This past year, Rural Utilities Service (RUS) staff received an inquiry about anchor bonding clamps, Item "ck" in the RUS Information Publication IP 201-2, "List of Materials Acceptable for Use on Systems of RUS Electrification Borrowers." The inquirer wanted to know whether these clamps were required by RUS and whether it was a National Electrical Safety Code (NESC) requirement.
As shown in the E type drawings included in RUS 15 and 25 kV overhead distribution construction specifications, RUS indeed does require the use of anchor bonding clamps on anchor assemblies.
The purpose of the anchor bonding clamp is to ensure the safety of the public and line crews. A properly installed anchor bonding clamp ensures there is a solid electrical connection between the anchor rod and the guy even during occasions when the guy in the anchor assembly goes slack.
On an anchor assembly with a slack guy that does not have an anchor bonding clamp installed, a person could come into contact with a guy wire that is solidly bonded to the neutral of the distribution system at the top of the pole and electrically is virtually disconnected from the anchor rod and anchor near where the person is standing. This could result in the person touching the guy wire and having direct contact to the electric system neutral and becoming exposed to a voltage that could be very different than the voltage of the earth the person is standing on. If the voltage difference is great enough, the person’s body could become part of an electric circuit and draw an electric current that may result in anything from an unpleasant tingle to serious shock and injury.
On an anchor assembly with a slack guy that does have an anchor bonding clamp installed, a person will be standing on earth that is essentially at the same potential as the guy/anchor assembly because of the electrical contact existing between the solidly interconnected guy wire, anchor rod, anchor and soil. With little difference in potential between the earth and the anchor guy, little if any electric current will flow in the person’s body minimizing the possibility of injury.
NESC Rule 215C2 requires that guys be effectively grounded. RUS specifications provide for this grounding assurance in part by requiring the guys to be bonded to the neutral at the top of the guy. On an ordinary tight guy, the effective grounding would be completed with the tight connection of the guy wire and anchor rod eye in contact with one another. However, as mentioned above, on an anchor assembly with a slack guy, this latter connection for assuring an effective bond between the anchor and guy is lost. RUS specifications require the guy anchor bonding clamp to make certain that the bond between the anchor and guy will remain effective in the event the guy becomes slack for whatever reason.
Borrowers should be certain to check that guy anchor bonding clamps are used on all their anchor assemblies.
If you would like more information or have any questions, please contact Jim Bohlk, Electrical Engineer, Distribution Branch, at 202-720-1967 or at jbohlk@rus.usda.gov.