Why there is no zero on 10 kV power lines and where does it come from later

Hello dear guests and subscribers of my channel! The other day I received a very interesting letter in my mail from a young subscriber who was interested in: "Why on 10 kV lines three wires, and at 0.4 kV (380 Volts) there are already four wires? "So in this article I want to give a detailed answer to this question. answer.

Why three wires, not four

Note. I must say right away, dear and respected experts, I understand that this material will not bring any practical benefit to you, but I think there are readers who will find this information useful.

So, let's figure out why there is no neutral wire on 6 kV, 10 kV and higher lines, but there is one on 0.4 kV lines.

The thing is that the high-voltage lines have a network with an isolated neutral. Such a network is quite enough for connecting three-phase consumers, and there are simply no single-phase consumers for such a high voltage.

Therefore, there is simply no need for a neutral wire on 6, 10 kV power lines.

At 0.4 kV, the situation is different. There is a network with a solidly grounded neutral. Thanks to this, it is possible to obtain not only line voltage, but also phase voltage.

Where zero appears

Next, we will consider the most common system in Russia - T-NC, in which zero and ground are combined in one wire.

In this case, the transition from a network with an isolated neutral to a network with a solidly grounded neutral occurs at distribution step-down substations.

As you probably noticed, the star connection is going on the low side. And the center point formed in this way is called "neutral".

So, this point (neutral) is just grounded at substations with a solidly grounded neutral.

Here it is the beginning of our neutral wire, which goes into the switchboard together with the phase wire.

Of course, there are also three-phase consumers in 0.4 kV networks. When connected, the neutral wire is used as a ground wire.

So why is zero needed

Well, everything is simple. It is needed for single-phase devices operating on a voltage of 230 Volts (according to GOST 29322-2014 (IEC 60038: 2009), namely this voltage should be in our sockets), and for safety, and to protect the equipment from the effects of a short closures.

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