138kV XLPE Cable Project

Project for Allegheny Power Service
PDC worked with Allegheny Power Service to design, prepare specifications and assist construction inspection on a 138kV cable circuit for a small commercial airport in Claridge, Pennsylvania. The cable project, "Harrison City Substation 138kV Loop", was under construction in July 1999 and will be commissioned later this summer.
The figure at left shows the cable trench after one of the phases has been installed.  The soil and trench conditions were such that shoring was not required for this particular section. The entire section was open trenched prior to laying cable.
A loop of spare cable was placed at the base of the riser structure to allow for a repair if a termination needs to be reconstructed. An advantage to this approach is faster restoration times because a spare cable section does not have to be located and spliced between the underground section and riser.
Fluidized Thermal Backfill was placed around the cable to reduce the effective soil thermal resistivity and optimize the circuit's rating. The photo to the left shows the trench shortly after the FTB was poured. This material provides optimal compaction around the cables. Geotherm, Inc. developed the FTB "recipe" for the project.
If you would like to know more, please contact John Cooper at PDC.