Question

There is one underground 500 kcmil copper service wire per phase for a three phase service. There are no phase to neutral loads. What's the smallest size copper ground wire necessary?

1. #1/0 AWG
2. #2 AWG
3. #2/0 AWG
4. No grounding wire necessary

Answer 1

The smallest size copper ground wire necessary for a three-phase service with one underground 500 kcmil copper service wire per phase and no phase to neutral loads is #2 AWG.

Step-by-step explanation:

In order to determine the smallest size copper ground wire necessary for a three-phase service with one underground 500 kcmil copper service wire per phase and no phase to neutral loads, we need to consider the National Electrical Code (NEC) requirements.

According to NEC, the ground wire size should be determined based on the size of the largest service entrance conductor. In this case, the largest service entrance conductor is the 500 kcmil copper wire.

Based on NEC Table 250.122, the minimum grounding conductor size for a 500 kcmil copper service wire is #2 AWG.

Therefore, the smallest size copper ground wire necessary is #2 AWG.