Static VAR

Steady On: the Davidson Static VAR Compensator

When TVA shuts down the Johnsonville Coal Plant in Middle Tennessee, this is the possibility that power quality could become compromised. But forward-thinking TVA engineers have the solution in the pocket: the Davidson Static VAR Compensator, which went live at the end of April.

When you flip a switch in the Tennessee Valley, you can expect a light to not only come on, but to shine with clear, steady light—no flickers or cycles of dimming and brightening. That’s because TVA takes care to not only provide reliable power, but power of high quality.

That means balancing generation with usage throughout the system. TVA has always benefitted from having geographic diversity among its major generation assets—be they hydroelectric, nuclear, coal or gas—allowing for naturally stable, high-quality electricity to be available throughout the Valley. Generation assets were located near population centers, meaning that electricity never needed to travel far to reach customers.

However, with the closing of its Johnsonville Coal Plant in 2017, the high-load Nashville area has the potential to take a quality hit. That’s because big generators—such as those found in coal plants—are operated in a way that provides dynamic voltage support to the grid. When they are removed from the system, and electricity must travel further to reach the end user, there is the potential for voltage destabilization and quality erosion.

Forward-thinking TVA engineers have the solution in the well before pocket before Johnsonville’s last burn. The Davidson Static VAR Compensator is a nifty piece of machinery that allows engineers adjust for voltage fluctuations due to system demands nearly instantaneously. True to its name, it “compensates” for the voltage support no longer available from the big coal plant. VAR stands for "voltage-ampere reactive," in reference to the reactive power that must be stabilized—along with real and apparent power—in the delivery of AC electricity. What's that all mean? In short, that TVA customers, especially those in the Nashville area, can continue to depend on smooth, steady power.

The best news of all? The static VAR compensator is already live, having gone online in late April.

Above, Tim Smith, general manager of Transmission Planning, Sharon Nesmith, senior manger for Substation Engineering and Antonio Hamler, electrician, explain why the Davidson Static VAR Compensator project is so important for Middle Tennessee.