Which arrangement is correct for a pad-mounted transformer?

• A. Primary on the left, secondary on the right
• B. Primary on the right, secondary on the left
• C. Both on the left
• D. Both on the right

Answer: (A)

The arrangement tested relates to a standard field convention for pad-mounted transformers: the high-voltage primary leads are placed on the left side, and the low-voltage secondary leads are on the right. This separation keeps the HV and LV circuits clearly distinct, which helps with safe wiring, labeling, and routing of conduits in the field.

Why this is the best arrangement: placing the primary on the left aligns with common distribution layouts where the feeder connections and switchgear are typically on that side, while the secondary side on the right routes service conductors to customers and meters more directly. It also reduces the chance of mixing up HV and LV connections during installation, simplifies maintenance, and supports consistent phasing and grounding practices across installations.

Configurations that put both windings on the same side or swap sides would blur the boundary between high voltage and low voltage, increasing safety risks and complicating connections, which is why they are not standard practice.