A general overview of the use of utility distribution poles, including for electric supply and communications applications
Overhead Distribution Lines: Design and Applications provides information on the design and use of power and communication distribution lines. An excellent resource for those in the power and communication utilities industry, this book presents information on the physical characteristics of utility poles, overhead supply and communication cables, installation practices, joint-usage issues, and safety rules, including the National Electrical Safety Code (NESC), California-specific rules, and others. It describes how to select the proper poles for specific applications. The especially valuable final chapter provides examples showing how it all works in practice, providing a background allowing more effective use of related industry software.
Rather than delving into detailed design and installation techniques, this book serves as an overview for engineers and non-technical audiences alike. At the same time, it serves as a compendium of technical information not readily available elsewhere. This unique book:
- Offers an overview of pole structures, pole installation and maintenance, wires and cables, and cable installation and maintenance - with examples
- Provides information on national standards documents such as the National Electrical Safety Code (NESC), ANSI O5.1, California General Order 95, and more
- Explores the "sag–tension" relationship between wires and poles
- Includes appendices that cover properties of messenger strands, wireless attachments, solution of equations to determine sag, under uniform and point loads
Overhead Distribution Lines: Design and Applications offers readers an understanding of the basic principles and various issues related to electric supply and communications distribution lines. It is a valuable resource for utility engineers, as well as those without a technical background.
About the Author xi
Preface xiii
Acknowledgments xv
1 Introduction 1
1.1 Scope 1
1.2 Background 2
2 Pole Structures 7
2.1 General 7
2.2 Wood Pole Strength 8
2.3 Loads 13
2.4 Embedment Depth 15
2.5 Guying 17
2.6 Column Buckling 19
2.7 Grounding and Bonding 22
3 Pole Installation and Maintenance 23
3.1 Pole Placement 23
3.2 Guys and Anchors 24
3.3 Pole Maintenance 26
4 Wires, Conductors, and Cables 31
4.1 Categories 31
4.2 Messenger Wire/Strand 31
4.3 Electric Supply (Power) Cables 33
4.4 Communications Cables 35
4.5 Wireless Attachments 38
5 Cable Installation 39
5.1 Conductor and Cable Placement 39
5.2 Lashing Operation 40
5.3 Overlashing 41
6 NESC® Requirements (Strength and Loading) 45
6.1 National Electrical Safety Code (NESC) 45
6.2 Loading Requirements 46
6.3 Strength Requirements 49
6.4 Wire Tensions 52
6.5 Guyed Poles 53
6.6 Extreme Wind Loads (“60 ft Limit”) 54
6.7 Allowable Deterioration 56
6.8 Overlashed Cables 57
6.9 Software Tools and Pole Loading Analysis 60
7 NESC® Requirements (Clearances) 63
7.1 Clearances 63
7.2 Clearance Zones 63
7.3 Clearances Above Surfaces and Buildings 66
7.4 Clearances Between Wires 67
7.5 Overlashed Cables 67
8 Principles of Wire Sag 71
8.1 Catenary 71
8.2 Initial and Final Sag 72
8.3 Sag–Tension Relationship 72
8.4 Determining Change in Sag (and Tension) 73
8.5 Ruling Span 76
8.6 Point Load 77
9 General Order 95 (California) 81
9.1 General Order 95 (GO 95) 81
9.2 Loading Requirements 81
9.3 Strength Requirements 83
9.4 Clearances 84
10 Examples 85
10.1 Purpose 85
10.2 Tangent Line 85
10.3 Line Angle 88
10.4 Line Angle – Buckling Consideration 90
10.5 Additional Attachment 94
10.6 Summary 96
Appendix A Properties of Messenger Strands 99
Appendix B Wireless Attachments 101
Appendix C Extreme Wind and Extreme Ice Loadings 103
Appendix D Solution of Cubic Equation 107
Appendix E Point Load 109
E.1 Parabolic Model 109
E.2 Intersecting Straight Lines Model 111
Glossary 115
References 121
Index 123
