1、 IEEE Guide for the Preparation of a Transmission Line Design Criteria Document Sponsored by the Transmission and Distribution Committee IEEE 3 Park Avenue New York, NY 10016-5997 USA 27 May 2011 IEEE Power including the sources of information used in design and the design approach used. Keywords: d
2、esign criteria, IEEE 1724, load factors, structure loads The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright 2011 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 27 May 2011. Printed in the Un
3、ited States of America. IEEE is a registered trademark in the U.S. Patent +1 978 750 8400. Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. Copyright 2011 IEEE. All rights reserved. ivIntroduction T
4、his introduction is not part of IEEE Std 1724-2011, IEEE Guide for the Preparation of a Transmission Line Design Criteria Document. The Line Design Methods Working Group of the Towers, Poles, and Conductors Subcommittee of the Transmission and Distribution Committee determined that guidance in the p
5、reparation and documentation of the data, methods of design, design approach, and sources of information used in the design of a transmission line was desirable to assist transmission line designers in gathering and documenting the material used in design so that a coherent design of the line struct
6、ures, conductors, conductor support systems, and foundations would result. This guide does not cover every possible consideration in line design, but includes topics covering most of the considerations that a line designer will encounter. It does not offer design guidance, but rather offers guidance
7、 in the documentation of the basis of design. The purpose of a design criteria is to gather and document the information required for the design of a transmission line in one convenient document. The information contained in a design criteria should include general information about the line, ambien
8、t conditions that the line will operate within, clearances, and electrical and structural requirements. This guide incorporates a representative list of items that could be included in design criteria. Not all of the topics listed in this guide are applicable to all lines. For example, ice-loading c
9、riteria are not applicable in certain warm climates. The outline of this guide is the suggested outline for any project-specific design criteria. In designing a transmission line it is useful to consider the forces acting on a line and the response of the line to those forces separately. The environ
10、mental forces acting on a line are wind, ice, lightning, and pollution. These forces are resisted structurally by the physical strengths of the line structural components. They are resisted electrically by the electrical properties of the insulators, grounding system, and structure configuration. Th
11、e sections of this guide discuss the forces and reactions in regard to electrical and structural actions and reactions. This separation of forces from reactions recognizes that the forces are outside of the control of the line designer. The environment determines the ambient loads that will impact a
12、 line. Ambient loads are statistical in nature and are characterized by their severity and frequency. Knowledge of the ambient loads allows the line designer to determine how to resist the loads. If a line is required to be very reliable, it can be designed to resist severe loads that happen infrequ
13、ently. If a line has a lower reliability requirement it can be designed to resist only loads that occur commonly, with the realization that there is a greater possibility of the line experiencing a more severe load during its operational life, and experiencing failure. The line designer is responsib
14、le for determining the philosophy of design. One philosophy is that the line should not fail under the most severe anticipated conditions. This requires designing for the historically worst loading conditions, combined with appropriate safety factors or load factors. Another philosophy is that the l
15、ine should be as low cost as possible. This philosophy may lead to selection of design loads that will occur more frequently, combined with lower safety or load factors. There is no “standard” guideline for the “right” philosophy which is more dependent on the business philosophy of the utility. Thi
16、s business case philosophy has to be applied by the line designer to suit the particular requirements of a line. It is equally wasteful to over design an unimportant line, as it is to undersign an important line. The first case can be classed as an “economic failure” and the second as a “physical fa
17、ilure.” Transmission lines are designed subject to safety codes, such as the National Electrical Safety Code(NESC)aB1.b _ aNational Electrical Safety Code(NESC) is a registered trademark in the U.S. Patent the sources of the data and assumptions; the conventions, standards, guides, and design manual
18、s used; and the design method(s) used in the design of the transmission line. The guide offers a comprehensive table of contents of the important criteria that should be taken into consideration in the design of transmission lines. The guide discusses the various criteria. The guide does not recomme
19、nd criteria values, as would a design manual, but lists and discusses the importance of the criteria. The design engineer must determine the values to use based on the location, ambient conditions, and importance of the line. IEEE Std 1724-2011 IEEE Guide for the Preparation of a Transmission Line D
20、esign Criteria Document Copyright 2011 IEEE. All rights reserved. 22. General overview and summary The overview is a concise summary of the information covered in detail in the guide. It provides a concise overview of the major factors used in the line design. 2.1 Project name, voltage, date, length
21、, location, etc. This section lists data about the line such as its terminal points, voltage, location, length, construction date, number of circuits, and any other information that would assist in generally describing the line. If the design criteria is a generic criteria used for a class of lines,
22、 information on its range of applicability should be stated. Long transmission lines, or lines that have great changes in topography, may require different design criteria for different sections of the line. For example, a line constructed partially in the mountains and partially in the plains could
23、 have two different loading criteria for the different line sections. 2.2 Applicable codes and standards used in the design In this section, list the safety codes that govern the design, or were used in the design of the line. Safety codes could include the National Electrical Safety Code (NESC) (Ac
24、credited Standards Committee C2-2007) B11, California GO-95 B4, Hawaii GO-6 B7, REA Bulletin 1724E-200 B10, etc. Other commonly used design manuals should be referenced if they are used in the design, such as the: ASCE Manual 74 B3 for design loads. ASTM, ACI, and ANSI have standards that cover mate
25、rial and design of elements of transmission lines. The date and/or edition of the code or manual should be included since the requirements of the various codes may change over time. 2.2.1 Federal Aviation Administration (FAA) requirements Lines located near airports or having tall structures may req
26、uire FAA review. Note that any requirements characteristics of the line location or structures that might fall under FAA jurisdiction. Several states have regulations concerning tall structures intended to enforce and enhance FAA recommendations and determinations. 2.2.2 State, Federal, or Local reg
27、ulations Describe any State, Federal, or Local laws or regulations that apply to the design or location of the line, or that will affect the design of the line. Highway or railroad crossings or occupations may have special design or clearance requirements. 2.3 Physical details 2.3.1 Wire sizes and c
28、ompositions The physical data for the energized conductors, shield wires, and fiber optic wires is discussed in this section. The code name for the wires should be included along with diameters, weights, and rated tensile 1Information in brackets can be found in Annex A. IEEE Std 1724-2011 IEEE Guid
29、e for the Preparation of a Transmission Line Design Criteria Document Copyright 2011 IEEE. All rights reserved. 3strength. If there are several different wire sizes, a tabular form is convenient for ease of reference. If there are bundled conductors data on the bundle including the number of subcond
30、uctors, configuration of the bundle, and spacing should be included. If there are special project considerations that led to wire selection, describe those considerations. If optical fiber ground wire (OPGW) will be used, the number of fibers and the type of fibers should be specified. Details of th
31、e physical construction, such as number and type of metal strands, diameter, weight, and strength, should be specified. Strength, physical characteristics, and communication characteristics of all dielectric self-supporting (ADSS) fiber optic wires should be included if they are to be used. 2.3.2 In
32、sulator types and configuration Insulators are needed for electrically insulating the energized conductor and for physical support of the conductor. Electrically, the purpose of the insulators is to provide an acceptable deterrence against flashover to grounded objects, such as the structure, and th
33、e other phases and shield wire (OHGW or OPGW). Physically, insulators also withstand the physical forces of wind and ice, and the wire weight and tension. In this section, indicate the type of insulators to be used (porcelain, composite, glass) and the configuration to be used (Vee or I string, Post
34、, etc.). Any special requirements, such as extra leakage distance or high strength requirements should be noted. The electrical and mechanical properties of the insulators should be tabulated. The electrical properties, such as power frequency wet and dry flashover, impulse withstand, and critical f
35、lashover are important to the electrical performance of the line and should be stated. The mechanical strength of the insulators is important for the physical integrity and reliability of the line and should be listed. Insulator material and physical configuration affect the mechanical and electrica
36、l properties. Selection of insulators should be based on strength requirements, resistance to physical damage from gun shot, pollution level, power frequency, and impulse voltage requirements. Requirements for live line work may influence the selection of insulation type, configuration, and insulati
37、on level. Properties of the insulators vary by manufacturer and type. The reasons for selection of the type and configuration should be documented. Electrical properties may be affected by altitude. Derating factors should be explained. The contamination level that is expected should be described. T
38、he performance of lines in the area or similar exposures may be referenced. 2.3.3 Structure material, description, and configuration Information on structures should be included in this section. The material selected should be specified; steel poles, lattice towers, wood poles, composite poles, or c
39、oncrete poles. The finish; painted, galvanized, self-weathering, etc. should also be listed. The configuration, such as H-Frame, single pole, square base or window lattice tower should be included. 2.3.4 Foundation material and types In this section, indicate the type of foundations to be used. For
40、example, direct embedment with native or select backfill, drilled pier caisson foundations, pad and pier foundations, and earth grillages may be described. If different foundations are used on different sections of the line, or for different soil conditions, they should be specified. IEEE Std 1724-2
41、011 IEEE Guide for the Preparation of a Transmission Line Design Criteria Document Copyright 2011 IEEE. All rights reserved. 42.3.5 Conductor accessories In this section list the types of conductor accessories that will be used. Compression type or bolted types should be specified. Spacers for bundl
42、ed conductor lines should be described, with any specific descriptive wording to cover special requirements. Minimum performance requirements should be specified. 2.3.6 Vibration protection methods In this section indicate how the line will be protected from aeolian vibration. Low conductor tensions
43、, cushioned supports, vibration dampers, and spacer dampers, or combinations of the forgoing are common. Information regarding vibration experience in the area or with lines of similar design should be included.3. Climate In this section, on climate the design criteria should accurately reflect the
44、climatological conditions in the area of the project. Safety codes such as the NESC have divided the United States into loading districts with specified loads intended to promote a high degree of safety. The Codes recognize that there are occurrences of higher loading in specific areas within the lo
45、ading districts. The Codes require that these loads be used in the design of lines. Experience in an area may indicate a greater ice or wind load than code-required loads. The National Climatological Data Center maintains records of climatological data that may be used to characterize the weather co
46、nditions in the area of the line. ASCE Manual 7 B2 and ASCE Manual 74 B3 provide excellent resources for extremes of weather that may be considered in the design of the line. The aim of selecting climatological factors is to determine a realistic set of weather conditions for use in design. Climatol
47、ogy also affects the pollution and lightning performance of a line. Areas subject to frequent rainfall may have good contamination performance due to the natural cleaning effect of the rainfall on the insulators. Conversely, dry areas may be more susceptible to airborne contamination because there i
48、s no natural insulator washing. Discussion of climate should include the isokeraunic level for the area, and the desired lightning performance for the line number of flashovers per 100 km/year. 3.1 Wind experience in the project area In this section, describe and document the wind loading that will
49、be used in design. Several wind speeds may be specified for different design purposes. Data can be obtained from weather records or the utilitys own experience. Care should be taken in using “folklore” about past high wind experiences. Wind speeds are typically overstated in newspapers and in oral tradition. Wind is characterized in terms of “fastest mile” or “3-second gust.” These are commonly used measures. Prior to the 2002 NESC, wind loads specified in the code were “fastest mile” wind speeds. This measure was based on how fast a “
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