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Lessons Learned from the Texas Synchrophasor Network by Presented at the

Lessons Learned from the Texas Synchrophasor Network by Presented at the North American Synchrophasor Initiative (NASPI) Meeting Toronto, Ontario Thursday, June 9, 2011. W. Mack Grady and Moses Kai, U.T. Austin Bill Flerchinger and David Costello, Schweitzer Engineering Labs

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Lessons Learned from the Texas Synchrophasor Network by Presented at the

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  1. Lessons Learned from the Texas Synchrophasor Network by Presented at the North American Synchrophasor Initiative (NASPI) Meeting Toronto, Ontario Thursday, June 9, 2011 W. Mack Grady and Moses Kai, U.T. Austin Bill Flerchinger and David Costello, Schweitzer Engineering Labs Karen Forsten and Daniel Brooks, EPRI 1

  2. The Texas Synchrophasor Network Six 120V single-phase PMUs, One 69kV three-phase PMU Blue outlines: Central ERCOT Brazos Electric PMU Waco Wind country McDonald Observatory Austin Energy PMU Austin 120V and Harris 69kV Boerne (SEL) Houston (SEL) • Funding provided by EPRI • Equipment provided by Schweitzer Engineering Labs UT Pan Am Concentrated distant load 2

  3. Lesson 1. Every Day has Synchrophasor Surprises 2 days Wind generation and West Texas phase angle can go through large daily swings Thur Fri West Texas voltage phase angle swings nearly 100º and back with respect to U.T. Austin in about 24 hours 48 3

  4. Texas Nodal Market Has Created a New West Texas Resonant Mode with Time Period = 30 minutes 12 hours ERCOT’s graph of West-to-North P flow Texas Synchrophasor Network’s graph of West-to-Central ERCOT Voltage Angle 4 Lesson 1. Daily surprises, cont.

  5. Transmission Events Also Produce Angle Rings 2011/06/03, 00:54 GMT • The angle ring observed at McD and Waco was likely caused by a transmission event and was a precursor to a gradual frequency slump. • Angle ring is approx. 1 degree peak to peak (2nd significant digit) • Frequency ring is only about 0.01 Hz peak to peak (4th significant digit) McD Angle 2 minutes 60.02 Hz McD, PanAm, Waco Frequencies 5 minutes 2 minutes 59.94 Hz Frequency Slump 3600 points 5 Lesson 1. Daily surprises, cont.

  6. Lesson 2. 120V Wall Outlets Work for Synchrophasors (of course, we would prefer to have three-phase grid PMUs) Voltage Ringdown at McDonald Observatory Observed at the Following Two Locations in Austin: a 120V Wall Outlet on Campus, and the Harris 69kV Substation that Feeds the Campus 20 seconds • The fixed net multiple of 30 degree phase shift between U.T. Austin 120V and Harris 69kV has been removed. The variable but steady power flow phase shift through the substation transformer has also been removed. 6

  7. Steady-State Voltage Angle Between Austin Energy 69kV Substation Monitor and UT ECE Building 120V Wall Outlet Varies Slowly with UT Generation and Load Week Starting Sunday, May 29, 2011 1 week Note – angles shown were rounded to 0.1º 7 Lesson 2. 120V OK, cont.

  8. Lesson 3. You Can Estimate Thevenin Equivalent Impedances Across the Grid with Synchrophasors Use the Excel Solver with angle measurements to minimize least-squared error and obtain Xth 8

  9. Lesson 4. A Small but Tightly-Clustered 2 Hz Mode in Ambient Oscillation Sometimes Forms with High Wind Generation Small Wind (2%) without 2 Hz Cluster Big Wind (20%) with 2 Hz Cluster 1 hour 9

  10. Lesson 5. Wind Generation Does Not Appear to Impact System Damping or Damped Resonant Frequency 5 minutes of frequencies 59.74 McD Modest wind 1 minute of angles PanAm Waco 10

  11. Let Excel Solver Curve Fit the 2nd Order Damped Response Damped Resonant Frequency, Hz Steady-State Change = 18.58 – 17.05 = 1.53 degrees Ring Magnitude, degrees Normalized Damping Ratio 10 seconds 11 Lesson 5. Wind does not impact damping, cont.

  12. Ringdown Analysis of More Than 100 Unit Trips Yields No Clear Relationship Between Wind MW and Normalized Damping Ratio Does Wind Generation Impact Grid Stability? 6 months 12 Lesson 5. Wind does not impact damping, cont.

  13. Lesson 6. Wind Generation Does Not Appear to Reduce System Inertia (but no generator operating at max power can contribute to governor response) EPRI Study. Purpose – to compute ERCOT System Inertia Constant H From Frequency Response During 42 Unit Trips Having 0.1 Hz or Greater Freq. Drop. 2 minutes Nadir slope Zoom Inertia slope 10 seconds 13

  14. 42 Major Unit Trips, 0.1 Hz or Greater.Any Correlation Between System Inertia and Wind Generation (% of Total Gen)? 6 months 14 Lesson 6. Wind does not reduce system inertia, cont.

  15. Texas Synchrophasor Network Thanks to • Schweitzer Engineering Laboratories, especially Mr. David Costello, for providing all the equipment and technical support that we need • EPRI, especially Ms. Karen Forsten and Mr. Daniel Brooks, for past, present, and future funding of graduate students and faculty summer support • Startup money in 2008 from the Texas Governor Rick Perry’s Emerging Technology Fund through CCET, Dr. Milton Holloway • Austin Energy, especially Mr. Scott Bayer, for installing the 69kV phasor measurement unit, and providing advice on system operating and protection • Mr. Andrew Mattei of Brazos Electric, Waco, for installing and operating a 120V PMU • PhD student Moses Kai at U.T. Austin for his dedication and research in synchrophasors and their applications to power grids 15

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