Motorola Standards and Guidelines for Communication Sites (R56) Practice Test

Lightning events generate very large surge currents, so the path that carries those currents must have very low impedance. The PBB serves as the main bonding/grounding point, and during a strike it needs to carry that surge current with minimal voltage rise to keep equipment bonded and protected. A larger conductor has lower resistance and higher current-carrying capability, which reduces heat buildup and the potential for voltage differences to develop across components connected to the grounding system. In high-lightning areas, you size the PBB conductor large enough to handle the surge reliably, typically using the heaviest practical standard size for this purpose, such as 4/0 AWG. Smaller conductors would raise impedance and heat under surge, increasing the risk of damage and bond breakdown.