Real Grounding Protection of Communication Sites
Traditionally, communication site grounding for lightning protection is achieved by ensuring that the tower, all external metal assemblies and all transmission and power lines are tied to the same external, buried ground grid. The tower legs are grounded to a tower base ground ring that is tied to ground radials interfaced with ground electrodes/rods that are also interconnected to the communication building's peripheral grounding system. Tied into this is also the ground conductor bonded to the Master Ground Bar (MGB) located inside the building's interior communication room, as well as ground connections tied to buried pipes and fuel tanks, etc. As long as all lines/cables entering the communication room are protected by surge arrestors or other Surge Protection Devices (SPD) and grounded, sufficient lightning protection is achieved. Motorola's R56 as well as most other grounding standards have emphasized the importance of single-point grounding, not only against lightning protection, but also its subsequent Ground Potential Rise (GPR) should a lightning strike occur in the vicinity of the communication site.
The importance of SPD on incoming transmission/power lines should not be underestimated, however assuming that the communication sites and towers are otherwise well grounded, the SPD will mostly tend to protect the front-end of transceivers if the incoming electrical surge is clamped and/or then shunted to ground. Often times the more serious equipment failures, not necessarily evident after each lightning activity, can come from the problems caused by GPR that can reduce substantially the life cycle of the equipment.
In a perfect world, all electrical power connections to the equipment inside a communications room would be disconnected during a thunder storm, leaving only your UPS batteries connected to the equipment. This would prevent elevated ground currents entering the equipment through the AC power grid's neutral connection, thereby isolating it from GPR. Since modern electronic equipment is often operating on very low voltages that can not tolerate even small changing voltage/current levels, the effects of GPR can render your communications equipment inoperative and/or reduce its life cycle significantly.
Conventional lightning protection is reactive: It assumes that the communication site will not sustain a direct lightning hit and if it does, that the lightning induced energy can be quickly and safely shunted to ground for charge dispersion. Depending on the intensity of the lightning strike and the ability of your ground electrode system and the soil to absorb the electrical charges quickly, some GPR is inevitable. New advanced engineering in lightning protection has now enabled us to become proactive: Prediction of possible lightning strikes now enable us to disconnect electrical/electronic equipment from the grid before the strike takes place.