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System Voltage Planning

System Voltage Planning Brian Moss PD / Transmission Planning Transmission Planning Overview October 30, 2007. System Voltage Planning. Nuclear LOCA Voltage Studies (February)

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System Voltage Planning

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  1. System Voltage PlanningBrian MossPD / Transmission PlanningTransmission Planning OverviewOctober 30, 2007

  2. System Voltage Planning • Nuclear LOCA Voltage Studies (February) • Identifies future nuclear switchyard voltage deficiencies by performing LOCA simulation coupled with contingency analysis on system planning models • Determines minimum nuclear switchyard voltage limits, used to create generator voltage schedules and the TCC’s SCADA/RTCA alarm setpoints for the current year • Annual System Voltage Screening (Spring) • Identifies future voltage deficiencies by performing contingency analysis on system planning models • Annual System Voltage Analysis (Fall) • Identifies existing voltage deficiencies by reviewing the past year’s system voltage performance using PI data System Voltage Planning

  3. System Voltage Planning • Annual Transmission Capacitor Optimization (Fall) • Identifies optimal sites for capacitor placement to mitigate voltage deficiencies • Annual System Voltage Optimization (Fall) • Identifies transmission transformer tap setting and switched capacitor control setting adjustments to improve system voltage performance • Seasonal System Voltage Optimization • Creates “Generator Voltage Schedules” to provide efficient utilization of system generator voltage support, while maintaining transmission system voltage guidelines and minimum nuclear switchyard voltage limits • Completed and distributed at least 2 weeks prior to start of each season (Spring, Summer, Fall, Winter) System Voltage Planning

  4. Nuclear LOCA Voltage Studies • Nuclear Generation Inputs (January) • Latest minimum grid voltage requirements, as well as shutdown and LOCA auxiliary loads for each unit • Normal, Pre-LOCA Base Cases • Latest summer peak and valley models • Sister Unit Off-Line, Pre-LOCA Base Cases • Dispatch variations of normal, pre-LOCA base cases • Outage non-LOCA unit at the nuclear station being evaluated • System redispatched to replace outaged unit and serve its shutdown auxiliary load System Voltage Planning

  5. Nuclear LOCA Voltage Studies • Pre-LOCA Contingencies • Pre-LOCA, post-contingency scenario solved to a new steady-state with all equipment (capacitors and transformer taps) allowed to adjust per their control settings System Voltage Planning

  6. Nuclear LOCA Voltage Studies • LOCA Event • Simulate the initiation of a LOCA event on each pre-LOCA, post-contingency scenario • LOCA unit is outaged and LOCA auxiliary load is applied • Energy is imported from off-system to replace outaged unit and serve its LOCA auxiliary load • In order to estimate the switchyard voltage immediately following the LOCA event, transformer taps and capacitors are prevented from adjusting in the solution due to their long (30+ seconds) response times • Post-LOCA Voltage Evaluation • Determine the “LOCA Voltage Drop” (post-LOCA minus pre-LOCA, post-contingency nuclear switchyard voltage) • Post-LOCA voltages are only supported by the pre-LOCA, post-contingency capacitor MVAr support and the generator MVAR output of all remaining on-line units adjusting to maintain their generator voltage schedules in response to the LOCA event System Voltage Planning

  7. Nuclear LOCA Voltage Studies • Pre-Contingency Voltage Limits • Equal to minimum grid voltage requirement plus the worst-case (maximum) “LOCA Voltage Drop” • Real-time nuclear switchyard voltage required to maintain minimum grid voltage requirement in the event of the worst-case, pre-LOCA contingency followed by the initiation of a LOCA event • Generator Voltage Schedule Creation • Maintains minimum nuclear switchyard voltage limits equal to the pre-contingency voltage limits plus 2 kV • Additional 2 kV provides an added margin of system voltage support to the system above the required pre-contingency voltage limits System Voltage Planning

  8. Generator Voltage Schedules • Pre-Optimization Generator Voltage Schedule (GVS) Cases System Voltage Planning

  9. Generator Voltage Schedules • Pre-Optimization GVS Cases (continued) • Latest summer peak, winter peak, or valley models • Add transmission projects installed and in-service for the majority of the season • Capacitors (including portables) • Transformers (including in-service system spares) • Transmission lines (including significant outages) • Generator maintenance outage schedule • Outage generators which are scheduled to be off-line for maintenance during the majority of the season • Typical dispatch with reduced (75%) generator MVAr capability • Provides a margin of additional MVAr capability not required to support the provided generator voltage schedules under typical conditions • Allows generators to follow the provided generator voltage schedules under varying system conditions • Firm, planned transactions System Voltage Planning

  10. Generator Voltage Schedules • Optimal Power Flow (OPF) Solution • Objectives • Minimize active (MW) and reactive (MVAR) power losses • Constraints • Power balance equation • Transmission system voltage guidelines • Minimum nuclear switchyard voltage limits • Calculated in “Nuclear LOCA Voltage Studies” • Nuclear generator bus voltage limits • Voltages limited by nuclear station auxiliary system design • Important 100 kV bus voltage limits • Significant load service points • Duke MVAr interface flow constraint • Prevent schedules from relying on off-system MVAr import (0 MVAr net interchange) • Generator voltage limits • Merchant (IPP) MVAr support requirements System Voltage Planning

  11. Generator Voltage Schedules • Optimal Power Flow (OPF) Solution (continued) • Transformer tap settings are fixed • Tap settings are optimized in “Annual System Voltage Optimization” and would not be adjusted seasonally • Controls • Generator voltage schedules (MVAr output) • Capacitors (MVAr voltage support) • Generator voltage schedules, Beckerdite SVC voltage setpoint, and reactors’ status are extracted from the optimized cases and provided to the SOC, TCC, and the generation operators as a guide for maintaining optimal system performance under typical seasonal Max Load, Peak, Off-Peak, and Weekend conditions System Voltage Planning

  12. System Voltage Planning

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