supply and communication wires and cables, joint-use issues and related safety rules, including national standards and other related documents. The single most relevant document is the National Electrical Safety Code (NESC^®), which is adopted or reflected in various regulations or industry practices throughout most of the United States and its territories. Other relevant documents include national standard ANSI O5.1 Wood Poles: Specifications and Dimensions and as well as various ASCE manuals, and documents produced by the Rural Utilities Service (RUS). The State of California is unique in that it has produced its own rules prescribed for overhead lines under the jurisdiction of its Public Utilities Commission, General Order No. 95 Rules for Overhead Electric Line Construction.

It was the original intention that this manual be published to include any new information contained in the upcoming (2022) edition of the NESC. However, the possible delayed availability of this edition, resulting from the COVID-19 pandemic, suggested that it would be more beneficial to base the manual on the current (2017) edition of the NESC, presented in a manner consistent with the publically available Pre-Print for the 2022 edition, rather than delay the publication of this manual. It is also recognized that, in most cases, based on the “grandfather” clause of the NESC, any new rules would only be applicable to newly constructed pole lines.

      The information in this document is believed to be accurate at the time of its preparation, but is provided without any warranty, expressed or implied.

      Lawrence M. Slavin, PhD

      New York University, 1969

Acknowledgments

      The author expresses his sincere appreciation to those that helped facilitate this publication, ranging from the courteous and efficient staff at Wiley-IEEE Press, and Ernesto Vega Janica at IEEE, to those that provided a technical review of this manual. In this regard, I particularly thank Trevor Bowmer and Dave Marne for their detailed formal review of the entire manual, which I recognize required a significant effort. I am also grateful to Martin Rollins, Andy Stewart, and Sam Stonerock for their review of specific portions of the manual. I consider myself fortunate to have colleagues that were willing to devote the extra time and energy, in addition to their many other obligations, to help me complete this project. However, any possible errors in the published document are my own responsibility, in spite of the best efforts of the reviewers.

1 Introduction

      1.1 Scope

      This manual presents a brief description of typical practices for the design, installation, and usage of overhead utility distribution lines, providing an understanding of the basic principles, and facilitating the subsequent pursuit of the technology and issues in greater detail, as desired or appropriate. It is not, however, the intention of this document to provide or duplicate existing detailed design, construction, or installation specifications and information as presently employed by the various electric supply and communications utilities for their overhead facilities. Such information is available within the individual utilities or their representative organizations.

      Although some of the information in this manual is applicable to a variety of overhead applications, including high-voltage transmission lines, the focus of the information is on the local distribution systems, closer to the customer or subscriber end of the grid. This portion of the network is typically characterized by efficient joint-use applications in which electric supply and communications facilities are in reasonably close proximity, supported on the same physical structures, but with strict rules and guidelines to help ensure reliable operation and the safety of both the public and the utility workers. These systems are characterized by significant variability between the facilities supported on each pole, and frequent changes based on customer need, and are generally not subject to the same level of physical design detail as the electrical transmission lines. Indeed, it would be neither practical nor cost-effective to perform a detailed, sophisticated structural analysis on every pole in a distribution line. In contrast, long-distance high-voltage power transmission facilities, along the same transmission line, are relative invariable and unchanging, with relatively uniform spans, and require the efforts of experienced structural engineers, often supported by the use of sophisticated software tools, to cost-effectively design reliable, safe overhead facilities.

This manual is divided into 10 sections or chapters. The background, including a description of the two general categories of construction methods relevant to outdoor utility lines, is provided in Chapter 1, including the overall characteristics and relative advantages and disadvantages represented by each category. Chapter 2 contains a description of pole structures and their physical characteristics, while Chapter 3 provides an overview of their installation, operation, and maintenance procedures. A description of the various types of suspended wires, conductors, and cables is contained in Chapter 4, and Chapter 5 discusses the methods of their installation. Chapters 6 (Strength and Loading) and 7 (Clearances) are primarily based on the rules of the National Electrical Safety Code (NESC^®), which govern the physical design and construction of the overhead lines, to help ensure safe facilities for the public and utility workers. Chapter 8 explains the principles regarding wire sags (and related tensions) and provides methods for determining these values under various weather and operating conditions. Chapter 9 contains a brief description of General Order 95, which governs overhead utility lines in California, and how it compares to the NESC. Example calculations are included in Chapter 10 for estimating the physical status of pole systems subject to storm loads. Additional details and explanatory information supporting the various chapters is contained in Appendices A–E. A glossary of terms and a list of references are also provided.

1.2 Background

      There are two basic modes of construction for outdoor utility lines for electric power supply and communication systems:

      1 Belowground (or underground) plant consisting of an array of parallel conduit paths, spanning the distance between manholes, typically located parallel to a main thoroughfare or highway; or, for more local distribution applications, direct burial of the cables within the soil, possibly placed along a road or street, with buried service drops to the residences. Routine access to such distribution facilities is typically provided by flush-mounted handholes or above ground terminals and pedestals.

      2 Aerial/overhead plant in which the cables are individually suspended between utility structures, including tall structures or towers for high-voltage transmission lines, spaced hundreds, or possibly thousands, of feet apart; or relatively short structures for distribution applications, typically individual poles, spaced up to a few hundred feet apart.

For both these modes of construction, the requirements and guidelines for the installation and operation of power supply and communications lines, including the shared usage of facilities (poles, underground conduit systems, trenches), are provided in utility industry standards and documents, the most significant of which is the NESC. Both construction methods are commonly used in the industry, with an increasing amount of belowground distribution facilities being placed relative to aerial plant in more recent decades, primarily driven by regulations. For example, the large majority of new construction in local (residential) subdivisions deploys belowground facilities, in response to the demands of communities and various levels of government for a greater