The effects of routing, structure type, insulation, shielding, and grounding on transmission lines are discussed. The way these transmission-line choices will improve or degrade lightning performance is also provided. An additional section discusses several special methods that may be used to improve lightning performance. Finally, a listing and description of the FLASH program is presented.

For this guide, a transmission line is any overhead line with a phase-to-phase voltage exceeding 69 kV and an average conductor height of more than 10 m. The transmission line is usually shielded by one or more overhead 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 redesigning a transmission line, the designer should consider certain limiting factors such as the voltage level, the beginning...

This guide contains simple mathematical equations, tables, and graphs that provide the information needed to design an overhead power transmission line with minimum lightning interruptions. Versions 1.6 and 1.7 of the FLASH program are provided on the diskette included with this guide. Annex B includes a description of the program. The FLASH program uses the models in the design guide along with a description of transmission line features to estimate the lightning outage rate that may be expected. These simplified models may also be adapted to assess the benefits of novel methods for improving lightning performance.