Which safety step should be taken before changing distribution transformer tap settings?

• A. Ensure secondary loaded to 80%
• B. Short both high and low sides
• C. Use energized equipment
• D. De-energize the transformer

Answer: (D)

Before changing distribution transformer tap settings, you must de-energize the transformer. Removing the energy source eliminates the risk of electric shock, arcing, or insulation damage while the taps are being moved. In practice this means opening the upstream switches, isolating the transformer with lockout/tagout, and verifying that both the primary and secondary sides are dead before touching any components. Only after confirming zero energy should the tap settings be adjusted, using proper procedures and PPE, and then the system can be re-energized safely. The other steps either keep parts live or involve dangerous practices that can cause severe equipment damage or injury.