standards and guidelines for communication sites - Radio And ...
standards and guidelines for communication sites - Radio And ... standards and guidelines for communication sites - Radio And ...
GROUNDING (EARTHING) ROOFTOP MOUNTED TOWER STRUCTURES CHAPTER 4: EXTERNAL GROUNDING (EARTHING) • Other metallic objects on the roof shall be bonded to the roof perimeter lightning protection system ring as required by BS 6651:1999, IEC 61024-1-2, NFPA 780-2004, or other standard in effect and recognized by the local authority having jurisdiction. • All grounding electrodes at the building shall be bonded together to form a single grounding electrode system. See “Common Grounding (Earthing)” on page 4-5. The rooftop mounted tower shall be effectively grounded by bonding to the lightning protection system. The rooftop mounted tower shall bond to the lightning protection system as follows: • The rooftop mounted tower support legs shall be interconnected with a conductor to form a roof tower ground ring. A guyed tower base plate can be used in place of the roof tower ground ring. The conductor shall be of the same size as the main roof perimeter lightning protection ring. • The roof tower ground ring shall be exothermically bonded to the tower unless specifically directed otherwise by the tower manufacturer. • The rooftop mounted tower ground ring or guyed tower base plate shall bond to the main roof perimeter lightning protection ring with a minimum of two opposing conductors at or within 610 mm (24 in.) of a grounding down conductor, or other main grounding conductor as defined by NFPA 780-2004, such as effectively grounded structural building steel. The conductor shall be of the same size and type as the main roof perimeter lightning protection ring. • The conductors shall meet the installation requirements of “Grounding (Earthing) Conductors” on page 4-28. • Conductor bonding shall be made using exothermic welding, listed irreversible highcompression fittings, or other fittings listed for use in lightning protection systems. See “Bonding to the External Grounding (Earthing) Electrode System” on page 4-40. • All tower guy/anchors that are attached directly to the building shall be bonded to the main roof perimeter lightning protection ring (ANSI T1.313-2003, section 10.3.3.). • The conductors shall meet the installation requirements of “Grounding (Earthing) Conductors” on page 4-28. • Conductor bonding shall be made using exothermic welding, listed irreversible highcompression fittings, or other fittings listed for use in lightning protection systems. See “Bonding to the External Grounding (Earthing) Electrode System” on page 4-40. See Figure 4-57 for an example of a typical rooftop tower grounding system. 4-80 68P81089E50-B 9/1/05
STANDARDS AND GUIDELINES FOR COMMUNICATION SITES SPECIAL GROUNDING (EARTHING) APPLICATIONS AIR TERMINAL TOWER GROUNDING CONDUCTOR BONDED WITHIN 24 INCHES OF THE GROUNDING DOWN CONDUCTOR BUILDING GROUND RING - PAR P T THE COMPLETE SYSTEM ROOFTOP TOWER GROUND RING FIGURE 4-57 TYPICAL ROOFTOP TOWER GROUNDING RING MAIN ROOF PERIMETER LIGHTNING PROTECTION RING ROOFTOP TOWER TOWER GROUNDDING CONDUCTORR 1 OF 2 MINIMUUM TO MGB GROUNDING DOWN CONDUCTOR 1 OF 4 SHOWN 4.10 SPECIAL GROUNDING (EARTHING) APPLICATIONS Some communications site locations and/or applications require special consideration for effective grounding (earthing). The following sections describe the grounding techniques for some common communications applications. Consultation with Motorola Engineering or other engineering firm may be required in some situations. 4.10.1 EXTERNAL GROUNDING (EARTHING) FOR DISPATCH CENTERS CO-LOCATED WITH COMMUNICATIONS TOWERS Dispatch centers co-located with communications towers require special protection considerations due to the critical nature of their operation and due to the inherent risk to personnel from lightning. For optimum protection of a dispatch center, the following shall be considered: • Site design recommendations given in “Design Considerations to Help Reduce Effects of Lightning” on page 2-19. • Internal grounding and bonding as defined in “Grounding (Earthing) for Dispatch Centers and Network Operator Positions” on page 5-62. • Transient voltage surge suppression (TVSS) As defined in “Surge Protection Considerations for Dispatch Centers and Operator Positions” on page 7-43. 68P81089E50-B 9/1/05 4-81
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STANDARDS AND GUIDELINES FOR COMMUNICATION SITES SPECIAL GROUNDING (EARTHING) APPLICATIONS<br />
AIR TERMINAL<br />
TOWER GROUNDING<br />
CONDUCTOR BONDED<br />
WITHIN 24 INCHES OF THE<br />
GROUNDING DOWN<br />
CONDUCTOR<br />
BUILDING GROUND RING -<br />
PAR P T THE COMPLETE<br />
SYSTEM<br />
ROOFTOP TOWER<br />
GROUND RING<br />
FIGURE 4-57 TYPICAL ROOFTOP TOWER GROUNDING RING<br />
MAIN ROOF PERIMETER<br />
LIGHTNING PROTECTION RING<br />
ROOFTOP TOWER<br />
TOWER GROUNDDING<br />
CONDUCTORR 1 OF 2 MINIMUUM<br />
TO MGB<br />
GROUNDING DOWN<br />
CONDUCTOR<br />
1 OF 4 SHOWN<br />
4.10 SPECIAL GROUNDING (EARTHING) APPLICATIONS<br />
Some <strong>communication</strong>s site locations <strong>and</strong>/or applications require special consideration <strong>for</strong> effective<br />
grounding (earthing). The following sections describe the grounding techniques <strong>for</strong> some common<br />
<strong>communication</strong>s applications. Consultation with Motorola Engineering or other engineering firm may<br />
be required in some situations.<br />
4.10.1 EXTERNAL GROUNDING (EARTHING) FOR DISPATCH CENTERS<br />
CO-LOCATED WITH COMMUNICATIONS TOWERS<br />
Dispatch centers co-located with <strong>communication</strong>s towers require special protection considerations due<br />
to the critical nature of their operation <strong>and</strong> due to the inherent risk to personnel from lightning. For<br />
optimum protection of a dispatch center, the following shall be considered:<br />
• Site design recommendations given in “Design Considerations to Help Reduce Effects of<br />
Lightning” on page 2-19.<br />
• Internal grounding <strong>and</strong> bonding as defined in “Grounding (Earthing) <strong>for</strong> Dispatch Centers <strong>and</strong><br />
Network Operator Positions” on page 5-62.<br />
• Transient voltage surge suppression (TVSS) As defined in “Surge Protection Considerations <strong>for</strong><br />
Dispatch Centers <strong>and</strong> Operator Positions” on page 7-43.<br />
68P81089E50-B 9/1/05 4-81
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