This past May, we experienced what is considered to be the largest geomagnetic disturbance (GMD) event in over two decades. Thankfully, the impact on our power system was minimal due to an early warning notification from the U.S. National Oceanic and Atmospheric Administration (NOAA) and existing NERC protocols which help the industry deal with GMD events.
The applicable NERC standards that address GMD events are:
- NERC Standard EOP-010-1 (Geomagnetic Disturbance Operations) provides mandatory requirements to mitigate the effects of geomagnetic disturbance (GMD) events by implementing Operating Plans, Processes, and Procedures.
- NERC Standard TPL-007-4 (Transmission System Planned Performance for GMD Events) provides requirements for Transmission system planned performance during geomagnetic disturbance (GMD) events.
Following this major GMD event, NERC is renewing its efforts to expand the industry’s knowledge in this area, with a focus on mitigating risks to power system reliability. With increased awareness of the characteristics of solar storm weather, stakeholders can be prepared for future GMD events, maintain regulatory compliance and protect their systems and assets.
What Happened During the May 2024 GMD Event?
During this most recent GMD event, reliability coordinators, transmission operators and other registered entities implemented pre-arranged operating procedures to mitigate the impact of GMDs on the power system. The power system remained stable as GMD conditions varied between Strong (G3) and Extreme (G5) over a three-day period. Operators observed isolated impacts to large power transformers, voltage support equipment, transmission line breakers and harmonic filters. Additionally, high levels of geomagnetically induced currents (GIC) and harmonics were reported by some operators and EPRI’s SUNBURST monitoring network.
A forecast K9 level notice was issued by NOAA’s space weather forecasting service on the afternoon of May 10 through the early morning of May 12. This notice required the implementation of the preplanned NERC EOP-010 operating procedures.
Steps taken by system operators to assure continued reliable operation of the power system included:
- Monitoring voltages and ground induced currents across the power system.
- Restoring out-of-service transmission facilities and delaying further transmission outages.
- Operating transmission lines and interfaces conservatively to reduce load levels from normal limits.
- Activating their respective alert level real time study cases to be solved to reduce transmission line loading.
- Extending unit commitment of selected generators to provide dynamic voltage support.
The operating reliability of the power system was unaffected but NERC’s data sources, which include the GMD Data System and various equipment data systems, will provide information to complement industry GMD direct observations. The results of the NERC GMD event review will inform the industry and potentially improve operating procedures, practices and technical guidelines used for planning and operating the power system.
NERC and Industry Activities
In past GMD workshops hosted by NERC and EPRI, representatives from planning and operating entities have identified the need for continued improvements to tools and capabilities for addressing GMD risk to the power system. Data and observations from the May GMD event have the potential to enhance applicable NERC standards and improve the accuracy and comprehensiveness of the GMD vulnerability assessments called for in TPL-007 and the effectiveness of operating procedures that are required by EOP-010. The review plan will focus on the following topics:
- Impact of GIC-related harmonics on the power system
- Transformer thermal impacts
- GMD benchmark review
- Ground Induced Current (GIC) model validation
- GMD operations best practices.
The effort will draw upon existing data captured through NERC’s data gatherings tools including its:
- Geomagnetic Disturbance Data System
- Transmission Availability Data System
- Generating Availability Data System
- Misoperation Information Data Analysis System
What will the Future Hold?
NERC plans to deliver a final report with recommendations in January 2025. Expectations for the report include recommended changes to the applicable NERC standards in the areas of the benchmark GMD event currently used to prepare vulnerability assessments (TPL-007) along with changes to operating procedures and prepositioning of the power system transmission line and transformer loading and voltage profile once GMD events of a significant level are forecasted (EOP-010).
Next Steps
By reviewing NERC’s full report on the data gathered during the latest GMD event when it is released, you will have a better understanding on how these seemingly random storms effect your portion of the bulk electric system and what actions will be required in the future. TRC will stay abreast of these developments and keep our clients informed. To be notified about NERC compliance news from TRC, sign up for our monthly NERC newsletter and stay ahead of the curve.
Resources
NERC GMD Event Review Plan
NERC Compliance Services
Space Weather Prediction Website
Emergency Management and Response Plan Solutions
Space Weather Power System Impacts
Power System Studies
EOP-010-1 Geomagnetic Disturbance Operations
TPL-007-4 Transmission System Planned Performance for GMD Events
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TRC closely follows the national, provincial, and state regulatory trends in all regions of North America. Our approach to power system security, engineering, planning, design, construction and commissioning testing, balances solutions that incorporate industry reliability risk trends, mandatory reliability standard requirements, regulatory guidance, compliance obligations, best practices, operational goals and budgets. With expertise in power system planning, engineering and operations. TRC supports public utilities and private energy providers in their efforts to stay ahead of the regulatory curve and to meet or exceed regulatory requirements as they evolve.
This regulatory update is provided as a service to TRC’s utility clients, helping to keep you informed of forward-looking issues that will impact your electric system reliability risks along with related topics regarding regulatory changes and compliance developments, to help you achieve your company’s business goals.
Dwayne Stradford
Dwayne Stradford serves as TRC’s NERC Compliance Director in the Power Division. He is leading and coordinating TRC’s NERC compliance support services with our various power utility clients. He is an accomplished, diverse energy professional with over 30 years of engineering experience regarding real-time transmission operations, short/long term transmission planning, NERC Reliability Compliance Standards (both NERC-CIP and NERC O&P), Transmission Reliability Assurance, utility scale renewables integration, FERC Regulatory/RTO policy, and Project Management. He spent the bulk of his career (close to two decades) working for AEP but has considerable working experience in the electric utility industry as a professional consultant. He has worked with utility clients on transmission and generation related projects in all three interconnections, so he has breadth of regional BES experience throughout the entire country. Please contact Dwayne Stradford for more information.