1, color discrimination: in power cables, yellow, green and red respectively represent phase A, phase B and phase C (three-phase live wire), blue represents zero line, and yellow and green represent grounding line.

2. Distinguish with electric pen: When the live wire is tested with electric pen, the neon tube will glow, but the zero line will not.

3. Distinguish by voltmeter: the voltage between different phase lines (i.e. live wires) is 380V, the voltage between phase line (live wires) and neutral line (or good grounding body) is 220V, and the voltage between neutral line and good grounding body is 0 V..

Extended data

In electrotechnics, the alternating voltage connected to the mains line is 220 volts (V for short), which is called "neutral line" and the other line is called live line. In electrical engineering, it is usually called neutral live wire or 101 fire. Generally, the circuit switch at home cuts off the live wire and is equipped with a leakage protector to prevent personal electric shock accidents.

Matters needing attention in power connection:

1 To prevent electric shock and short circuit;

2. Pay attention to the switch to control the fire line;

3, it is best not to connect the fuse on the zero line;

4, the central part of the lamp holder is connected with the fire line;

5, ground wire and zero line don't mix;

6, use electrical appliances to break the fire line, so that touching the electrical appliances will not get an electric shock. If the zero line is broken, people will get an electric shock.

Baidu encyclopedia-firewire

Baidu Encyclopedia-Zero Line Firewire