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

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.