(c) IRD 2002 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 Bethesda, MD

(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 post- restoration 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 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. Initial Sources of Power (cont.)

(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 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 GSU XFMR SE Gen. AUX XFMR Standby XFMR GSU Taps (5 no-load) AUX Taps (5 no-load) Standby Taps (5 on-load) System Bus (345 kV) Large Induction Motors (350 to 6000 Horse Power) AUX Load Bus (4.16 kV) AUX Load Bus (4.16 V) Generator Bus (18.0 kV) Generator: Max 185 MW Min 90 MW Normally Open

(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 GSU XFMR CT Gen AUX XFMR Local XFMR GSU Taps (6 no-load) AUX Taps (5 no-load) XFMR Taps (5 on-load) System Bus (115 kV) Local Load (7.5 MW) AUX Load (150 kW) Local Load Bus (34.5 kV) AUX Load Bus (480 V) Generator Bus (13.8 kV) Twin Generators (42 MVA, 85% PF)

(c) IRD 2002 A Typical Black Start System

(c) IRD 2002 Cumulative Starting & Running Auxiliaries

(c) IRD 2002 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