Exelon completes rehab of 572-MW Conowingo

Exelon Corp. reports it has successfully completed a $39 million rehabilitation program at the 572-MW Conowingo project on the Susquehanna River in northern Maryland.

The last four of the original 1928 units were rehabilitated over several years. Work included installation of new turbine runners, mechanical overhauls, rewinding of generators, and wicket gate seals. Two of the units received low-flow aerating runners, improving operational flexibility in low-flow conditions. The other two units were upgraded to 48 MW from 36 MW. Improvements bumped total capacity to 572 MW from 548 MW.

Voith Siemens Hydro Power Generation manufactured and supplied the turbines.

Unit 2 was the final unit rehabilitated; Units 5, 6, and 7 were the other units. The work on Unit 2, completed in October, included installation of a low-flow runner, a new generator stator, refurbished rotor, new wicket gates, and a babbitted turbine guide bearing, which replaced old-style wooden turbine guide bearings.

The new runner is an aerated runner. It allows air to be pulled into the water flow through the runner blades, increasing oxygen content in water discharged from the unit and benefiting fish and other species below the dam.

Licensees Susquehanna Power Co. and PECO Energy Power Co. have filed an application with the Federal Energy Regulatory Commission to transfer the license to operate the project to PECO’s parent company Exelon Generation Co. LLC. That application is pending. (HNN 11/25/08)

FERC previously certified efficiency improvements made to the project for renewable energy production tax credits. (HNN 3/20/07) Those improvements stemmed from replacing the Unit 5 runner and wicket gates, implementing a hydro monitoring and optimization system, and adding capacity by replacing the runners and stators for Units 6 and 7.

Conowingo has generated electricity since 1928. The original plant featured seven turbines totaling 252 MW. In 1964, an additional four units were constructed, adding 260 MW of capacity and bringing the plant’s total capacity to 512 MW. In 2001, an overhaul of Unit 3 was completed and included turbine replacement and generator upgrades resulting in an additional 12 MW. A similar overhaul of Unit 1 was completed in May 2002 and on Unit 4 in January 2004, increasing total capacity to 548 MW.

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