fuse and resistivity of soil (or ground) decided to requirements of protection grounding resistance value for control cabinet when equipments in a cabinet are case of failure; insulation performance and symmetrical performance of control system decided to requirements of working ground resistance value. B. The requirements of the working grounding resistance value for a control system is a property of the control system; and the requirements of the protection grounding resistance values is a property of the cabinet. The requirement of the grounding resistance value to be specified in the product specification of a control system shall be the requirement of the working grounding resistance value. C. The requirements of working grounding resistance for a control system are not same compared with the requirements of protection grounding resistance for a cabinet, and the expected value of grounding resistance value for a engineering design should be less than one of the smaller.

摘要： 控制系统对接地电阻值的要求，鲜有文献对该命题作详细讨论。国内许多控制系统的制造商往往沿用以4Ω作为对接地电阻值的要求。本文通过分析可得如下几点结论： A.控制机柜内设备在发生故障时,空开或熔断器的动作电流以及土壤(或地面)的电阻率决定控制机柜保护地对接地电阻值大小的要求；控制系统的绝缘性能与对称性能决定了对工作地接地电阻值大小的要求。 B.控制系统对工作地接地电阻值的要求系控制系统的属性；而对保护地接地电阻值的要求系控制机柜的属性。控制系统产品使用说明书中规定的接地电阻值应该是指对工作地接地电阻值的要求。 C.控制系统的工作地与控制机柜的保护地对接地电阻值的要求是不一样的，对一个工程设计，接地电阻的期望值应小于两者中的较小值。

关键词: 控制系统, 接地电阻, 接触电位差, 保护地, 工作地, Control system, grounding resistance, contact potential difference, protection grounding, working grounding