In a typical distribution system, how is voltage supplied?

• A. Primary voltage to feeders by substation bus and secondary voltage to consumer by service drop
• B. Secondary voltage to feeders by substation bus and primary voltage to consumer by service drop
• C. Primary voltage to customers by service line
• D. Voltage is the same on feeders and service drops

Answer: (A)

In distribution, voltage is delivered in two stages: feeders carry a higher distribution (primary) voltage from the substation bus, and then a transformer at or near the customer steps that voltage down to the lower (secondary) level delivered to the service entrance via the service drop. This keeps long-distance lines efficient (high voltage, lower current) and provides safe, usable voltage to homes and businesses.

So the correct description is that primary voltage is supplied to feeders by the substation bus, and secondary voltage is supplied to the consumer by the service drop. The other options don’t fit because feeders carry the higher distribution voltage, not secondary; customers get the low secondary voltage after transformation, not the primary; and the voltage is not the same on feeders and service drops due to the transformer step-down. Typical values are around 7–24 kV on feeders and 120/240 V for residential service drops.