SPP REPORT ON MAY 26, 2000 TLR EVENT

Transcription

1 SPP REPORT ON MAY 26, 2000 TLR EVENT On May 26, 2000, SPP initiated a TLR on the CraAshValLyd flow gate, #5008, that proceeded to the point of firm curtailments. NERC asked SPP to prepare a report on this event addressing thirteen bullet points associated with an initial investigation format contained in the May 30, 2000 draft Transmission Loading Relief Investigation Procedure document. The following is the response to NERC submitted by SPP for the May 26 CraAshValLyd TLR event addressing each of those points. 1. Description of purpose/cause of curtailment The purpose of the TLR initiated by SPP on May 26, 2000 was to relieve the Craig Junction-Ashdown West 138 kv transmission line (Monitored Element) of excessive line flows that would have resulted from an unexpected loss of the Valiant-Lydia 345 kv transmission line (Contingency Element). This facility is modeled as a flow gate labeled CraAshValLyd (flow gate # 5008) in the IDC for which an Outage Transfer Distribution Factor is calculated based on the loss of the Contingency Element. 2. Facility/flow gate limitations and flows at the time the TLR was initiated. The Monitored Element had an emergency rating of 210 MVA. This rating was based on an 800 Amp wave trap with a 110% 4-hour emergency loadability factor located at the Craig Junction end of the line. The post-contingency flow on the Monitored Element had reached 236 MW at the time TLR Level 5 was initiated. 3. TLR levels, timing and relief requested amounts Attachment A contains the NERC TLR log for the May 26 TLR event on the CraAshValLyd flow gate. All times are in CST. 4. Transmission and Generation outages or changes from prediction that may have contributed. Generation outages in and around the SPP region contributed significantly to the abnormally high flows on the Monitored and Contingency Elements. CSWS had a total of 1,123 MW of generation, located south of the flow gate, off-line on forced outage or on a forced deration on the 26 th. The following CSWS generators were derated or on forced outage on the 26 th. Generator Capacity CA Operator Outage Type Knox Lee #2 31 CSWS Forced Lieberman #4 110 CSWS Forced Pirkey 675 CSWS Derated to 132 MW Welsh #1 528 CSWS Derated to 143 MW Welsh #2 528 CSWS Derated to 474 MW

2 SPP Report on May 26, 2000 TLR Event Entergy also experienced generation outages that may have contributed to the heavy flows on the flow gate. The following Entergy generator outages were identified. Generator Capacity CA Operator Outage Type Sabine #3 420 EES Planned Sabine #4 530 EES Planned Willow Glen #3 500 EES Planned Little Gypsy #3 530 EES Planned Nine Mile #4 730 EES Planned Waterford #1 411 EES Planned Sterlington #7ABC 195 EES Unplanned Rex Brown #4 231 EES Unplanned Flows across the East HVDC tie into ERCOT also contributed to the heavy loading on the flow gate. Earlier in the afternoon flows had been up to over 500 MW into ERCOT from SPP. CSWS re-dispatched generation in ERCOT to serve load in the SPP Region as the event progressed, effectively reducing flows into ERCOT and on the flow gate. By 1500 CDT, the flows into ERCOT had been reduced to less approximately 250 MW. The combination of high loads and generation outages created a heavy north-to-south flow bias that severely affected the CraAshValLyd flow gate. 5. Procedures implemented prior to curtailment. CSWS had already begun to re-dispatch generation prior to SPP issuing the initial TLR notifications in an attempt to delay TLR curtailments. 6. Complete Transaction Curtailment lists & comparison to IDC Transaction Lists both before and after curtailment. Attachment B contains the TLR Level 5 curtailment list issued by the IDC for relief on the CraAshValLyd flow gate on May Known transactions not in the IDC & actions taken. SPP assumed that all transactions were in the IDC and was not aware of any transactions flowing that were not in the IDC. 8. SCIS or other system messages No additional messaging for this TLR was posted other than that through the IDC. 9. State Estimator snapshots and security analysis including any contingency analysis or stability analysis along with any other recorded data indicating need for Transmission Loading Relief Attachment C shows a screen print of Flowgate Detail from the SPP EMS used to monitor current and anticipated flows on the SPP flowgates. This particular print was made just after the TLR Level 5 was issued and clearly indicates that the flow gate SPP 2 11/3/00

3 SPP Report on May 26, 2000 TLR Event loading, 236 MW, was beyond its emergency limit of 210 MW. The EMS time stamp of 14:23:14 is CDT. Results from other periodic analyses of pre-contingency and postcontingency flows from the EMS can be found in the NERC TLR Report in Attachment A. 10. ATC limitations before, during and after the TLR event. SPP had observed firm ATC limitations on the CraAshValLyd flow gate prior to May 26 and had declared TLR Level 5 events on May 12 and 25. As a result of continued limitations, SPP had stopped accepting reservations for firm service affecting the flow gate since May 12. During this event, no ATC was available on the CraAshValLyd flow gate. After the event, non-firm ATC was available but only for off-peak periods. 11. Description of actions taken to avoid future curtailments Other than the expedited return to service of generators south of the flow gate, no actions were identified that would prevent future TLR events on the CraAshValLyd flow gate. For the period that the generators were expected to be out of service, SPP declined firm transmission service that affected the CraAshValLyd flow gate greater than 5%. 12. Re-dispatch actions taken. CSWS began re-dispatching from generation south of the flow gate to generation north of the flow gate before the TLR reached Level 2C in an effort to delay TLR curtailments as long as possible. As line flows increased and the TLR progressed into curtailments of both non-firm and firm transactions, CSWS continued to re-dispatch throughout the day by bringing on-line units south of the flow gate that were normally off-line. CSWS estimates that by the time of the afternoon peak hour, it had achieved 350 MW of generation re-dispatch within SPP and an additional 300 MW of re-dispatch across the East HVDC tie from CSWS ERCOT to CSWS SPP. 13. If firm transaction curtailment took place, description of Transactional Contribution Factor calculation and results as well as how necessary relief was obtained through network service and native load contribution. Because system conditions on the 26 th were essentially the same as those on the 25 th, SPP used the same Transactional Contribution Factor (TCF) calculation process that was used for the TLR Level 5 event on the CraAshValLyd flow gate on the 25 th. It is presented again here in its entirety. SPP used the Transactional Contribution Factor (TCF) calculation process that has been recommended by the NERC Parallel Flow Task Force (PFTF) and endorsed by the Security Coordinator Subcommittee (SCS) and Market Interface Committee (MIC) to determine the amount of relief required by native load and network service. This process identifies generators serving native load and network service that significantly contribute to the loading of the constraint and allocates a proportionate amount of the necessary firm relief to the control areas where those generators are located. The NERC Distribution Factor Task Force (DFTF) was charged by the SCS to produce a matrix for use during the summer of 2000 by the Security Coordinators that would indicate the proportion of relief allocated to native load and network service. Because the matrix was not yet available, SPP used the results of an example TCF calculation SPP 3 11/3/00

4 SPP Report on May 26, 2000 TLR Event already prepared for the CraAshValLyd flow gate that has been included in reports given to the SCS and MIC by the PFTF. The example calculation was updated to reflect the existing generator statuses as shown in the table below. Native Load Service (per generator basis) with Contribution Factors > 5% GLDF Generator Energy on Generator-to-CA Load (%) Loading Flow gate CSWS_COM1-1PW13.8 CSWS CSWS_COM2-1PW13.8 CSWS CSWS_COM3-PPW13.8 CSWS CSWS_MIDCON4 138 CSWS CSWS_NES CSWS CSWS_NES2-1PB22.0 CSWS CSWS_NES3-1PB22.0 CSWS CSWS_NES4-1PB22.0 CSWS CSWS_RSS1-1PT24.0 CSWS CSWS_RSS2-1PT22.0 CSWS SPP 4 11/3/00

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6 NERC TRANSMISSION LOADING RELIEF (TLR) PROCEDURE LOG FILE SAVED AS: Q:\SECURITY DOCUMENTS\NERC TLR Log\SPP_ X INCIDENT : SPP_ DATE: 05/26/00 IMPACTED SECURITY COORDINATOR : SPP ID NO: 1002 I N I T I A L C O N D I T I O N S Limiting Flowgate (LIMIT) Rating Contingent Flowgate (CONT.) ODF Craig Junction-Ashdown West 138 kv 210 Valliant - Lydia 345 kv 24% TLR Levels Priorities 0: TLR Incident Canceled NS Service over secondary receipt and delivery points 1. Notify Security Coordinators of potential problems. NH Hourly Service 2a, 2b, 2c: Halt additional "contributing" transactions. ND Daily Service 3: Curtail Non-firm transactions (state priorities being curtailed). NW Weekly Service 4. Reconfigure and redispatch to continue firm transactions if needed. NM Monthly Service 5: Curtail Firm Transmission Service. NN Non-firm imports for native load and network customers from 6: Implement emergency procedures. non-designated network resources F Firm Service T L R A C T I O N S TLR 3,5 LIMIT CONT. LEVEL TIME Priority MW Present Post-Cont. Present C O M M E N T S A B O U T A C T I O N S Curtail Flow Flow Flow Issued TLR Level Re-issued TLR Level Re-issued TLR Level 1 2c Re-issued TLR as Level 2c, hold 2c Re-issued TLR Level 2c ND Re-issued TLR as Level 5, requested 26 MW of relief, curtailed 2non-firm schedules providing 2 MW of relief and 20 firm schedules providing 24 MW of relief F Re-issued TLR Level Re-issued TLR Level Re-issued TLR as Level 3 - Firm schedules reloaded Re-issued TLR Level Re-issued TLR Level Re-issued TLR Level Re-issued TLR Level 3 2c Re-issued TLR as Level 2c, allowing non-firm schedules to start Re-issued TLR as Level 1, 7 schedules not allowed to reload due to other TLR's in progress Released TLR

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