High-Level Harmonic Distortion during Geomagnetic Disturbances CIGRE Grid of the Future Monday, 20th 2014 Jason Taylor, Ph.D. Geomagnetic Disturbances Impacts • Increased var losses • Transformer heating 1989 Blackout of Hydro Quebec System • Harmonics – Protection – Electronics – Generator heating – Loss of var support © 2014 Electric Power Research Institute, Inc. All rights reserved. Vulnerability Assessment Hurdles Models Transformer and system Methods GIC prediction → system harmonics Metrics Withstand capability 2 Agenda • Harmonic Injection during GMD – Half-cycle saturation – Single-phase transformer response – Three-phase transformers • Illustrative case • Harmonic analysis tools • Future research efforts © 2014 Electric Power Research Institute, Inc. All rights reserved. 3 Harmonic Injections during GMD 1000 1000 • Both even and odd harmonics 500 Flux Flux (Volt-Sec) 1500 0 0 -500 -1000 -1000 -1500 0 60 120 180 240 300 360 -500 Time(degrees) 500 • Generally decreasing with harmonic order 360 80 FFT of Iexc 60 40 20 • Harmonic currents can exceed the fundamental 300 Time(degrees) Current(Arms) 0 Current 240 180 120 60 0 500 1000 Frequency (Hz) © 2014 Electric Power Research Institute, Inc. All rights reserved. 0 -500 0 Excitation Current (Amps) 4 500 Single-phase Transformer Response Can be solved analytically • Simple magnetic structure • Magnetically balanced • Sequence components Harmonic magnitudes exhibit beating behavior © 2014 Electric Power Research Institute, Inc. All rights reserved. 5 Harmonic Phase Angles • Polarity of GIC offset • Fundamental voltage phase angle φ shift nth harmonic phase angle by nφ Must be linked with • GIC network calculations • Fundamental load-flow analysis © 2014 Electric Power Research Institute, Inc. All rights reserved. 6 Impact of Voltage Distortion on Current Injection Harmonic injections are a function of voltage ≠ ideal current sources © 2014 Electric Power Research Institute, Inc. All rights reserved. 7 Three-phase Transformers • More complex magnetic structure • Not magnetically balanced Five-Leg, Core-Form Behavior analysis requires timedomain models and/or transformer testing © 2014 Electric Power Research Institute, Inc. All rights reserved. 8 Illustrative Example Case 1.037 ∠34.5 1.073 ∠48.6 H T1 Dyn 1000 MW 59.4 MVAR E 320 km F 150 MVAR G 1.010 ∠23.5 500 kV 1.040 ∠39.3 D 100 MVAR 320 km 150 MVAR 100 MVAR 0.95 ∠0.0 1.00 ∠19.8 T2 Ynynd Z(f) SCC=3GVA 150 MVAR E-Field 6.2 V/km 1.138 ∠49.4 1.045 ∠36.0 1.040 ∠40.8 0.99 ∠25.1 500 kV 0.95 ∠0.0 0.952 ∠21.1 320 km Z(f) SCC=3GVA G 1000 MW 447 MVAR 320 km 484 MVAR 150 MVAR 449 A/ph GIC © 2014 Electric Power Research Institute, Inc. All rights reserved. 449 A/ph GIC 9 483 MVAR Illustrative Example Case 16% VTHD 10% VTHD 25% VTHD 27% VTHD 320 km Z(f) SCC=3GVA G Generator rotor heating current 0.25 p.u. I2 equivalent 320 km Capacitor current 140% of rating Capacitor kVA 106% of rating 2nd Harmonics seen at Generator T2 Contribution 0.20 ∠42 GMD harmonic impacts must be evaluated on a system basis T1 Contribution 0.15 ∠-111 Resultant 0.14 ∠-8 © 2014 Electric Power Research Institute, Inc. All rights reserved. 10 GMD Harmonics Analysis Harmonic analysis tools • Large-scale system analysis • Many coherent sources • Unbalanced injections • Non-ideal current sources • Link to GIC calculations and fundamental load-flow © 2014 Electric Power Research Institute, Inc. All rights reserved. 11 Continued R&D Transformer models • Laboratory testing • Time-domain models • In-situ monitoring Harmonic analysis tools Harmonic analysis assessment guidance Asset harmonic withstand capabilities EPRI Reports: • Electromagnetic Transient-Type Transformer Models for Geomagnetically-Induced Current (GIC) Studies (3002000832) • Analysis of Geomagnetic Disturbance (GMD) Related Harmonics (3002002985) © 2014 Electric Power Research Institute, Inc. All rights reserved. 12 Together…Shaping the Future of Electricity © 2014 Electric Power Research Institute, Inc. All rights reserved. 13
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