standards and guidelines for communication sites - Radio And ...

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES MINIMUM SITE GROUNDING (EARTHING) REQUIREMENTS
4.7.2 TYPE “B” SITE - STANDARD DUTY
• Using a site drawing, determine where to install the minimum required ground rods, while
maintaining equal separation between rods. See “External Building and Tower Ground Ring” on
page 4-22 for additional information regarding ground rod placement requirements along ground
rings.
• Determine if radial grounding (earthing) conductors should be installed at the site, such as when the
site is located in a high lightning prone geographic area or when the site is normally occupied, such
as a dispatch center. See “Radial (Counterpoise) Grounding Conductors” on page 4-24.
• Calculate the resistance of the grounding electrode system using “Calculating Resistance of
Complex Ground Rod Systems” on page B-30.
• If the required resistance cannot be met, recalculate using one or more of the follow techniques:
• Recalculate using longer ground rods.
• Recalculate using radial grounding conductors if not already included. See “Radial
(Counterpoise) Grounding Conductors” on page 4-24.
• Recalculate using closer spaced ground rods, resulting in more ground rods at the site (do not
install ground rods closer than one ground rod length apart from other ground rods).
• If the resistance requirement still cannot be met, see “Special Grounding (Earthing) Situations” on
page 4-88.
• Develop a detailed site grounding electrode system drawing based on the previous steps.
• Install the grounding electrode system using components and techniques as specified throughout
this chapter.
• Test the grounding electrode system resistance to earth as described in Appendix D.
• Bond all external metal objects to the grounding electrode system as required throughout this
chapter.
4.7.3 SPECIAL GROUNDING (EARTHING) SITUATIONS
• See “Calculating Multiple Grounding Electrode System Resistance (Electrodes In Straight
Line)” on page B-19 for the information required to calculate the resistance to earth of multiple
ground rods installed in a straight line.
• See “Multiple Grounding Electrode System Resistance Calculation (Electrodes In Ring
Configuration)” on page B-24 for the information required to calculate the resistance to earth of
multiple ground rods installed in a ring configuration.
• See “Calculating Multiple Grounding Electrode System Resistance (Ground Rod Grid
Configuration)” on page B-24 for the information required to calculate the resistance to earth of
multiple ground rods installed in a ground rod grid configuration.
68P81089E50-B 9/1/05 4-45