What is the required grounding distance between structural steel columns when used as downleads?

In lightning protection systems, grounding is essential to ensure that electrical energy from a lightning strike is safely dissipated into the earth. When structural steel columns are used as downleads, they serve to conduct the lightning energy to the ground. The required grounding distance between these columns is stipulated to maintain effective resistance to lightning discharge.

The correct choice of 60 feet as the grounding distance is based on standards that specify this distance to minimize the potential for lightning current to cause damage through induced currents or to bypass the grounding system. This distance ensures that the columns can effectively operate as part of the grounding system without interfering with one another, allowing for an optimal path for lightning energy to travel directly to the ground.

Having grounding distances that are too short could increase the chances of side-flash or other issues, while distances that are excessively long may not be practical or effective, which is why 60 feet is identified as the correct distance in this context.