Overhead Distribution Lines (eBook)

Lawrence M. Slavin, PhD, is Principal of Outside Plant Consulting Services, Inc. (OPCS). He represents the nation's telephone industry, via the Alliance for Telecommunications Industry Solutions (ATIS), on several NESC technical subcommittees, as well as the Executive Subcommittee, Main Committee and Interpretations Subcommittee. He also serves on Accredited Standards Committee ASC-O5 for wood products, including ANSI O5.1, Wood Poles, Specifications and Dimensions, and is a member of the ASCE 7 Atmospheric Ice Loads Subcommittee.

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