South Texas Electric Cooperative (STEC) recently energized its first transmission line with fiber-optic, overhead ground wire in a jointly owned, 100-mi installation of 345-kV, single-circuit transmission line on double-circuit-capable monopole structures. STEC employed fiber-optic control technology to compatibly connect to the Electric Transmission Texas, LLC (ETT) grid. ETT—a joint venture between subsidiaries of American Electric Power and MidAmerican Energy Holdings Company — owns 63 mi, and STEC owns 42 mi of the transmission line originating at the San Miguel Power Plant in Atascosa County, Texas, and terminating at the ETT’s Lobo Switching Station in Webb County, Texas.
STEC hired Burns & McDonnell to perform engineering, procurement management and construction management for its portion of the transmission line and the San Miguel 345-kV substation. Coordinating design between the two utilities, Burns & McDonnell designed this installation for two circuits of bundled, 1590-KCM, Lapwing conductor with one circuit not installed for future expansion. The structures and line hardware were designed to facilitate live-line maintenance. Burns & McDonnell coordinated between utilities, placed engineers on site during construction to provide quick responses to any potential issues and facilitated an energization that was ahead of schedule.