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Geomagnetic Disturbances (GMD) Causes and Effect on the North American Grid. Warren Whitson Southern Company Transmission NERC GMD TF Member IEEE Member April 16, 2012. Sunspots.

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geomagnetic disturbances gmd causes and effect on the north american grid

Geomagnetic Disturbances (GMD)Causes and Effect on the North American Grid

Warren Whitson

Southern Company Transmission


IEEE Member

April 16, 2012



During solar minimum the Sun's magnetic field, like Earth's, resembles that of an iron bar magnet, with great closed loops near the equator and open field lines near the poles. We call the Sun's magnetic field the "Interplanetary Magnetic Field" or “IMF." The Sun's dipolar field is about as strong as a refrigerator magnet, or 50 gauss. Earth's magnetic field is 100 times weaker.

During the years around solar maximum (2000 and 2001 are good examples) spots pepper the face of the Sun. Sunspots are places where intense magnetic loops -- hundreds of times stronger than the ambient dipole field -- poke through the photosphere. Sunspot magnetic fields overwhelm the underlying dipole; as a result, the Sun's magnetic field near the surface of the star becomes tangled and complicated.


11 year cycle

  • Entering more active phase
  • Max in May 2013
  • Increased media attention
types of space weather storms
Types of Space Weather Storms
  • Solar Flares: These are intense temporary releases of energy, which cause burst of radio and X-ray wavelengths, lasting from minutes to hours. They travel at the speed of light, but generally they do not cause impact to the electrical grid. They can result in Radio Blackouts which can affect critical systems like GPS.
  • Radiation Storms: Typically occur during a solar flare, they shower the earth, generally within 30 minutes of the flare, with solar particles, typically protons which penetrate the earth’s atmosphere. They are a threat for satellite and space operations, but typically do not affect the grid.
  • Geomagnetic Storms: These are caused by a Coronal Mass Ejection, which is a cloud of solar material and magnetic fields, which, if they contact the earth, creates a disruption in the earth’s magnetic field. Timing is usually one to four days after the solar flare. This is the condition which can affect our transmission grid.
magnets and electricity
Magnets and Electricity

Magnetic Fields


Electric Generator

(Reverse input/output for motors)

how does this impact the grid
How Does this Impact the Grid?
  • Ionized particles bombard the Earth
  • Earth’s magnetic field disrupted
    • Electric potential induced on earth’s surface
  • DC current (GIC) induced in neutral of transmission lines
  • Transformer saturation
    • Overheating -> damage (especially older equipment)
    • Produce harmonics
    • Increased reactive power requirements
  • SVCs, Caps, etc… tripped by protection
  • Potential for system collapse - blackouts

Power Transformer Saturation

  • GIC can increase exciting current 3x during saturation
  • leakage flux also increases dramatically, causing overheating
  • Produces harmonics
  • Increased Var (reactive power) demand
  • Distorted AC current on nearby line
the u s grid
The U.S. Grid

High Voltage Grid

U.S. is split into three separate grids

latitude and orientation
Latitude and Orientation
  • Impact is greater at more northern latitudes
    • Magnetic field lines are closer together near the poles
    • Hence stronger GIC
    • Historically below 35th parallel considered safe
    • In 1989 storm GIC at Mississippi coast was equal to those in Hydro Quebec blackout
  • Orientation of storms vary
    • Direction of transmission lines determines GIC mag.
transmission line susceptibility
Transmission Line Susceptibility
  • Long high voltage lines are more susceptible
    • Potential difference is a function of distance
    • High voltage lines have low impedance
major historical events
Major Historical Events
  • Sept. 1859 “Super Storm”
    • Largest GMD event ever recorded
    • 2x stronger than 1921 storm
  • May 1921
    • 10x stronger than 1989 storm
    • Northern lights seen from Puerto Rico
    • “100 year storm” - debatable
  • March 1989
    • Significant grid impacts
    • Hydro Quebec blackout
hydro quebec blackout 1989
Hydro Quebec Blackout - 1989
  • Hydro Quebec’s (TransE’nergie) electric transmission system collapsed in 92 seconds
    • Seven of seven SVC’s tripped within the first few seconds
    • At the same time reactive demand increased by 1600 MVAR
    • Long HV lines - generation far from load
    • The storm left six million people without service for nine hours or more
  • Several transformers failed (cause of failure is disputed)
    • A GSU transformer failed at a nuclear plant in the USA
    • Two large network transformers failed in the UK
    • Two additional transformers failed on the HQ system due to load rejection
  • NERC, in their post analysis, attributed over 200 significant anomalies across the continent to this one storm
    • Many capacitors tripped due to harmonics
    • Low voltages
mitigation methods
Mitigation Methods
  • GIC Reduction Device (GRD)
    • Resistor or capacitor in transformer neutral or in series on line
    • Unproven technologies
  • Operational
    • Increase awareness
    • Increase import capabilities
    • Increase real & reactive reserves
    • Decrease loading on susceptible equipment
  • Robust spare equipment program
  • Specification of transformers with better GIC immunity
  • Shielding and hardening of our relay and control devices
  • Backup communication systems
nasa s solar programs
NASA’s Solar Programs
  • STP, STEREO, SOHO, MMS, Solar-B, TIMED, ACE etc…
  • Several satellites in various orbits
  • Provide images and video
  • Warning of earth directed CME a day or more ahead
  • Accurate projection 30-60 minutes ahead
    • Magnitude
    • Polarity
    • Location
space weather prediction center
Space Weather Prediction Center

Occurrence of Kp values

from 1932 to 1991

~1700 per cycle

~600 per cycle

~200 per cycle

~100 per cycle

~4 per cycle

ferc activity
FERC Activity
  • Study by Storm Analysis Consultants (SAC)
    • Congressional EMP Commission
  • Worst-Case results:
    • 100,000 MVARs of increased reactive demand
    • Widespread blackouts in eastern U.S.
    • 350 transformers damaged or destroyed
    • $1-$2 Trillion in damage in 1st year
    • Up to 10 years for full recovery
    • Impacts shown at southern latitudes
      • Previously only at more northern latitudes
  • FERC becomes concerned about GMD
    • Prompting NERC to take action

Storm Analysis Consultants

Source: The Vulnerability of the US Electric Power Grid to Severe Space Weather Events and Future Outlook, John G. Kappenman, Metatech Corp.


Location of At-Risk Transformers

4800 nT/min at 45o (GIC > 90 Amps/phase)

Storm Analysis Consultants

the shield act

“To amend the Federal Power Act to protect the bulk-power system and electric infrastructure critical to the defense and well-being of the United States against natural and manmade electromagnetic pulse (‘‘EMP’’) threats and vulnerabilities.”

  • In response to the EMP Commission Report
    • 60% casualty rate for ‘prolonged’ power outage
  • HR668 – Proposed by Rep. Franks : Arizona (Feb, 2011)
    • Secure High-voltage Infrastructure for Electricity from Lethal Damage Act
    • Different from Senate’s SHIELD Act (classified info)
    • Still waiting for vote
  • Mandates FERC to develop standards and enforce compliance
nerc activity
NERC Activity
  • GMD Task Force formed - 2010
  • Industry Advisory issued on GMD – May 2011
    • Information only
    • No response required
  • Preliminary Report released – Spring 2012
    • Space weather prediction/detection
    • Mitigation options
    • Operational practices
  • FERC pressure for further action (Level 2 alert?)
    • Recommended actions
epri gic project
EPRI GIC Project
  • Assumptions:
    • Maxwell’s equations instead of Earth Surface Potential (ESP)
    • DC model
    • 500 kV lines + autos (for now)
    • 100 year storm (~1921)
  • Steps:
    • Model GIC flows (DC amps)
    • VAR demand
    • Harmonic production
    • System protection (CT saturation, relays)
    • Blocking options and effectiveness
the epri sunburst project










Solar Wind Data



Utility Site


Electric Research





Web Pages



Your Grid


Xfmr 1


Data Sent to


Near Real









View GIC Data at any location:

System Operations


Power Plants



Corporate Office

Utility Sites

  • SUNBURST is an EPRI Collaborative R&D project
  • SUNBURST’s objectives are:
    • Monitor actual transformer neutral currents at SUNBURST member sites
    • Provides a local & global view of GIC impacts in near real-time
    • Conducts critical research on behalf of the project members
  • Increased focus on GMD in power industry
    • Congressional EMP Commission
    • Storm Analysis Consultants’ study
    • Solar storm/sunspot cycle
  • FERC is pushing for action
  • NERC alert and report has been issued
    • Still vetting SAC study
    • Developing study realistic scenarios/assumptions
    • Developing modeling expertise/capabilities
    • Determining potential for damage to transformers
  • EPRI is heavily involved
  • There is still much uncertainty and little consensus, but we are making great progress
acknowledgements and recommended reading
Acknowledgements and Recommended Reading

Some of the material in this presentation was obtained from the following sources:

  • NERC, Effects of Geomagnetic Disturbances on the Bulk Power System February 2012
  • NERC, High Impact, Low-Frequency Event Risk to the North American Bulk Power System dated June 2010.
  • NERC, Report on the March 13, 1989 Disturbance
  • US Department of Defense, Low latitude auroras; The Magnetic Storm of May 1921
  • EPRI, Approaches for Minimizing Risks to Power System Infrastructure
  • EPRI – Presentation titled “Research into GIC’s”
  • Wikipedia, articles on GIC, GMD, Electromagnetic Pulses, and the K Index
  • NOAA Space Weather Prediction Center (
  • Space - Various information and references
  • FERC EMP-GIC Metatech Reports 319-324.
  • Alton Comans, Chief Engineer, Southern Company Services