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Grounding on wood pole transmission structures

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Figure 3. – Example ground cluster bar attached to wood pole
Figure 3. – Example ground cluster bar attached to wood pole. The bar provides convenient point of attachment for protective grounds and a bond to the pole structure ground wire, if provided.

Preferred three-phase grounding applications on wood pole structures using grounding cluster bars are shown in figures 1 and 2.

Grounding cluster bars must be positioned just below the lowest elevation of the lineman’s feet for the work zone (approximately the elevation of the phase conductors) and shall be bonded to the pole structure ground leads if provided.

The position of the cluster bar defines the lower boundary of the equipotential work zone on a pole.
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Figure 3 shows an example of an installed grounding cluster bar.

Figure 1. – Protective grounding jumper installation for two-pole
Figure 1. – Protective grounding jumper installation for two-pole and three-pole structures (grounded structures). OGW denotes overhead ground wire. OGWs must be bonded to the worksite grounding system if within reach of linemen. OGWs may be bonded to the cluster bars or to the grounded phase conductors with protective grounds.

Before installing protective grounds, permanent grounding for pole footings should be examined for damage, omission, or other indication of poor continuity between the structural hardware and pole ground electrode.

If in question, a temporary ground rod should be installed next to the pole and bonded to the worksite site grounding system (figure 2).

Figure 2. – Example protective grounding jumper installation
Figure 2. – Example protective grounding jumper installation showing use of ground rod for ungrounded structures or structures with questionable grounding integrity. OGW denotes overhead ground wire.

In addition, other conductive objects, such as guy wires, shall be bonded to the worksite grounding system if within reach of the linemen.

SOURCE: Personal protective grounding for electric power facilities and power BY U.S. Department of the Interior Bureau of Reclamation Denver, Colorado

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Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry fascilities. Professional in AutoCAD programming. Present on