What precaution should be taken before adjusting taps on a transformer?

Before adjusting taps on a transformer, it is crucial to de-energize the transformer. This precaution is essential because adjusting taps while the transformer is live exposes workers to the risk of electric shock or arc flash, which can lead to severe injuries or fatalities. By ensuring that the transformer is de-energized, workers can safely make adjustments without the danger posed by high voltage or electrical currents being present.

De-energizing allows for safe handling of equipment and minimizes the risk of accidental short circuits or damage to the transformer itself. This step ensures that proper lockout/tagout procedures are followed, which is critical in maintaining safety standards in electrical work. Overall, this precaution prioritizes the protection of personnel working on or near the transformer, making it the correct choice in this scenario.