8 Outcome 2: Pole Structures, Framing, Guys, and Anchors
Section Information
Outcome/Competency You will be able to describe pole structures, framing, guys and anchors.
Timing: 3.5h
Rationale:
Why is it important for you to learn this skill?
As a powerline technician you will be required to climb various pole structures using guys and anchors. It’s important that you understand how each of these pieces of equipment work together, and ensure that you do so safely to avoid injury or death.
Objectives:=
To be competent in this area, the individual must be able to:
- Identify and describe common pole structures and their components
- Identify and describe wood pole characteristics
- Identify and describe guys and anchors
Learning Goals
- Identify and describe common pole structures and their components and characteristics.
- Identify and describe guys and anchors
Introduction:
In this section you will learn about pole structures, installing hardware, pole framing, transformer structures, wood pole characteristics, and guys and anchors. You will be presented with content and then given opportunities to test your understanding with short review exercises.
Topic: Pole Structures (1h)
Instructions:
- Cover the following content as a group (either reading out loud or independently) then give an opportunity to answer any questions.
- Have students do the review questions independently, then take up answers.
Installing Hardware (25kV and Lower)
We have learned that the face or back of a pole is its strongest side. Therefore, we frame poles to always “face the strain”. All crossarms, timbers or spars which carry conductor are fastened to the back side of the pole (pole top equipment.)
Pole Framing
There are some general rules which should be followed when poles are framed.
Poles
- Proper class of pole and size of bolts in accordance with CSM
- Poles should not be gained (only done by the manufacturer.)
- Overhead guy poles should be 5 feet shorter than the pole it supports.
Bolts and Hardware
- Bolt holes should be 1/16 inch larger than the bolt being used. Example: 5/8 inch bolts use a 11/16 inch drill bit. ¾ inch bolts use a 13/16 inch drill bit.
- All hardware must be galvanized.
- The strongest part of a bolt is the unthreaded (bolt head) portion, so a bolt is positioned with the most strain on the bolt head.
- Bolts which are not under tension require double coil washers.
- Anti-split bolts are used on deflections where a pole may split.
Framing Practices
- A minimum number of holes should be drilled.
- Always frame the pole to leave room for climbing.
- Danger signs are used on all poles where equipment is accessible from ground level (switch handles, cable guards, ground wires, etc.)
- Ground wires are framed to the opposite side of the pole from cut-outs (prevents second point of contact accidents.)
- Crossarms are square to the pole.
- On three phase rural construction, the first two crossarms must face the deadend.
- Guy wire must be a minimum of 5/16 inch galvanized steel.
- Bail clamps must be used on ACSR or aluminum.
- Bonding must be done on hardware separated by less than 4 inches and on hardware within 6 inches of ground wires.
Three Reasons to Bond
- Prevent communication interference
- Safety to powerline technician (allows currents to flow around workers.)
- Fire prevention (if the potential between two objects is large enough, tracking can cause fires). For example, a gulf-port structure having all hardware at phase level or higher must be bonded to the ground wire.
Transformer Structures
When framing transformer structure, some general rules should be followed:
Grounding
- Ground wires to arrestors are kept short and snug (a blown arrestor can break and dangle on a pole.)
- Ground wires must be covered with molding (protects workers and the public.)
- Primary and secondary bushings may need to be grounded in some circumstances. This can be done by using one ground wire for both, referred to as a “common neutral.”
- Ground wires on the opposite side of a cut-out.
- On systems with a system neutral, only one path to ground is needed.
- On systems with no system neutral, two paths to ground are needed. Ground wires are put on opposite sides of the pole so if damage occurs, there is always another path to ground.
- Copper risers are preferred.
Apparatus
- Lightning arrestors are used on all transformers (some exceptions will occur on 3 phase banks).
- Cut-outs are located 90 degrees from the H1 bushing
- Minimum size of pole used:
- 13.7 m (45 feet) in urban
- 12.2m (40 feet) in rural
- Transformer poles are never raked.
- Voltage and phase rotation checks are always completed before a customer is connected. Serious damage can occur if voltage is too high, or the rotation is backwards.
Review Questions: Pole Structures (30m)
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(True / False) |
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The strongest part of a bolt is the: Bolt head and unthreaded portion Threaded portion Threaded portion, if double nutted
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(True / False) |
On ACSR or aluminum conductor, hot-taps may be used on armour rod if no bail clamp is present. |
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On severe deflections, poles may split if: Double timbers are not used Copper conductor is used Ant-split bolts are not used
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Overhead guy poles should be: Five feet higher than the pole it supports The same height as the pole it supports Ten feet shorter than the pole it supports
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(True / False) |
Danger signs are necessary on all poles which have equipment accessible from ground level. |
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On poles with cut-outs, the ground wire is located: Opposite the back Away from personnel operating the cut-out with a hotstick Opposite the belly
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A system neutral Two paths to ground Primary and secondary grounds hooked together
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(True / False) |
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(True / False) |
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With coils to allow movement Short and snug Only to ground grids
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(True / False) |
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Answer Key
1. 1/16, 2. F, 3. A, 4. F, 5. C, 6. D, 7. T, 8. B, 9. Prevent communication interference, safety to powerline technician, fire prevention. 10. 4, 6, 11. C, 12. T, 13. F, 14. Rural 40’, urban 45’, 15. B, 16. Copper, 17. F, 18. Voltage, phase rotation.