At the beginning of 2006, the new IEC standards on lightning protection, Parts 1 to 4 of the series IEC 62305 were published. Almost after each 3 to 4 years of revision
and time, now they became effective as new Asian Lightning Protection Standards MS IEC 62305, SS 555 and SNI 62305.
This is the oldest concept in lightning protection. The technology was developedin Year 1752 when Benjamin Franklin first started experimenting with thelightning
mechanism. As shown in Figures 1 and 2, the Franklin Rod offers acone of protection based upon its installed height above the structure. It assumesa positive angle from
projections and the structural components within the coneare deemed to be protected against direct strikes.
The current recommendation for applying the cone is for structure of protective angle a as a function of height h depending on the class of lightning protection system as
shown in Figure 3.
The lightning protection systems for this design method should be manufactured from materials having highly corrosion-resistive characteristic. The design concept of Faraday Cage is very similar to Franklin Rod and theory of Rolling Sphere as shown in Figure 4, the Faraday Cage comprises of horizontal air termination where external down conductors
descend vertically from the air terminations.
These should be horizontally bonded at set intervals.The structural steel of reinforcing bars, if bonded, may be used to conduct the lightning current. This
technique, however, allows a pseudo random current flow of lightning current within the building. The vertical down conductors should be spaced around the perimeter of the structure.
The essence of Rolling Sphere method is based on an imaginary sphere, typically 20m to 60m in radius for standard class of protection to roll over the structure. All surface contact points by this sphere are deemed to require protection against lightning strikes.