If a DC system has a 250 kcmil copper grounded neutral conductor, how large can the grounding electrode conductor be?

In a DC system equipped with a 250 kcmil copper grounded neutral conductor, the size of the grounding electrode conductor is determined by the applicable electrical code, which specifies the minimum size based on the size of the grounded conductor. According to the National Electrical Code (NEC), the grounding electrode conductor should be sized in relation to the largest ungrounded conductor.

For a 250 kcmil copper conductor, the NEC dictates that the minimum grounding electrode conductor size should be 3/0 copper. This is because the code provides specific tables that outline how to select the grounding electrode conductor size based on the ampacity of the largest conductor, and for 250 kcmil copper, the value corresponds to 3/0 for effective grounding.

Therefore, while larger sizes are available (such as 4/0 copper), the option of 3/0 copper adheres to the requirements set forth in the code for maintaining safety and ensuring proper grounding practices in the system. Thus, the choice of 3/0 copper is accurate and aligns with the guidelines for grounding systems in electrical installations.