Burns & McDonnell was the design-build firm for Aquila’s 161-kV underground transmission line. This underground cable is the first XLPE solid dielectric cable installed in Aquila’s transmission system.
- Construction management
Burns & McDonnell furnished equipment and materials, managed the trenching and concrete encased conduit system and installed the cable.
Installation of approximately one mile of underground transmission line to replace a previously existing overhead line. The underground line was needed because a new golf course and subdivision were built on previously undeveloped property.
The overhead line carried 69-kV. Eventual plans called for upgrading the line to 161-kV. Therefore, the new underground line was installed as a 161-kV line in anticipation of future needs.
To allow for easy access, the underground line was re-routed to run adjacent to an existing road. Golf course aesthetics played a role in construction as well. The developer requested that a line of trees on the edge of the greens be avoided. In order to do this, Burns & McDonnell designed a 3-ft. diameter x 340-ft long boring through solid limestone to accommodate the new duct bank. The routing was further complicated by the discovery of some archeologically sensitive areas containing pre-Civil war graves.
The 161-kV underground transmission cable is a XLPE cable with 1500 kcmil copper conductor and a corrugated copper sheath. The project included 5800’ of underground reinforced concrete ductbank with four (4) 6” pvc ducts and one (1) 2” pvc duct for future fiber optic cable, a substation termination structure and foundation, and a deadend/termination structure and foundation which ties back into the overhead line. One splice was required in the middle of the line due to pulling strength requirements and cable reel limitations. The splice was housed by a 8’ wide x 20’ long x 8’ deep precast manhole.
Managing construction power outages were an added concern. To avoid replacing additional structures on the overhead portion of the project, the riser structure/deadend structure was placed directly beneath the existing overhead line. During construction, this would require several line outages. During the peak of the summer, power outages are difficult to initiate without causing difficulties for people who rely on this power source. We limited our outages by outlining all of the tasks required for outages and completing most of the construction tasks requiring outages at the end of the project, prior to energization of the new underground line.
- First XLPE solid dielectric cable
- 1500 kcmil copper conductor and corrugated copper sheath