Power System Restoration (Black Start) Black Start Panel Session IEEE PES Summer Meeting Chicago, Illinois July 23, 2002 M. M. Adibi IRD Corp., P.O. Box 34901 Bethesda, MD 20827 madibird@aol.com (c) IRD 2002 Pre-disturbance Conditions • • • • Peak load, low voltage, large network loads Light load, high voltage, no cycling units Long weekends (Labor Day) Scheduled maintenance (c) IRD 2002 Post-disturbance Status • Complete collapse with no interconnection assistance • Partial collapse with interconnection assistance • Power system beak-up (System Islands) (c) IRD 2002 The Three Restoration Stages • Preparation stage, actions are time critical (1-2 hours) • System integration, achieving postrestoration target system (3-4 hours) • Load restoration, minimizing MWH (8-10 hours) (c) IRD 2002 Initial Sources of Power • Combustion Turbines, Start-up in 5-15 min., probability of success 30 –50%, limited under-excitation, use low voltage links • Run-of-the-River Hydro, Pumped- Storage, Start-up 5-10 min., probability of success is high, can use HV links (c) IRD 2002 Initial Sources of Power (cont.) • Once-through Units with full-load rejection, probability of success 20-80%, maximum elapsed time to min. loading 30 minutes, coordinated loading problem to min. gen. • Low Frequency Isolation Scheme (LFIS) and Controlled Islanding, probability of success is low. (c) IRD 2002 Initial Critical Loads • Cranking drum-type units, high priority • Pipe-type cable pumping plants, high priority • Transmission and distribution stations, high to medium priority depending on locations • Industrial load, medium to low priority (c) IRD 2002 Black Start Steam Electric Units (Drum Type Boilers) • • • • • Are base load units, supply large portions of demand Max. elapsed time for hot re-start is 30-45 minutes Min. elapsed time for cold start-up is 3-4 hours Are remote from the load centers Need cranking power 5-7% of their ratings • Min. generation 25 to 30 % (c) IRD 2002 One-Line diagram of a SE Unit System Bus (345 kV) GSU Taps (5 no-load) GSU XFMR Generator Bus (18.0 kV) Generator: Max 185 MW Min 90 MW AUX Taps (5 no-load) SE Gen. AUX XFMR Standby Taps (5 on-load) Standby XFMR Normally Open AUX Load Bus (4.16 V) AUX Load Bus (4.16 kV) Large Induction Motors (350 to 6000 Horse Power) (c) IRD 2002 Combustion Turbine Units (cranking source) • • • • • • Are peaking units, supply daily peak load Cold start up within 5 – 10 minutes Possibility of successful start up is 1 in 3 Are close to the load centers Need small local cranking for start ups Hot restart within 2 – 3 hours (c) IRD 2002 One-Line diagram of the CT Unit System Bus (115 kV) GSU Taps (6 no-load) GSU XFMR Generator Bus (13.8 kV) Twin Generators (42 MVA, 85% PF) AUX Taps (5 no-load) CT Gen AUX XFMR Local XFMR XFMR Taps (5 on-load) AUX Load Bus (480 V) Local Load Bus (34.5 kV) AUX Load (150 kW) Local Load (7.5 MW) (c) IRD 2002 A Typical Black Start System (c) IRD 2002 Cumulative Starting & Running Auxiliaries 50 MVAR Generation 40 Start-up MVAR Required 30 20 10 0 -10 Running MVAR Required -20 0 1 2 3 4 5 6 7 8 Motor Start-up Sequence (c) IRD 2002 9 10 11 12 13 14 Conclusions • Characteristics of steam units dictate parallel start ups (45 to 60 minutes) • SE units should be individually matched with black start CT units • Systems are sectionalized into subsystems, each at least having one SES & one CTS • Cranking operation uses generation, transmission and distribution facilities (c) IRD 2002 Recommendations • CT units should be able to absorb line & cable charging currents • CT units should be able to supply reactive power required for the start ups of large induction motors • Each black start operation should be planned, analyzed/simulated, field tested and then operators trained and exercised in its implementations (c) IRD 2002