How to detect the leakage of live wire or neutral wire with multimeter
Commonly used multimeters are divided into pointer multimeter and digital multimeters; However, most of pointer multimeter has no gear for measuring AC current, so there is no way to directly measure leakage current; The digital multimeter has an AC current measuring gear, so it can completely measure the leakage value of the power supply line; It is most convenient to measure leakage current if there is a digital clamp meter.
Leakage range: line leakage and electrical equipment leakage;
(1) line leakage refers to the leakage current of the line itself which forms a loop with the earth due to the reduction of insulation performance when the load in the line is not connected to the power supply.
(2) the leakage of electrical equipment refers to the leakage current formed by the insulation resistance between the coil inside the equipment and the earth after the equipment is connected to the power supply.
No matter what multimeter, the insulation resistance value of the measured line is not standard (the insulation resistance value of the measured line must be a special megohmmeter). Even if you measure the insulation resistance value of the line with a multimeter, 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 voltages of AC power supply lines are 220V and 380V.
If you are using a digital multimeter, you can set the multimeter to the AC current position.
(1) It is relatively simple to measure the line leakage. The current measured by 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 in the output of the circuit breaker and the line connector at the lower end of the power supply circuit breaker (the line connector needs to be disconnected). Note that the common digital multimeter has just started to set the current gear a little higher. The above picture shows that the multimeter I use is automatically switching the range. At this time, the measured current value is the leakage current in the line.
Leakage measurement of electrical equipment is very troublesome, because the installation of electrical equipment shell is basically grounded by mechanical devices. If the leakage is measured by multimeter, the electrical equipment needs to be vacated. When the equipment is electrified, one end of the multimeter is connected to the ground and the other end is in contact with the electrical equipment. At this time, the current measured by the multimeter is leakage current.
(2) How to measure the live wire in the circuit with a digital multimeter? First, set the digital multimeter to the AC ~750V gear, and use the red or black probe wire of the multimeter to wind it on your hand for 3~5 times, and insert the other probe into or contact the metal pile head or socket of the conductor.
