When is it appropriate to work on a transformer?

Working on a transformer is appropriate only when it is fully powered down because this ensures the safety of personnel and prevents the risk of electric shock. Transformers operate at high voltages, and working on an energized unit poses significant hazards not only to the worker but also to the integrity of the equipment.

When a transformer is de-energized, technicians can safely inspect, maintain, or repair it without the fear of electrical injury or causing potential fault conditions that might affect the power supply system. Proper lockout/tagout procedures must also be implemented to ensure that the transformer cannot be inadvertently re-energized while maintenance work is being performed.

The other scenarios presented can lead to dangerous situations, as they do not prioritize safety and proper procedure during maintenance operations.