Why the Neutral Wire Sometimes Has Voltage and Sometimes Doesn’t

Under normal conditions, the neutral wire will not give an electric shock.

In reality, current does flow through the neutral wire.
However, when you test the neutral with a voltage tester screwdriver, the tester will not light up.

This is because the system uses a TN-S grounding system.
Both the protective earth (PE) and the neutral (N) originate from the transformer’s neutral point, and the neutral is connected to earth.

In other words, the working neutral has approximately zero potential relative to ground.
Therefore, under normal conditions there is no voltage between neutral and earth.

When a person stands on the ground and touches the neutral wire, the feet and the hand are at the same electrical potential (equipotential), so no current flows through the body.

Everything is safe under normal conditions.

However, once the neutral conductor is broken (open circuit), a potential difference appears between the neutral and the earth.
If you touch the neutral wire at that moment, it is equivalent to standing on the ground and touching the live (phase) wire — which is dangerous and can cause electric shock.