Analysis finds adequate Eastern Interconnection frequency response

by Ethan Howland
APPA News
November 24, 2020

The Eastern Interconnection should be able to maintain system frequency for at least the next five years, according to a group of transmission planning coordinators.

However, with the addition of non-synchronous generation (intermittent wind and solar) and planned power plant retirements, maintaining frequency in the Eastern Interconnection is a concern that warrants continued study, the Eastern Interconnection Planning Collaborative (EIPC) said in a report issued Nov. 11.

The Eastern Interconnection electric grid covers about two-thirds of North America from the Rocky Mountains to the East Coast.

The North American Electric Reliability Corporation asked the EIPC, a coalition of 19 transmission planning coordinators, to study how the changing resource mix could affect frequency response in the Eastern Interconnection.

Frequency response is a measure of the grid’s ability to stop and stabilize frequency changes after the sudden loss of generation or load. If unchecked, sharp frequency changes can lead to power outages.

Load along with large fossil-fueled and nuclear power plants provide inertia to help maintain the grid’s frequency, but some plants are being replaced with renewable resources, which until a 2018 decision by the Federal Energy Regulatory Commission generally didn’t provide frequency response. To help maintain the grid’s stability, FERC ordered that all new generating facilities be able to provide frequency response.

The loss of inertia from the large power plants could trigger “under-frequency load shed” events, or blackouts, according to the EIPC.

At NERC’s request, the EIPC finished an initial frequency response study in April 2019.

“As the generation resource mix continues to evolve over time to incorporate new and emerging technologies and address energy and environmental policies, it is essential to understand how the Eastern Interconnection will be poised to maintain system frequency under a wide range of operating conditions,” said Keith Daniel, senior vice president of transmission policy at Georgia Transmission Corp. and chairman of the EIPC Executive Committee.

The EIPC task force that wrote the report studied four hypothetical events, including including generation losses of 2,300 megawatts, 3,850 MW and 4,500 MW as well as a 10,000 MW event.

The EIPC’s Frequency Response Working Group will continue to update its analysis, according to Daniel.

The EIPC is conducting additional power system analysis that will provide information to help maintain grid reliability and to inform state and federal regulators and policy makers, Daniel said.

The EIPC’s frequency response analysis will supplement NERC’s 2021 Long-Term Reliability Assessment.

The EIPC members include public power entities Municipal Electric Authority of Georgia (MEAG Power) and Santee Cooper.