RELIABILITY: Our Advantages, Challenges, and Opportunities

Transcription

1 RELIABILITY: Our Advantages, Challenges, and Opportunities NERC Reliability Leadership Summit March 21, 2017 Edmund O. Schweitzer, III Ph.D. President, Schweitzer Engineering Laboratories, Inc. Copyright SEL 2017

2 Thesis Legacy systems had a lot of margin, that we need back. Time-domain control theory, already at work in our microgrids, holds great promise for wide-area solutions. Faster protection improves stability margins, and we can transmit more power over the same lines. Electric power systems deliver energy at the speed of light!

3 Power Systems Are Changing Quicker Dynamics, Intermittent Sources, Stiffer Loads, Longer Lines

4 Traditional Generation Has MASS P mech P elec = M d2 δ F = ma dt 2 As we reduce M, we experience more acceleration for the same change in power: twitchier.

5 The Need for Speed 15 MW more per millisecond saved Smaller M needs faster speed for same stable power Smaller M R. B. Eastvedt, BPA, 1976 WPRC

6 Distribution Feeders Are Becoming Buses Looped feed, pilot protection Instantaneous tripping Virtually no loss of service Accept generation anywhere Rooftop solar, small wind, batteries Integrate and dispatch backup gensets Islands?microgrids? match load to source and control frequency and voltage

7 Stiff Loads Don t Brown Out Fewer resistive loads: P = V 2 / R More switchers: Constant Power: P = V * I Computers, Data Centers, Lamps, Motor Drives Increasing risk of voltage collapse Conservation voltage reduction (brownout) may be counter-productive. Reducing voltage causes current to increase adding to losses, reactive power, and decreasing efficiency. Wasteful and detrimental to stability.

8 50 Flat-Panel TV Test I P I P Old TV (est.) V

9 How Do We Automate Wide-Area Control Today? Model the system Analyze contingencies Decide if special systems are needed Respond to contingencies in milliseconds

10 WECC Limited Power Plant to 65% Jim Bridger 2120 MW Rock Springs, WY Angular stability could be lost for: Transmission line loss or severe faults when plant operates at full power Solutions: Build more transmission, or Build a Remedial Action Scheme to fast-trip generation, and Speed up protection

11 Contingency-Based RAS Acts in ms f Trigger Inputs Contingency Crosspoint Switch Preloaded and Ready to Go Trip G1 Trip G2 Output Remediation Trip G3 Trip G4 Bypass C1 Bypass C2 CB Opens t N1 X X N2 X X N3 X X Tripping Outputs N4 X X X N5 X X X

12 but, RAS Can Get Complicated Fast! Consider IEEE 39-bus 45-line system Number of k line outages = 45 kk Millions k

13 High k Contingencies Traditionally rare But they cause the largest outages Intermittent resources increase k Generation and load flow change quickly today Intentional attacks are high k Each k is an if-then-else statement

14 Here s What Happens When You Miss a Few k s! A Supply Chain Problem 120 vac 104 vac

15 Undervoltage Tripping Would Have Saved the Day Without Communications! 15 Seconds Voltage (pu)

16 Automatically Maintaining Load and Generation in Balance View system as interconnected regions. Directly measure state in each region and share with neighbors, and master. If asset is lost; system starts to move to predictable new state. If prediction is undesirable, act quickly to preserve as much generation and load as possible.

17 Directly Measure the State V 1 Network Power System State V 2... V n Sub 1... Sub n Detect bad data Average measurements V 1 Determine topology V n Calculate V at adjacent stations: V = V + ZI

18 N = j + k + l + m + n Broadly Share the Complete State Vector Generation Transmission Distribution V j V k V l = S V m V n V 1.. V j = V k V l V m V n V j j k l m... n

19 Relay-Speed Processing, Anywhere State Equations: Stability, Thermal Phasor Math: Self-Checks, Interpolation

20 Predict and Respond Before Instability Potential Stable: Do Nothing Trajectory Prediction Unstable: Act With Controls Angle

21 We Can Now Directly Measure E and δ

22 Sampling for Traveling Waves Reveals 1 MHz Some Surprises! 10 khz

23 Traveling Waves Reveal Landmarks Redmond Yew Ave. Tap Brasada Brothers Tap Hampton Tap Riley Tap Harney

24 Line Energization From Brasada Identifies Landmarks Amperes Pole Closures Yew Ave. Tap Hampton Tap Brothers Tap Riley Tap Harney Time (s)

25 Faster, Simpler Control and Protection Improve Reliability Changes in sources, loads, expectations Systems will require automated controls Share state information in real time between G, T, and D Faster Protection enables more power transmission Distributed feedback control will be simpler and better Principles are at work today, around the world