How to measure leakage current using multimeter
Using a multimeter to measure whether there is leakage in a 220 volt line is not a good method, as multimeter measurements can have significant errors. The minimum current that the human body can perceive is 1 milliampere; A leakage current of around 5-7 milliamps can cause spasms in the finger muscles; Leakage of more than 10 milliamps can cause pain and burning sensation in fingers and palms; When it exceeds 30mA, it is impossible to independently get rid of the power supply, and breathing begins to become numb. It cannot be accurately detected through a multimeter, which can easily create the illusion of no leakage and continue to pose a danger.
The method of using a multimeter to determine leakage is to measure resistance, but since the multimeter only supplies 9 volts, there will be significant errors when measuring high resistance values. After disconnecting the main circuit breaker and all electrical loads, the resistance value of the live and neutral wires can be measured. The resistance value should be infinite, but this method can only be roughly estimated and cannot be used as an accurate judgment. But when measured with a shaking table, if the resistance value is greater than 1M Ω, it can be considered that the insulation is good.
Using a multimeter to measure leakage is far inferior to using a leakage protector to determine. Select a leakage protector with an operating current of 6mA and connect it to the bus. If the reset button pops up after tripping, it can be determined that there is a leakage phenomenon in the circuit. According to this method, connect the leakage protector to each branch and gradually investigate, and finally determine the leakage position. Why choose a leakage protector with an operating current of 6mA for inspection? Because leakage current less than 6mA does not pose a threat to the human body, and the electricity meter does not measure it.
In summary, it is best to use a professional megohmmeter (rocking meter) to measure the insulation resistance of the circuit to determine the leakage. This is the most accurate way to make a preliminary judgment before using a multimeter. At the same time, it is strongly not recommended to perform live measurement and maintenance on power lines. Most electrical accidents are caused by live maintenance, so do not attempt live maintenance unless absolutely necessary.
