Grounding protection plays a crucial role in preventing electric shock accidents. Electric shock injuries and fatalities caused by ineffective equipment grounding are frequent. Examples include the 2024 death of a worker at Zhongshan Gangyu Precision Technology Co., Ltd. due to the lack of grounding on the casing of a mixing machine and control box; the 2020 death of a worker at a Jiangsu synthetic materials company due to the lack of grounding protection on the casing of a distribution box; and the death of a workshop director at Chenghua Weida Plastic Toy Factory in Chenghai District, Shantou City, due to the lack of grounding on a plastic crusher. The basic principle of grounding is to divert leakage current to the earth to protect human safety and to provide a discharge path for fault currents and lightning currents. Common grounding types include protective grounding, lightning protection grounding, functional grounding, and signal grounding.
To ensure the safety of personnel and equipment, all electrical equipment should be protected by grounding according to the national standard GB14050 "Forms and Safety Technical Requirements for System Grounding". Technical requirements for grounding devices include: the grounding electrode can be made of galvanized round steel, angle steel, or steel pipe, and its burial depth should exceed the local frost line, with a minimum burial depth of 0.6 meters; the connection between the grounding wire and the grounding electrode should use lap welding; the grounding resistance value is generally required to be no greater than 4 ohms, and should be tested regularly using a dedicated instrument (such as a ZC-8 grounding resistance tester). Equipment that must be protectively grounded includes the casing of motors, the casing of distribution panels and control panels, the casing of cable junction boxes and the metal sheath of cables, the metal base or casing of switches and their transmission devices, etc.
Daily inspection of grounding devices includes checking whether the connecting bolts are loose or corroded, checking whether the grounding wires and grounding electrodes below ground are corroded or detached, and checking whether the grounding wires on the ground are damaged, broken, or corroded. The grounding resistance should be tested regularly to ensure it is qualified; testing should be carried out during the spring and autumn seasons when rainfall is low.