February 19, 2000
Geomagnetic Storm Forecasting
Capabilities Developed for the
Electric Power Industry
Solar Cycle 23 is forecast to be a major solar cycle
Large Geomagnetic Storms are likely to occur over the next few years
Geomagnetic Storm activity can occur for as much as 20% of the year during this cycle
Large Storms can erupt on a Planetary level within a few minutes time
Northern Hemisphere Power Grid infrastructure is exposed to and vulnerable to large geomagnetic storms
United Kingdom's National Grid Company has implemented extensive preparations for Geomagnetic Storm Activity and will be an important industry proving ground for this advanced forecasting technology
Geomagnetic Storm Forecasting Services are available that provide detailed
minute-by-minute storm notification and power-system operator display information,
with a typical 45 Minute Lead-Time
Power Grids & Space Weather Background
Society reliance on electricity for meeting essential needs has steadily increased for many years. This unique energy service requires coordination of electrical supply, demand, and delivery—all occurring at the speed of light. Disturbances caused by solar activity can disrupt these complex power grids. When the Earth's magnetic field captures ionized particles carried by the solar wind, Geomagnetically-induced currents (GIC) can flow through the power system, entering and exiting the many grounding points on a transmission network. GICs are produced when shocks resulting from sudden and severe magnetic storms subject portions of the Earth's surface to fluctuations in the planet's normally stable magnetic field. These fluctuations induce electric fields in the Earth that create potential differences in voltage between grounding points—which causes GICs to flow through transformers, power system lines, and grounding points. Only a few amps are needed to disrupt transformer operation, but over 200 amps have been measured in the grounding connections of transformers in affected areas. Unlike threats due to ordinary weather, Space Weather can readily create large-scale problems because the footprint of a storm can extend across a continent. As a result, simultaneous widespread stress occurs across a power grid to the point where widespread failures and even regional blackouts may occur. Systems in the upper latitudes of the Northern Hemisphere are at increased risk because Auroral activity and its effects center on the magnetic poles. North America is particularly exposed to these storm events because the Earth’s magnetic north pole tilts toward this region and therefore brings it closer to the dense critical power grid infrastructure across the continent. (Figure 1- Exposed Regions of the Northern Hemisphere)
The rest of the North American system also reeled from this storm. Over the course of the next 24 hours, five more large disturbances propagated across the continent, the only difference being that they extended much further south and very nearly toppled power systems from the Midwest to the Mid-Atlantic Regions of the US. The NERC, in their post analysis, attributed over 200 significant anomalies across the continent to this one storm. In spite of the considerable events that were observed, it is now recognized that North America was very lucky that day. This same storm produced surges twice as intense over the lower Baltic, than any that were experienced in North America. But for the providence of that accident of timing, North American power system operators likely avoided even larger-scale failures. Over the next 5 years, smaller storms demonstrated time and again for the power industry that significant impacts could be triggered at even lower storm levels.
For perspective, the limited climatologic data available suggests that storms of even larger intensity and with a larger planetary footprint are possible than the one that occurred in March 1989.Also, the power industry realizes that its vulnerability continues to incrementally grow over time. As a result, the challenges of this solar cycle may be even greater than those posed 10 years ago. This is not an easy problem to analyze and will not be easy to solve. Only now, are methods being developed and adopted by the industry to better manage this risk.
Advanced Geomagnetic Storm Forecasting – Critical for Power Industry Risk Management
In the long run, improvements in forecasts will play an important role in managing these risks. Utility companies concerned about storms, rely on contingency strategies for weathering severe magnetic disturbances. Choosing the best contingency procedures depends on being able to predict storm severity and how it affects the local system. NASA and NOAA have put in place important real-time solar wind monitoring with the ACE Satellite, which has been operational since January 1998.This capability allows, for the first time, the ability to accurately predict the occurrence of large threatening storms with enough lead-time to take meaningful well-informed actions to better prepare the power grid for the impact of the storm.
The first of these advanced forecast systems has been developed by Metatech and is now operational at National Grid Company, the utility that provides service to England and Wales. National Grid is the largest electric transmission operating company in the world and is providing the vital proving ground for this advance in Space Weather forecasting for the power industry. This forecasting capability has been operational at National Grid since May of 1999 as a Phase 1 system and in a fully complete mode of operation since January 31, 2000.Similar forecast systems may soon be adapted by Metatech for application in other critical infrastructures that may be impacted by severe Space Weather as well.
Methods of classifying geomagnetic storm activity in the past have typically used two letter indices (for example K1 to K9 for the smallest to largest geomagnetic storm) to rank the severity of the storm over broad three-hour time windows and planetary or large region locations. Space Weather is a very complex, detailed, and dynamic process that is ever-changing over the course of the storm. Just as the diversity of terrestrial weather impacts to critical operational infrastructure (such as rain/snow, thunderstorms, heat/cold, hurricanes, etc.) cannot be adequately classified by 3-hour, 2-letter, planetary indices; neither should the inherently dynamic impacts of space weather remain with this outdated classification approach. The operation of critical infrastructures such as power grids is a continuous minute by minute coordinated and supervised operation. Thus, the forecasting capability for geomagnetic activity also needs to provide continuous updates of the rapidly changing space environment conditions to best meet the operational needs of power systems in managing this storm risk.
Figure 1: Exposed Regions of the Northern Hemisphere. The footprints of a superstorm can be extensive, the above diagram shows the regions of the Northern Hemisphere that can be exposed to intense storm activity such as the Great Geomagnetic Storm of March 1989. For perspective, the level of storm severity that precipitated the Hydro Quebec collapse was observed at locations as far south as those depicted by the green contour line, which would encompass most of North America and Europe (as shown in green). Much stronger intensities were observed at more northerly locations (as outlined in red), these intensities are approximately 5 times more severe than the levels that triggered the Hydro Quebec collapse. Levels of one-half the intensity of those that triggered the Hydro Quebec collapse have also shown to be capable of causing power reliability problems, which for this storm extended to even lower latitudes (as shown in blue).
The advanced and comprehensive forecast technologies now employed provide power system operators with a clear and to-the-point summary of Space Weather conditions, similar to the way we see ordinary weather information, such as radar and satellite imagery. (Figure 3 – Detailed Ground Level Impact Areas are Forecast) As depicted in Figure 3, this system assesses the environment created by the storm in detail. An even more important feature of this forecast system is provided by the ability to assess the storm’s impact on the power grid. A detailed model of the power grid is calculated to provide a quantifiable assessment for the system operator of the potential impact on a short-term basis to enable well-informed judgments about appropriate operational response measures. (Figure 4 – Detailed Power Grid Model Display) Space Weather forecasting is more difficult than ordinary weather forecasting. Because of the inherent dynamic nature of storms, forecasting models like this need to be continuously updated. Magnetospheric, ionospheric and power grid models all need to be continuously re-calculated by data provided by a solar wind monitoring satellite located one-million miles upstream of the Earth. This data provides the lead-time, because it takes another 45 minutes to one-hour typically for the solar wind to arrive at the Earth. The solar wind data updates are then provided to the models for recalculation of space weather forecasts on a continuous one-minute cadence.
The enormous US power network is controlled regionally by more than 100 separate control centers that coordinate responsibilities jointly for the impacts upon real-time network operations. Other power networks around the world use similar regional control center approaches for providing the 24-hour continuously supervised operation of their networks. Not one of these large power system control centers would do without continuous high quality weather data in managing the operation of their systems. The same paradigm needs to be developed and adopted by the power industry for the threats posed by Space Weather.
|Figure 2: Four Minutes of a Superstorm. Space weather conditions capable of threatening power system reliability can rapidly evolve. The system operators at Hydro Quebec and other power system operators across North America faced such conditions during the March 13, 1989 superstorm. The above slides show the rapid development and movement of a large geomagnetic field disturbance between the times 7:42 - 7:45 UT ( 2:42 - 2:45 EST ) on March 13,1989. The disturbance of the magnetic field began intensifying over the Eastern US-Canada border and then rapidly intensified while moving to the west across North America over the span of a few minutes. From calm conditions, the Hydro Quebec system collapse took only an elapse time of 90 seconds to occur during this storm. Without better forecast warnings, sudden storm events provide essentially no time for meaningful human intervention. The magnetic field disturbances observed at the ground are caused by large electrical currents (electrojet currents) located in the ionosphere at 100 km altitude that interact with the Earth's magnetic field. The electrojet currents act much like the high altitude wind patterns associated with the jet stream that transport and shape the ordinary or terrestrial weather patterns. With Space weather, the speed and the size of these patterns can develop extremely fast and on a planetary scale. The large ionospheric (electrojet) currents that created these magnetic field disturbances, as shown in the above slides, moved from Eastern Canada to Alaska in less than 8 minutes, a velocity exceeding 1000 km/min.|
Figure 3: Detailed Ground Level Impact Areas are Forecast. The above shows the Northern Hemisphere display of the forecast impact areas due to a geomagnetic storm. As shown above, a large impact area extends from approximately Canada to Western Europe.. This model uses real-time solar wind data from the NASA ACE satellite to forecast the expected storm conditions both for the United Kingdom region and worldwide. The model provides important details on the storm intensity, the equator-ward boundaries and temporal variations of the electrojet currents in the ionosphere that are used to estimate ground-level magnetic field disturbances and impacts to critical infrastructures. The estimate is made nominally 45 minutes in advance, which allows important lead-time for impacted systems. Because large-scale changes can occur rapidly, this model recalculates the electrojet current continuously at a one-minute intervals.
|Figure 4: Power Grid Model. The storm visualization shown above is designed to provide a clear and concise picture of the location and intensity of storm impacts across the transmission network. In this example, the storm conditions are displayed for National Grid over England and Scotland. The 400kV and 275kV transmission system is displayed with small circles indicating the magnitude (circle size varies) and polarity (circle color changes) of the GIC (ground Induced current) at each transformer. Also shown are the vector icons of the magnitude and direction of the local magnetic field during the storm, which is responsible for the GIC flows. Text and graphic summaries can also be provided on System or Region reactive power demands, numbers of transformers in saturation and other important system impact details. This PowerCast calculation is made in a Forecast and Nowcast mode and both are recalculated at one-minute intervals. The Forecast mode utilizes data from the electrojet model output of SpaceCast and effectively provides a nominal 45 minute warning of storm impacts. The Nowcast mode utilizes locally sensed magnetic field data and provides a system-wide assessment of current conditions.|