Three phase voltage measurement with a multimeter method
How to use the first multimeter? As shown in the picture below, it is a digital multimeter. When selecting the jack, you need to choose the two jacks with V and the COM end. Insert these two holes as shown in the picture. Do not do this. Wrong, otherwise it is dangerous. Then there is the range and gear selection. Some multimeters only have gears and do not need to select the range separately, but the one shown in the picture must be set to the AC voltage gear, that is, the symbol is V followed by a wavy line, and the range selection is better than yours. The voltage level to be measured is large. Now you are ready to start measuring.
Which two wires did the test pen touch during the second measurement? Usually three-phase electricity has three colors: yellow, green and red to represent the ABC three-phase according to national standards. If you want to measure the AB two-phase voltage, just put the test leads on the yellow and green wires. Note that there is no need to separate the positive and negative poles. In the same way, if you want to measure the BC phase voltage, just touch the green and red wires respectively. By analogy, touching the yellow and red wires is measuring the AC phase voltage.
Switch the multimeter to the voltage measuring position, and use the red and black test leads of the multimeter to measure the two-phase voltages of the three-phase power supply to see if they are around 380V. It is also necessary to check whether the three-phase voltages are accurate and balanced. While doing this work,. Be sure to pay attention to safety. This is a kind of protection for oneself
What setting should the multimeter set for leakage check?
1. First disconnect the main isolating switch of our power incoming line and turn off all the user's electrical loads, such as unplugging the refrigerator, turning off the water pump switch, etc.
2. Place the digital multimeter on the 200M ohm range, place one test lead on one of the two outlet wires on the load side, and touch the other test lead to the wall, preferably to the ground wire or a temporary Ground wire. After the number displayed on the multimeter stabilizes, what is read is the insulation resistance value of the main line. If the insulation resistance value is less than 0.5 megohm, then there is a problem with the main line. If the insulation resistance is above 0.5 megohm, it can be ruled out. There is a problem with the main line. Use the same method to measure the other wire and check the value to see if there is a problem with the main line.
3. Check the insulation resistance values of the branch circuit and each electrical appliance, and use the same method to detect them one by one until the fault point is found.
