An AC system operating at less than 50 volts is required to be grounded under which of the following conditions?

Grounding an AC system operating at less than 50 volts is essential to ensure safety, and this requirement is applicable under various conditions. Grounding becomes crucial for several reasons, such as preventing electric shock and ensuring that the system remains safe even in the event of a fault.

When the equipment has a metallic enclosure, grounding is necessary to protect individuals from accidental contact with live parts that may become energized due to faults. Similarly, in the presence of permanent structures, grounding helps to ensure that any fault current can safely dissipate into the ground, reducing the risk of shock or fire. Additionally, when personnel are working in proximity to the electrical system, grounding provides a vital layer of protection against electrical hazards that could arise from equipment failure or misuse.

Considering all these factors, grounding is required in the presence of any or all of these conditions, making it crucial for safety in environments where electrical equipment is used and where there are potential risks to human safety.