Protective ground circuit

Protective grounding is a technical measure that connects the metal casings of motors and household appliances through conductors and metal grounding bodies buried underground
. This method is used in three-phase power supply neutral point ungrounded systems, as shown in Figure 14-1. Its function is that once the insulation of electrical equipment is damaged and leakage occurs
, the human body comes into contact with the live shell. At this time, the resistance of the human body is much greater than the resistance of the ground body (4fl). A large amount of current leaks to the earth through the metal shell, and the voltage
to the earth can drop below the safe voltage of 36V, thereby ensuring personal safety.