Which scenario describes when a transformer should not be adjusted?

A transformer should not be adjusted while it is energized and in operation due to safety concerns and the potential for equipment damage. Transformers are designed to operate at specific settings, and making adjustments while they are live can cause unstable voltage, create arcs or sparks, and lead to accidental electrocution for personnel working nearby. Furthermore, adjustments made while the transformer is running can result in immediate problems, like overheating or damaging internal components that are meant to remain stable when the transformer is under load.

In contrast, adjusting a transformer when there's no load would generally be safe. Similarly, detecting a voltage imbalance may indicate a need for investigation or adjustment, but it should be diagnosed adequately first, ideally with the transformer de-energized. Prior to scheduling an inspection, one typically evaluates the condition of the equipment rather than making adjustments, which is a staged activity. Therefore, understanding the operational safety protocols helps ensure the longevity and efficient functioning of transformers.