IEEE 1243-1997 pdf download IEEE Guide for Improving the Lightning Performance of Transmission Lines
1. Overview
1.1 Scope
For this guide, a transmission line is any overhead line with a phase-to-phase voltage exceeding 69 kV andan average conductor height of more than 10 m. The transmission line is usually shielded by one or moreoverhead ground wires (OHGWs), at least for a short distance from a substation. While reference is primarily made to ac transmission characteristics, the guide is also relevant for high-voltage direct-current(HVDC) overhead lines.
The guide is written for the transmission-line designer, When given the problem of designing or redesigninga transmission line, the designer should consider certain limiting factors such as the voltage level, the beginning and ending points for the transmission line, and the desired ampacity of the line. Sometimes the exactroute, and the type of conductor and structure have already been determined. Usually the designer maychoose structural details, the geometry of the structure, the structure height, the exact placement of theOHGWs, the amount and type of insulation, the type of grounding, and other design features of a line. Thisguide is written to show the designer which choices will improve or degrade lightning performance. Sectionsof the guide discuss the effect of routing, structure type, insulation, shielding, and grounding. An additionalsection discusses several special methods, which may be used to improve lightning performance. Finally, inAnnex B, a listing and description of the FLASH program is presented.
The line designer should be aware that lightning performance is not of primary importance in the economicsof line designing. Other factors, such as line length, right-of-way costs, construction costs, material costsand losses affect the economics of a line design much more than lightning performance. The designer shouldalways balance the costs of higher insulation levels, mproved grounding, better shielding, or line relocationagainst the benefits of improved reliability
1.2 Purpose
This guide contains simple mathematical equations, tables, and graphs that provide the information needed todesign an overhead power transmission line with minimum lightning interruptions. Versions 1.6 and 1.7 of theFLASH program are provided on the diskette included with this guide. Annex B includes a description of theprogram. The FLASH program uses the models in the design guide along with a description of transmissionine features to estimate the lightning outage rate that may be expected. These simplified models may also beadapted to assess the benefits of novel methods for improving lightning performance
1.3 Disclaimer
The FLASH program is included in this guide as a convenience to the user. Other numerical methods may bemore appropriate in certain situations. The IEEE Working Group on Estimating the Lightning Performanceof Overhead Transmission Lines of the Lightning and Insulator Subcommittee has made every effort toensure that the program yields representative calculations under anticipated conditions. However, there maywell be certain calculations for which the method is not appropriate. It is the responsibility of the user tocheck calculations against field experience or other existing calculation methods.
2. References
This guide shall be used in conjunction with the following standards. When the following standards aresuperseded by an approved revision, the revision shall apply.
ANSI C2-1997,National Electrical Safety Code(NESC).
ANSI C29.1-1988 (Reaff 1996), American National Standard for Electric Power Insulators–Test Methods.”
ANSI C29.2-1992,American National Standard for Insulators-Wet Process Porcelain and ToughenedGlass-Suspension Type.
ANSI C29.8-1985 (Reaff 1995),American National Standard for Wet-Process Porcelain Insulators (Apparatus, Cap,and Pin Type).
3 Definitions and Acronyms
3.1 Definitions
3.1.1 active air terminal: An air terminal which has been modified to lower its corona inception gradient.
3.1.2 air terminal (lightning protection): The combination of an elevation rod and brace, or footing placedon upper portions of structures, together with tip or point, if used.
3.1.3 back flashover (lightning): A fashover of insulation resulting from a lightning stroke to part of a network or electric installation which is normally at ground potential. See also: direct-stroke protection.
3.1.4 back-flashover rate: The annual outage rate on a circuit or tower-line length basis caused by backflashover on a transmission line.
IEEE 1243-1997 pdf download
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