standards and guidelines for communication sites - Radio And ...
standards and guidelines for communication sites - Radio And ... standards and guidelines for communication sites - Radio And ...
FALL-OF-POTENTIAL METHOD TESTING PROCEDURE APPENDIX D: GROUNDING (EARTHING) ELECTRODE SYSTEM TESTING/VERIFICATION 4. Connect the Y lead to the measurement (Y) probe. 5. Determine the required placement of outer reference probe (Z) in accordance with paragraph “Testing Area Requirements” on page D-5. 6. Place the outer reference probe (Z) into the soil at the determined location. Connect the outer reference probe (Z) to meter terminal Z. 7. Note the distance of the outer reference probe (Z) from the grounding electrode system (this distance will be used in determining subsequent measurements). On the photocopy of the Fall-of- Potential Test Worksheet, write this distance in the “100%” space. 8. Place the measurement probe (Y) in the soil starting close to the area of the grounding electrode system under test. Take a measurement. 9. On the photocopy of the Fall-of-Potential Test Worksheet (page D-21), write the reading in the “0%” row of the worksheet. 10. Place the measurement probe (Y) at 5% of the distance between the grounding electrode system 'X' connection and the outer reference probe (Z). Take a measurement. Example: Assuming a “100%” distance of 131 m (430 ft.), Y probe would be placed at 6.55 m (21.5 ft.) for “5%” measurement location. NOTE: Placement of the measurement probe (Y) must be along a straight path between the grounding electrode system 'X' connection and the outer reference probe (Z). 11. On the photocopy of the Fall-of-Potential Test Worksheet, write down the reading in the appropriate row of the worksheet. 12. Place the measurement probe (Y) at 10% of the distance between the grounding electrode system 'X' connection and the outer reference probe (Z). Take a measurement. Example: Assuming a “100%” distance of 131 m (430 ft.), Y probe would be placed at 13.1 m (43 ft.) for “10%” measurement location. 13. On the photocopy of the Fall-of-Potential Test Worksheet (, write down the reading in the appropriate row of the worksheet. 14. At every 10% point, repeat steps 12 and 13 for the remaining spaces on the worksheet. 15. On the photocopy of Fall-of-Potential Test Graph Form, plot a graph of the measured resistances for all points listed on the worksheet. 16. Using Figure D-5, assess the test results as follows: • Valid Test: At approximately 62% of the total distance (“100%” distance), a plateau or “flat spot” should be noticeable in the plot, as shown in “VALID TEST GRAPH” in Figure D-5. The resistance at this plateau is the validated resistance of the system under test. • Invalid Test Graph (insufficient distance of Z-probe): If there is no plateau on the plot, shown in “INVALID TEST GRAPH (Z-Probe Spacing)” in Figure D-5, the test is considered invalid because the Z probe is not far enough from the X probe. D-10 68P81089E50-B 9/1/05
STANDARDS AND GUIDELINES FOR COMMUNICATION SITES FALL-OF-POTENTIAL METHOD TESTING PROCEDURE • Invalid Test Graph (erroneous connection to neutral): If there is no plateau on the plot, shown in “INVALID TEST GRAPH (Connection to neutral)” in Figure D-5, the test is considered invalid because an erroneous connection of the grounding electrode system to a power company neutral , or other utility ground, remains. NOTE: If the electrical service provided by the Power Company does not contain a neutral wire that is bonded to an extensive power company grounding system, such as a 3-phase delta service, the fall-of-potential test can be performed on the grounding electrode system without disconnecting it from the power company. This is because the neutral wire is locally derived at the transformer and is not part of the extensive Power Company grounding system. All other utility connections must still be removed, such as the telephone company ground connection and ground through water/gas metallic pipes. NOTE: If sufficient access area exists, the entire procedure above should be repeated in different directions facing away from the center of the grounding electrode system. Repeating the procedure is recommended in case metal pipes or similar conductive objects are buried in a given test area. The presence of metal pipes or similar conductive objects may result in an inaccurate reading. Grounding Electrode Under Test TESTER X Xv Y Z X Y Z Outer Probe Measurement Probe Site Boundary FIGURE D-4 TYPICAL GROUND RESISTANCE TESTER CONNECTION 68P81089E50-B 9/1/05 D-11
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- Page 467 and 468: APPENDIX C PROTECTING AGAINST ELECT
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STANDARDS AND GUIDELINES FOR COMMUNICATION SITES FALL-OF-POTENTIAL METHOD TESTING PROCEDURE<br />
• Invalid Test Graph (erroneous connection to neutral): If there is no plateau on the plot, shown<br />
in “INVALID TEST GRAPH (Connection to neutral)” in Figure D-5, the test is considered<br />
invalid because an erroneous connection of the grounding electrode system to a power<br />
company neutral , or other utility ground, remains.<br />
NOTE: If the electrical service provided by the Power Company does not contain a neutral wire that is bonded<br />
to an extensive power company grounding system, such as a 3-phase delta service, the fall-of-potential<br />
test can be per<strong>for</strong>med on the grounding electrode system without disconnecting it from the power<br />
company. This is because the neutral wire is locally derived at the trans<strong>for</strong>mer <strong>and</strong> is not part of the<br />
extensive Power Company grounding system. All other utility connections must still be removed, such<br />
as the telephone company ground connection <strong>and</strong> ground through water/gas metallic pipes.<br />
NOTE: If sufficient access area exists, the entire procedure above should be repeated in different directions<br />
facing away from the center of the grounding electrode system. Repeating the procedure is<br />
recommended in case metal pipes or similar conductive objects are buried in a given test area. The<br />
presence of metal pipes or similar conductive objects may result in an inaccurate reading.<br />
Grounding Electrode<br />
Under Test<br />
TESTER<br />
X Xv Y Z<br />
X Y Z<br />
Outer Probe<br />
Measurement<br />
Probe<br />
Site Boundary<br />
FIGURE D-4 TYPICAL GROUND RESISTANCE TESTER CONNECTION<br />
68P81089E50-B 9/1/05 D-11
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