Lightning can reach the installation by three means of access. Of the three listed below, the latter two are introduced via the ground system of an installation (e.g. Coax shield).
1. Excess Voltages due to strikes on lines.
Lightning strikes on overhead lines lead to over voltage of several thousand volts spreading onto the HV and LV networks.
2. Excess Voltages due to feedback from earth.
A lightning strike on the ground causes an increase in the earth potential, which can spread to the installation (fed back from earth/gnd circuit).
3. Excess voltages due to electromagnetic induction.
Associated with lightning discharge is an electromagnetic field with a wide frequency spectrum which, as it connects to the loops in the installation, will give rise to destructive induced currents.
This will be a simple case of survival of the fittest with the weaker of the species dying.
It doesn't make one iota of difference if the camera is isolated from the building or not in electrical storms. The real culprit is the coax shield.
Isolating the camera from building metal-work will help reduce ground loops in a system, but do sfa in the event of lightning strikes.
It depends on how much are the cameras worth and how often are they knocked out due to lightning. If it is an expensive installation, you might want to look into products from .
If the system is relatively cheap, you might find lightning arrestors are not economically viable.
Unfortunately we live in a throw away society with quality being the victim.
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