Study of Lightning Safety Distance Using Rolling Sphere Method

The development of a computer program for evaluation of lightning safety distance between the tower and satellite dish is written in M-File MATLAB. The 3-dimensional illustrative graphics model is used to capture better understanding on how lightning protection system (LPS) works. The study of physical length of grounding electrode used on the tower is found to be significantly affecting the grounding system performances where they depend on magnitude of dispersed lightning strikes current and the settling time for the current to completely disperse. The grounding system performance is studied by using lightning impulse current (LIC) generator, simulated in OrCad PSpice software. It is found that the optimum length of vertical lightning rod in LPS is the same with the striking distance. There is no significant improve- ment is observed in lightning safety distance if the length of vertical lightning rod is higher than striking distance. The lightning strike peak current that has larger magnitude than the withstanding insulation level of specified object causes no physical damage. It is because the lightning safety distance increases when the lightning strike peak current becomes higher. It is also found that the lower grounding impedance generates higher magnitude of dispersed peak current and faster settling time.