Why does 380V appear in the sockets when the neutral wire breaks? Accessible explanation and advice on how to reliably protect yourself from this
The article Why does zero burn out more often under load, and not the phase?the reasons for zero burnout and methods of protection against it were identified. This usually happens in houses where the wiring is old. And the consequences of a break (burning off) of the neutral wire are really serious. Overvoltage appears in the outlets. With a complete break, 380V will appear. And at the same time, electrical equipment and devices, lighting lamps burn out.
The phase imbalance is shown due to the uneven distribution of the neutral wire resistance.
In apartment buildings, in the apartments themselves, single-phase wiring. But all phases are at the entrance with a common zero. If there is a zero break, current will flow from phase to phase. If someone in some apartment connects a large load, then his voltage drop will be less than in the one where a low-power electrical appliance is turned on.
And since in the event of a zero break, all consumers will be connected in series to the 380 V voltage circuit (the same current in circuits flowing from phase to phase), then the load that will have less power burns out consumption. It can be schematically represented as follows:
The following analogy can also be cited. Everyone knows a Christmas tree garland, consisting of low-power incandescent lamps, designed, for example, for a voltage of 5 V. Then there are 44 of them in the chain. The tension is evenly distributed on each. But if a more powerful load is soldered instead of one, then all the other lamps will begin to shine brighter and may even burn out.
Who wants to be convinced of this phenomenon, you can watch the experiment in this video: https://youtu.be/zKiMdUUToT4
What kind of zero break protection can be installed? You need to make sure that a separate machine is not installed on the neutral wire. Or the machines must be connected (simultaneous disconnection of all phases and zero). The neutral wire in a private house must have a high-quality grounding with a resistance parameter of no higher than 30 ohms.
And the third is the installation of a voltage relay for each phase. At present, most of the technical specifications for connecting the site to the power grids in the private sector are issued in three phases.
In a city apartment, these additional protections are more difficult to install. A zero break occurs, as a rule, in old apartment buildings.