What are the primary distribution voltage levels?

What are the primary distribution voltage levels?

• A. 4 kV, 13 kV, 27 kV, 33 kV
• B. 4 V, 13 V, 27 V, 33 V
• C. 480 V, 2.4 kV, 12 kV, 24 kV
• D. 120 V, 240 V, 480 V, 720 V

Answer: (A)

Primary distribution voltages are the medium-range voltages carried on distribution feeders from substations to neighborhoods. They must be high enough to keep current and conductor sizes reasonable, yet not so high that insulation and switching equipment become prohibitively expensive. The kilovolt-range values commonly used for distribution feeders—4 kV, 13 kV, 27 kV, and 33 kV—best reflect these typical levels. The other options mix voltages that are either far too low to be feeder voltages (in volts), or combine voltages that aren’t standard for primary distribution (for example, 480 V is usually a secondary service voltage). Hence, the set including 4 kV, 13 kV, 27 kV, and 33 kV is the correct representation.

Primary distribution voltages are the medium-range voltages carried on distribution feeders from substations to neighborhoods. They must be high enough to keep current and conductor sizes reasonable, yet not so high that insulation and switching equipment become prohibitively expensive. The kilovolt-range values commonly used for distribution feeders—4 kV, 13 kV, 27 kV, and 33 kV—best reflect these typical levels. The other options mix voltages that are either far too low to be feeder voltages (in volts), or combine voltages that aren’t standard for primary distribution (for example, 480 V is usually a secondary service voltage). Hence, the set including 4 kV, 13 kV, 27 kV, and 33 kV is the correct representation.