Assessing the Impacts of Geomagnetic Disturbance on Transmission System Reliability

Transcription

1 Assessing the Impacts of Geomagnetic Disturbance on Transmission System Reliability Midwest Reliability Organization Fall Reliability Conference St. Paul, Minnesota November 2, 2016 James McCalley, Professor of Electrical and Computer Engineering Anne Kimber, Director of the ISU Electric Power Research Center Rishi Sharma, Ph.D. Student Iowa State University 1

2 Overview 1.GMD basics 2.NERC documents 3.Recent Federal actions 4.MEC/ISU/USGS research efforts 5.1 D vs 3 D Earth conductivity model 6.Improved GIC computation 7.Benchmarking 8.Takeaways 2

3 GMD Basics: phenomena During a solar flare, high energy charged particles escape the sun s atmosphere called coronal mass ejection (CME). The electrojet produces its own magnetic field, varying the Earth s magnetic field. Slowly varying geomagnetic field induces geoelectric field on the Earth s surface, as a function of the Earth s conductivity structure. Fluctuating electroject D. Boteler, Geomagnetic effects on power systems, in Solar storms and power grids, IEEE Electrification, Dec., 2015, Vol. 3, N 4. When the CME interacts with Earth, the charged particles due to CME produce ionospheric currents known as an electrojet. Geoelectric field causes potential difference and quasi DC currents flow. gallery part one the day we lost quebec/ Geomagnetic disturbances, IEEE PES Society Tech Council Task Force on Geomagnetic Disturbances, IEEE Power & Energy Magazine, July/August 2013,. 3

4 GMD basics: impacts & mitigation measures Mitigation measures: Operational, e.g., deploy reactive supply devices Infrastructure hardening, e.g., install blockers or reducers 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. 4

5 NERC Documents Special Reliability Assessment Interim Report: Effects of Geomagnetic Disturbances on the Bulk Power System February 2012 Attachments: 1. Acronyms 2. April 2011 NOAA SWPC Workshop 3. NERC Industry Alert 4. Public GMD Response Procedures 5. Public OEM Documentation on GMD Chapters: 1. Space Weather and the Power System 2. Monitoring and Predicting Space Weather 3. Existing Response Capability 4. Credible Threat Concept and GIC Calculation 5. Power Transformers 6. Protection and Control 7. Other Equipment 8. Power System Analysis 9. Grid Monitoring Enhancement 10. GIC Reduction Devices 11. Operating Procedures to Mitigate GIC 12. Managing Geomagnetic Disturbance Risks 13. Recommendations 6. Monitoring & Measurement Architecture 7. View on Risk Management 8. Example of GIC Calculations 9. NERC GMDTF Roster 5

6 GMD effects in planning studies. Assessment of eqpmnt impacts & protection/control systems during severe event. Methods to conduct pwr xfmr thermal analysis to determine if xfmrs can withstand thermal transient effects from benchmark event. Justification for TPL screening criterion. NERC Documents TPL Transmission System Planned Performance for Geomagnetic Disturbance Events Requirements for xmission system planned performance during GMD events; R1: Who is responsible for models/studies R2: Maintain models for GMD vul assessmnt R3: Steady stage voltage criteria during GMD R4: GMD vul assessmnt once/60 mnths. R5: Provide GICs for each xfmr; also GIC(t) R6: Thermal impact assessmnt when GIC>75a R7: Tab1 Rqrmnts not met CrrctvActnPlan 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. 6

7 NERC Documents- From TPL Latitude Earth conductivity structure 7

8 NERC Documents- From TPL

9 Recent Federal Actions September 22, 2016, FERC Final Rule, Order No. 830: ( 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: ( 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. 9

10 MEC/ISU/USGS Research Activities 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. ISU/MEC/USGS RESEARCH ACTIVITIES 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. (1) Can we gain access to other existing monitoring nodes? (2) Can we install additional monitoring equipment? This is an MRO wide collaboration opportunity. 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. 10

11 1 D Earth model or 3 D Earth model Improved GIC Computation Computation of transmission line induced voltage (Matlab) GIC module to compute GICs (PSSE). Equivalent current source (J) [V] = [J] Geomagnetic Field data 1. Measured geomagnetic field OR 2. Benchmark geomagnetic field Y bus Matrix Power Grid Network data Calculated GICs Power flow case & line locations Line outage data GIC analysis data (substation R, xfmr, connection/design) 11

12 1-D, 3-D Earth Conductivity Models Resistivity at 4 km depth based on EarthScope MT data. White circles indicate station locations. Loses fidelity where geological structures create large lateral variations in conductivity. Not accurate at sea coasts because high conductivity of sea water compared to that of land. Resistivity data results from 3D inversion of measured EarthScope data. Modeling by Paul Bedrosian, USGS. pbedrosian@usgs.gov 12

13 Comparison of Calculations using 1 D and 3 D Earth Models Magnetometer data for recorded event Actual Event NERC specified procedures using 1 D Earth model Adjustments to various parameters based on sensitivities Improved procedures using 3 D Earth model Adjustments to various parameters based on sensitivities Measured GICs for recorded event Computed GICs 1 Computed GICs 2 + 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? 13

14 A recorded event: Dec 2015 measurement Geomagnetic field sampled at 1 Hz; GIC sampled at 0.5 Hz. B X moderategeomagnetic storms observed 20 december B Y GIC 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). 14

15 Benchmarking Highly controversial, in part because of limited occurrences Can be addressed via repeated, accurate guided Monte Carlo simulation GMD EVENT CONSTRUCTION LOGIC ACCURATE GIC COMPUTATION POWER GRID ASSESSMENT 15

16 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) 16

17 Spring GMD Seminar Course Power Grid Effects of Geomagnetic Disturbances: Fundamentals, Requirements, & Solutions What: 15 week seminar course 1 hour per week Where: Iowa State University campus & video streamed to your office 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 experts Objectives: 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 17

18 1-D and 3-D Earth conductivity models in GMD assessment Assessment with 1 D data 1. Seismic Survey 2. Magnetotelluric Survey Initial Source Assessment with 3 D data Magnetotelluric Survey 1 D Layered Earth conductivity structure Single valued, Earth impedance obtained for each frequency using recursive calculations 1 μ 1 reflection coefficient; propagation constant; layer n impedance ω ω ω ω ω ω Conductivity structure Earth impedance Geoelectric field calculation Inversion techniques used to determine 3 D conductivity structure 3 D Earth impedance obtained from 3 D conductivity structure, in form of Geoelectric fld component linearly related to only its orthogonal magnetic fld component Inference Geoelectric fld components linearly related to geomagnetic fld components along and orthogonal to it 18