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
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
• 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.
Graphic Depiction of a Coronal Mass Ejection
Magnets and Electricity
Magnetic Fields
Electromagnets
Electric Generator
(Reverse input/output for motors)
How Does this Impact the Grid?
1.
2.
Ionized particles bombard the Earth
Earth’s magnetic field disrupted
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3.
4.
DC current (GIC) induced in neutral of transmission lines
Transformer saturation
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5.
6.
Electric potential induced on earth’s surface
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
Effects of GIC in an HV Transmission Network
The U.S. Grid
High Voltage Grid
U.S. is split into three separate grids
Latitude and Orientation
• Impact is greater at more northern latitudes
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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.
Percent Probability of Occurrence of Hourly
Peak dB/dt greater than 300 nT/min
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
• 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’s (TransE’nergie) electric transmission system collapsed in
92 seconds
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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
Geomagnetic intensity – March 1989 Storm
Mitigation Methods
• GIC Reduction Device (GRD)
– Resistor or capacitor in transformer neutral or in series on line
– Unproven technologies
• Operational
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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
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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
Location of NASA Satellites between Earth and Sun
Space Weather Prediction Center
• http://www.swpc.noaa.gov/
Occurrence of Kp values
from 1932 to 1991
~1700 per cycle
~600 per cycle
~200 per cycle
~100 per cycle
~4 per cycle
• http://spaceweather.com/
FERC Activity
• Study by Storm Analysis Consultants (SAC)
– Congressional EMP Commission
• Worst-Case results:
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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.
Storm Analysis Consultants
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
• 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
NERC GMD TF’s Proposed GMD Risk
Mitigation Strategy
Components
Phased Approach
EPRI GIC Project
• Assumptions:
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Maxwell’s equations instead of Earth Surface Potential (ESP)
DC model
500 kV lines + autos (for now)
100 year storm (~1921)
• Steps:
1.
2.
3.
4.
5.
Model GIC flows (DC amps)
VAR demand
Harmonic production
System protection (CT saturation, relays)
Blocking options and effectiveness
The EPRI SUNBURST Project
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•
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
EPRI
SUNBURST2000
NOAA
Solar Wind Data
Utility Site
Utility
Site
SUNBURST Center
Geomagnetic
Monitoring
Database
SUNBURST
Web
Server
Electric Research
Power
System
Data
Utility
Site
Internet
Web Pages
Your Grid
Xfmr 1 DC
Data Sent to
Electric
Research
Utility
Site
Near Real-Time
SUNBURST Web Site
Utility
Site
View GIC Data at any location:
International
Utility Sites
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System Operations
Engineering
Power Plants
Substations
Corporate Office
Summary
• 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
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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
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 (www.swpc.noaa.gov)
 Space Weather.com - Various information and references
 FERC EMP-GIC Metatech Reports 319-324.
 Alton Comans, Chief Engineer, Southern Company Services
Questions?