1. Look at the line color
If the project is constructed according to the standard, it will be distinguished on the line color.
In a single-phase circuit (home circuit), red is a hot line, green is a zero line, and yellow-green is a ground line. In some single-phase circuits, blue may be used as the neutral or yellow as the ground. Although not standard enough, the polarity of the wires can be seen from the appearance.
In the three-phase circuit, the A phase is yellow, the B phase is green, the C phase is red, the neutral line is blue, and the ground line is yellowish green.
2. Look at the wire diameter
The single-phase circuit rarely distinguishes the wire diameter, but in the three-phase circuit, especially the circuit is relatively large, the wire diameter of the phase line is slightly thicker, and the wire diameter of the neutral wire and the ground wire is slightly thinner.
3. Look at the wiring
If the color of the wire does not conform to the regulations, but as long as the color is distinguished, the properties of the other device can be judged by observing the wiring of other devices.
A. Socket - Remove the socket and there will be three wires at the back. When a person faces the front of the socket, the line on the left hand side is a zero line, the line on the right hand side is a fire line, and the line in the middle is a ground line.
B. Switch - Remove the switch, the red color of the switch is red.
C, distribution box - there is a zero row and one row in the distribution box, the color of the zero line is the zero line of the room; the color of the line on the ground line is the ground line; the color of the 1P circuit breaker outlet, For the fire line.
Electric pen measurement
Close the circuit breaker while unplugging all the plugs in the circuit and turning off all switches.
The electric pen measures three lines in turn, and the fire line that can illuminate the electric pen. After finding the fire line, take a light bulb (or a small power appliance such as a charger), one end connected to the fire line and the other end connected to any one line. If the light bulb is lit, the line is proven to be zero line; otherwise it is ground.
2, multimeter measurement
Turn the multimeter to V~, hold the black test lead with your left hand, and wrap the line of the test pen around your hand for a few turns.
In the right hand, the red test leads are used to measure three lines in turn. The high voltage is the hot line, the low voltage is the zero line, and the voltage is zero.
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