Where should grounding electrodes be connected when using structural steel for lightning down conductors?

Grounding electrodes should be connected near the base of the column because this location provides the most effective path for lightning currents to be dissipated into the ground. By positioning the grounding electrode at the base, it minimizes the distance that the lightning current must travel through the structural steel before reaching the earth. This ensures that the energy from a lightning strike is efficiently channeled away from the structure, reducing the risk of damage to the building and its occupants.

Additionally, grounding near the base means that the connection point is often closer to the ground itself, where the grounding system can be established more effectively. Having the grounding electrode at this level allows for a more reliable earthing system, leading to better performance during lightning strikes.

Connecting grounding electrodes at the top or in the middle of the column is less effective since the current would need to travel further down to reach the ground, which can lead to higher resistance and potential issues with ground fault currents. Similarly, connecting them anywhere along the column lacks the reliability and effectiveness of a strategically placed connection near the base.