Oncor 345 kV Tower Relocation

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Client: Oncor Electric Delivery
Location: Texas, USA 

Oncor Electric Delivery needed to relocate a critical line that also housed telecommunication facilities. With careful planning, up-front coordination and some weather cooperation, the line was relocated in record time without any loss of electrical or telecommunication services.

Oncor required the relocation of five double circuit 345 kV towers on its Royse Switching Station – NW Carrollton Switching Station line near Plano, Texas. Four towers in one stretch of the line had to be moved 10 feet laterally in the right-of-way to accommodate the addition of a new double circuit 138 kV line.  The fifth tower had to be relocated 80 feet in-line to accommodate the addition of the Austin Ranch Substation. 

This double circuit 345 kV line is a critical segment of a heavily loaded grid in the Dallas MetroPlex area.  Oncor joined forces with POWER Engineers for this 345 kV tower relocation project. POWER Engineers determined the best way to limit the 345 kV outage was to relocate the towers up or down the line 55 feet and then moving them laterally 10 feet. This approach would allow the installation of new stub angle, drilled pier foundations outside the footprint of the existing towers. With low headroom drilling equipment, the foundations could be installed without taking either an electrical or telecommunications outage.

Early field reviews and meetings made it clear that this relocation was not going to be a simple task.  Besides two city street crossings and an apartment complex with parking under the EHV line, other challenges included a third-party-owned fiber optic cable (OPGW) in the shield wire position on one of the circuits, a Burlington Northern-Santa Fe railroad crossing between towers, and a third-party-owned telecommunications antenna and an OPGW splice. 

POWER Engineers was quick to meet with key parties involved and solutions were developed for each challenge presented. For example, POWER Engineers’ design considered the location of the existing telecommunication cabinets and equipment.  By moving the tower 55 feet west and 10 feet south, the tower could be lifted over the equipment, thus the telecommunication cabinets and their associated telephone and power infrastructure would not have to be relocated. 

Relocation time proved to be imperative, as the electrical outage window was limited to six days. Red Simpson Incorporated (RSI) out of Louisiana, was awarded the construction contract and when the time came, production was limited to one tower per day because the crawler crane had to be dismantled and hauled from one side of the BSNF railroad to the other. 

All planning and coordination efforts paid off in this critical relocation.  All five towers were relocated in a four-day period, beating the electrical outage window by two days.

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