Which of the following is a major SPD site entrance?

• A. AC Power
• B. Grounding Lugs
• C. Lightning Arrestor
• D. Ground Wire

Answer: (A)

Surge protection is most effective when the main entry point for surge energy into a facility is protected. The major SPD site entrance is the AC power service entrance, because the power feed from the utility is the primary path that surge currents—whether from lightning strikes, utility switching, or other events—use to reach all equipment inside the site. Placing a properly rated SPD at the AC service entrance intercepts and clamps these large surge energies before they can propagate through panels, racks, and devices, substantially reducing potential damage.

Grounding lugs, ground wires, and lightning arrestors all play important protective roles, but they do not represent the main entry point for surge energy into the building. Grounding components provide bonding and a return path for fault and surge currents, while lightning arrestors divert high-energy surges to ground along specific lines or at the point of entry; they support protection but do not serve as the primary site where surge energy first enters.