The U.S. has agreed to reduce its CO2 emissions, utilities are adding new wind and solar farms and high-voltage power lines that carry renewables are sprouting up all over the country.
When combined with hydropower, renewables now make up a fifth of America’s electricity generation capacity, more than double what it was in 2008.
This trend is not going away, but getting all that clean electricity to homes and factories is a challenging task. There are new power lines sprouting all over the country. But the electricity they carry can sometimes clash with existing infrastructure. “There are some unintended consequences,” says Robert D’Acquila, Senior Technical Director with GE’s Energy Consulting Group.
When the utility that operates the local grid, NV Energy, decided to revamp their existing grid to accommodate more renewables, Newmont invited D’Acquila’s team to check out the impact the changes to the grid would have on its steam turbine. “We ran it through our software and realized that the power plant faced a big challenge,” D’Acquila says. “The technology the new grid used to carry electricity over long distances would create power disturbances that could damage Newmont’s turbine.”
Here’s how. As the name implies, alternating current (AC) oscillates as it travels through the wire. When the frequency of the current gets out of synch with the tiny vibrations of the steam turbine, they can add up and cause so-called sub-synchronous resonance that could break the shaft of the machine. “When you drive a car on a road with grooved surface, your dashboard or your windows sometime start to vibrate,” D’Acquila says. “The rattling is the sound of resonance and the power plant would experience a similar thing.”
D’Acquila and his team were able to spot the danger because they were using big data modeling software from GE with access to grid information pooled from all over the U.S. They used the results to design a power filter that keeps out the dangerous frequencies. They also added a special “last resort” mechanical brake that can “trip” the power plant and disconnect it from the grid.
The team installed the solution in 2014 and the power plant has been humming along ever since. But more work is coming.
For example, the Electricity Reliability Council of Texas, which operates and manages the electric grid over three quarters of the state, is adding hundreds of miles of new power lines to bring renewable electricity to customers. “The new grid integrates renewables, gas, coal, nuclear and other sources of the electricity,” D’Acquila says. “The mix is changing and we have to make sure that our infrastructure can accommodate that.”