When are disconnect switches used in a distribution system?

Disconnect switches are essential components in a distribution system, primarily used to isolate equipment for maintenance or during overload conditions. This function is critical for ensuring safety; when technicians need to perform maintenance on electrical equipment, they must ensure that the power source is fully de-energized to avoid accidental electrocution or equipment damage.

The use of disconnect switches allows for clear separation between the power source and the equipment, enabling maintenance workers to conduct their tasks safely without the risk of electrical accidents. Furthermore, during overload conditions, disconnect switches can be employed to isolate sections of the distribution system, protecting sensitive equipment from damage due to high currents.

In contrast, while equipment operates normally, disconnect switches are typically not engaged, as there's no need for isolation. Similarly, when connecting transformers to the grid or installing new circuits, alternative devices like circuit breakers, fuses, or bus bars are generally utilized to manage power flow without the need for complete isolation provided by a disconnect switch. Thus, option C accurately reflects the primary function and purpose of disconnect switches in a distribution system.