Neutral conductor (N)

Neutral conductor (N) – meaning and function in transformers

The neutral conductor is a central component of electrical energy distribution systems, especially in AC networks. It serves as a return conductor for the current and enables the formation of a reference potential (usually earth potential) for the power supply. In conjunction with transformers, the neutral conductor plays a decisive role in the safety, functionality and stability of the power grid.

Basics of the neutral conductor

In a three-phase alternating current system (three-phase system), the connection consists of three phase conductors (L1, L2, L3) and a neutral conductor (N). The neutral conductor carries the current back to the transformer if the loads on the phase conductors are unbalanced – i.e. not evenly distributed.

Neutral conductor for transformers

Transformers convert electrical energy from one voltage level to another. The neutral conductor can be integrated in various ways:

Star connection (Y connection): In this common transformer circuit, the three windings are connected in such a way that a common point is created – the so-called star point. This point is often connected to the neutral conductor and earthed. This creates a zero potential that serves as a reference point for the voltages.

Earthing the neutral point: Connecting the neutral point to earth via the neutral conductor enables fault current detection (e.g. in the event of insulation faults) and improves operational safety. Dangerous voltages could occur without an earthed neutral conductor.

Single-phase consumers: The neutral conductor allows single-phase appliances to be connected to a three-phase network by serving as a return conductor for the current. This is particularly relevant in households and commercial operations.

Special features and protective measures

Current load: The neutral conductor can be subjected to high loads if the load is unbalanced. In modern networks with many electronic devices, harmonics can occur that place additional stress on the neutral conductor.

Fault protection: In conjunction with residual current circuit breakers (RCCBs), the neutral conductor is monitored in order to quickly interrupt the power supply in the event of residual currents.

Marking: In Europe, the neutral conductor is marked light blue in accordance with DIN VDE standards.