Why is the voltage between the neutral wire and live wire measured by a multimeter 380V?
The most likely reason that the voltage between the neutral line and the live line is around 380V is because during maintenance of the power supply and distribution lines, a careless maintenance electrician mistakenly connected the original single-phase 220V distribution neutral line to a phase line with a different phase sequence. As a result, the "neutral line" of the 220V voltage user becomes 380V voltage to the live line (although this situation is very rare, but this possibility is not ruled out).
Some so-called "experts" who have no practical experience are keen to answer electricity questions by pretending to understand. They think that this is because the neutral line source of the three-phase four (five) wire distribution is open, causing the voltage of 380V between the neutral line and the live line. The view is extremely wrong. Because the neutral point displacement of the three-phase load caused by the open circuit of the neutral line source of the three-phase four (five) wire distribution, the voltage of each phase cannot reach the user's voltage and be fixed within a voltage value. Moreover, because of the zero line When the power source is disconnected, the electrical appliances turned on by users with different phase sequences will form loops between phase lines with different phase sequences through the electrical appliances turned on by users with different phase sequences. Therefore, the voltage at both ends of the electrical appliances depends on the load of each phase. Different sizes and constantly changing.
That is to say; if the neutral point of the three-phase load is displaced due to the open circuit of the neutral line source of the three-phase four (five) wire distribution, when the load is large when the load is turned on (including automatic start and stop such as fixed-frequency air conditioners, refrigerators, etc.) The voltage of one phase will decrease, and when the load is turned on, the voltage of one phase will increase. As the loads (electrical appliances) turned on and burned out among the three-phase users continue to change, the voltages of the three phases will also continue to change. , if it is not handled in time at this time, most of the power receiving appliances (equipment) in the entire power distribution system will eventually burn out.
Recently I happened to be exposed to three-phase alternating current. The potential difference between each phase line and the neutral line is exactly 220V, which is also the kind used at home, and the potential difference between the phase lines is exactly 380V. In other words It is very likely that one of the phase wires in your home's electrical wiring is connected to the neutral wire, so there will be a potential difference of 380V.
If this happens at home, you must consider asking power grid staff to troubleshoot the fault, otherwise the high voltage will easily burn out the electrical appliances.
In fact, you can simply judge whether this is the case. You can find an electric pen and insert it into the two socket holes in sequence to see if there is power in each socket. If there is power, it is the situation I mentioned. The neutral wire is connected. It's time to reach the phase line. I think the question is about using a multimeter to measure the voltage, which means that if you have a multimeter at home, you can insert the red test lead of the multimeter into the socket separately, leaving the black test lead unplugged, but try not to touch the black test lead with your hands, if there is voltage in both sockets , then it can also be judged that this is the situation I mentioned.
