For copper service-entrance conductors larger than 1,100 kcmil, what is the minimum area of the grounded conductor relative to the largest service-entrance phase conductor?

For copper service-entrance conductors larger than 1,100 kcmil, the minimum area of the grounded conductor should be at least 12.5% of the area of the largest service-entrance phase conductor. This requirement ensures proper grounding and safety in electrical installations, as the grounded conductor plays a critical role in fault conditions by providing a path for fault current to return to the source.

The 12.5% figure is derived from standard electrical codes, which are designed to ensure sufficient capacity for any unbalanced loads and to maintain the integrity of the electrical system. This percentage helps in reducing the risk of overheating and potential hazards that could stem from an undersized grounded conductor.

The other options fall short in providing adequate safety margins for larger conductors. For instance, a smaller percentage would potentially allow for inadequate grounding, which could lead to unsafe conditions during fault signals. Therefore, adhering to the 12.5% minimum gives a practical balance between efficient system operation and safety.