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Cogeneration Plant 138 kV Tie-Line

In 1997, Oxy-Chem completed construction of a 600 MW cogeneration plant that was capable of supplying all of their local plant power requirements as well as exporting approximately 450 MW to the local utility company. The cogen unit substation exported this power through two 138 kV transmission lines to the plant main substation and through one transmission line to the local utility substation. This transmission system was fully rated to carry the 600 MW cogen output, but loss of a single transmission line or breaker would force shutdown of one or more generators.


Colwell was engaged by Oxy-Chem to develop a preliminary design and cost estimate for transmission system improvements that would allow full cogeneration export with any one transmission line out of service.


Colwell developed a design and routing plan for a new 138 kV transmission line from the Cogeneration substation to a nearby AEP substation. The line design utilized single circuit 795 ACSR on 80 ft. Class H1 wood poles with 161 kV standoff type insulators. Additions and modifications were required at both substations including new 138 kV gas breakers and isolation switches, metering transformers and bus modifications. A new line protection relay and control panel was also required at the cogeneration substation.


Colwell provided preliminary engineering services for this project including feasibility analysis, preparation of design drawings, construction plan and AFE level cost estimate.

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