Case Studies

Tennessee Valley

Peaking Turbine Plant, Synchronous Condensing
Article lead image
Image courtesy of GE

500 MW of flexible generation capacity added by the Tennessee Valley Authority (TVA) using GE LM6000 Aeroderivative Gas Turbines with SSS Clutches integrated into the gearbox.

Tennessee Valley Authority (TVA) is placing 10 gas turbine and generator sets at the Johnsonville Aeroderivative Plant in middle Tennessee. Construction is underway and the units are scheduled to be operational by the end of 2024. The 10-unit project will add 500 MW of new modern generation and is a first for TVA.

Aeroderivative gas turbines allow for extreme generation flexibility and grid stability as TVA integrate more solar power generation and respond to rapid power demand changes. The turbines also allow the flexibility of using carbon-free hydrogen in the future.

With the increase in intermittent renewable generation and the closure of coal fired generation sets, these peaking power plants are required for security of supply both in terms of active power to meet demand and also grid support.

The generation sets have SSS Clutches that quickly and easily disconnect the gas turbine drive and leave the generator synchronised to the grid as a synchronous condenser providing reactive power, inertia, voltage control and short circuit current.

TVA expect about 300 starts and 1000-2000 generating hours per year per unit and even if the generating hours reduce, these machines will have an important role to support the grid. So important is this grid support that TVA expect that 2-4 units will be continuously operate in synchronous condensing mode, unless they are running for generation needs.

Quill shaft arrangement

The GE LM6000 is a 60MW gas turbine and is connected to the generator through a speed reducing gearbox. The 240T SSS Clutch is integrated into the gearbox mounted on the gas turbine side of the main gear wheel in a quill shaft configuration. In this way the addition of the clutch does not add any extra length/footprint to the machine.

The 240T SSS Clutch can engage at any generator speed and therefore changeover from synchronous condensing mode to power generation mode can occur seamlessly without disconnecting the generator from the grid. The SSS Clutch includes an internal thrust bearing so that the clutch is a fixed length and locates the generator from the gas turbine thrust bearing.