If the human body touches the line end of the power supply, that is, the live line, or the internal leakage of the electrical equipment, the current flows from the phase line through the human body or the electrical equipment casing to the earth without flowing through the neutral line, and the current of the phase line and the neutral line is Will be equal, the leakage protector detects that this part of the current value reaches the rated action value and immediately trips to protect the safety of the person and the appliance within the corresponding action time. Generally, the action value is selected below 30 mA, and the action time is below 0.2S. If the neutral point of the power supply is directly grounded (this is not allowed in the construction of electricity), the leakage protector will lose its function and cannot protect the short circuit of the human body and electrical equipment.
This "single-phase three-wire" is the phase line L, and the voltage between the neutral line 接地 and the ground line PE.L and Ñ is 220V AC. That is, single-phase AC. Civil power supplies are powered by single-phase AC 220V.