What is true about the ability to establish an equipotential zone in a substation?

Establishing an equipotential zone in a substation is crucial for ensuring safety and minimizing the risk of electrical shock. This involves creating a safe area where voltage differences are minimized to protect individuals working in and around the substation.

The assertion that it "cannot be established due to the size of the ground grid" is justified. The ground grid plays a vital role in forming an equipotential zone by effectively dissipating electrical energy into the ground. However, if the ground grid is insufficiently sized or improperly designed, it may fail to provide the necessary uniform voltage distribution, making it impossible to establish a reliable equipotential zone. This is particularly true in larger substations where the size and configuration of the ground grid may limit the effectiveness of achieving equipotential conditions.

In contrast, the other options do not accurately reflect the principles of establishing an equipotential zone. There are generally guidelines and best practices that dictate how and when an equipotential zone can be effectively created, which may vary based on specific design and operational conditions. Thus, understanding the limitations posed by ground grid size is essential for effective grounding system design and safety in substations.