SECTION 5: SITE GROUNDING AND LIGHTNING PROTECTION
SITE GROUNDING AND LIGHTNING PROTECTION
The conditions that make a site desirable for two-way radio communications are the same that make a site an excellent target for lightning strikes. Proper lightning protection methods can prevent equipment damage in all but the most severe strikes. Even then, equipment damage may be kept to a minimum. Lightning protection is intended to prevent the electrical energy from a strike from entering the equipment room, and then preventing damage to the equipment as a result of induced voltages on power, signal, and control lines to the equipment.
Proper site grounding and light-ning protection are vitally important considerations. Failure to provide proper lightning protection may result in catastrophic damage to the paging station equipment.
One of the most important considerations when designing a communications site is the grounding and lightning protection systems. While proper grounding techniques and lightning protection are closely related, the general category of site grounding may be divided as follows:
Electrical Ground — Ground wires carrying electrical current from circuitry or equipment at the site is included in the category of electrical ground. Examples include the ac or dc electrical power used to source equipment located at the site, telephone lines, and wires or cables connected to alarms or sensors located at the site.
RF Ground — This type of ground is related to the transmission of radiofrequency energy to earth ground. An example of rf grounding is the use of shielding to prevent (or at least minimize) the leakage of unwanted rf transmissions from communications equipment and cables.
Lightning Ground — Providing adequate lightning protection is critical to a safe and reliable communications site. Telephone lines, rf transmission cables, and ac and dc power lines must all be protected to prevent lightning energy from entering the site building.
Nucleus Advanced Control Equipment Grounding Guidelines
DO NOT work on stations during thunderstorms or when lightning is in the area!
Paging Station cage is equipped with a single ground lug located on the rear panel of the cage. Use this lug to connect the cage to the site ground point. It is assumed that all telephone lines, antenna cables, and ac or dc power cabling have been properly grounded and lightning protected.
Although a comprehensive coverage of site grounding techniques and lightning protection is not within the scope of this instruction manual, there are several excellent industry sources for rules and guidelines on grounding and lightning protection at communication sites. Motorola recommends the following reference source:
Quality Standards — FNE Installation Manual (Motorola No. R56) (Motorola Part No. 68P81089E50)
Failure to observe proper anti-static grounding procedures may cause catastrophic dam-age to the equipment. ALWAYS wear a grounded wrist strap when handling modules or cards.
All Nucleus Advanced Control stations have provisions for electrostatic grounding. The formed tube at each side of the card cage chassis is marked with the grounding symbol (
). When handling any module or circuit board, be sure to wear an anti-static wrist strap and plug the banana plug connector into the ground receptacle (formed tube) on the card cage.