Which pair of ground sizes are the minimums for distribution and transmission, respectively?

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Multiple Choice

Which pair of ground sizes are the minimums for distribution and transmission, respectively?

Grounding conductor size is chosen to carry the fault current safely and allow the protective device to trip quickly. Transmission systems handle much higher fault currents than distribution systems, so they require a larger grounding conductor. Distribution circuits can get by with a smaller minimum, while transmission systems need the bigger size to keep impedance low during a fault. That’s why the minimum for distribution is a #2 grounding conductor, and for transmission it’s 2/0. The pair that matches these minimums is #2 for distribution and 2/0 for transmission. Using a smaller ground for transmission wouldn’t meet the protection needs, and using a larger ground for distribution isn’t necessary to meet the minimums.

Grounding conductor size is chosen to carry the fault current safely and allow the protective device to trip quickly. Transmission systems handle much higher fault currents than distribution systems, so they require a larger grounding conductor. Distribution circuits can get by with a smaller minimum, while transmission systems need the bigger size to keep impedance low during a fault. That’s why the minimum for distribution is a #2 grounding conductor, and for transmission it’s 2/0. The pair that matches these minimums is #2 for distribution and 2/0 for transmission. Using a smaller ground for transmission wouldn’t meet the protection needs, and using a larger ground for distribution isn’t necessary to meet the minimums.

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