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Composite Load Model Implementation Update

Composite Load Model Implementation Update. Craig Quist, PacifiCorp June 20, 2012 M&VWG Meeting. Status at last TSS Meeting (April 25-27, 2012). WECC got responses from all but one area coordinator, in some cases default data was submitted. 2012 hs base case would be used,

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Composite Load Model Implementation Update

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  1. Composite Load ModelImplementation Update Craig Quist, PacifiCorp June 20, 2012 M&VWG Meeting

  2. Status at last TSS Meeting(April 25-27, 2012) • WECC got responses from all but one area coordinator, in some cases default data was submitted. • 2012 hs base case would be used, • dyd was initially released for current load model, • dyd with long ID was available shortly thereafter; • Staff needed 2012 ls to be posted before full data is available. • Letter with a recommended report format was distributed. • PTI impacts, RV 32/33 is being modified to accommodate 5000 composite load bus models. • Reports due to PacifiCorp (CQ) by May 15, 2012; • Report to TSS/RS to distributed in July, about one month ahead of fall meetings.

  3. Composite Load Model – Status Update… • To date, reports have been received from TID, CAISO, NVE, SNPD, SCE, APS, PG&E, SRP and PAC. Initial Conclusions & Recommendations… • Turlock Irrigation District (TID) • Post-Composite Load Model WCA Results report the newly created bus, not the original bus. This can be confusing. It is recommended that the results being displayed report the original bus, not the new one. • Post Composite Load Model log files suggest there are multiple iterations of the fault being applied. It is recommended to determine if this is true and why it might be happening if it is not the desired results.

  4. Composite Load Model – Status Update… • Turlock Irrigation District (TID) [cont.] • The Post-Composite Load Model Transient Stability study took almost twice the time as compared to the Pre-Composite Load Model study. This may or may not be due to the suspected iterations mentioned above. This may or may not be a GE PSLF issue. Transient Stability studies take too long currently so it is recommended to work with GE to streamline the process to keep the length of time to a minimum. • The results of the Post-Composite Load Model Study were comparable to the Pre-Composite Load Model Study. Additional buses reported to have a “violation”. Implementing the load shedding scheme for TID did not change this result.

  5. Composite Load Model – Status Update… • California ISO (CAISO) • The composite load model works and gives reasonable results • For some contingencies, the system performance in the simulations was the same with the interim load model and with composite load model. • For other contingencies, composite load model showed tripping of some parts of the loads (or reduction in load). • The contingencies that showed load tripping not necessarily were the ones with highest flow on the transmission lines that were out with contingencies.

  6. Composite Load Model – Status Update… • California ISO (CAISO) [cont.] • Composite load model shows significant difference in the results compared with the interim load model in case of a fault on a bus that has large load connected to it (for example Valley 500 kV). In this case, large amount of load was tripped in the composite load model case both by under-frequency relays and because of motor stalling.

  7. Composite Load Model – Status Update… • NV Energy (north) • Transient Study Results: Transient Analysis was performed on the pre and post Composite load 12HS4 base cases. The same contingencies were run in transient analysis for WECC paths 16, 32 and 76. NVEN-A64 did not observe any adverse voltage or frequency impacts from the new composite load model. • Conclusions: At this time NVE-A64 is familiarizing itself with the composite load model and further testing and analysis will be required to identify and understand performance issues. This preliminary evaluation has not resulted in any significant problems.

  8. Composite Load Model – Status Update… • NV Energy (South) • Conclusion: Two WECC Transmission Paths were considered in the transient stability analysis, namely (a) WECC PATH 35 (Red Butte – Harry Allen 345 kV Line) and WECC PATH 77 (Crystal – Harry Allen 345/230 kV XFMR Bank). Two system components that limit the capacity of the transmission paths were independently faulted to simulate a transient response. The transient responses were monitored at selected load buses near the fault location. From the simulation results obtained, no improper system responses were observed. • Recommendations: If the results obtained from all participants, it might be necessary to define fault type and point of monitoring. For instance, faulting a transmission path and observing generator bus and load bus responses.

  9. Composite Load Model – Status Update… • Public Utility District No.1 of Snohomish County • SNPD has conducted a composite load model testing for the 2012 HS4 case by evaluating Category B and C contingencies against the WECC System Performance Criteria. The contingencies for the testing were developed in accordance with the NERC Table I and the evaluation was similar to a TPL type study. The findings of the composite load model testing are summarized below. • Bus voltages and frequencies were within the WECC System Performance Criteria. • In most cases, during a fault, the composite load model had more buses with greater voltage dips than the current 20% induction motor model. However, after the fault had been cleared, the bus voltages recovered properly.

  10. Composite Load Model – Status Update… • Southern California Edison • Transmission Path or Facility Evaluated: Path 26 & PDCI at their WECC approved ratings • Study Assumptions: This study was based on the 2012 HS4A approved operating base case. The base case was modified to model System Operating limit (SOL) at Path 26 (Northern CA- Southern CA) and PDCI. • Transient Stability Case Results: • A notable finding for the Composite load model is that after a faults clears, the voltage at key buses tends to overshoot compared the MOTORW bus voltage results. • The composite load model voltage at post transient (i.e. 10 sec. – 30 sec.) after settles at a new higher voltage than the base voltage. This observation may be because there at loads being dropped. • An observation was made that in area 11 ( El Paso) there is under-voltage tripping with composite load model and not with MOTORW model. The reason for this is that the model monitors the “new” lower voltage of the bus (created by the dyd initialization) which is different from what the MOTORW model does.

  11. Composite Load Model – Status Update… • Southern California Edison (cont.) • Conclusion: • Composite load model seems to have some differences with the existing interim model which need further studying. Although no WECC voltage violations were identified for this study, further evaluations is recommended. • Recommendations: • Perform further evaluations for more base case conditions.

  12. Composite Load Model – Status Update… • Arizona Public Service • Transient Stability Case Results: • A notable finding for the Composite load model is that after a faults clears, the voltage at key buses tends to overshoot compared the MOTORW bus voltage results. • The composite load model voltage at post transient (i.e. 10 sec. – 30 sec.) after settles at a new higher voltage than the base voltage.

  13. Composite Load Model – Status Update… • Pacific Gas & Electric • Transmission Path or Facility Evaluated: Path 66 (COI) • Study Assumptions: This study was based on the 2012 HS4A approved operating base case. The base case was modified to model System Operating Limit (SOL) at Path 66 (COI) and Path 26 (Northern CA – Southern CA). • Model the Table Mt – Rio Oso 230kV line Reconductoring Project with estimated in-service date of June 2012. This project will increase line ratings (SN=SE=604MVA) of the Table Mt – Rio Oso #1 230kV line and the Colgate – Rio Oso #1 230kV line. • Model Path 66 north-to-south flow at one of the nomogram operating points (4,700MW with northern CA hydro generation at 79%), • Model the maximum net output of 101.5 MW at Hatchet Ridge Wind Farm, and 673.7 MW at Colusa generation station. • Model Path 26 north-to-south flow at the path rating of 4,000MW.

  14. Composite Load Model – Status Update… • Transient Stability Cases Results: • Composite load model could significantly increase transient voltage dip, but it would have insignificant impact on minimum frequency at a load bus. (See Attachment 1 and 2.) • The transient voltage dip could be more than 30% that would violate the WECC Disturbance Performance Criterion (TPL-001-WECC-CRT-2) for Category “C” contingency. (See Attachment 1.) • Transient voltage dip at load buses in Area 10 (New Mexico) could be more than 30% for PDCI bipolar outage, or Palo Verde G-2 outage. • Transient voltage dip could be more than 30% at the following load buses in Area 22 (San Diego) and Area 24 (SCE) for San Onofre G-2 outage. 3. The above transient voltage dips are below 20% for less than 40 cycles that would still meet the WECC Disturbance Performance Criterion (TPL-001-WECC-CRT-2) for Category “C” contingency. (See Attachment 4.)

  15. Composite Load Model – Status Update… • Transient Stability Cases Results (cont.) • Study results also show instability for some small generators (9.11kV units) in Northern California for loss of the Round Mt - Table Mt #1 and #2 500kV line, or loss of the Table Mt – Tesla and Table Mt – Vaca Dixon 500kV lines. Further analysis would be needed to evaluate whether the instability is caused by bad generator data or composite load model. • Sensitivity cases were also run on 12hs4a base case modeling COI north-to-south flow at 4115MW and Path 26 north-to-south flow at 3527MW. Sensitivity cases results show that a decrease on COI north-to-south flow would improve transient voltage dip at load buses in Area 10 for PDCI bipolar outage. The results also show that a decrease on COI north-to-south flow would not improve transient voltage dip at load buses in Area 10 for Palo Verde G-2 outage, and at load buses in Area 22 and 24 for San Onofre G-2 outage. (See Attachment 3.)

  16. Composite Load Model – Status Update… • Conclusion: Composite load model could significantly increase transient voltage dip that would violate the existing WECC Disturbance Performance Criterion (TPL-001-WECC-CRT-2). A decrease on COI north-to-south flow would not improve the transient voltage dips in New Mexico for Palo Verde G-2 outage, and in Southern California for San Onofre G-2 outage. • Recommendations: Re-evaluate transient voltage dip requirement in the existing Disturbance Performance Criterion (TPL-001-WECC-CRT-2).

  17. Composite Load Model – Status Update… • Salt River Project • Conclusion: Phase 1 of the composite load model has minor impact on first voltage swing than current load model. • Recommendations: Will wait to make recommendation when phase 2 of the composite load model is complete and ready to be tested.

  18. Composite Load Model – Status Update… • PacifiCorp Composite load modeling efforts (PSS/E) have been initiated to review: (1) composite load model – performance evaluation, and (2) simulation of previous system disturbance (southern Utah, MidValley 138 kV, etc.) • Internal Composite Load Model – Performance Evaluation • In the study we have compared different model settings to help us to understand what will be the impact to our Available Transfer Capability for this new load model in the future. • Based on this study, the performance of the Composite Load Model, which provided by WECC, is more closer to existing model (type 1 in this document) or even better result.

  19. Composite Load Model – Status Update… 1. Internal Composite Load Model – Functionality (cont.) • Model type 4 (see below definition) has the worst voltage result (slow recovering, post transient voltage deviation), since 3 phase motor tripping had been disabled and allowed single phase motor stall. • Model type 5 (allow 3 phase motor tripping and single phase motor stall) might be the future load model WECC wants to use. • If WECC choose to use the type 5 model or any other model settings other than WECC provided, then our suggestion should be that the existing Performance Criteria needs to modify to avoid reducing existing path transfer capability. • We need to evaluate the SOL rating for each major path by using different model setting to verify if there is any suggestions to WECC for changing the Performance Criteria. It has been also noticed that the only local buses will be affected by this new model, remote buses may not have the voltage deviation like local buses do. More results can be found in Appendix.

  20. Composite Load Model – Status Update… • Internal Composite Load Model – Functionality (cont.) • Five model settings had been compared for the noted contingencies, • Model type 1: Original load model • Model type 2: Composite Load Model (provided by WECC, enabled 3 phase motor load tripping and restore, and also blocked single phase motor stalling) • Model type 3: Composite Load Model with setting modification, disable 3 phase motor load tripping and keep blocking single phase motor stalling. • Model type 4: Composite Load Model with setting modification, disable 3 phase motor load tripping and unblocking single phase motor stalling. • Model type 5: Composite Load Model with setting modification, enable 3 phase motor load tripping and restore, and unblocking single phase motor stall.

  21. Composite Load Model – Status Update…

  22. Composite Load Model – Status Update… • PacifiCorp (cont.) • Simulation of Previous Disturbances • August 8, 2008, St. George – Utah, system disturbance was simulated • Phase-to-Phase(-to-Ground) fault occurred on a 69 kV line, close to the bus • After approximately 48 cycles, the fault developed into a 3-phase fault • 3-phase fault was cleared after approximately 12 cycles

  23. What was Observed? • Voltage dropped between 72-80% during the initial fault • Minimum voltage of 60% during the three phase fault • Slow voltage recovery due to heavy motor load

  24. What was Simulated? 70% induction motor load Composite Load Model Note: High Speed Switching appears to be an error in the SGSVC Model

  25. Differences Between Composite Load Model and 70% Motor Load Quicker voltage decline with composite load model

  26. Differences Between Composite Load Model and 70% Motor Load Higher voltage during the fault

  27. Differences Between Composite Load Model and 70% Motor Load Quicker voltage recovery

  28. Differences Between Composite Load Model and 70% motor load Higher post-contingency voltage

  29. Why the Differences? • Differences, mostly due to load tripping during the fault: • Composite load model is tripping loads at certain voltage levels • Composite load model is restoring loads quickly after the voltage recovers • Composite load model is assuming a permanent loss of load

  30. Load Profile During the Fault 70% induction motor load Composite Load Model

  31. Load Profile During the Fault 70% induction motor load Composite Load Model More load dropping during the fault

  32. Load Profile During the Fault Less load post- contingency

  33. Composite Load Model Motor Behavior During a Fault Negligible speed deviation of the motor during a fault

  34. Composite Load Model – Status Update… • PacifiCorp will be performing further Composite Load Model analysis relative to previous system disturbances, including: • August 8, 2008, St. George – Utah • July 28, 2009, MidValley 138 KV • Others as needed.

  35. Composite Load Model Implementation – Going Forward… • PSLF Users: • Initial PSLF User study findings submitted to PacifiCorp (CQ) by 6/15/2012. • PSLF User composite load model study findings will be compiled and submitted to M&VWG • Where do we go from here… • PSS/E Users: • PacifiCorp initialPSS/E composite load model study findings compiled and submitted to M&VWG. • GE PSLF Ver. 18.x will need be modified to write out the composite load model data correctly in the “dyd” file.  • PSS/E Rev. 32.x program is being modified to accommodate 5000 composite load bus models to fully test model.  • M&VWG: • Review initial study findings. • Potential updatesto Composite Load Model software and/or data • Rewind process, including analysis by PSS/E users

  36. Questions

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