How to use a multimeter to check whether the zero line is leaking
Ordinary multimeters are not reliable in measuring leakage current. Measuring and distinguishing between zero and live wires is what ordinary multimeters do.
What is Leakage?
We know that the circuit through which current flows is called a loop. If current is lost in a circuit, it is leakage.
The main cause of line leakage is that the line insulation layer is aging or damaged, or the insulation layer is broken down by a large current.
The symptom of leakage is usually that the leakage switch trips, but it can be closed, and then trips again soon, that is, uninterrupted and irregular tripping. Once the leakage current is too large, a short circuit to ground will be formed and the switch cannot be closed.
Leakage measurement is mainly to measure the insulation resistance of wires and equipment to the ground. The value measured by ordinary multimeters is not accurate because the voltage is too low. The megohmmeter is the first to measure the insulation resistance of wires. Usually the electrical insulation resistance requirement is not less than 0.5 megohm.
If you must use a multimeter to measure leakage, a clamp-on multimeter is the best choice and the most accurate. The premise is to replace the leakage protector with an air switch and measure the current with electricity.
The circuit needs at least two lines to form a loop, and the sum of the currents of the two lines of the loop is zero. Using this principle, we can clamp the two wires with the clamp multimeter at the same time. If the current is 0, the wire is normal. If the current shows a reading, the two wires have leakage.
This method can also be used to determine the approximate range of the leak point. If the line distance is relatively long and long, we can choose to start measuring from the middle, which can save half the time. After judging whether it is the front-end or the back-end leakage, we use the same method to divide the line into two, and gradually narrow the scope of inspection until the leakage point is locked.
It should be commonplace for electricians to use a multimeter to distinguish between zero and live wires.
We just need to turn the multimeter to the highest voltage file. Then test the voltage between the two wires, the two with a voltage of 380 volts are live wires, the one with a voltage of 220 volts is a live wire, and the other is a ground or neutral wire.
