Nulleitung

Nulleitung, in electrical engineering often called the neutral conductor, is the electrical conductor that carries current back to the source in alternating current installations. It is connected to the neutral point of the transformer or generator and works together with the line conductor (L) to complete the circuit. Although it is typically near earth potential under normal operation, the neutral can carry current and pose a shock or burn hazard.

The primary function of the Nulleitung is to provide a return path for current and to help stabilize system voltages. In single-phase and many regional three-phase networks, the neutral helps ensure that devices connected between L and N operate at the intended voltage. In several distribution systems, the neutral is bonded to earth at a central point (for example at the service entry), while in other system types the bond to earth may occur only at the transformer or at the consumer’s installation in a specific arrangement such as TT, TN, or IT systems.

In cables and wiring, the neutral is typically designated as N and is color-coded blue in many European standards, with live conductors labeled L and protective earth labeled PE (green-yellow). In older installations, color codes can differ, so the exact color scheme may vary by country and standard.

Safety considerations include the fact that the neutral can carry significant current, especially under unbalanced loads, and faulty or broken Nulleitung connections can cause abnormal voltages, shock risks, and malfunction of appliances. Proper bonding, protection, and adherence to national electrical codes are essential to ensure safe and reliable operation.