Why is it dangerous for a lineman to open a primary neutral?

Opening a primary neutral is particularly dangerous because it can lead to current from an unbalanced load being present on the neutral. In a three-phase system, the neutral wire is designed to carry the unbalanced current from the phases. If the neutral is opened, the return path for this current is disrupted, which may cause unexpected voltage levels to appear on the neutral. This can create hazardous conditions, as the lineman may encounter voltages that are higher than expected, potentially leading to electrical shock or other dangerous situations.

The danger is compounded by the fact that with an unbalanced load, the neutral wire is not just carrying no current; rather, it may be subject to the full effect of what residual voltage or current might be induced in the system. Therefore, understanding the implications of working with a primary neutral is crucial for safety in lineman operations.