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Power Outages Hasten Deere Plant Conversion To Underground
Baker Electric, Des Moines, IA, was the primary contractor for the project to replace three aerial feeders. Also included in the project was replacing underground feeders containing duct banks of four, five inch conduits approximately 2,500 feet long and placement of three, 8 by 10 by 8 foot precast manholes at feeder intersection points.
Contributing to the decision to replace the old feeders were failures of two of the three aerial feeders within a two week period, causing serious disruptions of plant operations, said Floersch.
"Baker Electric restored power to the plant in each of the two failures and was instrumental in the decision to replace the feeders which was considered urgent," said Floersch. "Corporate specified the cable, the cable supplier, the terminations and required training for the terminations. Baker Electric submitted the design proposals.
“John Deere Des Moines Works, Facility Engineering, reviewed and approved the proposals, and Baker Electric completed the installation with no further interruptions of production in the plant."
The three new feeders serve the plant's 15 KV distribution system.
"Baker Electric furnished components and installed the complete system," said Roger Innis, Baker project manager/estimator. "Feeders were 15 KV, 500 mcm, copper cables. These fed from overhead distribution at utility company drops to pad mounted 15 KV switch gear at individual buildings. The pad mounted switch gear was existing and 15 KV system fed into plant buildings from there."
Digging and drilling
Innis said most of the duct bank was installed by open cut, using a backhoe for excavation. The trench was 24 inches wide and average depth ranged from 36 to 48 inches. Open-cut construction was used because it was most cost effective. The conduit's route was in open areas, and width and depth requirements were a little to big for trenching, Innis said. One of the feeders was rerouted around a building, rather than through it, which fit with the company's plans to extend the structure.
Two segments were directionally drilled. "One shot," said Innis, "took four 5 inch ducts approximately 100 feet under existing railroad tracks. The other was for one 5 inch duct going approximately 300 feet from the road to a substation near a building. Duct used for these bores was Carlon Boreguard."
The decision to place power cable underground depends on cost, whether the system is new, to make repairs or like the Deere project to replace old cable, said Innis.