Clamp Jaws - hdbk10920150

DOE-HDBK-1092-98

7.5.3.4.7.2 CLAMP JAWS

Bus clamps should be furnished with smooth jaws for installation on copper, aluminum, or silver-

plated bus work without marring the surface. Conductor or metal structure clamps should be

furnished with serrations or cross-hatching designed to abrade or bite through corrosion products on

surfaces of the conductor or the metal structure being clamped. Several styles of conductor and

ground-end clamps have jaws that can be replaced when the serrations have worn. Self-cleaning jaws

are recommended for conductor-end clamps used on aluminum or aluminum conductor steel

reinforced (ACSR) conductors. Several styles of ground-end clamps are designed with a cup-point

set screw which should be tightened with a wrench (after the serrated jaws have been securely

tightened) to break through paint, rust, galvanized coating, or corrosion on the surface that is to be

clamped.

A typical grounding cable for transmission line work used by line crews consists of a 2/0 (AWG)

copper cable with an insulating jacket, terminated with an all-angle, self-cleaning aluminum

conductor clamp at one end, and a flat-faced clamp with a set screw at the other end for connecting

to a tower leg or ground wire/rod.

7.5.3.4.8 GROUNDING CLUSTER BARS

When climbing wood-pole structures, workers may use a grounding cluster bar to connect the phase

cables to the pole ground wire, if the ground wire has sufficient capacity to carry the fault current.

Cluster bars must have an attached bonding lead. If there is no pole ground wire, the cluster bar for

each pole is connected to a common driven or screw-in ground rod with a grounding cable (or cables).

In substation grounding, a copper bar is sometimes used to connect the three-phase cables and a

fourth cable to a riser from the station ground mat. When installing personal grounds on wood

structures from a bucket, the ground cables may be connected between the overhead ground wire

(OGW), and the phases without the use of cluster bars provided that an electrical bond of sufficient

current carrying capacity exists between the OGW and the structure ground.

7.5.3.4.9 TEMPORARY GROUND RODS

Some typical examples of temporary ground rods used for grounding ungrounded structures or

mobile equipment, or during conductor splicing operations, are either:

1. A minimum 5/8-inch diameter bronze, copper, or copper-weld rod at least 6 feet long, driven

to a depth of at least 5 feet; or

2. A 6-foot, screw-type ground rod, consisting of a minimum 5/8-inch diameter copper-weld

shaft with a bronze auger bit and bronze T-handle, screwed to a depth of at least 5 feet

(preferred). The T-handle must be tightly connected to the rod.

If a temporary rod cannot be driven or screwed to a depth of 5 feet, additional rod(s) should be driven

or screwed so that a total of at least 5 feet of rod is buried. These rods shall be bonded together with

grounding cables prior to installing phase grounds. The rods should be placed 6 to 8 feet apart;

however, the 10-foot clearance from the rods should be maintained. OGWs may be used at any time

7-16