Use a multimeter to measure whether the 220v line is leaking

Use a multimeter to measure whether the 220v line is leaking

Use a multimeter to measure whether the 220V line is leaking. The easiest way is to cut off the power first, put the multimeter to the electric barrier (500 ohms), connect the neutral wire and live wire to the ground wire with two pens of the multimeter, if the measured result is 0 , so that you can determine which wire is grounded, and there will be leakage.

To measure whether the 220V line is leaking or not, it should be accurate to use a 500V or 1000V shaking meter to measure whether it is accurate. It is not appropriate to use a multimeter to measure whether the 220V line is leaking. Test with a double-pole leakage circuit breaker in normal use. If the leakage circuit breaker is connected and closed, the leakage circuit breaker opens immediately, and its reset button protrudes again (Note: if the reset button does not protrude, it is overload protection and short circuit. Protection trip) proves that there is leakage in the line. This method is relatively simple and accurate.

The problem of measuring 220V leakage with a multimeter is not suitable, because what you want to measure is the leakage current. The multimeter is weak in measuring weak AC current, and it is troublesome to measure inaccurately. If you insist on measuring, you need to use a current transformer. Use a clamp meter to measure, but choose a clamp meter with a suitable range and better sensitivity.

If you suspect that the circuit is leaking, you can use a circuit breaker with a leak protection to judge, judge the range of the leakage segment by segment, and troubleshoot.

As for using electricity to block the leakage of the measurement line, I don't think it is appropriate. Because since it is a leakage, the resistance between the live wire and the protective ground is not infinite, but the voltage of the multimeter is not enough to explain the insulation between them, that is to say, the insulation resistance at 9V is completely different from that at 220V. Therefore, the insulation resistance is measured at a condition higher than the electrical voltage to obtain reliable data. So you have to use a shaker.

Of course, if you just test whether there is a short circuit or a path between the live wire and the protective ground, it is also possible to use a multimeter to block it. Just can't measure the insulation data between them.

First cut off the power! Then connect the black test lead of the multimeter to the ground wire (yellow-green two-color wire). If the line does not have a ground wire, it can be connected to a metal pipe or earth soil. The red pens measure the zero line and live line respectively. The digital multimeter uses 2M files, displaying 1 is normal, and displaying other numbers is leakage. For the pointer multimeter MF47, use the 10kΩ gear to carefully watch the needle move a little and there will be leakage. You can use the test pen and the line to touch and open, and observe the needle many times. The above is for industrial power consumption. If it is in a residential building, it is a little more complicated. Our country uses three-level power supply and two-level protection, which is very safe. That is, the leakage protector installed in the main distribution box will trip when the leakage current is 30 mA. Indoors The electrical box is equipped with a secondary leakage protector, and it will trip when the leakage current is 15 mA. Line leakage! The socket can be removed. If you have a multimeter, use the intermediate method. Disconnect the wiring in the middle of all the lines. It will trip when the power is supplied. socket. And so on until the leakage point is found, just change the line. If there is no multimeter, use the backtracking method, that is, remove it from the second socket at the end. If it does not trip, it means that there is leakage between the last socket and the second-to-last socket. If it still trips, disconnect the wire from the third-to-last socket, and so on. . In one special case, the grounding resistance of the wires between adjacent sockets can be disassembled, but the leakage point cannot be found at the end of the disassembly, and it still trips when installed, especially in old buildings, indicating that the line is aging. , can not be measured separately, and the leakage will trip when the sum is added up. The only way is to change all the lines. Note that the neutral ground is also tripped!

Leakage should be divided into two situations. There is leakage between the live wire and the neutral wire of the whole power supply circuit (between the live and neutral wires without electrical appliances). discharge. In this case, the entire power supply circuit will be completely disconnected, and all electrical appliances and objects that may form the circuit will be removed. Use a 10K multimeter to measure the resistance value between the live wire and the neutral wire. Under normal insulation conditions, the resistance value should be infinite. If There is a resistance value of several megaohms to tens of megaohms or more, indicating that there is a very slight leakage. If the multimeter shows a resistance value of tens of kiloohms to hundreds of kiloohms, it means a slight leakage. If the multimeter shows only a few thousand ohms or A smaller resistance value indicates that the line has strong leakage. You can search one by one along the source of the line. You must not miss each branch circuit. You can definitely find the leakage part in the aging and damp parts of the line insulation.

The second leakage situation is the leakage of the total power circuit to the ground or the leakage of electrical equipment to the ground. In this case, it is necessary to check each electrical appliance one by one, especially those with metal casings such as refrigerators or other machines with grounding wire equipment. If a qualified leakage protector is installed in the main power supply circuit, if the function of the leakage protector does not fail, any electrical appliance that leaks electricity to the ground can prompt the leakage protector to trip for protection. This principle can be used as a method of inspection. , If the original leakage protector is broken or unreliable, replace it with a new leakage protector in the main circuit, which can disconnect live wire and neutral wire at the same time when leakage occurs. Turn on the always trip protection of the main power supply, and disconnect all electrical appliances one by one from the power supply. When a certain electrical appliance is disconnected, the leakage protector will no longer trip and cut off the power. In the same way, it can be checked that if a certain line is disconnected, the leakage protector will no longer trip and power off, and the disconnected part of the line will have leakage. In the case of power failure, a multimeter can be used to measure the resistance value of the line or equipment to the ground wire. Below a few hundred thousand ohms, it means that the line or equipment has a strong leakage. If it is above 3__5 megohms, it will basically not affect the circuit work. Device power-off protection, the circuit cannot supply power.