Master Electrician Exam 2025 – 400 Free Practice Questions to Pass the Exam

The smallest grounded conductor permitted for an electric service that utilizes 1000 kcmil copper ungrounded conductors is 2/0 AWG copper. This standard is based on the requirements set forth in the National Electrical Code (NEC), which specifies that the size of the grounded conductor must be determined based on the size of the ungrounded conductors.

For systems using 1000 kcmil copper conductors, the NEC dictates a specific minimum size for the grounded conductor to ensure it can safely carry any fault current and provide proper grounding. In this case, 2/0 AWG copper is the minimum size required to match the capacity and potential fault conditions of the 1000 kcmil ungrounded conductors.

The other conductor sizes presented (3/0, 4/0, and 1/0 AWG) either do not meet the minimum requirement or exceed it, which is not necessary for proper grounding in this context. Therefore, 2/0 AWG copper is correctly identified as the suitable choice that adheres to the NEC guidelines.