Previously, in any Soviet apartment one could observe a standard picture: an electric meter and 2 "plugs". One was mounted on "phase", the second - on "zero". But why install protection on a neutral wire, through which a life-threatening potential does not pass? Can't all electricians of the last century be wrong? Or maybe?
What is phase and line voltage?
Before dealing with the unfortunate "traffic jams" at "zero", you need to remember a little the basics. Namely, what is the phase and line voltage.
First, the phase voltage is the potential difference between phase and zero, in our power grids it is 220 V. The standard voltage that comes to every apartment. In this case, the dangerous potential is located only on the phase conductor, while the "zero" can be taken with bare hands.
But if one "phase" is not enough for the consumer, he can connect himself 3 phase wires and a working "zero". And then the potential difference between any two "phases" will be 380 V - this voltage is called linear. It is used when connecting three-phase electric motors, various machine tools, etc. And it is very convenient to have 2 spare "phases" at hand. There will always be light in several rooms.
As it was before…
In Soviet times, even at the origins of electricity, home power grids had some differences from the more familiar modern ones, namely:
- Linear (between "phase" and "phase") voltage was 220 V.
- The phase voltage was 127 V.
And after a while, the tops decided to switch to the more familiar potential difference - 220 V and leave 127 V in the past. To ensure such an innovation at no extra cost, it was necessary to simply bring 2 phase wires to each apartment, because the voltage between them is 220 V. It turns out that in the outlet there should have been not a phase wire with zero, but only two "phases".
That is why 2 "plugs" were installed near the electric meter - one for each "phase". Such a decision cannot be called rash and even more stupid. Even if there were simple fuses in the "traffic jams", protection was still present, and each of the lines was not afraid of a short circuit or prolonged heating.
Do you need to set machines to zero in modern power grids?
When the voltage changes to the usual 380/220 V, the need to install the protection for 2 conductors has disappeared. After all, if in the last century 2 phase conductors entered the apartment, now it is “phase” and “zero” with the same potential difference.
Even if a circuit breaker is installed on the neutral conductor, such a step will not provide additional safety. There is a problem of "zero" burning out and the machine in such a situation becomes a completely useless device.
That is why the bag is installed only on the phase wire, without neglecting additional protective devices such as RCDs, voltage relays, etc. But in the Soviet Union the situation was somewhat different, and the simultaneous alteration of all power grids would lead to colossal expenses that he could not afford. nobody.