Direct Lightning Protection

A lightning rod is fixed on the upper structure of a building. It is dedicated to capture the lightning discharge and then channeled it safely to the ground. There are four major lightning rod types:

     . Single rod : Metallic rod fixed on the roof ridge. The lightning current is then routed to the ground via two down conductors fixed on two opposite sides of the building.

 
. Meshed Cage : Meshed conductors are fixed on the protected structure. The conductors can be equipped with lightning rods of the roof. All the conductors are interconnected and grounded

. Taut wires : Made of wires that are stretched above the protected structures. This is widely used for example for overhead HV power lines.

. Early Streamer Emission air terminals: Advanced lightning rods that provide a large protection area compared to a Single Rod, thanks to a specific ionization device. The lightning current is then routed to the ground via minimum two down conductors fixed on two opposite sides of the building.

Indirect Lightning Protection

Protection against overvoltage : The indirect protection lies on installation of Surge Protection Devices (SPD) in the electrical switchboards of the building. Overvoltage is generated by a direct lightning discharge on the building, on the overhead power supply lines or by induction.

Overvoltage effects range from the destruction or fast ageing electronic components, circuit boards destruction…All electrical appliance can be damaged/affected as soon as they are plugged in.

A deadly phenomenon … for humans

•          Burns: by arc or by flash if the lightning stays in surface; in that case, the consequences are rarely severe.

•          Neurological effects: Coma is not rare; it can be either superficial or profound. Amnesia of the accident is frequent. It is due to the bypassing of lightning through the encephalic structures. After effects are frequent (hemiplegia, cortical atrophy, epilepsy, extrapyramidal syndrome, spinal and peripheral nervous lesions).

•          Cardio-vascular lesions: Circulatory arrest happens by asystolia or ventricular fibrillation. A direct myocardic lesion by Joule effect, a myocardic contusion by the shock wave, a thrombosis of the coronary or peripheral arteries can also be seen.

•          Respiratory lesions: it can be a tetanization of the respiratory muscles for a short time, a direct lesion of nervous centres, a bronchial or pleural rupture, or a lesion of the alveolo-capillar membrane when the over-heated air explodes (blast).

•          Neuro-sensory effects: ocular lesions due to retinal detachment and potential cataracts must be screened for. Auditory lesions including tympanic membrane rupture and balance impairments as a consequence of labyrinth damage can also occur.

•          Muscular effects: extensive muscular breakdown with deep necrosis and rhabdomyolysis may occur allong the pathway of conduction.

•           Renal effects: there are mainly three consequences: tubular pathology due to the muscle lysis (early fluid balance is vital); parenchymal lesions due to arterial thrombosis; traumatic lesions.

•          Cutaneous lesions: burns of all severities, in particular at the points of lightning entry (restorative surgery is frequently required) and at points in contact with metal (climbing equipment, jewellery); fernlike patterns are classic (Lichtenberg bodies)

… and a destructive phenomenon for structures

Few examples of damages caused by lightning : (pictures)