SHIELD is a very powerful tool for the evaluation of the protection of structures from direct lightning strokes.
SHIELD can calculate the protected volume using the Rolling Sphere method and the collection area using the Eriksson method.
SHIELD is full 3D graphical application for the evaluation of the protection of structures from direct lightning strokes using the Rolling Sphere and the Eriksson methods.
The Rolling Sphere Method is considered by standards and is (EN, NFPA, AS …) and is an universal method for shielding design, and particularly recommended for complex geometry.
Alternative methods like the protection angle or mesh method are suitable for simple-shaped buildings or for buildings where plane surfaces are to be protected.
The Rolling Sphere Method can be applied to the structure to be protected. In such case, SHIELD can identify the parts of the structure exposed to a direct lightning stroke, that are the points where is more effective to install the air termination system.
Then the Rolling Sphere Method can be applied to air termination + down conductor system. In such case SHIELD generates a 3D surface corresponding to the protected volume.
The protected volume is then superposed to the structure to be protected. The parts of the structure to be protected that protrudes over this surface are not protected.
The Rolling Sphere Method has been implemented taking into account two different models.
A numerical model based on a geometrical scan over a calculation grid, suitable for structures with height lower than 60 m.
An analytical model based on the evaluation of the surfaces generated by the intersection of the rolling spheres in the 3D space and suitable for general purposes.
The numerical model will consider essentially vertical lightning strokes while the analytical model will be able to consider also lateral lightning strokes.
When the Eriksson Method is set, SHIELD generates the collection area of air termination + down conductor system and structure to be protected.
The lightning protection system is effective when collection area of air termination + down conductor system includes collection area of structure to be protected.
The User can modify the lightning protection system and generate again the protected volume or collection areas.
Lightning Shielding is an increasing important topics. In many areas the flash density is growing and on the other side the values to be protected (people, buildings, systems …), are also increasing. A good lightning shielding design is the first step for a good lightning protection system installation.