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

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES FALL-OF-POTENTIAL METHOD TESTING PROCEDURE
D.3.3.2 SITE AC POWER DISCONNECT REQUIREMENTS
This test requires disconnection of the site grounding (earthing) electrode system from the power
company grounded conductor (may be a neutral wire). This is required in order to allow testing that is
limited only to the site grounding electrode system. Attempting to perform measurements while the site
remains connected to the extensive ground/ neutral system of the power company artificially enhances
the grounding electrode system reading, resulting in measurement error. Therefore, for an existing site
supplied by commercial AC power that contains a neutral wire which is part of an extensive power
company grounding system, the following steps must be taken first:
1. Coordinate the test with the customer and/or site owner and all other affected parties.
2. Arrange for the site to have the power company AC power turned off. If the site must remain
operational while testing is being done, the site will have to be switched to a back-up power source
if it is available.
WARNING
Check for current on the grounding electrode conductor before disconnecting. Never
disconnect the ground of a live circuit. Disconnecting the ground of a live circuit could
cause death or severe injury.
3. Have the site grounding electrode system isolated from the power company grounded conductor
(may be a neutral wire) by a qualified electrician, ensuring that it has no secondary path to the site
via a conduit or other connection (this can be verified with the use of a multi-meter). The only way
to achieve this (especially at a communications site with a multi-bonded/multi-grounding electrode
system) may be having the power company grounded conductor (may be a neutral wire)
disconnected from the site.
4. Remove any other grounding electrode connection that may influence the measurement of the onsite
grounding electrode system, such as the telephone company ground connection and metallic
water/gas pipes.
D.3.3.3 FALL-OF-POTENTIAL TEST PROCEDURE
Figure D-4 shows typical ground resistance tester connections and test probe orientations.
WARNING
Follow ground resistance tester manufacturer's warning and caution information when
using tester. Follow furnished instructions when inserting and removing test rods into
soil. Make certain this procedure is fully understood before proceeding with test.
Perform the fall-of-potential test as follows:
1. On Ground Resistance Tester, connect test leads to the X, Y, and Z terminals.
2. Short the X and Xv connections on the Ground Resistance Tester.
3. Connect the X lead to the grounding electrode system under test. (This is typically via a test clip
connection to an external ground bus bar.)
68P81089E50-B 9/1/05 D-9