Lawrence M. Slavin - Overhead Distribution Lines

1 Cover

2 Title Page Overhead Distribution Lines Design and Application Lawrence M. Slavin, PhD

3 Copyright

4 Dedication

5 About the Author

6 Preface

7 Acknowledgments

8 1 Introduction1.1 Scope 1.2 Background

9 2 Pole Structures2.1 General 2.2 Wood Pole Strength 2.3 Loads 2.4 Embedment Depth 2.5 Guying 2.6 Column Buckling 2.7 Grounding and Bonding Notes

10 3 Pole Installation and Maintenance3.1 Pole Placement 3.2 Guys and Anchors 3.3 Pole Maintenance

11 4 Wires, Conductors, and Cables4.1 Categories 4.2 Messenger Wire/Strand 4.3 Electric Supply (Power) Cables 4.4 Communications Cables 4.5 Wireless Attachments

12 5 Cable Installation5.1 Conductor and Cable Placement 5.2 Lashing Operation 5.3 Overlashing Notes

13 6 NESC ®Requirements (Strength and Loading) 6.1 National Electrical Safety Code (NESC) 6.2 Loading Requirements 6.3 Strength Requirements 6.4 Wire Tensions 6.5 Guyed Poles 6.6 Extreme Wind Loads (“60 ft Limit”) 6.7 Allowable Deterioration 6.8 Overlashed Cables 6.9 Software Tools and Pole Loading Analysis Notes

14 7 NESC ®Requirements (Clearances)7.1 Clearances 7.2 Clearance Zones 7.3 Clearances Above Surfaces and Buildings 7.4 Clearances Between Wires 7.5 Overlashed Cables Note

15 8 Principles of Wire Sag8.1 Catenary 8.2 Initial and Final Sag 8.3 Sag–Tension Relationship 8.4 Determining Change in Sag (and Tension) 8.5 Ruling Span 8.6 Point Load Note

16 9 General Order 95 (California)9.1 General Order 95 (GO 95) 9.2 Loading Requirements 9.3 Strength Requirements 9.4 Clearances

17 10 Examples10.1 Purpose 10.2 Tangent Line 10.3 Line Angle 10.4 Line Angle – Buckling Consideration 10.5 Additional Attachment 10.6 Summary Note

18 Appendix A: Properties of Messenger Strands

19 Appendix B: Wireless Attachments

20 Appendix C: Extreme Wind and Extreme Ice Loadings

21 Appendix D: Solution of Cubic Equation Note

22 Appendix E: Point Load E.1 Parabolic Model E.2 Intersecting Straight Lines Model

23 Glossary

24 References

25 Index

26 End User License Agreement

1 Chapter 2 Table 2.1 Class loads for wood poles.

2 Chapter 6Table 6.1 Rule 250B storm loadings.Table 6.2 NESC load and strength factors for Rule 250B district loadings.

3 Chapter 7Table 7.1 Prior storm loadings.Table 7.2 Vertical clearances for typical distribution wires and cables (ft).

4 Chapter 9Table 9.1 GO 95 storm loadings.

5 Appendix CTable C.1 Rule 250C and 250D storm loadings.Table C.2 NESC load and strength factors for Rule 250C and 250D extreme loads...Table C.3 Rule 250D pressure vs. wind speed.

1 Chapter 1 Figure 1.1 Typical belowground construction. Figure 1.2 Typical joint-use utility pole application.

2 Chapter 2 Figure 2.1 Distribution pole and associated hardware. Figure 2.2 Basic pole load geometry (class loads). Figure 2.3 Brand/mark on poles. Figure 2.4 Wood pole strength variability. Figure 2.5 Pole loadings. Figure 2.6 Bending moment, including “ P -delta” due to lateral deflection.Figure 2.7 Guying.Figure 2.8 Unbalanced load on pole resulting from wire tension.Figure 2.9 Modes of column buckling (instability).

3 Chapter 3Figure 3.1 Hole boring and pole placement.Figure 3.2 Installation of lightweight pole.Figure 3.3 Guy hook and sample application.Figure 3.4 Guys and markers.Figure 3.5 (a) Expansion anchor and (b) screw anchor.Figure 3.6 Decay severity zones for wood utility poles.Figure 3.7 Pole maintenance.Figure 3.8 Inspected poles. (a) Pole with inspection tag and (b) rejected po...Figure 3.9 Rehabilitated or reinforced poles.

4 Chapter 4Figure 4.1 Steel messenger wire.Figure 4.2 Use of hoops to support heavy communication cable.Figure 4.3 Electric supply messenger.Figure 4.4 Multiplex (quadruplex) cable.Figure 4.5 Hendrix covered conductors.Figure 4.6 Hendrix covered conductors.Figure 4.7 Electric supply conductors. (a) AAAC and (b) ACSR/TW.Figure 4.8 Typical metallic service drops.Figure 4.9 Typical coaxial and fiber service drops.Figure 4.10 Typical copper pair cables.Figure 4.11 Jacketed and unjacketed coaxial cables.Figure 4.12 All dielectric self-supporting fiber cable.Figure 4.13 Wireless antennas mounted on utility poles. (a) Pole-top mountin...

5 Chapter 5Figure 5.1 Stringing overhead communications cable – stationary reel method....Figure 5.2 Stringing Hendrix-type supply cable – stationary reel method.Figure 5.3 Stringing overhead communications cable – moving reel method.Figure 5.4 Typical cable lasher.Figure 5.5 Lashing communications cable – stationary reel method.Figure 5.6 Stringing and lashing overhead communication cable – moving reel ...Figure 5.7 Overlashed cable bundles.

6 Chapter 6Figure 6.1 Storm loading districts for determining strength (Rule 250B).Figure 6.2 Storm loading on ice-covered bundle.Figure 6.3 Transverse loads applied to pole acting as a cantilever, resultin...Figure 6.4 Strength factors applied to average strength of wood pole (Rule 2...Figure 6.5 Conductor loads for determining wire tension.Figure 6.6 Guy supporting storm load.Figure 6.7 Comparison of transverse wind loads for multiple cables (Rule 250...Figure 6.8 Incremental storm tension for multiple overlashed cables (Rule 25...

7 Chapter 7Figure 7.1 Installed facilities.Figure 7.2 Clearance zones for determining clearances.Figure 7.3 Comparison of midspan sags for multiple overlashed cables under i...Figure 7.4 Comparison of midspan sags for multiple overlashed cables at nomi...

8 Chapter 8Figure 8.1 Comparison of hyperbolic and parabolic representations for suspen...Figure 8.2 Non-level slope.Figure 8.3 Inward movement of support point(s).Figure 8.4 (a) Point load – peak sag occurs away from load. (b) Point load –...Figure 8.5 Very heavy point load.

9 Chapter 9Figure 9.1 Storm loading districts for California.

10 Chapter 10Figure 10.1 Example pole with supply and communications lines.Figure 10.2 Example pole at line angle supported by guys.Figure 10.3 Example pole subject to vertical loads from guy tension.

11 Appendix EFigure E.1 Point load vs. peak sag.

1 Cover Page

2 Table of Contents

3 Begin Reading

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