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Home My WebLink About2023-06-23 IMC Agenda and docs INTERTIE MANAGEMENT COMMITTEE (IMC) REGULAR MEETING AGENDA June 23, 2023 9:00 AM Alaska Energy Authority Board Room 813 W Northern Lights Blvd, Anchorage, AK 99503 To participate dial 1-888-585-9008 and use code 212-753-619# 1. CALL TO ORDER 2. ROLL CALL FOR COMMITTEE MEMBERS 3. PUBLIC ROLL CALL 4. PUBLIC COMMENTS 5. AGENDA APPROVAL 6. APPROVAL OF PRIOR MINUTES – May 5, 2023 7. NEW BUSINESS 8. OLD BUSINESS 9. COMMITTEE REPORTS A. Budget to Actuals Report B. IOC Report C. Operator’s Report 10. MEMBERS COMMENTS 11. NEXT MEETING DATE – July 28, 2023 12. ADJOURNMENT Alaska Energy Authority AK Intertie Budget to Actual Revenues and Expenses 07/01/2022 to 05/31/2023 Page 1 of 4 FY23 Approved Budget BUDGET 07/01/2022 - 05/31/2023 Actuals YTD Actuals as a % of Total Annual Budget OVER (UNDER) YTD Variance Revenue From Utilities AKI-GVEA 2,659,180 2,440,005 1,574,810 59%(865,195) AKI-CEA 405,435 384,158 384,158 95%- AKI-MEA 440,368 409,819 420,663 96%10,844 Total Revenue From Utilities 3,504,984 3,233,981 2,379,630 68%(854,351) Interest - - 53,681 0%53,681 Total Revenues 3,504,984 3,233,981 2,433,311 69%(800,670) Total Revenues 3,504,984 3,233,981 2,433,311 69%(800,670) 56200 Station Expenses Golden Valley Electric AK Intertie-Substation Electricity Usage - - 478 0%478 Golden Valley Electric Total - - 478 0%478 56600 Misc Transmission Expense Alaska Energy Authority AK Intertie-Cell Phone Comm. Svc. for Wx Monitorng 13,000 11,917 9,982 77%(1,934) AK Intertie-Miscellaneous Studies as Needed 546,000 500,500 - 0%(500,500) Alaska Energy Authority Total 559,000 512,417 9,982 2%(502,434) Golden Valley Electric AK Intertie-Private Line Telephone Service SCADA 10,000 9,167 3,936 39%(5,231) Golden Valley Electric Total 10,000 9,167 3,936 39%(5,231) 56601 Weather Monitoring Batteries Alaska Energy Authority AK Intertie-SLMS Support & Intertie Ground Patrol 140,000 128,333 106,850 76%(21,484) Alaska Energy Authority Total 140,000 128,333 106,850 76%(21,484) 56700 Rents Alaska Energy Authority AK Intertie-Alaska Railroad 700 642 1,500 214%858 Alaska Energy Authority Total 700 642 1,500 214%858 Matanuska Electric Association AK Intertie-Talkeetna Storage 7,200 6,600 6,000 83%(600) AK Intertie-Equipment Rental - - 102 0%102 Matanuska Electric Association Total 7,200 6,600 6,102 85%(498) 57000 Maintenance of Station Equip Chugach Electric Association AK Intertie-Teeland Substation 173,200 158,767 65,070 38%(93,696) Chugach Electric Association Total 173,200 158,767 65,070 38%(93,696) Golden Valley Electric AK Intertie-Healy, Cantwell, Goldhill 75,000 68,750 115,562 154%46,812 AK Intertie-SCADA Maint Healy, Cantwell, Goldhill 5,000 4,583 - 0%(4,583) AK Intertie-Cantwell 4S2 Switch Repair 156,000 143,000 33,112 21%(109,888) AK Intertie-Maint & Repaint Reactors Healy SVC Yd 80,000 73,333 4,472 6%(68,861) Golden Valley Electric Total 316,000 289,667 153,146 48%(136,520) Matanuska Electric Association AK Intertie-Douglas Substation 25,000 22,917 - 0%(22,917) Matanuska Electric Association Total 25,000 22,917 - 0%(22,917) 57100 Maint of OH Lines Golden Valley Electric AK Intertie-Northern Maintenance 100,000 91,667 63,914 64%(27,753) Golden Valley Electric Total 100,000 91,667 63,914 64%(27,753) Matanuska Electric Association AK Intertie-Special Patrols (Incl Foundation Insp) 10,000 9,167 488 5%(8,679) ALASKA ENERGY AUTHORITY AK INTERTIE BUDGET TO ACTUAL REVENUE AND EXPENSES FOR THE PERIOD 07/01/2022 THROUGH 05/31/2023 Page 2 of 4 FY23 Approved Budget BUDGET 07/01/2022 - 05/31/2023 Actuals YTD Actuals as a % of Total Annual Budget OVER (UNDER) YTD Variance ALASKA ENERGY AUTHORITY AK INTERTIE BUDGET TO ACTUAL REVENUE AND EXPENSES FOR THE PERIOD 07/01/2022 THROUGH 05/31/2023 AK Intertie-Southern Maint. (Incl Ground Insp) 140,000 128,333 4,153 3%(124,180) AK Intertie-Equipment Repair & Replacement 684,000 627,000 - 0%(627,000) Matanuska Electric Association Total 834,000 764,500 4,641 1%(759,859) 57102 Maint OH Lines-ROW Clearing AK Intertie-Northern ROW Clearing 400,000 366,667 20,961 5%(345,706) Golden Valley Electric Total 400,000 366,667 20,961 5%(345,706) Matanuska Electric Association AK Intertie-Southern ROW Clearing 500,000 458,333 525,520 105%67,187 Matanuska Electric Association Total 500,000 458,333 525,520 105%67,187 58306 Misc Admin AK Intertie-IMC Admin Cost (Audit, Meeting, Legal) 20,000 18,333 10,022 50%(8,312) Alaska Energy Authority Total 20,000 18,333 10,022 50%(8,312) 58401 Insurance Premiums Alaska Energy Authority AK Intertie-Insurance 25,000 22,917 22,183 89%(734) Alaska Energy Authority Total 25,000 22,917 22,183 89%(734) Total Total Expense 3,110,100 2,850,925 994,304 32%(1,856,621) Total Operating Expenses 3,110,100 2,850,925 994,304 32%(1,856,621) 71001 Total Expense, Budget Administrative Support Services 200,000 183,333 123,828 62%(59,505) Alaska Energy Authority Total 200,000 183,333 123,828 62%(59,505) Total Total Expense 200,000 183,333 123,828 62%(59,505) Total AEA Administration Expenses 200,000 183,333 123,828 62%(59,505) Total Expenses 3,310,100 3,034,258 1,118,133 34%(1,916,125) Surplus (Shortage)194,884 199,723 1,315,179 675%1,115,455 Page 3 of 4 Alaska Intertie FY23 Budget to Actuals Status Report for the Period 07/01/2022 through 05/31/2023 Budgeted Usage Actual Usage to Date GVEA MEA CEA TOTAL GVEA MEA CEA TOTAL MONTH MWH MWH MWH MWH MONTH MWH MWH MWH MWH Jul 32,301 1,918 - 34,219 Jul 10,865 2,252 - 13,117 Aug 36,741 1,968 - 38,709 Aug 19,648 2,239 - 21,887 Sep 37,596 1,951 - 39,547 Sep 21,418 2,080 - 23,498 Oct 40,739 2,003 - 42,742 Oct 35,865 2,205 - 38,070 Nov 35,783 2,269 - 38,052 Nov 16,159 2,213 - 18,372 Dec 35,761 2,455 - 38,216 Dec 16,826 2,535 - 19,361 Jan 35,543 2,139 - 37,682 Jan 13,942 2,363 - 16,305 Feb 30,397 2,018 - 32,415 Feb 36,444 2,162 - 38,606 Mar 33,294 2,171 - 35,465 Mar 20,752 2,355 - 23,107 Apr 38,537 1,906 - 40,443 Apr 13,294 2,132 - 15,426 May 33,177 1,867 - 35,044 May 15,603 2,247 - 17,850 Jun 38,652 1,811 - 40,463 Jun - - - - TOTAL 428,521 24,476 - 452,997 TOTAL 220,816 24,783 - 245,599 INTERTIE PROJECTED ENERGY USAGE TO DATE (MWH)412,534 INTERTIE ACTUAL ENERGY USAGE TO DATE (MWH) 245,599 Budgeted Operating Costs for the Period 2,850,925$ Actual Operating Costs for the Period 994,304$ (based on amended budget) Budgeted Usage Revenue for the Period 2,112,174$ Actual (Billed) Usage Revenue for the Period 1,257,467$ (budgeted rate * projected usage)(budgeted rate * actual usage) Estimated Budgeted Energy Rate per MWH 5.77$ (based on budgeted costs and usage) Annual Budgeted Energy Rate (Billed Rate)5.12$ Projected Actual Energy Rate per MWH 3.38$ (based on minimum contract value)(based on actual costs and usage) Page 4 of 4 Intertie Management Committee Meeting IOC Report June 9, 2023 1.Intertie Operating Committee a.On May 16 an underfrequency load shed event occurred. A preliminary report of the event was drafted by the southern controller, CEA, and is attached. Preliminary analysis shows an event at Healy 2 resulted in the loss of 45.8 MWs of generation. This loss of generation resulted in a frequency excursion to 59.06 Hz. Spinning reserves were able to bring frequency back up to 59.373 Hz before a trip occurred on multiple EGS units resulting in the loss of 46.68 MWs of generation. Frequency then dipped to 58.714 Hz before arresting and stage one underfrequency load shed was triggered at 59.0 Hz. Additional information on the event is available in the report. 2.System Studies Subcommittee a.The SSS presented an update on the sychrophaser project. Dates for when utilities would be ready to integrate sychrophaser data with EPG’s cloud-based system were still being determined. Once utility schedules can be determined, the contract can be finalized and executed. b.The SSS is finalizing the scope of work for the inverter-based resource (IBR) study and a study that looks at the impacts of upgrading the Northern Intertie to 230 kV. Once scopes are finalized, the studies will move forward. 3.SCADA & telecommunications Subcommittee a.An agreement between AEA and Chugach for Chugach to install AEA owned communication between Anchorage and Douglas is drafted and pending final approval. A copy of the agreement and the scope of work for the communication infrastructure is attached. The annual maintenance cost for the new communication infrastructure is estimated to be $20,000 and would go into the IMC’s annual budget. b.The subcommittee is looking into a project to extend communication between Douglas and Healy through a similar agreement with AEA. Preliminary scope is being developed for this project. 4.Operations, Maintenance & Scheduling Subcommittee a.Installation of marker balls is underway. The installation is anticipated to run through the middle of July. Draft 4 Event – Healy and EGS Trip Causing UFLS Date 05/16/2023 Time 13:13:40 Purpose This document describes the events leading to the underfrequency load shed event on 05/16/2023 and the sequential events that follow. Provided are the sequence of events from the SCADA systems of CEA, MEA, and GVEA. Introduction On 5/16/2023 an underfrequency load shed event occurred. Initially, a unit trip of Healy 2 caused frequency to drop, but not enough to cause load shed. While system was recovering, approximately 10 seconds later, six EGS units tripped and dropped frequency enough to cause stage 1 load shed to be activated. Event At 13:13:40, GVEA’s Healy 2 unit tripped which dropped system frequency to 59.1Hz. As system was recovering, at 13:13:48, six EGS units tripped in the span of 2 seconds in the following order: Unit 5, Unit 9, Unit 8, Unit 1, Unit 5, and with Unit 2 tripping at 13:13:50. This second event dropped frequency to 58.719 Hz causing Stage 1 Underfrequency Load Shed to occur. The EGS units tripped on overload because they were over their maximum output due to droop response to the Healy 2 trip. The sequence of events is shown visually in Figure 1. Figure 1. System Frequency with Sequence of Event Labels, Data Source is the CEA ITSS Tesla recorder. Draft 4 For the initial Healy 2 event, GVEA SCADA data shows that Healy 2 tripped 45.8 MW and then settled back up to 3.3 MW. Given the information GVEA provided, it is unknown at the time why the unit stayed online. The magnitude of the tripped unit’s power and the frequency deviation from the pre-event frequency was used to calculate Beta. The Railbelt beta was calculated to be 4.8 MW/0.1 Hz. CEA had a spin requirement of 26 MW and was purchasing 21 MW from GVEA. GVEA had a spin requirement of 12 MW, MEA had a spin requirement of 8 MW, and HEA had a spin requirement of 10 MW. From the Healy 2 trip, CEA responded with 16.3 MW, GVEA responded with 7.9 MW, MEA responded with 9.9 MW, and HEA responded with 11.5 MW. Prior to the load shed event, the total CEA unit response was 20.5 MW plus the 21 MW spin purchased from GVEA. CEA total spin was 41.5 MW meeting required spin of 26 MW. Total GVEA unit response was 37 MW, meeting their 12 MW required spin and the 21 MW spin for CEA. Total HEA unit response was 10.9 MW meeting their 10 MW required spin. Prior to the EGS units tripping, MEA had total unit response of 9.9 MW meeting their 8 MW required spin. It can be observed that hydro units were more responsive by the time the EGS units tripped since a longer time has passed from initial event. With all utilities providing primary frequency response, the Railbelt was in compliance with the requirement R3.2 of the AKBAL-002 standard to activate Contingency Reserve before Protection Reserve. At the time of the load shedding event, CEA was carrying 258 MW of load and shed 29.25 MW, 11.3%, of the total load. From the SCADA alarms, the following feeders were shed beginning at 13:13:51: Sub 20 Feeder 2 and 6, Sub 22 Feeder 5, 6, and 7, Sub 6 Feeder 7, Dowling Breaker 212 and 412, LaTouche Breaker 192, and Arctic Breaker 212. At 13:39:32, all feeders were confirmed closed and returned to normal. Power restoration was just under half an hour. MEA was carrying 101 MW of load and shed 9.95 MW, 9.9% of their total load. From MEA’s SCADA alarms, the following feeders were shed beginning at 13:13:51: TH415, MA415, MC415, MC425, MC445, MZ425, and MR435. At the time of writing this report, there was no reference for when feeders were closed back in. HEA was carrying 53.22 MW of load at the time. At this time, no information was available to the amount of load that was shed. GVEA system load or quantity of load shed was also not available for this report. CEA SCADA systems report ACE mode return to Tie Line Bias at 13:54:54, andMEA reports return to Tie Line Bias at 13:57:35. Data was not available for when GVEA or HEA returned to Tie Line Bias at the time of writing this report. Pre-Disturbance Generation Dispatch Table 1. Generation Dispatch for Railbelt Utility Unit MW Output Bus Voltage (KV; line- line) MW and kV Source Draft 4 CEA SPP 10 35.147 138.5 ITSS Tesla CEA SPP 11 37.609 138.1 ITSS Tesla CEA SPP 12 37.756 138.3 ITSS Tesla CEA SPP 13 36.235 138.8 ITSS Tesla CEA Sullivan 9 44.956 116.5 Plant 2A Unit 9 Tesla CEA Sullivan 10 offline offline Plant 2A Unit 10 Tesla CEA Sullivan 11 offline offline Plant 2A Unit 11 Tesla CEA Eklutna 1 18.51 12 Eklutna Hydro Tesla CEA Eklutna 2 16.28 12 Eklutna Hydro Tesla CEA MSESS 0.045 35.38 IGT Tesla CEA Bradley Lake 1 25.59 12.8 BRD Tesla CEA Bradley Lake 2 0.309 13.4 BRD Tesla CEA Fire Island 0.97 35.2 FIWF Tesla GVEA North Pole Unit 1 offline offline GVEA SCADA GVEA North Pole Unit 2 17.393 138.4 NPS Tesla GVEA North Pole Unit 3 offline offline GVEA SCADA GVEA North Pole Unit 4 offline offline GVEA SCADA GVEA Healy 1 25.554 139.31 GVEA SCADA GVEA Healy 2 45.8 139.31 GVEA SCADA GVEA BESS 0.165 138.54 ZNS Tesla MEA EGS T1 30.877 117.4 EGS Tesla MEA EGS T2 31.882 116.6 EGS Tesla MEA EGS T3 63.73 117.4 EGS Tesla HEA Nikiski offline offline NIK Tesla HEA HEA BESS 0.615 116.7 HEA BESS Tesla HEA Soldotna CT 44.923 116.7 SCT CT Tesla SVC MVAR Output Bus Voltage (kV; Line- Line) Source Teeland SVC 21.76 13.46 CEA SCADA Daves Creek SVC -5.3 116.6 CEA SCADA Soldotna SVC -20.4 16.3 CEA SCADA Table 2. System Load Draft 4 Utility System Load (MW) Source CEA 258.31 CEA SCADA MEA 101.01 MEA SCADA HEA 53.22 CEA SCADA GVEA N/A N/A Table 3. Air Temps Location Ambient Air Temperature Source SPP 48.30 F CEA SCADA Sullivan CC 49.06 F CEA SCADA Cooper Lake 43.10 F CEA SCADA Teeland 51.51 F CEA SCADA Table 4. CEA Units Available Spin Unit Spin Available SPP 10 6.833 SPP 11 1.391 SPP 12 1.244 SPP 13 2.785 Sullivan 9 2.6 Sullivan 10 offline Sullivan 11 offline Eklutna 1 0.957921 Eklutna 2 2.404446 MSESS 1.955 Bradley Lake 15 Fire Island - Purchased Spin 21 Total Spin 54.215367 SCADA Sequence of Events Date/Time Source Event 05/16/2023 13:13:40 HLS Tesla Healy 2 Trip 05/16/2023 13:13:44 MEA SCADA AGC: Frequency Excursion ACE Mode changed to CF Draft 4 05/16/2023 13:13:44 CEA SCADA AGC: Frequency Excursion ACE Mode changed to CF 05/16/2023 13:13:50 MEA EGSY Tesla GENERATOR 5 Breaker Open 05/16/2023 13:13:50 MEA EGSY Tesla GENERATOR 9 Breaker Open 05/16/2023 13:13:51 CEA SCADA Sub 20 Fdr 6 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 20 Fdr 2 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 22 Bkr 7 2411-1 Fdr 7 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 22 Sub 22 Bkr 6 2411-1 Fdr 6 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 22 Bkr 5 2411-1 Fdr 5 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 6 Fdr 7 Tripped 05/16/2023 13:13:51 MEA SCADA REED MR435S336-TC Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 8 Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 1 Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 6 Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 2 Breaker Open 05/16/2023 13:13:52 MEA SCADA COTTLE COSS_351S_MC425_Breaker 52A Breaker Open 05/16/2023 13:13:52 MEA SCADA LAZALLE LASS_351S_MZ425_Breaker 52A Breaker Open 05/16/2023 13:13:52 MEA SCADA COTTLE COSS_351S_MC445_Breaker 52A Breaker Open 05/16/2023 13:13:52 MEA SCADA COTTLE COSS_351S_MC415_Breaker 52A Breaker Open 05/16/2023 13:13:52 CEA Dowling Bkr 212 Tripped 05/16/2023 13:13:52 CEA LaTouche Bkr 192 Tripped 05/16/2023 13:13:52 CEA Dowling Bkr 412 Tripped 05/16/2023 13:13:53 CEA Sub 15 Fdr 7 Tripped 05/16/2023 13:13:53 CEA Arctic Bkr 412 Tripped 05/16/2023 13:13:54 MEA SCADA ANDERSON AND_351S_MA415_52A Breaker Open 05/16/2023 13:13:56 MEA SCADA THSS THSS_451_TH415_52A Breaker Open 05/16/2023 13:15:54 MEA SCADA GCCC GCCC_BRKR_STAT Breaker Open 05/16/2023 13:21:20 MEA SCADA EGS GENERATOR 2 Breaker Close 05/16/2023 13:23:30 MEA SCADA EGS GENERATOR 8 Breaker Close 05/16/2023 13:23:59 MEA SCADA EGS GENERATOR 9 Breaker Close 05/16/2023 13:26:08 MEA SCADA EGS GENERATOR 5 Breaker Close 05/16/2023 13:27:43 MEA SCADA REED MR435S336-TC Breaker Close 05/16/2023 13:28:02 MEA SCADA EGS GENERATOR 6 Breaker Close 05/16/2023 13:28:41 CEA SCADA Sub 22 Bkr 5 2411-1 Fdr 5 Closed 05/16/2023 13:28:46 MEA SCADA THSS THSS_451_TH415_52A Closed 05/16/2023 13:29:08 MEA SCADA LAZALLE LASS_351S_MZ425_Breaker 52A Closed 05/16/2023 13:29:15 CEA SCADA Sub 22 Bkr 6 2411-1 Fdr 6 Closed 05/16/2023 13:29:51 CEA SCADA Sub 22 Bkr 7 2411-1 Fdr 7 Closed 05/16/2023 13:30:05 MEA SCADA ANDERSON AND_351S_MA415_52A Closed 05/16/2023 13:30:37 CEA SCADA Sub 20 Fdr 2 Closed 05/16/2023 13:31:04 CEA SCADA Sub 20 Fdr 6 Closed Draft 4 05/16/2023 13:31:41 CEA SCADA Sub 15 Fdr 7 Closed 05/16/2023 13:33:28 CEA SCADA Sub 6 Fdr 7 Closed 05/16/2023 13:34:00 CEA SCADA Arctic Bkr 412 Closed 05/16/2023 13:34:54 CEA SCADA Dowling Bkr 212 Closed 05/16/2023 13:35:39 CEA SCADA Dowling Bkr 412 Closed 05/16/2023 13:39:32 CEA SCADA LaTouche Bkr 192 Closed 05/16/2023 13:51:40 MEA SCADA EGS GENERATOR 5 Breaker Closed 05/16/2023 13:54:54 CEA SCADA AGC ACE Mode TLB 05/16/2023 13:57:35 MEA SCADA AGC ACE Mode TLB Tesla Analysis Tesla Recordings were collected from CEA, MEA, GVEA, and HEA. Appendix A shows plots of each unit output when frequency first arrested at 59.1Hz and then from 59.0 Hz, right before Stage 1 Load Shed began. Table 5. Unit Response at 59.1 Hz and 59.0 Hz Unit Response from Healy 2 Trip @ 59.1 Hz (MW) Response @ 59.0 Hz (MW) Source SPP 10 0.662 2.234 ITSS Tesla SPP 11 5.409 9.131 ITSS Tesla SPP 12 2.434 5.421 ITSS Tesla SPP 13 2.382 5.394 ITSS Tesla Sullivan 9 1.064 3.207 Plant 2A Unit 9 Tesla Sullivan 10 offline offline Plant 2A Unit 10 Tesla Sullivan 11 offline offline Plant 2A Unit 11 Tesla Eklutna 1 0.319 3.234 Eklutna Hydro Tesla Eklutna 2 0.868 3.951 Eklutna Hydro Tesla MSESS 2.131 0.971 IGT Tesla Bradley Lake 1 0.157 2.613 BRD Tesla Bradley Lake 2 0.486 5.403 BRD Tesla Fire Island 0.357 0.031 FIWF Tesla North Pole Unit 1 offline offline North Pole Sub Tesla North Pole Unit 2 2.382 12.094 North Pole Sub Tesla North Pole Unit 3 offline offline GVEA SCADA Draft 4 North Pole Unit 4 offline offline GVEA SCADA Healy 1 0 (online but no response) 0 (online but no response) GVEA SCADA Healy 2 -55.3 (tripped)(tripped)CEA SCADA ZNS 1 offline offline GVEA SCADA ZNS 2 offline offline GVEA SCADA BESS 5.487 24.94 WLS Tesla EGS T1 3.582 -4.926 (tripped)EGSY Tesla EGS T2 2.026 -14.558 (tripped)EGSY Tesla EGS T3 4.261 -27.198(tripped)EGSY Tesla Nikiski Steam offline offline Nikiski Tesla Nikiski Unit 1 offline offline Nikiski Tesla HEA BESS 10.297 9.365 SOT Tesla Soldotna CT 1.16 1.298 SOT Tesla Table 6. Total Utility Response at 59.1 Hz and 59.0 Hz Utility Total Response @ 59.1 Hz Total Response @ 59.0 Hz CEA 16.269 41.59 GVEA 2.382 37.034 MEA 9.869 9.869 HEA 11.457 10.663 Conclusion The first event occurred when Healy 2 tripped and the system responded and started to recover with frequency arresting at 59.1Hz. Each utility met their spin requirements before the UFLS event began. A second event occurred when six EGS units were forced over their maximum power output causing the units to trip on overload. The sudden loss of these units caused frequency to drop to 58.7 Hz leading to the UFLS event. The system recovered after the UFLS Stage 1 activation. Draft 4 Appendix A – Tesla Recordings of Unit Generation Plot 1. SPP Unit 11 response @ 59.1Hz Plot 2. SPP Unit 11 response @ 59.0Hz Draft 4 Draft 4 Plot 3. SPP Unit 10, Unit 12, and Unit 13 response @ 59.1Hz Draft 4 Plot 4. SPP Unit 10, Unit 12, and Unit 13 response @ 59.0Hz Draft 4 Plot 5. Sullivan 9 response @ 59.1Hz Draft 4 Plot 6. Sullivan 9 response @ 59.0Hz Draft 4 Plot 7. Eklutna 1 and Eklutna 2 response @ 59.1Hz Draft 4 Plot 8. Eklutna 1 and Eklutna 2 response @ 59.0Hz Draft 4 Plot 9. MSESS response @ 59.1Hz Draft 4 Plot 10. MSESS response @ 59.0Hz Draft 4 Plot 11. Fire Island Wind Farm response @ 59.1Hz Draft 4 Plot 12. Fire Island Wind Farm response @ 59.0Hz Draft 4 Plot 13. Bradley Lake response @ 59.1Hz Draft 4 Plot 14. Bradley Lake response @ 59.0Hz Draft 4 Plot 15. North Pole Unit 2 response @ 59.1Hz Draft 4 Plot 16. North Pole Unit 2 response @ 59.0Hz Draft 4 Plot 17. GVEA WLS BESS response @ 59.1Hz Draft 4 Plot 18. GVEA WLS BESS response @ 59.0Hz Draft 4 Plot 19. SCT CT and HEA BESS response @ 59.1Hz Draft 4 Plot 20. SCT CT and HEA BESS response @ 59.0Hz Draft 4 Plot 21. MEA EGS Units response @ 59.1Hz Draft 4 Plot 22. MEA EGS Units response @ 59.0Hz Draft 4 Appendix B - System Frequency Draft 4 Appendix C – EGS Unit Trips Date/Time Unit Source 5/16/2023 13:13:48.21 EGS Unit 5 EGSY Tesla 5/16/2023 13:13:49.81 EGS Unit 9 EGSY Tesla 5/16/2023 13:13:50.35 EGS Unit 8 EGSY Tesla 5/16/2023 13:13:50.43 EGS Unit 1 EGSY Tesla 5/16/2023 13:13:50.46 EGS Unit 6 EGSY Tesla 5/16/2023 13:13:50.93 EGS Unit 2 EGSY Tesla The EGS units listed on the table above all tripped in the span of 2 seconds. They all ramped up to 110% of their maximum output causing the units to trip. EGS Units 7 and 10 stayed online, so T3 didn’t drop to zero MW. The table below describes the generation on each unit 10 seconds before they tripped and 30 seconds after. Unit 10s before 30s after Unit 1 16.545 0.897 Unit 2 16.297 0.913 Unit 5 15.968 1.302 Unit 6 16.0269 1.131 Unit 7 16.407 17.822 Unt 8 16.909 1.41 Unit 9 15.969 1.243 Unit 10 16.779 17.707 Draft 4 M e m o r a n d u m o f A g r e e m e n t P a g e | 1 A E A / C h u g a c h D o u g l a s C o m m s Memorandum of Agreement Between Alaska Energy Authority & Chugach Electric Association, Inc. Regarding the Management of a Douglas Substation Communications Project Award 1.Parties This Memorandum of Agreement (MOA) is made and entered into between the Alaska Energy Authority (AEA), a corporation of the State of Alaska and Chugach Electric Association, Inc. (Chugach), an Alaska not-for-profit electric cooperative, relating to the proposed conveyance of a State of Alaska appropriation from AEA to Chugach. 2.Terms and Conditions a.AEA’s Role and Responsibilities: AEA will manage the State appropriation of funds awarded to Chugach to complete the project. AEA will review progress reports and project accounting statements provided by Chugach. AEA will be responsible for any reporting obligations related to the project and use of funds. b.Chugach’s Role and Responsibilities: Chugach will manage the project to upgrade communications to Douglas Substation including but not limited to the engineering, licensing, procurement, labor, and contractors. Chugach will provide progress reports and project accounting statements at least quarterly to AEA. Chugach will provide timely invoicing to AEA for reimbursement, referencing Chugach’s project number C2290297. 3.General Provisions a.Termination: This MOA may be terminated with 180 days prior written notice to any Party at any time without liability to the other Parties. If terminated, any funds spent, or materials ordered by Chugach shall be reimbursed by AEA prior to termination. b.Amendments: This MOA may be amended by written mutual agreement of the parties. c.Governing Law/Jurisdiction/Venue: This MOA, for all purposes, shall be construed in accordance with the laws of Alaska without regard to conflicts of law principles. Any action or proceeding by any of the Parties arising under or relating to this MOA shall be brought only in a state or federal court located in Anchorage, Alaska. The parties hereby irrevocably submit to the exclusive jurisdiction of such courts and waive the defense of inconvenient forum to the maintenance of any such action or proceeding in such venue. d.Reasonable Best Efforts: The Parties will use their reasonable best efforts to effectuate the intent and purpose of this MOA. e.No Third-Party Beneficiaries: Nothing herein is intended or shall be construed to confer upon any person or entity other than the Parties and their successors or assigns any rights or remedies under or by reason of this MOA. f.No Assignment: Neither this MOA nor any rights or obligations hereunder may be assigned, delegated, or conveyed by any Party without the prior written consent of the other Parties. M e m o r a n d u m o f A g r e e m e n t P a g e | 2 A E A / C h u g a c h D o u g l a s C o m m s g.Indemnification: Parties shall indemnify, hold harmless, and defend each other against all losses, damages, liabilities, claims, actions, judgements, settlements, penalties, fines, costs, or expenses of whatever kind, including reasonable attorney fees, that are incurred arising out of or related to any negligent or more culpable act or omission of the Parties in connection with the performance of its obligations under this agreement. h.Costs and Expenses: Except as otherwise agreed herein, each Party shall be responsible for its own costs and expenses associated with pursuing the proposed project described in this MOA, including without limitation (i) pursuing any approvals necessary to effectuate this MOA and/or (ii) resolving disputes between the Parties that arise out of this MOA. i.Term of Agreement: This MOA will be deemed to be successfully ended upon completion of the project to establish microwave communications from Teeland Substation to Douglas Substation or the decision by any of the Parties to cease continued work on the Project as effectuated by the termination of this MOA via written notice as stated in Section 3(a) of this MOA. 4.Contact Information Bill Price, P.E. Alaska Energy Authority 813 W Northern Lights Blvd. Anchorage, AK 99503 Tel: (907) 771-3000 wprice@akenergyauthority.org Bill Murray, PMP Chugach Electric Association, Inc. 5601 Electron Drive Anchorage, AK 99518 Tel: (907) 762-4542 bill_murray@chugachelectric.com 5.Counterparts This MOA may be executed manually or by electronic signature in counterparts, each of which shall be deemed an original, but all of which together shall be deemed one and the same agreement. A signed copy of this MOA delivered by email or other means of electronic transmission shall be deemed to have the same effect as delivery of an original signed copy of this MOA. M e m o r a n d u m o f A g r e e m e n t P a g e | 3 A E A / C h u g a c h D o u g l a s C o m m s IN WITNESS WHEREOF, the Parties hereto have executed this MOA as of the last day set forth below. Alaska Energy Authority By: Date: Name: Curtis Thayer Title: Executive Director Chugach Electric Association, Inc. By: Date: Name: Arthur Miller Title: Chief Executive Officer Douglas Communications Project Scope Utility communications from Teeland Substation to Douglas Substation are provided by two means, an independent DS1 service provided by the State of Alaska Public Safety Communications Service (APSCS) on their microwave network, and a leased Metro Ethernet service from MTA. The DS1 is used by Chugach, MEA, and GVEA for tele-protection, SCADA, telephone, and relay engineering access. The bandwidth of this DS1 circuit is fully allocated and more is currently needed. The MTA leased service is for MEA’s sole use. Currently, the DS1 interconnection is provided via microwave between Chugach’s International Transmission Substation (ITSS) and APSCS’ Tudor Tower. Upgrades at the following three State of Alaska sites are needed to complete a utility- owned and maintained microwave path from Douglas Substation to Teeland Substation: Tudor Tower Willow Creek Douglas Substation Chugach is proposing to overbuild the microwave path to Douglas Substation with a private, high-speed microwave network from the State’s Tudor Tower Site to Douglas Substation. Once Chugach has established an interconnection point on our existing high-speed microwave network, communications to Teeland and Ship Creek Water Tower* will be available via multiple routes. This will allow both GVEA and MEA to have private high speed connections to Douglas with common points of interconnection for data services between utilities. Joint use of APSCS antenna/feedline infrastructure would allow Chugach to install a second set of radios on the RF systems to vastly increase the Railbelt Utilities' capabilities at Douglas Substation, increase substation security, and allow Chugach to diversify the communications paths on our existing network. This approach is used successfully at other sites Chugach jointly operates with APSCS. Licensed FCC frequencies have been coordinated and Chugach has discussed colocation with APSCS to complete this effort. In these discussions, APSCS identified some site infrastructure upgrades that will be needed to ensure site reliability for the link to Douglas Substation. Upgrades include replacement of site generators, battery plants, HVAC systems, a new shelter at Douglas Substation, and changes to tower structural elements and shared antenna systems at the sites. A map of the project area and costs estimates can be found below. Chugach and APSCS have an existing MOU that allows for similar arrangements as is proposed for this project and is in the process of updating to include the 2 links and associated sites. The MOU will need to be completed prior to initiating the procurement phase of the project. *GVEA manages the lease of a DS-1 circuit between SCWTF and GVEA PROJECT MAP TUDOR TOWERMaterial CostProfessional Svcs.Chugach LaborChugach PMSubtotal20kW Kubota Generator41,580.00$ 1,600.00$ -$ 800.00$ 43,980.00$ VRLA Battery Plant17,086.00$ -$ -$ 800.00$ 17,886.00$ DPS Telecom 2-HVAC Controller4,636.00$ -$ -$ -$ 4,636.00$ DPS Telecom 6-String 4x12VDC Battery Monitor7,214.00$ -$ -$ -$ 7,214.00$ Aviat Microwave51,554.00$ 2,500.00$ 12,000.00$ 800.00$ 66,854.00$ Commscope Feed Line, Connectors, Ground Kits, Hangers, etc.2,500.00$ -$ 4,000.00$ 800.00$ 7,300.00$ Miscellaneous Materials - Fuse Panel, Breakers, Wire, Cable2,500.00$ -$ 4,000.00$ 800.00$ 7,300.00$ Tudor Tower155,170.00$ WILLOW CREEKMaterial CostProfessional Svcs.Chugach LaborChugach PMSubtotalBard HVAC Right Side - W24AB-A05ZXXXXJ8,677.70$ 600.00$ -$ 400.00$ 9,677.70$ Bard HVAC Left Side - W24LB-A05ZXXXXJ8,677.70$ 600.00$ -$ 400.00$ 9,677.70$ 12kW Kubota Generator from ESI - KPG-12-V15-MCR3 KPG-12-V15MR3 TG41014,145.00$ 3,200.00$ -$ 800.00$ 18,145.00$ DPS Telecom 2-HVAC Controller4,636.00$ -$ -$ 4,636.00$ DPS Telecom 6-String 4x12VDC Battery Monitor7,214.00$ -$ -$ 7,214.00$ Aviat Microwave56,701.00$ 2,500.00$ 12,000.00$ 800.00$ 72,001.00$ Commscope Feed Line, Connectors, Ground Kits, Hangers, etc.5,000.00$ -$ 4,000.00$ 800.00$ 9,800.00$ Miscellaneous Materials - Fuse Panel, Breakers, Wire, Cable2,500.00$ -$ 4,000.00$ 800.00$ 7,300.00$ Willow Creek138,451.40$ DOUGLASS (ARR)Material CostProfessional Svcs.Chugach LaborChugach PMSubtotalNANA Construction Pre-fab Shelter220,000.00$ -$ -$ 4,000.00$ 224,000.00$ Bard HVAC Right Side - W24AB-A05ZXXXXJ8,677.70$ 600.00$ -$ 400.00$ 9,677.70$ Bard HVAC Left Side - W24LB-A05ZXXXXJ8,677.70$ 600.00$ -$ 400.00$ 9,677.70$ VRLA Battery Plant17,086.00$ -$ 800.00$ 17,886.00$ 12kW Kubota Generator from ESI - KPG-12-V15-MCR3 KPG-12-V15MR3 TG41014,145.00$ 3,200.00$ -$ 800.00$ 18,145.00$ DPS Telecom 2-HVAC Controller4,636.00$ -$ -$ 4,636.00$ DPS Telecom 6-String 4x12VDC Battery Monitor7,214.00$ -$ -$ 7,214.00$ Aviat Microwave34,914.00$ 2,500.00$ 12,000.00$ 800.00$ 50,214.00$ Commscope Feed Line, Connectors, Ground Kits, Hangers, etc.2,500.00$ -$ 4,000.00$ 800.00$ 7,300.00$ Miscellaneous Materials - Fuse Panel, Breakers, Wire, Cable2,500.00$ -$ 4,000.00$ 800.00$ 7,300.00$ Douglas356,050.40$ Total649,671.80$ Intertie Management Committee Meeting Operator Report June 23, 2023 1. Alaska Intertie usage report a. MWh usage – Measured at Douglas Substation GVEA MEA Total i. July – May FY23 220,816 24,783 245,599 ii. July – May FY22 187,649 22,955 210,604 iii. Delta - FY23 to FY22 17.67% 7.96% 16.62% 2. No Alaska Intertie trips to report Date Event SCADA Indication Cause No trip events to report 3. IOC quarterly Reliability Report For generation trips or transmission line trips where the loss of load is known, the Railbelt-wide frequency response is calculated. The magnitude of the tripped power and the change in frequency from the pre-trip value to the peak or nadir are used to calculate the MW/0.1Hz value often known as ‘Beta’. Chugach has calculated the Beta for several events and the table of the results is pasted below. Events without data for the MW magnitude of the trip were excluded, as were events that did not cause a frequency deviation of greater than 0.2 Hz. Frequency data is sourced from the Teeland Tesla disturbance fault recorder. MW data is sourced from Chugach SCADA, which receives data from other utilities via ICCP. Event Date MW Tripped Pre-Trip Frequency (Hz) High /Low Frequency (Hz) Frequency Response (MW/0.1Hz) NPCC GT3 Trip 4/4/2023 37.46 59.959 59.462 7.5 SSQ Trip 4/13/2023 18.02 60.015 59.782 7.7 Healy 2 Trip 4/16/2023 47.1 60.021 59.551 10.0 Beluga Line 2 Trip 4/22/2023 - 59.995 59.38/60.78 Nikiski Rapid Ramp 5/5/2023 6.85 60.009 59.745 2.6 UFLS 5/16/2023 See Attached Bradley Lake Trip 6/14/2023 53.94 59.998 59.25 7.2 Oscillation Event 6/16/2023 - Untriggered Oscillation 0.2Hz/5 sec period PART 2: EVENT SUMMARY 06/20/2023 TO04/01/2023 06/30/2023 IOC QUARTERLY RELIABILITY REPORT Event Num Date/Time Duration Description Freq extreme Intertie Kenai opened opened Unit Line Trip Trip BESS Silos Load Shed Comments 1,235 04/13/2023 11:05:07 115 KV tie trip between Sterling and Quartz substations, No cause identified 60.36 X 0.0 0.0 0.02.7 1,236 04/16/2023 00:56:45 HLP ST2 Trip 59.56 X 0.0 0.0 7.61.5 1,237 04/04/2023 18:12:02 NPC GT3 Trip 59.43 X 0.0 0.0 0.03.4 2.53Average Duration *has sub event Draft 5 Event – Healy and EGS Trip Causing UFLS Date 05/16/2023 Time 13:13:40 Purpose This document describes the events leading to the underfrequency load shed event on 05/16/2023 and the sequential events that follow. Provided are the sequence of events from the SCADA systems of CEA, MEA, and GVEA. Introduction On 5/16/2023 an underfrequency load shed event occurred. Initially, a unit trip of Healy 2 caused frequency to drop, but not enough to cause load shed. While system was recovering, approximately 10 seconds later, six EGS units tripped and dropped frequency enough to cause stage 1 load shed to be activated. Event At 13:13:40, an event occurred at GVEA’s Healy 2 which dropped system frequency to 59.1Hz. As system was recovering, at 13:13:48, six EGS units tripped in the span of 2 seconds in the following order: Unit 5, Unit 9, Unit 8, Unit 1, Unit 5, and with Unit 2 tripping at 13:13:50. This second event dropped frequency to 58.719 Hz causing Stage 1 Underfrequency Load Shed to occur. The EGS units tripped on overload because they were over their maximum output due to droop response to the Healy 2 trip. The sequence of events is shown visually in Figure 1. Figure 1. System Frequency with Sequence of Event Labels, Data Source is the CEA ITSS Tesla recorder. Draft 5 For the initial Healy 2 event, GVEA SCADA data shows that Healy 2 lost 45.8 MW and then came back online to settle back on 3.3 MW. Given the information GVEA provided, it is unknown at the time why the unit stayed online. The magnitude of the tripped unit’s power and the frequency deviation from the pre-event frequency was used to calculate Beta. The Railbelt beta was calculated to be 4.8 MW/0.1 Hz. For the Healy 2 event, CEA had a spin requirement of 26 MW and was purchasing 21 MW from GVEA. GVEA had a spin requirement of 12 MW, MEA had a spin requirement of 8 MW, and HEA had a spin requirement of 10 MW. Within 3.7 seconds of the Healy event: CEA responded with 16.3 MW, GVEA responded with 7.9 MW, MEA responded with 9.9 MW, and HEA responded with 11.5 MW with frequency arrested at 59.1 Hz 7.65 seconds after the Healy 2 event, six EGS units tripped 110.4 MW in the period of 2 seconds causing UFLS to occur when frequency hit 59.0Hz. When EGS units tripped, within 2.3 seconds before UFLS activated, each utility had the following unit responses. CEA unit response was 20.5 MW plus the 21 MW spin purchased from GVEA. Total GVEA unit response was 37 MW which met the 21 MW CEA was purchasing. The larger response from GVEA was due to the increase response of their BESS when frequency went below 59.1 Hz. Total HEA unit response was 10.9 MW. It can be observed that hydro units were more responsive by the time the EGS units tripped since a longer time has passed from initial event. Total hydro response was 15.2MW, 9.92 seconds after the Healy event. With all utilities providing primary frequency response, the Railbelt was in compliance with the requirement R3.2 of the AKBAL-002 standard to activate Contingency Reserve before Protection Reserve. Ten seconds after the Healy 2 event when frequency was at 59.0 Hz, CEA was carrying 258 MW of load and shed 29.25 MW, 11.3%, of the total load. From the SCADA alarms, the following feeders were shed beginning at 13:13:51: Sub 20 Feeder 2 and 6, Sub 22 Feeder 5, 6, and 7, Sub 6 Feeder 7, Dowling Breaker 212 and 412, LaTouche Breaker 192, and Arctic Breaker 212. At 13:39:32, all feeders were confirmed closed and returned to normal. Power restoration was just under half an hour. MEA was carrying 101 MW of load and shed 9.95 MW, 9.9% of their total load. From MEA’s SCADA alarms, the following feeders were shed beginning at 13:13:51: TH415, MA415, MC415, MC425, MC445, MZ425, and MR435. At the time of writing this report, there was no reference for when feeders were closed back in. HEA was carrying 53.22 MW of load at the time. At this time, no information was available to the amount of load that was shed. GVEA system load or quantity of load shed was also not available for this report. CEA SCADA systems report ACE mode return to Tie Line Bias at 13:54:54, and MEA reports return to Tie Line Bias at 13:57:35. Data was not available for when GVEA or HEA returned to Tie Line Bias at the time of writing this report. Pre-Disturbance Generation Dispatch Table 1. Generation Dispatch for Railbelt Utility Unit MW Output Bus Voltage (KV; line- line) MW and kV Source Draft 5 CEA SPP 10 35.147 138.5 ITSS Tesla CEA SPP 11 37.609 138.1 ITSS Tesla CEA SPP 12 37.756 138.3 ITSS Tesla CEA SPP 13 36.235 138.8 ITSS Tesla CEA Sullivan 9 44.956 116.5 Plant 2A Unit 9 Tesla CEA Sullivan 10 offline offline Plant 2A Unit 10 Tesla CEA Sullivan 11 offline offline Plant 2A Unit 11 Tesla CEA Eklutna 1 18.51 12 Eklutna Hydro Tesla CEA Eklutna 2 16.28 12 Eklutna Hydro Tesla CEA MSESS 0.045 35.38 IGT Tesla CEA Bradley Lake 1 25.59 12.8 BRD Tesla CEA Bradley Lake 2 0.309 13.4 BRD Tesla CEA Fire Island 0.97 35.2 FIWF Tesla GVEA North Pole Unit 1 offline offline GVEA SCADA GVEA North Pole Unit 2 17.393 138.4 NPS Tesla GVEA North Pole Unit 3 offline offline GVEA SCADA GVEA North Pole Unit 4 offline offline GVEA SCADA GVEA Healy 1 25.554 139.31 GVEA SCADA GVEA Healy 2 45.8 139.31 GVEA SCADA GVEA BESS 0.165 138.54 ZNS Tesla MEA EGS T1 30.877 117.4 EGS Tesla MEA EGS T2 31.882 116.6 EGS Tesla MEA EGS T3 63.73 117.4 EGS Tesla HEA Nikiski offline offline NIK Tesla HEA HEA BESS 0.615 116.7 HEA BESS Tesla HEA Soldotna CT 44.923 116.7 SCT CT Tesla SVC MVAR Output Bus Voltage (kV; Line- Line) Source Teeland SVC 21.76 13.46 CEA SCADA Daves Creek SVC -5.3 116.6 CEA SCADA Soldotna SVC -20.4 16.3 CEA SCADA Table 2. System Load Draft 5 Utility System Load (MW) Source CEA 258.31 CEA SCADA MEA 101.01 MEA SCADA HEA 53.22 CEA SCADA GVEA N/A N/A Table 3. Air Temps Location Ambient Air Temperature Source SPP 48.30 F CEA SCADA Sullivan CC 49.06 F CEA SCADA Cooper Lake 43.10 F CEA SCADA Teeland 51.51 F CEA SCADA Table 4. CEA Units Available Spin Unit Spin Available SPP 10 6.833 SPP 11 1.391 SPP 12 1.244 SPP 13 2.785 Sullivan 9 2.6 Sullivan 10 offline Sullivan 11 offline Eklutna 1 0.957921 Eklutna 2 2.404446 MSESS 1.955 Bradley Lake 15 Fire Island - Purchased Spin 21 Total Spin 54.215367 SCADA Sequence of Events Date/Time Source Event 05/16/2023 13:13:40 HLS Tesla Healy 2 Trip 05/16/2023 13:13:44 MEA SCADA AGC: Frequency Excursion ACE Mode changed to CF Draft 5 05/16/2023 13:13:44 CEA SCADA AGC: Frequency Excursion ACE Mode changed to CF 05/16/2023 13:13:50 MEA EGSY Tesla GENERATOR 5 Breaker Open 05/16/2023 13:13:50 MEA EGSY Tesla GENERATOR 9 Breaker Open 05/16/2023 13:13:51 CEA SCADA Sub 20 Fdr 6 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 20 Fdr 2 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 22 Bkr 7 2411-1 Fdr 7 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 22 Sub 22 Bkr 6 2411-1 Fdr 6 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 22 Bkr 5 2411-1 Fdr 5 Tripped 05/16/2023 13:13:51 CEA SCADA Sub 6 Fdr 7 Tripped 05/16/2023 13:13:51 MEA SCADA REED MR435S336-TC Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 8 Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 1 Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 6 Breaker Open 05/16/2023 13:13:52 MEA EGSY Tesla GENERATOR 2 Breaker Open 05/16/2023 13:13:52 MEA SCADA COTTLE COSS_351S_MC425_Breaker 52A Breaker Open 05/16/2023 13:13:52 MEA SCADA LAZALLE LASS_351S_MZ425_Breaker 52A Breaker Open 05/16/2023 13:13:52 MEA SCADA COTTLE COSS_351S_MC445_Breaker 52A Breaker Open 05/16/2023 13:13:52 MEA SCADA COTTLE COSS_351S_MC415_Breaker 52A Breaker Open 05/16/2023 13:13:52 CEA Dowling Bkr 212 Tripped 05/16/2023 13:13:52 CEA LaTouche Bkr 192 Tripped 05/16/2023 13:13:52 CEA Dowling Bkr 412 Tripped 05/16/2023 13:13:53 CEA Sub 15 Fdr 7 Tripped 05/16/2023 13:13:53 CEA Arctic Bkr 412 Tripped 05/16/2023 13:13:54 MEA SCADA ANDERSON AND_351S_MA415_52A Breaker Open 05/16/2023 13:13:56 MEA SCADA THSS THSS_451_TH415_52A Breaker Open 05/16/2023 13:15:54 MEA SCADA GCCC GCCC_BRKR_STAT Breaker Open 05/16/2023 13:21:20 MEA SCADA EGS GENERATOR 2 Breaker Close 05/16/2023 13:23:30 MEA SCADA EGS GENERATOR 8 Breaker Close 05/16/2023 13:23:59 MEA SCADA EGS GENERATOR 9 Breaker Close 05/16/2023 13:26:08 MEA SCADA EGS GENERATOR 5 Breaker Close 05/16/2023 13:27:43 MEA SCADA REED MR435S336-TC Breaker Close 05/16/2023 13:28:02 MEA SCADA EGS GENERATOR 6 Breaker Close 05/16/2023 13:28:41 CEA SCADA Sub 22 Bkr 5 2411-1 Fdr 5 Closed 05/16/2023 13:28:46 MEA SCADA THSS THSS_451_TH415_52A Closed 05/16/2023 13:29:08 MEA SCADA LAZALLE LASS_351S_MZ425_Breaker 52A Closed 05/16/2023 13:29:15 CEA SCADA Sub 22 Bkr 6 2411-1 Fdr 6 Closed 05/16/2023 13:29:51 CEA SCADA Sub 22 Bkr 7 2411-1 Fdr 7 Closed 05/16/2023 13:30:05 MEA SCADA ANDERSON AND_351S_MA415_52A Closed 05/16/2023 13:30:37 CEA SCADA Sub 20 Fdr 2 Closed 05/16/2023 13:31:04 CEA SCADA Sub 20 Fdr 6 Closed Draft 5 05/16/2023 13:31:41 CEA SCADA Sub 15 Fdr 7 Closed 05/16/2023 13:33:28 CEA SCADA Sub 6 Fdr 7 Closed 05/16/2023 13:34:00 CEA SCADA Arctic Bkr 412 Closed 05/16/2023 13:34:54 CEA SCADA Dowling Bkr 212 Closed 05/16/2023 13:35:39 CEA SCADA Dowling Bkr 412 Closed 05/16/2023 13:39:32 CEA SCADA LaTouche Bkr 192 Closed 05/16/2023 13:51:40 MEA SCADA EGS GENERATOR 5 Breaker Closed 05/16/2023 13:54:54 CEA SCADA AGC ACE Mode TLB 05/16/2023 13:57:35 MEA SCADA AGC ACE Mode TLB Tesla Analysis Tesla Recordings were collected from CEA, MEA, GVEA, and HEA. Appendix A shows plots of each unit output when frequency first arrested at 59.1Hz and then from 59.0 Hz, right before Stage 1 Load Shed began. Table 5. Unit Response at 59.1 Hz and 59.0 Hz Unit Response from Healy 2 Trip @ 59.1 Hz (MW) Response @ 59.0 Hz (MW) Source SPP 10 0.662 2.234 ITSS Tesla SPP 11 5.409 9.131 ITSS Tesla SPP 12 2.434 5.421 ITSS Tesla SPP 13 2.382 5.394 ITSS Tesla Sullivan 9 1.064 3.207 Plant 2A Unit 9 Tesla Sullivan 10 offline offline Plant 2A Unit 10 Tesla Sullivan 11 offline offline Plant 2A Unit 11 Tesla Eklutna 1 0.319 3.234 Eklutna Hydro Tesla Eklutna 2 0.868 3.951 Eklutna Hydro Tesla MSESS 2.131 0.971 IGT Tesla Bradley Lake 1 0.157 2.613 BRD Tesla Bradley Lake 2 0.486 5.403 BRD Tesla Fire Island 0.357 0.031 FIWF Tesla North Pole Unit 1 offline offline North Pole Sub Tesla North Pole Unit 2 2.382 12.094 North Pole Sub Tesla North Pole Unit 3 offline offline GVEA SCADA North Pole Unit 4 offline offline GVEA SCADA Draft 5 Healy 1 0 (online but no response) 0 (online but no response) GVEA SCADA Healy 2 -55.3 (tripped) (tripped) CEA SCADA ZNS 1 offline offline GVEA SCADA ZNS 2 offline offline GVEA SCADA BESS 5.487 24.94 WLS Tesla EGS T1 3.582 -4.926 (tripped) EGSY Tesla EGS T2 2.026 -14.558 (tripped) EGSY Tesla EGS T3 4.261 -27.198(tripped) EGSY Tesla Nikiski Steam offline offline Nikiski Tesla Nikiski Unit 1 offline offline Nikiski Tesla HEA BESS 10.297 9.365 SOT Tesla Soldotna CT 1.16 1.298 SOT Tesla Table 6. Total Utility Response at 59.1 Hz and 59.0 Hz Utility Total Response @ 59.1 Hz Total Response @ 59.0 Hz CEA 16.269 41.59 GVEA 7.869 37.034 MEA 9.653 9.869 HEA 11.457 10.663 Conclusion The first event occurred when Healy 2 output decreased causing frequency to drop and the system responded and started to recover with frequency arresting at 59.1Hz. Each utility met their spin requirement for the Healy 2 event except GVEA. For the EGS event, each utility met their spin requirements before the UFLS event began. The cause of the second event was becasue EGS units were forced over their maximum power output causing the units to trip on overload. The sudden loss of these units caused frequency to drop to 58.7 Hz leading to the UFLS event. The system recovered after the UFLS Stage 1 activation. Draft 5 Appendix A – Tesla Recordings of Unit Generation Plot 1. SPP Unit 11 response @ 59.1Hz Plot 2. SPP Unit 11 response @ 59.0Hz Draft 5 Draft 5 Plot 3. SPP Unit 10, Unit 12, and Unit 13 response @ 59.1Hz Draft 5 Plot 4. SPP Unit 10, Unit 12, and Unit 13 response @ 59.0Hz Draft 5 Plot 5. Sullivan 9 response @ 59.1Hz Draft 5 Plot 6. Sullivan 9 response @ 59.0Hz Draft 5 Plot 7. Eklutna 1 and Eklutna 2 response @ 59.1Hz Draft 5 Plot 8. Eklutna 1 and Eklutna 2 response @ 59.0Hz Draft 5 Plot 9. MSESS response @ 59.1Hz Draft 5 Plot 10. MSESS response @ 59.0Hz Draft 5 Plot 11. Fire Island Wind Farm response @ 59.1Hz Draft 5 Plot 12. Fire Island Wind Farm response @ 59.0Hz Draft 5 Plot 13. Bradley Lake response @ 59.1Hz Draft 5 Plot 14. Bradley Lake response @ 59.0Hz Draft 5 Plot 15. North Pole Unit 2 response @ 59.1Hz Draft 5 Plot 16. North Pole Unit 2 response @ 59.0Hz Draft 5 Plot 17. GVEA WLS BESS response @ 59.1Hz Draft 5 Plot 18. GVEA WLS BESS response @ 59.0Hz Draft 5 Plot 19. SCT CT and HEA BESS response @ 59.1Hz Draft 5 Plot 20. SCT CT and HEA BESS response @ 59.0Hz Draft 5 Plot 21. MEA EGS Units response @ 59.1Hz Draft 5 Plot 22. MEA EGS Units response @ 59.0Hz Draft 5 Appendix B - System Frequency Draft 5 Appendix C – EGS Unit Trips Date/Time Unit Source 5/16/2023 13:13:48.21 EGS Unit 5 EGSY Tesla Draft 5 5/16/2023 13:13:49.81 EGS Unit 9 EGSY Tesla 5/16/2023 13:13:50.35 EGS Unit 8 EGSY Tesla 5/16/2023 13:13:50.43 EGS Unit 1 EGSY Tesla 5/16/2023 13:13:50.46 EGS Unit 6 EGSY Tesla 5/16/2023 13:13:50.93 EGS Unit 2 EGSY Tesla The EGS units listed on the table above all tripped in the span of 2 seconds. They all ramped up to 110% of their maximum output causing the units to trip. EGS Units 7 and 10 stayed online, so T3 didn’t drop to zero MW. The table below describes the generation on each unit 10 seconds before they tripped and 30 seconds after. Unit 10s before 30s after Unit 1 16.545 0.897 Unit 2 16.297 0.913 Unit 5 15.968 1.302 Unit 6 16.0269 1.131 Unit 7 16.407 17.822 Unt 8 16.909 1.41 Unit 9 15.969 1.243 Unit 10 16.779 17.707 From the EGS Tesla Recorder, the total MW tripped was 110 MW, summarized in the table below. Draft 5