In normal weather conditions, positive and negative charges maintain balance, the ground can be more negatively charged than the air, and the elements are placed on the ground. A charge polarization is created as the storm clouds form. The negative charge is more on the lower part of the cloud that induces a positive charge at the ground and other elements on it. The electric field at the atmosphere can reach 10s of kilovolts. The positive charge induced is more evident at pointed objects, trees and metallic objects. The cloud discharges the electric field towards the ground, if it is high enough. Downward leader is the path formed by the electric discharge. It produces sharp electric field variations, which cause corona effect. It is a point when an object that can form an upward leader is required. It will form a straight discharge path from cloud to the ground. It will receive the lightning strike and discharge it. It can control several damages. Following are the different effects of lightning:
Electrical effects: Equipment destruction. Equipment connected to electrical network can be damaged by rises and surges in ground voltage.
Electrodynamical effects: Structural damages. Deformations and rupture can be caused when conductors submitted to mechanical strengths are placed inside a magnetic field originated in another conductor.
Thermal effects: Fires. Fire can be caused by heat dissipation by Joule effect.
Effects on living beings: Burns and electrocutions. Even during a short lapse, current passed is enough to electrocute and burn.
Induction effects: As the electromagnetic field is variable, induced currents appear in every conductor. Damages can be severe if these conductors are connected to electronic equipment.
Lightning strike and fires due to electric discharge can cause severe damages in buildings and equipment, thus drive economical losses. Service interruptions, halt in production processes and damaged control equipment due to lightning can incur high costs.
Lightning impulse current (10/350): 50 KA Iimp
Nominal discharge current (8/20): 50 KA In
Response time Ta: Less than 100ns
Follow current interrupting rating at Uc 25 KA Ifi Max. back-up fuse 500 AgL/gG