A 19-day testing process is underway for the Tennessee Valley Authority’s (TVA) Paradise combined-cycle plant, including ‘first fire’ of the turbine and grid synchronisation. TVA said the 1,025-MW gas power plant is now 84% complete – all tests should be successful by early 2017 for the CCGT to enter into commercial operation before the coming summer.
Day 2 of the testing process saw TVA Major Projects refire the turbine to bring it to operating speed, and then match frequency and voltage to the grid for initial synchronisation. That day, the first electricity from the new units was made available to the grid operator.
On Wednesday, the third day of testing, the unit was again synchronized with output being incrementally ramped up to full load. From now on, engineers keep fluctuating the load over the following days to simulate a variety of dispatch scenarios.
“We will go to low loads and make sure our control systems and voltage regulators are working,” Roger Waldrep, general manager of TVA Major Projects explained. “Then we’ll move the load around, going up to 200-225 MW and coming back down, focusing on testing, control and tuning in the subsequent days.”
Another three weeks is thereafter spent on refiring the gas turbines to make steam that is circulated through the boilers and steam piping systems. This period is referred to as ‘steam blows’ and Waldrep said “that way we’ll ensure that the steam system is sound and that all the piping systems are free of any debris.”
By early next year, full load testing with all three gas turbines and the steam turbine will start at the Paradise CCGT. Kiewit and GE will also have to complete all contractual performance and reliability acceptance tests – the aim is to have the flexible gas power plant up and running before the 2017 peak summer demand sets in.
Referring to lessons learned from the construction of the John Sevier CCGT, Waldrep said “we had enough delay between that plant and here to really do a good job of incorporating those things into the Paradise specifications.”
CCGT replaces Kentucky’s largest coal generator
Located two hours north of Nashville, KY, the GW Paradise CCGT project will replace two of TVA oldest coal-fired units at the Paradise Fossil Plant with natural gas-fired units. The new 3x1 combined-cycle plant will be driven by three GE 7FA.05 turbines and includes a Vogt HRSGs – it has been realised by Kiewit under a contract to engineer, procure and construct the project.
TVA decided to retire two of the three coal-fired units at its Paradise Fossil Plant, bowing to pressure from more stringent pollutant standards, pushed through by the Obama administration via the Environmental Protection Agency. EPA's initial, much contested carbon rule outlines a limit for coal-fired plants with attached carbon capture and storage (CCS) of 1,100 lb CO2/MWh. In contrast, natural gas combined cycle plants will have an emission limit of 1,000 lb CO2/MWh for larger units and 1,100 lb CO2/MWh for smaller units.
Court proceedings over the legality of the Clean Carbon Plan are ongoing.
TVA has set up an Integrated Resource Plan, examining its options under a variety of economic, regulatory and market scenarios. The utility currently operates 106 natural gas- and fuel oil-fired generators at 14 sites - seven in Tennessee, five in Mississippi, one in Alabama and one in Kentucky. Together, they have a generation capacity of about 7,000 MW. In late August, TVA adopted a $10.7 billion spending plan for fiscal 2016 that will raise electricity rates by 1.5%. The rate hike, the same as in each of the past two years, will raise an extra $200 million from customers.