Fiber optics and high voltage (>100 kV) transmission lines

Fiber Planners also designs fiber systems for high voltage transmission lines. Either OPGW (optical groundwire) or ADSS (all-dielectric self-supporting) cable can be used for these systems according to customer preference.

We use advanced software tools to aid in our designs
Transmission line conductor design has traditionally been done using manual drafting aids and catenary templates, perhaps supplemented by computerized sag and tension calculations of worst case weather conditions. Even though newer, advanced software design tools such as PLS-CADD and SAGSEC have been available for over a decade, many transmission designers still use the old methods -- after all, they still work. And in most cases, all the conductors on a tower were going to change sag by the same amount as weather and loading changed.

Unfortunately, fiber cables don't necessarily change sag with changes in temperature and loading at the same rate conductors do. This is true to a certain degree with some OPGW designs and always true of ADSS. As a result, the fiber cable may clash with the conductors at some intermediate weather load. For example, for one design we worked, 45 knot winds brought the ADSS much closer to the conductors (which were heavier and had not blown out much at this wind speed) than full hurricane winds (where both ADSS and conductors were both fully blown out horizontally). Here are PLS-CADD screenshots of one example.

In an ice storm, the conductors may be fully loaded with ice or they may be partially or fully ice-free due to of resistive warming. Both ADSS and OPGW will ice fully since they carry no current and are at ambient temperature For this reason, cable to conductor clash checks should be run under each icing scenario.

Coming the week of July 1: information on electric field analysis including the new jacket current tool developed by Bonneville Power Administration

• Typical Fiber Planners scope of work: ADSS distribution projects

 

• Fiber optics on high voltage (>100 kV) transmission lines