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Assessing the Impacts of Geomagnetic Disturbance onTransmission System Reliability
Assessing the Impacts of Geomagnetic Disturbance onTransmission System Reliability
James McCalley, Professor of Electrical and Computer EngineeringAnne Kimber, Director of the ISU Electric Power Research Center
Rishi Sharma, Ph.D. Student
Iowa State University
James McCalley, Professor of Electrical and Computer EngineeringAnne Kimber, Director of the ISU Electric Power Research Center
Rishi Sharma, Ph.D. Student
Iowa State University
Midwest Reliability OrganizationFall Reliability Conference
St. Paul, MinnesotaNovember 2, 2016
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Overview1.GMD basics2.NERC documents3.Recent Federal actions4.MEC/ISU/USGS research efforts5.1‐D vs 3‐D Earth conductivity model6.Improved GIC computation7.Benchmarking 8.Takeaways
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GMD Basics: phenomena
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http://popularlogistics.com/2013/05/celestial‐shooting‐gallery‐part‐one‐the‐day‐we‐lost‐quebec/
http://www.cmso.info/cme
D. Boteler, “Geomagnetic effects on power systems,” in “Solar storms and power grids,” IEEE Electrification, Dec., 2015, Vol. 3, N 4.
“Geomagnetic disturbances,” IEEE PES Society Tech Council Task Force on Geomagnetic Disturbances,” IEEE Power & Energy Magazine, July/August 2013,.
Fluctuating electrojectSlowly varying geomagnetic field induces geoelectricfield on the Earth’s surface, as a function of the Earth’s conductivity structure.
Geoelectric field causes potential difference and quasi‐DC currents flow.
During a solar flare, high energy charged particles escape the sun’s atmosphere called coronal mass ejection (CME).
When the CME interacts with Earth, the charged particles due to CME produce ionospheric currents known as an electrojet.
The electrojet produces its own magnetic field, varying the Earth’s magnetic field.
GMD basics: impacts & mitigation measures• DC currents flow in xfmr neutral, and split into each phase winding;
• Causes unidirectional shift in core flux;• Results in core saturation and thus very large magnetizing currents;
• Magnetizing currents comprised of many harmonics beyond the fundamental;
• Three problems result:• Saturated magnetizing current increases xfmr reactive consumption;
• Harmonics/strayflux cause xfmr heating;• Harmonics injected into power grid.
Mitigation measures:• Operational, e.g., deploy reactive supply devices• Infrastructure hardening, e.g., install blockers or
reducers
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NERC Documentshttp://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/2012GMD.pdf
Chapters:1. Space Weather and the Power System2. Monitoring and Predicting Space Weather3. Existing Response Capability4. Credible Threat Concept and GIC Calculation5. Power Transformers6. Protection and Control7. Other Equipment8. Power System Analysis9. Grid Monitoring Enhancement10. GIC Reduction Devices11. Operating Procedures to Mitigate GIC12. Managing Geomagnetic Disturbance Risks13. Recommendations
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2012 Special Reliability Assessment Interim Report:
Effects of Geomagnetic Disturbances on the Bulk Power System
February 2012
Attachments:1. Acronyms2. April 2011 NOAA SWPC Workshop3. NERC Industry Alert4. Public GMD Response Procedures5. Public OEM Documentation on GMD
6. Monitoring & Measurement Architecture7. View on Risk Management8. Example of GIC Calculations9. NERC GMDTF Roster
NERC Documentswww.nerc.com/pa/Stand/Pages/Project-2013-03-Geomagnetic-Disturbance-Mitigation.aspx
TPL‐007‐1 Transmission System Planned Performance for Geo‐magnetic Disturbance Events
‐ GMD effects in planning studies. ‐ Assessment of eqpmnt impacts & protection/control systems during severe event.
Theory used in commercial GIC modeling software and for setting up a GIC calculation procedure.
Defines GMD event via (1) ref peak geoelectric field ampltd; (2) scaling factors for latitude and for local Earth conductivity; (3) ref geomagnetic field time series.
Requirements for xmission system planned performance during GMD events; R1: Who is responsible for models/studiesR2: Maintain models for GMD vul assessmntR3: Steady‐stage voltage criteria during GMDR4: GMD vul assessmnt once/60 mnths.R5: Provide GICs for each xfmr; also GIC(t)R6: Thermal impact assessmnt when GIC>75aR7: Tab1 Rqrmnts not metCrrctvActnPlan
…
Justification for TPL‐007‐1 screening criterion.
Methods to conduct pwr xfmr thermal analysis to determine if xfmrs can withstand thermal transient effects from benchmark event.
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NERC Documents- From TPL-007-1www.nerc.com/pa/Stand/Pages/Project-2013-03-Geomagnetic-Disturbance-Mitigation.aspx
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Latitude
Earth conductivity structure
NERC Documents- From TPL-007-1www.nerc.com/pa/Stand/Pages/Project-2013-03-Geomagnetic-Disturbance-Mitigation.aspx
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Recent Federal Actions
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September 22, 2016, FERC Final Rule, Order No. 830: (www.ferc.gov/whats‐new/comm‐meet/2016/092216/E‐4.pdf )• Approved Reliability Standard TPL‐007‐1;• Other directives on next slide…
October 13, 2016 White House Executive Order: (www.whitehouse.gov/the‐press‐office/2016/10/13/executive‐order‐coordinating‐efforts‐prepare‐nation‐space‐weather‐events )• National Science & Technology Council (NSTC) to establish Space Weather Operations,
Research, & Mitigation Subcommittee;• Secretary of Energy to facilitate protection/restoration of power grid reliability during a
presidentially declared grid security emergency associated with a GMD;• Secretaries of Defense, Interior, Commerce, Transportation, Energy, Homeland Security, NASA
Admin, NSF Director to develop models, observation systems, technologies, approaches to inform/enhance national preparedness for space weather events, including how they may affect critical infrastructure and change the threat landscape with respect to other hazards;
• Within 120 days, Secretary of Energy shall develop a plan to test/evaluate devices to mitigate GMD effects on the electrical power grid.
MEC/ISU/USGS Research Activities
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FERC ORDER 803 DIRECTIVES(i) Revise benchmark GMD event definition, so that it is not based solely on spatially‐averaged data.
(ii) Collect GIC monitoring & magnetometer data;make such data publicly available.
(iii) Include 1‐yr deadline for completion of corrective action plans; 2‐ & 4‐yr deadlines to complete mitigation actions involving non‐HW/HW mitigation.
Submit GMD research work plan within 6 months of Final Rule effective date and, subsequently, one or more informational filings addressing specific GMD‐related research areas,including spatial averaging, conductivity models, and thermal impact analysis.
(1) Can we gain access to other existing monitoring nodes? (2) Can we install additional monitoring equipment? This is an MRO‐wide collaboration opportunity.
USGS is proposing extreme value theory to compute geoelectric field map for once per‐century geomagnetic inductions. ISU Is proposing Guided Monte Simulation to estimate probability of violating performance threshold.
ISU/MEC/USGS RESEARCH ACTIVITIES
Improve GIC modeling and analysis using USGS 3‐D Earth model
Develop automated GIC process to assess many possible realistic but severe GMD events to identify highest‐risk transformers.
1. Measured geomagnetic field OR 2. Benchmark geomagnetic field
Geomagnetic Field data
.
Computation of transmission line induced voltage (Matlab)
Power Grid Network data
GIC module to compute GICs (PSSE)
‐
Y bus Matrix
Equivalent current source (J)
[V] = [J]
Calculated GICs
Improved GIC Computation1‐D Earth model or3‐D Earth model
Line outage data
GIC analysis data (substation R, xfmr, connection/design)
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Power flow case & line locations
1-D, 3-D Earth Conductivity Models
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• Loses fidelity where geological structures createlarge lateral variations in conductivity.
• Not accurate at sea coasts because highconductivity of sea water compared to that of land.
Resistivity at 4 km depth based on EarthScopeMT data.
White circles indicate station locations.
Resistivity data results from 3D inversion of measured EarthScope data.
Modeling by Paul Bedrosian, USGS. [email protected]
Comparison of Calculations using 1‐D and 3‐D Earth Models
Actual Event
Magnetometer data for
recorded event
NERC‐specified proceduresusing 1‐D Earth model
Improved procedures using 3‐D Earth model
Measured GICs for recorded
event
Computed GICs1
Computed GICs 2
Adjustments to various parameters based on sensitivities
Σ
Σ
+‐
+‐
What is learned from this?1. How different are GIC
computations from GIC measurements? To what extent can we trust computations to replicate events?
2. How different are GICs computed using 1‐D Earth model from those using 3‐D Earth model? What is the cost/benefit of using the 3‐D Earth model?
3. What parameters influence results the most?
Adjustments to various parameters based on sensitivities
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A recorded event: Dec 2015 measurementGeomagnetic field sampled at 1 Hz; GIC sampled at 0.5 Hz.
BX
GIC
BY
NOAA Space Weather Prediction Center: “Two asymmetrical full‐halo coronal mass ejections (CMEs) were observed in SOHO/LASCO C2 …on 16 Dec…Both CMEs were determined to be Earth‐directed and arrived at Earth late on 19 Dec.…” ftp://ftp.swpc.noaa.gov/pub/warehouse/2016/WeeklyPDF/ (see prf2103).
http://www.swpc.noaa.gov/news/g2‐moderate‐geomagnetic‐storms‐observed‐20‐december
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Benchmarking•Highly controversial, in part because of limited occurrences• Can be addressed via repeated, accurate guided Monte Carlo simulation
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ACCURATE GIC COMPUTATION
GMD EVENT CONSTRUCTION
LOGIC
POWER GRID ASSESSMENT
Takeaways• Increase number/availability of geomagnetic/GIC event recordings
• Improve GMD modeling and assessment process•Avoid under‐ or over‐ investing for correctives• Investigate alternative benchmark approaches•Additional work in transformer thermal modeling, harmonic assessment, and reactive power influences.
• ISU/USGS/MEC ‐ contributing to the response to 9/22 FERC Order 830 and 10/13 White House Executive Order;
•MRO participation is encouraged!•Upcoming GMD course (next slide)
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Spring GMD Seminar CoursePower Grid Effects of Geomagnetic Disturbances:
Fundamentals, Requirements, & Solutions
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Where: • Iowa State University campus• & video‐streamed to your office
What: • 15‐week seminar course• 1 hour per week
Logistics: • $400 per person• PDH available• Wednesdays 12:00‐1:00 pm CT• Begins January 11, 2017
Instructors: • Iowa State faculty• Geophysicists+space‐weather scientists• Engineers from NERC/FERC, industry• Commercial grade software expertsObjectives: • Understand GMD fundamentals• Learn what you must do/how to do it• Learn what you should do/how to do it• Identify best practices and latest
research developments
1‐D Layered Earth conductivity structure
Single valued, Earth impedance obtained for each frequency using recursive calculations
μ1
1 ‐ reflection coefficient; ‐ propagation
constant; ‐ layer n impedance
ω ω ωω ω ω
1. Seismic Survey2. Magnetotelluric Survey
Geoelectric fld component linearly related to only its orthogonal magnetic fld component
Inversion techniques used to determine 3‐D conductivity
structure
3‐D Earth impedance obtained from3‐D conductivity structure, in form of
Magnetotelluric Survey
Geoelectric fld components linearly related to geomagnetic fld components along and orthogonal to it
Initial Source
Conductivity structure
Earth impedance
Inference
Geoelectric field calculation
1-D and 3-D Earth conductivity models in GMD assessment
Assessment with 1‐D data Assessment with 3‐D data
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