Thank you Youcef for your answer

Can you tell me what's the possible risks in the other case?

Omar

Dear Omar,

The transient nature of lightning with its associated fast rise times and large magnitude currents mean that special consideration needs to be given to the good grounding, for lightning protection to be effective. Thus, the main aim of a direct strike grounding system is to efficiently dissipate lightning energy into the ground as fast as possible and to help protect equipment and personnel. 

Why fast ? for the sake to reduce peak voltages induced in the connections.

The voltage generated by a lightning discharge depends primarily on the risetime of the current and the impedance (primarily inductance) of the path to ground.

Extremely fast rise times result in significant voltage rises due to any series inductance resulting from long, indirect paths, or sharp bends in the routing of ground conductors. This is why short, direct ground connections are important.

Best regards.

Thank you Youcef for your answer

Can you tell me what's the possible risks in the other case?

Omar