FRCC System Restoration 2016 FRCC System Operator Seminar FRCC System Restoration 2 Training Objectives System Assessment Restoration Strategies Restoration Considerations Assessment of Elements System status Generation resources Transmission facilities System Assessment Generation Resources Identify Surviving Generators Stabilize Surviving Units Determine status of other generators Get start up power to off line units Initiate unit start ups Determine start up sequence Identify Surviving Generators Current loading level Location Connected load Boundaries of island Plant capabilities Unit stability region Stabilize Surviving Units Add additional load to stabilize Station load Distribution load Determine areas of separation May be difficult Location and size of islands may effect restoration strategy Status of Generation Lost During Event Damage incurred Type of unit and characteristics Determine Start Up Sequence Start-up sequencing is dependent on operation prior to event Surviving generation Outaged generation Offline generation Need to understand the Size Types State of operation going forward Determine Start Up Sequence Blackstart Capability and location Off-line Generation Status prior to event Type of unit Power requirements Start up times Nuclear plants Company obligations Determine Start Up Sequence Start Up Times (estimates) Hydro usually quickest Combustion Turbines Smaller CTs quick-start (10 minutes) Large CTs may take longer (up to 1 hour) Steam - Drum-type 1-20 hours away Steam - Super Critical 4-20 hours away System Assessment Transmission Facilities EMS/SCADA Operational? Identify Energized Facilities Identify Faulted Equipment Restoration Identify Facilities Energized EMS/SCADA Operational? 12 Are consoles up? Check data quality (watchdog, heartbeat, etc.) Are ICCP links valid? Determine Faulted Equipment Digital Fault Recorders (DFRs) Inspections by field personnel Relay targets in substations Smart Relays Identify Facilities Energized Breaker indications Open Permanent faults Out-of-Step conditions Temporary faults Closed De-energized line with no problem Faulted equipment that never cleared Equipment damaged after event Identify Facilities Energized Station Batteries Capabilities Hour until depletion Open-close-open operation Relay Reliability Adequate fault current available Most questionable relays Re-closing relays Station hot bus-dead line re-closing Identify Facilities Energized Underfrequency relays Status of what activated Sequence of restoration Facility status with regards to plan May not have what you thought you would May impact restoration plan Restoration Two general restoration strategies: All Open All circuit breakers at affected substations are opened Controlled Open Only circuit breakers necessary to allow restoration to proceed are opened All Open Strategy Can be accomplished by: Station Operators EMS/SCADA systems Advantages Simpler and safer configuration to restore Only breakers in restorations process will be closed Unlikely to experience inadvertent load pick-up Disadvantages Longer time to accomplish More breaker operations Controlled Open Strategy Advantages Less energy requirements Breakers not involved in sectionalizing and restoration remain closed Postpone operation of some breaker to later in process May be quicker Disadvantages Higher emphasis on isolation between restored and de-energized systems Restoration Methods Inside-Out / Blackstart Starts with formation of islands Utilizing blackstart generation Serve as basis for restoration plan Different methodologies Multiple Island Core Island Backbone Island Restoration Methods Outside-In / Outside Assistance Utilizes outside source of power to begin restoration Only option without blackstart Combination Utilizes both approaches Inside-Out - Blackstart Outside-In Neighbor Assistance Restoration Methods Restores transmission from outside source while building internal islands Islands can be connected to either other internal islands or outside interconnection points Priority vs. Critical Loads Priority Loads Highest priority Station service for nuclear facilities Service to facilities needed to restore the system Critical Loads Generating plant fuel supply depots Military facilities Law enforcement organizations Facilities affecting public health Public communication facilities Restoration Considerations Cold Weather Switching SF6 Breakers Temperature and pressure dependent Compressors and heaters supplied by AC power Breaker operability could be reduced to as short as 30 minutes Low pressure will block operation Restoration Considerations System Sectionalizing (Load disconnect) Regardless of strategy sectionalizing should occur Disconnect load and capacitors from transmission system Load should be restored in small blocks Open station and controlled distribution capacitors Help prevent high voltages Restoration Considerations Voltage Control Bulk Electric System maintained +/- 10% Maintaining voltages at minimum levels will reduce charging current Local load must be restored as transmission lines are energized to reduce voltages Station light and power Customer load Restoration Considerations Interconnecting Generating plants or stations with synchro scopes Phase angle should be 10 o or less Transmission Stability Only facilities expected to carry significant load should be energized Restoration Considerations Load/Frequency Control Small increments of generation and load Minimize frequency impacts Load pick-ups 5% total synchronized generating capability Example: You have 1000 MW of synchronized capacity maximum load pick-up is 50 MW Frequency maintained between Hz Regulate toward Hz Restoration Considerations Surge Impedance Loading The Surge Impedance Loading is the MW loading required to cancel the capacitance effect on the line. (VARS IN = VARS OUT) A line loaded below its SIL (MW) generates VARS A line loaded above its SIL (MW) absorbs VARS Restoration Considerations AGC Control Set AGC control to CFC (Constant Frequency Control) when islanded Set AGC control to TLBC (Tie Line Bias Control) when tied with the Interconnection When tied to the Interconnection, all actions go through the Reliability Coordinator (RC). RC might direct one system to remain on CFC and the other to go on TLBC Restoration Considerations Conditions to synchronize Voltage matched as close as possible Frequency close to identical Voltage phase angle within tolerance The goal in synchronizing two systems is to match frequency and phase angle so that there will be little or no transfer of energy between the two systems when the breaker is closed. Restoration Considerations Synchronizing Phase Angle must be within 40 Raise generation on the side with the smaller voltage angle. Lower generation on the side with the larger voltage angle. Remember, it is easier to adjust the smaller system than the larger system Restoration Considerations Voltage Magnitude when Synchronizing The greater the difference translates into a greater reactive power that will flow when the breaker is closed Angular difference between Running and Incoming Buses Incoming Bus Voltage 90180270360 Running Bus Voltage Restoration Considerations Matching Frequency when synchronizing The greater the difference translates into a greater real power that will flow when the breaker is closed Running Bus Frequency 60Hz Incoming Bus Frequency Hz SOS Discussion There is more I can add onto this such as: Island Identification Synchronous Control Isochronous control ETC. Currently at 29 slides, with questions this could be 45minutes to an Hour. Bob is working on a IncSys Tutorial PowerPoint to be taught as well. Let me know of suggested changes. Questions? 36