Where does 400 volt in an outlet come from? How to protect appliances and home from power surges

Surely you have heard the stories of electricians about when a zero break occurs at the entrance and microwaves, light bulbs, and some TVs and even refrigerators burn out in houses.

We will tell you why 380-400V appears in the outlet as if by magic. This happens more often in cold weather, when many people turn on additional appliances to keep warm.

Our houses (private or multi-apartment) are supplied with electricity, which has 3 phases: A, B, C.

So, the most common circuit is as follows: 3 phases and a neutral conductor.

Several houses are connected to phase A, another group is powered by phase B and a third on C. According to this scheme, apartment buildings and private houses are connected.

Along the riser, apartments in a high-rise building are alternately connected to different phases. This can be visualized like this:

Let's say that the owners of apartments that are connected to phase B went on New Year's holidays to relatives in another city. Before leaving, they turned off all household appliances, including the refrigerator. At this phase, it turns out, there is no load.

Other apartment owners who stayed in their home during the New Year's holidays consume electricity as before. They have a refrigerator, other devices are periodically connected (microwave oven, electric kettle, washing machine, etc.).

In this situation, there are no problems yet. In 220-230V sockets. Everything works as usual until one moment happens.

Zero burns out and then trouble happens. Between phase C and A 380-400 V. Phase B is "resting". It turns out that 400V is divided between A and C.

The current flows alone, but the resistance is not the same. We explain it again with an example. Suppose that some have powerful appliances connected (iron, heater, electric stove), while others have gone to bed and they have only a refrigerator working or one light bulb is on.

Those with a low load resistance (who consume more electricity with an iron, kettle, heater) will have a low voltage.

For those who went to bed and left the light bulb on in the kitchen (the load is small), it turns out that the resistance is high. The voltage in this case will be high - 350-400V.

Those who sit and warm themselves with a heater and iron linen with an iron have a 50V outlet. Those who have one bulb turned on are all 380V.

The one who went to bed and left the light on will have problems. The light bulb will shatter into small pieces.

Those who bask near the heater will be more fortunate - nothing bad should happen to them. But there were cases when refrigerators burned out even from a small amount of stress.

How to protect yourself and your equipment from this?

There are such devices: a voltage relay and a stabilizer (most preferable).