nulleder

Nulleder, or neutral conductor, is the return path in electrical installations for alternating current. It forms one of the conductors in a typical single-phase circuit, alongside live conductors (L) and, in many systems, a protective earth (PE). The neutral is connected to the source’s midpoint or transformer star point and is intended to be at or near zero potential relative to earth. Its primary function is to complete the circuit so current can return to the source, enabling appliances to operate reliably.

In many distribution systems the neutral is bonded to earth at the service entrance or transformer, establishing a defined voltage reference and helping limit the touch voltage under fault conditions. The neutral is not a protective conductor; it should not be used as the primary means of fault protection. If a fault occurs, the protective devices (circuit breakers or fuses) should interrupt current, and any fault path relies on earth or protective conductors.

Neutral wiring varies by system: in TN-C-S, the neutral and earth are combined (PEN) in part of the installation and separated later; in TT systems, the neutral is connected to earth only at the service point. Color codes differ by country, but neutral is commonly blue in many European standards; earth is green-yellow; live conductors are brown, black, or grey. Adherence to local electrical codes and proper terminations are essential.

This provides a concise overview of the role and considerations surrounding nulleder.