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

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES GROUNDING (EARTHING) ELECTRODE SYSTEM COMPONENT AND INSTALLATION
REQUIREMENTS
4.4.1.8 GROUND TEST WELLS
Ground test wells are not required, but may be desired for troubleshooting and/or inspecting the
grounding (earthing) electrode system components. Ground test wells are typically constructed of PVC
tubing 203 mm (8 in.) or more in diameter and have a detachable cover to keep debris out. A typical
PVC ground test well is shown in Figure 4-21.
FIGURE 4-21 TYPICAL GROUND TEST WELL
4.4.1.9 GROUNDING (EARTHING) ELECTRODE ENCASEMENT MATERIALS
Cover (typically metal,
removable for inspection of
grounding electrode)
Test Well
Ground Rod Exothermically
Welded to Ground Ring
Ground Rod
The resistance to earth of a grounding (earthing) electrode is directly proportional to soil resistivity and
inversely proportional to the total area in contact with the soil. Grounding electrode encasement
materials (also known as backfill or ground enhancing material) may consist of the following: bentonite
or bentonite containing material, concrete, or conductive concrete or cement made with graded granular
carbonaceous aggregate in place of the conventional sand or gravel. Grounding electrode encasement
materials can absorb water from surrounding soil and have hydration and water retention properties.
When placed around grounding electrodes and their interconnecting cable, grounding electrode
encasement materials greatly increase the effective area in contact with soil, which in turn reduces the
resistance of the grounding electrode system. See MIL-HDBK-419A Volume I, section 2.9 and
BS 7430:1998, section 8.5 for more details.
Grounding electrode encasement material may be used as needed to improve the grounding electrode
system resistance and/or to protect the grounding electrode system components from corrosive soil
(BS 7430:1998, section 19.6.1). Grounding electrode encasement material is generally used with
electrolytic ground rods, but may also be used on grounding conductors, standard ground rods, and
ground plates as a way to improve the resistance to earth of a grounding electrode system. Requirements
for the use of grounding electrode encasement material are as follows:
68P81089E50-B 9/1/05 4-27