Above which value is a structure AC voltage-to-ground considered hazardous?

A structure's AC voltage-to-ground is considered hazardous when it reaches levels that can pose a risk of electric shock to individuals. The correct threshold for this is 15 Volts AC at full power line load.

At this voltage level, the potential exists for harmful effects when someone comes into contact with the electrical system, especially if the ground path is compromised or if the individual is in a position that increases their conductivity (such as being in wet conditions).

In accordance with electrical safety standards, voltages above this threshold require special attention and bolstering safety measures. The concern at 15 Volts AC arises from the fact that it can cause a significant enough current to flow through a human body, which might lead to fibrillation or other serious injuries. Therefore, careful monitoring and management of voltage levels in structures are vital in preventing hazardous conditions for personnel working around these electrical systems.