What are the methods for measuring neutral line leakage?

Commonly used multimeters are divided into analog multimeters and digital multimeters; most analog multimeters do not have a range for measuring AC current, so there is no way to directly measure leakage current; and digital multimeters have AC current measurement ranges, so it is It is completely possible to measure the leakage value of the power supply line; if you have a digital clamp meter, it is most convenient to measure the leakage current.

Leakage range: Line leakage and electrical equipment leakage:

① Line leakage refers to the leakage current that forms a loop with the earth due to the reduced insulation performance of the line itself when the load in the line is not connected to the power supply.

②Leakage of electrical equipment refers to the leakage current caused by the insulation resistance value between the coils inside the equipment and the earth after the equipment is powered on.

No matter what kind of multimeter, the insulation resistance value of the line measured is not standard (the insulation resistance value of the line must be measured with a special megohmmeter). Even if you use a multimeter to measure the insulation resistance value of the line, it is only a reference value. , and it is very different from the actual insulation resistance value; because the multimeter itself is a 9V stacked battery, only 9V DC voltage is applied to the line measurement, while the voltage of the AC power supply line is 220V, 380V.

If you are using a digital multimeter, you can set the multimeter to the AC current range.

(1) Line leakage is relatively simple to measure. The current measured by the multimeter is connected in series in the line or equipment. When the load is not connected to the power supply, the line is directly connected in series at the lower end of the output of the power supply circuit breaker (the line connector needs to be disconnected). In the circuit breaker output and line connector, please note that the ordinary digital multimeter initially sets the current range a little higher. The picture above shows that the multimeter I use automatically switches the range. The current value measured at this time is the leakage current in the line.

Measuring leakage of electrical equipment is very troublesome, because the installation of electrical equipment shells is basically a mechanical device grounded. If you use a multimeter to measure leakage, you need to make the electrical equipment empty. When the equipment is powered on, use a multimeter to connect one end to the ground and the other end. One end is in contact with electrical equipment. At this time, the current measured by the multimeter is leakage current.

(2) How to use a digital multimeter to measure the live wire in the circuit? First, set the digital multimeter to the AC ~750V range. Use either the red test lead or the black test lead of the multimeter, wrap it around your hand 3 to 5 times, and insert the other test lead into or touch the metal pile head of the conductor. Or go into the socket. Please see the picture below.

This is based on the principle that a wire will form distributed capacitance when it comes into contact with the human body (the more turns the conductor has, the greater the capacitance formed with the human body), and the sensitivity of the digital multimeter itself is higher than that of the analog multimeter. Therefore, the displayed value of the response to the digital multimeter will be larger.

The above 1 is a measurement method that I often use. Generally, I wrap it around my hand 4 times. The measurement result at this time is ~57V. There is no doubt that it is the live wire. If the test lead wire wrapped around your hand does not move, use the black test lead to touch the other ground wires N and PE protective ground respectively.

Please see Figure 2 below.

At this time, the digital multimeter measurement result displays 000, which means that the live wire, neutral wire, and PE protective grounding in the line have all been detected.

As we all know, capacitors can block DC and AC. Using this method is mainly safe, convenient, and can be used under any circumstances.