What is primary distribution voltage?

• A. Voltage applied by a substation transformer and applied to distribution lines
• B. Voltage on the service drop after distribution
• C. The customer's internal wiring voltage
• D. A voltage that is not used in distribution

Answer: (A)

Primary distribution voltage is the higher voltage carried on distribution feeders right after the substation. The substation transformer steps transmission voltage down to this distribution level, and those lines deliver power to transformers further down the line that reduce it to service voltage for customers. This higher distribution voltage is used to minimize losses and allow efficient delivery over long spans. In practice, primary distribution voltages are several kilovolts (range varies by utility, commonly around 4 kV to 34 kV). The voltage after distribution at the service drop and the customer’s internal wiring are lower voltages used for end-use equipment, so they aren’t the primary distribution voltage.