The left pole of single-phase 2-hole socket is connected with N line (zero line), and the right pole is connected with L line (live wire); the left pole of single-phase three hole socket is connected with N line, the right pole is connected with L line, and the middle pole is connected with e line (protective ground

wire); the left pole of three-phase four hole socket is connected with L3 wire (live wire 3), the right pole is connected with L1 wire (live wire 1), the upper pole is connected with e line, and the lower pole is connected with L2 line (live wire 2). The single-phase three wire power plug is used for all the

household appliances whose shell is metal. The three plugs are arranged in a three-dimensional arrangement. The longest and thickest copper plug on the top is the earth wire, which has a special grounding symbol. The two lines below the ground wire are the live wire (the sign letter is "L" live wire) and

the zero line (the sign letter is "n" neutral wire), and the order is left zero and right fire. It is difficult to distinguish the neutral line from the ground wire if the wire is not connected according to the standard specification. If the power supply has leakage protector, plug the socket into the electrical appliance. If

it trips, it indicates that the one connecting the zero line is actually the ground wire; if it does not jump, it is connected to the right one. It is better to use standard conductor colors in application: yellow for a line, green for B line, red for C line, light blue for N line, and yellow green for PE line. In single-phase

lighting circuit, generally yellow means live wire, blue is zero line, and yellow green phase is ground wire. In some places, red is used to indicate the live line and power line, black means the zero line, and the yellow green line is the ground wire. Live wire L is usually red or yellow or green, and neutral line

n (neutral line) is generally blue ground wire (English earth) e is generally yellow green or black three pole power plug. As shown in the figure below, the shell of electrical equipment is connected with the grounding end of three core power plug through wire, and this plug needs to be inserted into three

pole socket.