A simple way to measure whether a circuit is leaking with a multimeter
Use a multimeter to measure whether there is leakage in the 220V line. The simplest way is to cut off the power first, connect the multimeter to the electrical barrier (500 ohms), and connect the neutral wire and the live wire to the ground wire with two pens of the multimeter. If the measurement result is 0 , so that you can be sure that the wire is grounded, and there will be leakage.
To measure whether a 220V line is leaking, you should use a 500V or 1000V megger to measure it accurately. It is not appropriate to use a multimeter to measure whether a 220V line is leaking. If you don’t have a megometer on hand, you can temporarily install one at the beginning of the suspected leakage line. Test with a normally used bipolar leakage circuit breaker. Connect the leakage circuit breaker and close it. If the leakage circuit breaker immediately opens and its reset button protrudes (note: if the reset button does not protrude and the opening is overload protection and short circuit Protection opening) proves that the line has leakage. This method is relatively simple and accurate.
The multimeter is not suitable for measuring 220V leakage, because what you want to measure is the leakage current. The multimeter is weak in measuring weak AC currents, and it is troublesome to measure inaccurately. If you insist on measuring, you need to use a current transformer, you might as well Use a clamp meter to measure, but choose a clamp meter with a suitable range and better sensitivity.
If you suspect circuit leakage, you can use a circuit breaker with leakage protection to determine the scope of the leakage section by section and troubleshoot.
As for using electrical blocking to measure line leakage, I don't think it's appropriate. Since it is 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 is completely different between 9V and 220V. Therefore, the insulation resistance is measured at a value higher than the power voltage to obtain reliable data. So a shaker must be used.
Of course, if you just test whether there is a short circuit or path between the live wire and the protective ground, you can also use a multimeter to electrically block it. Just can't measure the insulation data between them.
If the insulation of the circuit is damaged, it can be seen visually and it can be dealt with when the time comes. Another situation is that the rolled skin is not damaged, but has some cracks, causing it to be grounded when it is wet, or the damaged area is very hidden and cannot be directly seen with the naked eye. At this time, you can cut off the power to the line and shake the meter directly. For low voltage circuits, a 500 volt meter should be used. Measured against ground, if insulation is less than 0.5 megohms. It can be considered that the insulation is not very good and should be checked section by section. One thing to note is that when measuring with a megometer, no electrical appliances can be connected to the circuit. Otherwise, the measured value may be inaccurate.
If you use a multimeter to check if there is any leakage. It may not be accurate. Because the voltage of the general meter is very low. Unless the leakage is serious, it can only be detected.
As an aside from the topic, it is best to use leakage protector switches for sockets at home. In this way, once leakage occurs, the power supply can be cut off quickly to ensure personal safety.
1. Power-off measurement: Turn off all electrical appliances, use the RX10K setting of the multimeter, one test lead is connected to the live wire, and the other test lead is connected to the ground (or faucet). The resistance should be infinite, otherwise there will be leakage.
2. Live measurement: Use a multimeter at the 250V AC voltage range to measure the metal casing of the electrical appliance that is suspected of leaking. Connect one test lead to the casing and the other to ground (or faucet). When the pointer shows that the voltage is higher than 30-50 volts, replace it. Use AC 50 volts. If the power supply is confirmed to be higher than 30 volts, it is a leakage, and if it is lower than 30 volts, it is normal. Then swap the zero and hot power supply plug wires and measure it again to confirm.
3. Leakage measurement between the live wire and the neutral wire (or the live wire and the live wire): Turn off and disconnect all electrical appliances, and measure the resistance between the live wire and the neutral wire. It should be infinite, otherwise it is leakage.
The accuracy of the above method for troubleshooting is 99.9%, which is convenient, fast and practical. However, the special megohm meter must be used only during engineering, and its use is inefficient during maintenance. It is only used when the multimeter measurement is confirmed to be good, but the line is indeed leaking. I used a meter, but the multimeter couldn't detect the leakage.
In addition, calculate the length of time that the electrical equipment in the home is turned on. For a 4×6 square meter, if there are many electrical equipment and are used for a long time, about 200 degrees a month is not too much. If it is much greater than this number, you can judge that there is a leakage in the home. Condition.
