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) SYSTEM COMPONENTS AND INSTALLATION REQUIREMENTS CHAPTER 5: INTERNAL GROUNDING (EARTHING) TABLE 5-1 MGB SPECIFICATIONS Item Specification Material Bare, solid Alloy 110 (99.9%) copper bus bar or plate of one piece construction. May be electrotin-plated. Minimum Dimensions NFPA 70-2005, Article 250.64) Mounting brackets Must be suitable for the application. Height: 50.8 mm (2 in.) Thickness: 6.35 mm (0.25 in.) Length: Variable to meet the application requirements and allow for future growth. 305 mm (12 in.) is recommended as the minimum length. Insulators Polyester Fiberglass 15 kV minimum dielectric strength Flame resistant per UL 94 VO classification Conductor mounting hole: Number and Dimensions Method of attachment of grounding electrode conductor. Dependent on number of conductors to be attached Holes should be 11 mm (0.4375 in.) minimum on 19 mm (0.75 in.) centers to permit the convenient use of two-hole lugs Exothermic welding Irreversible crimp connection Other suitable irreversible crimp connection process NOTE: A single properly installed integrated cable entry port of solid copper construction, electrically continuous between the interior and exterior of the structure through which it is mounted and with adequate surface area for proper termination of the internal grounding conductors, may be used as the MGB and external ground bus bar only if the site is properly designed for such a configuration. See “Grounding (Earthing) Electrode System Component and Installation Requirements” on page 4-7 for additional information on the external ground bus bar (EGB). Figure 5-7 shows an integrated cable entry port. 5-10 68P81089E50-B 9/1/05
STANDARDS AND GUIDELINES FOR COMMUNICATION SITES GROUNDING (EARTHING) SYSTEM COMPONENTS AND INSTALLATION REQUIREMENTS FIGURE 5-7 INTEGRATED CABLE ENTRY PORT BULKHEAD (OUTSIDE AND INSIDE VIEWS) 5.3.1.2 MGB LOCATION NOTE: Coaxial ground kits are located within the integrated panel and are not shown. Whenever practical, the MGB should be located within 610 mm (24 in.) of the transmission line entry into the building, equipment shelter, room, vault, enclosure or cabinet, preferably on the same wall or at the same entry location as the electrical service and the telecommunications cables. This configuration allows for a single point ground window to be established for the internal grounding (earthing) system. Figure 5-8 shows an example of this configuration for a stand-alone equipment shelter. 68P81089E50-B 9/1/05 5-11
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GROUNDING (EARTHING) SYSTEM COMPONENTS AND INSTALLATION REQUIREMENTS CHAPTER 5: INTERNAL GROUNDING (EARTHING)<br />
TABLE 5-1 MGB SPECIFICATIONS<br />
Item Specification<br />
Material Bare, solid Alloy 110 (99.9%) copper bus bar or plate of one piece construction. May be<br />
electrotin-plated.<br />
Minimum Dimensions<br />
NFPA 70-2005, Article 250.64)<br />
Mounting brackets Must be suitable <strong>for</strong> the application.<br />
Height: 50.8 mm (2 in.)<br />
Thickness: 6.35 mm (0.25 in.)<br />
Length: Variable to meet the application requirements <strong>and</strong> allow <strong>for</strong> future growth.<br />
305 mm (12 in.) is recommended as the minimum length.<br />
Insulators Polyester<br />
Fiberglass<br />
15 kV minimum dielectric strength<br />
Flame resistant per UL 94 VO classification<br />
Conductor mounting hole:<br />
Number <strong>and</strong> Dimensions<br />
Method of attachment of grounding<br />
electrode conductor.<br />
Dependent on number of conductors to be attached<br />
Holes should be 11 mm (0.4375 in.) minimum on 19 mm (0.75 in.) centers to permit the<br />
convenient use of two-hole lugs<br />
Exothermic welding<br />
Irreversible crimp connection<br />
Other suitable irreversible crimp connection process<br />
NOTE: A single properly installed integrated cable entry port of solid copper construction, electrically<br />
continuous between the interior <strong>and</strong> exterior of the structure through which it is mounted <strong>and</strong> with<br />
adequate surface area <strong>for</strong> proper termination of the internal grounding conductors, may be used as the<br />
MGB <strong>and</strong> external ground bus bar only if the site is properly designed <strong>for</strong> such a configuration. See<br />
“Grounding (Earthing) Electrode System Component <strong>and</strong> Installation Requirements” on page 4-7 <strong>for</strong><br />
additional in<strong>for</strong>mation on the external ground bus bar (EGB). Figure 5-7 shows an integrated cable<br />
entry port.<br />
5-10 68P81089E50-B 9/1/05
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