C H A P T E R
N ° 16
Space Weather, Power Grid Systems, and Mitigation Measures
Space weather can produce large clouds of electrically and magnetically charged plasma that can induce electric currents (i.e., Geomagnetically Induced Currents (GICs)) into the ground on Earth and on high-voltage transmission lines. These currents can interact with grounded grid equipment like powerlines or cables located in the ground, leading to an effect on power transformers. This is possible due to the Geomagnetically Induced Current’s (GIC) ability to create conditions that stresses the operating system, consequently causing either inefficiency in the functioning of the grid or blackouts. Reducing the impact of Geomagnetically Induced Currents (GICs) on electrical power networks is, therefore, an essential step to protect network assets and maintain reliable power transmission during and after space weather events.
*Plasma is the fourth state of matter and a gas that is so hot that some or all of its constituent atoms are split up into electrons and ions, which can move independently of each other. *
In previous articles we looked closer at the relation between space weather and the energy sector, how space weather affects the power grid system directly and indirectly, and the main damage and failure modes associated with Geomagnetically Induced Currents (GIC) loading in power grids, and we explored and discussed potential mitigation measures. In today’s article, we will look closer at different mitigation measures currently used and/or recommended against space weather impact in the form of Geomagnetically Induced Currents (GIC) on power grid systems.
Image Credit: Dynamic Ratings: Cartoon illustrating what causes Geomagnetically Induced Currents (GICs).
Mitigation Measures for Power Grid Systems
Mitigation measures against the impact from space weather on power grid systems is a continuous debate. In recent years collaborations have been done between university professors and industry in order to create resilient power grid systems against the impact of Geomagnetically Induced Currents (GIC). In the following sections we will explore some of the countries where research and work has been done towards this goal. These countries share similarities but also differences in their way of pursuing a resilient power grid system.
New Zealand
In New Zealand, Professor D.H Mac Manus from the department of Physics at University of Otago and fellow scientists worked with the energy company Transpower New Zealand Ltd. to test four mitigation strategies that could be implemented within the transmission network throughout the North and South Islands of the country. The investigation was made by running simulations of nine extreme space weather event scenarios based on some of the country’s worst recorded storms and by modeling potential mitigation responses. As a result of the direct work with the energy sector, a mitigation strategy in the form of targeted line disconnections was developed.
The mitigation strategy proved to be more effective than previous strategies created to reduce Geomagnetically Induced Current (GIC) magnitudes and durations within transformers most at risk to Geomagnetically Induced Currents (GICs) while still maintaining the continuous supply of power throughout the country. Under this mitigation plan, the average 60-minute mean Geomagnetically Induced Current (GIC) decreased for 27 out of the top 30 at-risk transformers, and the total network Geomagnetically Induced Current (GIC) was reduced by 16%. Furthermore, simulations additionally showed that the installation of 14 capacitor blocking devices at specific transformers reduced the total sum of the Geomagnetically Induced Currents (GICs) in the network by an additional 16%.
The updated implementation of mitigation measures has currently been adopted as an operational procedure in the New Zealand national control room to manage Geomagnetically Induced Current (GIC).
The United Kingdom
In the United Kingdom the national grid relies on design such as Geomagnetically Induced Current (GIC)-resistant transformer design, voltages lower than 400 kV, and backup transformers. Furthermore, their national grid relies on operation mitigation measures such as return to service of items out for maintenance and switching in of all circuits, and connection of all Supergrid Transformers. Supergrid transformers are vital high voltage devices that boost substations’ capacity and resilience. Additionally, they work closely with the Met Office (UK’s national meteorological service) which offers advanced space weather forecasting and warnings, and helps with the creation of operating and emergency strategies.
After the implementation of these mitigation measures, an assessment of the potential space weather risks to the United Kingdom’s transmission grid got conducted by the European Commission suggesting that only a Carrington-type of space weather event could cause a disruption to the grid. An event at the size of the Carrington event has a ~50-100-year return period. However, widespread transformer damage and a total power grid collapse is estimated to be highly unlikely. Estimations suggest that only 20 transformers would be affected by extreme space weather, which constitutes only ~1 percent of all transformers in the UK grid. According to the 2016 European Commission’s report on space weather and critical infrastructures, only local blackouts are to be expected.
The Carrington Event is a historical space weather event that took place in 1859 [Read more about this event in SR Hoplon’s blog; C H A P T E R N ° 2’¹ Historical Space Weather Events.
The work towards a more resilient power grid system did, however, continue after the investigation in 2016. In 2023 the British scientist David H. Boteler published a paper suggesting that transformers like the 3-phased 3-legged core type are to be less susceptible to saturation from Geomagnetically Induced Currents (GICs) and may, therefore, work as an additional mitigation measure to the power system. He does, however, explain that changing existing transformers to a 3-phased core type is not necessarily feasible for every country due to the high expenses and its size. Alternatively, David H. Boteler, therefore, suggests that one could try to block the flow of the Geomagnetically Induced Current (GIC) by placing blocking capacitors in the power transmission lines as done in the Canadian power supplier Hydro-Québe. However, these mitigation measures are not economically friendly nor do they insure a hundred percent resilience. They may only work as an addition to other mitigation measures.
The United States of America
On the evening of May 10, 2024, the United States of Americas grid operator PJM Interconnection activated a rare Geomagnetic Disturbance (GMD) system procedure after it observed persistent Geomagnetically Induced Currents (GICs) at multiple stations within its 13-state footprint. PJM Interconnection is a regional transmission organisation that coordinates the movement of wholesale electricity in Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and the District of Columbia. The activation of the system procedures for Geomagnetic Disturbance (GMD) caused a 14-hour period of high alert before it was downgraded to a Geomagnetic Disturbance (GMD) warning, which continued for two additional days.
The activation of the power grids Geomagnetic Disturbance (GMD) alert was a response to what later was found out to be a historic space weather event. Prior to the event, the national meteorological institute The National Oceanic and Atmospheric Administration (NOAA) had warned about a space weather event potentially reaching G4 or G5 levels on the Planetary K-index (Kp scale) – The space weather scales and benchmarks are currently under revision. A G4 or G5 event indicates the potential of a severe or extreme space weather event in the form of a geomagnetical storm and their impact. The space weather scales and benchmarks were created by The National Oceanic and Atmospheric Administration (NOAA) to categories and explain the potential impact of various intensity levels of space weather on space and terrestrial infrastructures.
The power transmission system is installed with special equipment to detect and measure Geomagnetically Induced Currents (GICs). When The National Oceanic and Atmospheric Administration (NOAA) sends out a space weather warning for Geomagnetically Induced Currents (GICs), the grid operators at PJM Interconnection initiates a warning for Geomagnetic Disturbance (GMD) that alerts all generation members. If the measurements of Geomagnetically Induced Currents (GICs) exceed operating limits (in amperes) at two or more monitored transformers, the grid operator will then initiate an action that re-dispatches generation to control the Geomagnetic Disturbance (GMD) transfer limits.
However, mitigation measures are still needed in the U.S., among other countries. The U.S. Pacific Northwest National Laboratory (PNNL) and the Electric Power Research Institute (EPRI) have in separate reports highlighted the necessity of electromagnetic shielding to protect critical components. They suggest mitigation measures such as using shielded control/signal cables with proper grounding, modifications to substation control houses to enhance shielding properties, and employing conductive concrete for control houses.
Moreover, they suggest mitigation measures such as using devices like neutral blocking devices (NBDs) and Geomagnetically Induced Current (GIC) reduction devices as they could be effective at blocking or reducing the flow of Geomagnetically Induced Currents (GICs) into transformers and prevent impacts from part-cycle saturation. Other recommendations involve the deployment of low-voltage surge protection devices (SPDs) like metal oxide varistors and hybrid surge protective device (SPD) to shield electronic equipment from voltage surges caused by Geomagnetic Disturbance (GMD) events.
Finally, they argue the importance of effective space weather monitoring and early warning systems, mitigation measures such as always having updated and fully fueled transformer spares, and advise effective grounding and bonding practices to ensure Geomagnetically Induced Currents (GICs) are safely dissipated.
Image Credit: Dynamic Ratings: Picture of a transformer.
Closing remarks
The recent years of collaborations between universities and industry has pushed towards the development of more resilient power grid systems. However, it has also shown that there is a need for the creation and implementation of multiple types of mitigation measures, from engineered-based to non-engineering-based.
Power system operators need the implementation of engineering-based shielding properties to ensure that the power grid is as physically resilient as possible with current engineering capabilities. However, power system operators additionally have to understand and be aware of the threshold of the engineering-based shielding and be equipped with emergency plans and procedures. These are needed in order to guide them on how to ensure the safety of the power system in cases where the impact of the space weather event exceeds the capabilities of the implemented engineering-based shielding.
In order to enable all of this, operators rely on space weather forecasts and alerts. Operators need to understand the intensity level of the space weather events and when they will interact with Earth. This is because power systems do not immediately show that the system is reacting to a Geomagnetic Disturbance (GMD). It will start by showing numerous issues and slowly indicate stresses within the system. It is only later that the operator is informed that the stresses are due to Geomagnetically Induced Currents (GICs). By having forecasts and alerts, the operators will know why the system starts to show anomalies and act accordingly. A resilient power system is, thus, one where a combination of engineering-based shielding, operating and emergency plans, and forecasting and alerts are implemented.
Sources
Mac Manus, D.H. et al. (2023): “Protecting power grids from space weather”. AGU, Space Weather Vol. 21, Issue 11. DOI: https://doi.org/10.1029/2023SW003533
Krausmann, Elisabeth et al. (2016): “Space weather and critical infrastructures: Findings and Outlook”.European Commission, JRC Science For Policy Report. DOI: 10.2788/152877
The National Oceanic and Atmospheric Administration (NOAA) (n.d.): “Planetary K-index”. https://www.swpc.noaa.gov/products/planetary-k-index
