Alberta Electric System Operator
Long Range Significant Transmission Outages for the period of 24 months starting 2025-12-06

The table below contains the significant transmission outages submitted as tentative to the AESO.
These Outages have not yet necessarily been approved, but are listed for awareness and coordination purposes.
An Outage has been considered significant for this table if it meets any one (1) or more of the following criteria:
  1. it affects a transmission facility operating at two hundred and forty (240) kV or greater;
  2. it affects an intertie;
  3. it affects an element connecting facilities owned by two (2) or more different legal owners of transmission facilities;
  4. it affects an element that connects a generating unit or an aggregated generating facility to the interconnected electric system;
  5. it requires the ISO to issue a dispatch or directive for generation in order to facilitate the planned outage;
  6. it affects a cutplane limit;
  7. it limits or reduces the operability of a synchronous condenser, static VAr compensator, static compensator or other similar dynamic device; or
  8. it affects high voltage direct current facilities.
Note: Where a transmission outage requires generation curtailments, the adjustments to generation will typically happen in the hours before the scheduled transmission outage and in the hour after the element is returned to service.

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Owner From To Duration Element Scheduled Activity Affected Intertie
EPCOR 25-Jul-25 17:01 20-Feb-26 17:00 210.04 Days
Continuous		 T2 (EP Riverview) bushing test failure (found during OE110184)  
ALTALINK 20-Aug-25 17:00 17-Dec-25 17:00 119.04 Days
Continuous		 1075L (28s West Brooks - 132s Ware Junction) restoration from real time storm  
ALTALINK 01-Nov-25 12:00 01-Feb-26 18:00 92.29 Days
Continuous		 AML 511s ACF12 (AML 511s Crossings) forced outage  
ATCO 24-Nov-25 09:00 08-Dec-25 17:30 14.35 Days
Continuous		 2075s ACF21 (2075s Newell), 2075s 902T (2075s Newell), 2075S 930 (2075s Newell) valve cooling skid modifications  
Syncrude, ATCO 30-Nov-25 08:00 09-Dec-25 16:00 9.33 Days
Continuous		 RL2 (848s Ruth Lake - D05), D05 512 (D05), D05 513 (D05), D05 512B (D05), D05 513B (D05), 848s RL-2D1 (848s Ruth Lake) D05 substation zone 3 260 kV maintenance  
BCH 01-Dec-25 09:00 16-Dec-25 17:00 15.33 Days
Daily		 1L274 (48s Pocaterra - 978s BCH Britt Creek) for LLP work AB-BC
ENMAX, ALTALINK 02-Dec-25 13:00 11-Dec-25 09:00 8.83 Days
Continuous		 693L (42s Sarcee - SS-10), 10.2TR (SS-10), 10MD138-10.2TR (SS-10) 10.2TR 'S' protection replacement. Trip test 10B138-693L. Protection operation 10MD138-10.2TR.  
ENMAX, ALTALINK 02-Dec-25 13:00 11-Dec-25 09:00 8.83 Days
Continuous		 693L (42s Sarcee - SS-10) 10.2TR 'S' protection replacement. Trip test 10B138-693L. Protection operation 10MD138-10.2TR.  
ALTALINK 04-Dec-25 11:00 19-Dec-25 18:00 15.29 Days
Continuous		 931L (28s West Brooks - 132s Ware Junction) install new structures as part of the 1075L storm restoration.  
ALTALINK 07-Dec-25 07:15 07-Dec-25 13:45 6.5 Hours
Daily		 801L (62s Brazeau Plant - 294s Brazeau Plant Outlet Works) Replacing insulator on structure 38  
EPCOR, ALTALINK 08-Dec-25 07:00 08-Dec-25 17:00 10 Hours
Continuous		 657s T3 (657s Summerside), 657s SU2401 (657s Summerside), 657s SU2405 (657s Summerside) Summerside: TX3 Zone, Lighting Upgrade on Pole #1  
EPCOR 08-Dec-25 07:00 11-Dec-25 17:00 3.42 Days
Continuous		 240BA3 (629s Argyll Transfer Station - 814s Bellamy), 814s B2406 (814s Bellamy), 814s B2407 (814s Bellamy) Bellamy: 240BA3 Metering Upgrade Cutovers  
EPCOR 08-Dec-25 07:00 12-Dec-25 17:00 4.42 Days
Continuous		 557s T1 (557s Castle Downs) Castledowns: TX1 Surge Arrestor LCR  
ATCO 08-Dec-25 10:00 09-Dec-25 17:30 31.5 Hours
Continuous		 977s 901T (977s Salt Creek), 7L135 (820s Hangingstone - 977s Salt Creek) NSERC Alliance Research Geomagnetic Impacts Project - 977s Salt Creek

- Tie in CT circuits on 901T for GIS Monitor		  
ALTALINK 08-Dec-25 12:30 08-Dec-25 15:00 2.5 Hours
Daily		 887L (48s Pocaterra - 978s BCH Britt Creek) RAS 3 timing test for BC Hydro  
ATCO 08-Dec-25 13:00 12-Dec-25 17:00 4.17 Days
Continuous		 732s 901 (732s Mitsue), 732s 902 (732s Mitsue), 9L40 (732s Mitsue - 809s Louise Creek) 240kV Bus and 144kV Breaker Fail Protection upgrade + Scada Upgrade.
Cutover 901, 902, and 9L40 to new Scada system, including end to ends with SOC.		  
EPCOR, ALTALINK 09-Dec-25 07:00 10-Dec-25 17:00 1.42 Days
Continuous		 657s T2 (657s Summerside), 657s SU2402 (657s Summerside), 657s SU2403 (657s Summerside) Summerside: TX2 Zone, Lighting Upgrade on Pole #2, #4, #5  
ALTALINK 09-Dec-25 07:00 11-Dec-25 17:00 2.42 Days
Continuous		 949L (275s Jenner - 306s Halsbury) We are planning to finish the punchlist items provided by AltaLink in order to finish transfer of ownership from Potentia Renewables to AltaLink.  
ALTALINK 09-Dec-25 07:00 12-Dec-25 17:30 3.44 Days
Continuous		 38s 7252 (38s East Edmonton) Replace Koncar CTs associated with 38s7252  
ALTALINK, ATCO 09-Dec-25 11:00 09-Dec-25 16:00 5 Hours
Continuous		 830L (562s Cypress - 840s McNeill Station), 840s 901T (840s McNeill Station), 840s 701 (840s McNeill Station), 840s 702 (840s McNeill Station), 840s 703 (840s McNeill Station), 840s 701T (840s McNeill Station) Emergency Outage Bleed 901T 63A Gas Detector relay. Need outage to bleed the relay since there is no non-electrical blocking switches or FT's at this site. AB-SK
ATCO 10-Dec-25 09:30 10-Dec-25 17:30 8 Hours
Continuous		 7L22 (790s Poplar Hill - 7L88 tap), 790s 702 (790s Poplar Hill) 702CT oil leak repairs  
ALTALINK 11-Dec-25 07:30 11-Dec-25 12:30 5 Hours
Daily		 205s 352 (205s Castle Rock Ridge) ACC Visibility SCADA upgrade - alarm splitting + wiring modifications  
ENMAX, ALTALINK 11-Dec-25 09:00 11-Dec-25 15:00 6 Hours
Continuous		 832L (SS-10 - SS-12), 10.1TR (SS-10), Protection & Control (SS-10), 10MD138-10.1TR (SS-10) Trip testing 10BA8-10.1TR, 10BB8-10.1TR, 10B138-832  
ENMAX, ALTALINK 11-Dec-25 09:00 11-Dec-25 16:00 7 Hours
Daily		 832L (SS-10 - SS-12) Trip testing 10BA8-10.1TR, 10BB8-10.1TR, 10B138-832.  
ALTALINK 11-Dec-25 12:30 11-Dec-25 17:30 5 Hours
Daily		 205s 452 (205s Castle Rock Ridge) ACC Visibility SCADA upgrade - alarm splitting + wiring modifications  
ALTALINK 12-Dec-25 07:30 12-Dec-25 12:30 5 Hours
Daily		 205s 152 (205s Castle Rock Ridge) ACC Visibility SCADA upgrade - alarm splitting + wiring modifications  
ALTALINK, TRANSALTA 13-Dec-25 08:00 13-Dec-25 17:00 9 Hours
Daily		 33s T2 (33s Spray) Maintenance/Protection relay change  
ENMAX, ALTALINK 13-Dec-25 08:00 14-Dec-25 16:00 1.33 Days
Continuous		 20.82L (SS-20 - SS-21), 21.80L (42s Sarcee - SS-21), 21.1TR (SS-21), 21.4TR (SS-21) 21.1TR Replacement. Punch bolts into plate.  
ENMAX, ALTALINK 13-Dec-25 08:00 14-Dec-25 16:00 1.33 Days
Continuous		 21.80L (42s Sarcee - SS-21) 21.2TR Replacement. Punch bolts into plate.  
EPCOR 15-Dec-25 07:00 19-Dec-25 17:00 4.42 Days
Continuous		 557s T2 (557s Castle Downs) Castledowns: TX2 Surge Arrestor LCR  
ENMAX, ALTALINK 15-Dec-25 08:00 15-Dec-25 16:00 8 Hours
Continuous		 833L (SS-2 - SS-12), 12.2TR (SS-12) 12 SUB - 12.2TR MD west phase not fully down on stops  
ENMAX, ALTALINK 15-Dec-25 09:00 15-Dec-25 16:00 7 Hours
Continuous		 833L (SS-2 - SS-12) Transfer from JMUX to JPAX circuits  
ENMAX, ALTALINK 15-Dec-25 09:00 15-Dec-25 16:00 7 Hours
Continuous		 833L (SS-2 - SS-12) Transfer from JMUX to JPAX circuits  
ATCO 15-Dec-25 10:00 16-Dec-25 17:30 31.5 Hours
Continuous		 959s SVC (959s Lanfine) Troubleshoot cause of recent SVC tripping event.  
ATCO 15-Dec-25 14:00 16-Dec-25 14:00 24 Hours
Continuous		 7L91 (715s Leming Lake - 826s Marguerite Lake) Install aerial nest platform pole and transfer osprey nest from 7L91-158  
ALTALINK, TRANSALTA 17-Dec-25 10:00 17-Dec-25 14:00 4 Hours
Daily		 250p T1 (250p Bighorn Plant) maintenance  
ALTALINK, TRANSALTA 18-Dec-25 10:00 18-Dec-25 14:00 4 Hours
Daily		 250p T2 (250p Bighorn Plant) maintenance  
ATCO 05-Jan-26 10:00 12-Jan-26 12:00 7.08 Days
Continuous		 9L40 (732s Mitsue - 809s Louise Creek) Replace 4 damaged poles ( Need winter access) Structures 221, 286, 299 and 304  
ATCO 06-Jan-26 08:00 09-Jan-26 17:00 3.38 Days
Continuous		 732s 902T (732s Mitsue), 732s 503R (732s Mitsue) Protection upgrade. Remove old protection, cut over to new protection and cut over equipment status, control and alarms to new station controller.  
ALTALINK 07-Jan-26 08:00 20-Jan-26 18:00 13.42 Days
Continuous		 931L (28s West Brooks - 132s Ware Junction) Install steel self-supporting structure NEW 931L37P,Salvage ahead and back spans Existing 931L37P, Salvage Existing structure 931L37P,Install new span 931L37O – NEW 931L37P part of Brooks storm restoration.  
ATCO 12-Jan-26 09:00 21-Jan-26 15:00 9.25 Days
Continuous		 9L57 (939s Livock - 960s Birchwood Creek) 9L57 Line to Ground Clearance Mitigation  
ALTALINK 14-Jan-26 23:00 15-Jan-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 15-Jan-26 03:00 15-Jan-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ALTALINK 22-Jan-26 07:00 22-Jan-26 18:30 11.5 Hours
Daily		 922L (17s Benalto - 310p Sundance) Floating 922L OHSW between strs 922L1 and 922L7, in preparation to raise str 922L4. See also SAP: 401750 926L RB required due to proximity  
ALTALINK 22-Jan-26 07:15 22-Jan-26 17:45 10.5 Hours
Daily		 202L (61s Lodgepole - 62s Brazeau Plant) replacing arm and insulators str 85  
ALTALINK 22-Jan-26 19:00 23-Jan-26 18:30 23.5 Hours
Continuous		 926L (17s Benalto - 310p Sundance) Floating 926L OHSW between strs 926L1 and 926L7, in preparation to raise str 922/926L4 See also SAP: 401746 922L RB required due to proximity  
ALTALINK 24-Jan-26 07:15 24-Jan-26 17:45 10.5 Hours
Daily		 1206L (12s Heartland - 89s Ellerslie) Replacing insulator on structure 43  
ATCO 26-Jan-26 09:00 04-Feb-26 15:00 9.25 Days
Continuous		 9L57 (939s Livock - 960s Birchwood Creek) 9L57 Line to Ground Clearance Mitigation  
ALTALINK 02-Feb-26 07:00 02-Feb-26 18:30 11.5 Hours
Daily		 922L (17s Benalto - 310p Sundance) Clipping in 922L OHSW between strs 922L1 and 922L7, after raising 922/926L4. See also SAP: 401749 926L RB required due to proximity  
ALTALINK 02-Feb-26 19:00 03-Feb-26 18:30 23.5 Hours
Continuous		 926L (17s Benalto - 310p Sundance) Clipping in 926L OHSW between strs 926L1 and 926L7, after raising str 922/926L4 See also SAP: 401745 922L RB required due to proximity  
ATCO 09-Feb-26 09:00 18-Feb-26 13:00 9.17 Days
Continuous		 9L57 (939s Livock - 960s Birchwood Creek) 9L57 Line to Ground Clearance Mitigation  
ATCO 17-Feb-26 09:00 03-Mar-26 17:00 14.33 Days
Continuous		 972s 240kV Bus 900BS1 (972s Tinchebray) Install Breaker 904 and 904CT
On release leave Bkr 904, 904A/904B closed as feed through (disable bkr trips), Bkr 901 still protecting 9L93		  
ATCO 23-Feb-26 09:00 04-Mar-26 13:00 9.17 Days
Continuous		 9L57 (939s Livock - 960s Birchwood Creek) 9L57 Line to Ground Clearance Mitigation  
SUNCOR 01-Mar-26 08:00 05-Mar-26 20:00 4.5 Days
Continuous		 29EDD-1 Millennium, 29EDD-1 T2 (29EDD-1 Millennium) 29EDD-1S - Correct leaning structure for 29CVT-13 (T2 Outage) - 300551776  
SUNCOR 02-Mar-26 08:00 08-Mar-26 20:00 6.46 Days
Continuous		 29PL9-16 (29EDD-1 Millennium - 29EDD-94 Voyageur) 29EDD1;29PT418/29PL9-16 SYSTEM;PM 5y,10y
  
ALTALINK 03-Mar-26 07:00 09-Mar-26 17:00 6.38 Days
Continuous		 944L (132s Ware Junction - 275s Jenner) Line outage to replace line protection relays at 132s Ware Junction, replace relay comm cards and update settings on line protections at 275s Jenner and implement third terminal 1080s Jurassic line protection relays. End to end testing between all three sites.  
ALTALINK 04-Mar-26 07:00 05-Mar-26 18:00 1.46 Days
Continuous		 1002L (163s Amoco Empress - 275s Jenner) South Crew will be doing component replacement on 1002L (STR 67-99)  
ALTALINK 04-Mar-26 23:00 05-Mar-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 05-Mar-26 03:00 05-Mar-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ALTALINK 05-Mar-26 07:00 05-Mar-26 18:00 11 Hours
Daily		 1037L (138s Windy Flats - 266s SC1), 1037L (237s Foothills - 266s SC1) South Crew will be doing component replacement on 1037L (STR 280-342)See also SAP: 401547 1038L RB Required due to proximity.  
SUNCOR 09-Mar-26 08:00 15-Mar-26 20:00 6.5 Days
Continuous		 29PL9-17 (29EDD-1 Millennium - 29EDD-94 Voyageur) 29EDD1;29PT419/29PL9-17 SYSTEM;PM 5y,10y
  
ATCO 09-Mar-26 13:00 18-Mar-26 09:00 8.83 Days
Continuous		 9L57 (939s Livock - 960s Birchwood Creek) 9L57 Line to Ground Clearance Mitigation  
ALTALINK 10-Mar-26 07:00 10-Mar-26 18:00 11 Hours
Daily		 1072L (103s Goose Lake - 205s Castle Rock Ridge) South Crew will be doing component replacement on 1072L15  
ATCO 10-Mar-26 09:00 14-Apr-26 17:00 35.33 Days
Continuous		 972s 240kV Bus 900BS2 (972s Tinchebray) Install Breakers 905/906, 905CT/906CT, switches 905A/906B
On release leave Bkrs 905/906, 905A/905B, and 906A/906B closed as feed through (disable bkr trips), Bkr 903 still protecting 9L93, leave new 9L62D1 open for future line connection		  
ALTALINK 12-Mar-26 07:00 13-Mar-26 18:00 1.46 Days
Continuous		 1325L (510s Sunnybrook - AML 511s Crossings) South Crew will be doing component replacement on 1325L (STR 501-542)  
ALTALINK 13-Mar-26 07:15 13-Mar-26 17:45 10.5 Hours
Daily		 199L (268s Whitecourt - 199AL tap) Replace keeper keys at structure 375  
ALTALINK 16-Mar-26 07:00 25-Mar-26 18:00 9.46 Days
Continuous		 87s 240kV West Bus (87s Gaetz), 87s T1 (87s Gaetz), 914L (63s Red Deer - 87s Gaetz) Installing new 87s1752 & 87s1952. Closing Open Points 'F', 'G', 'H'.  
ATCO, SUNCOR 16-Mar-26 08:00 22-Mar-26 20:00 6.5 Days
Continuous		 29PL9-1 (29EDD-1 Millennium - 848s Ruth Lake) 29EDD1;29CVT-3 SYSTEM;PM 5y,10y
  
ATCO 16-Mar-26 10:00 16-Mar-26 16:00 6 Hours
Continuous		 715s 701 (715s Leming Lake), 7L583 (715s Leming Lake - 970s Bourque) PRC-005 Trip Coil Testing, 701CT Inspection/ Testing  
ATCO 17-Mar-26 10:00 17-Mar-26 16:00 6 Hours
Continuous		 715s 702 (715s Leming Lake), 7L91 (715s Leming Lake - 826s Marguerite Lake) PRC-005 Trip Coil Testing, 702CT Inspection/ Testing  
ATCO 18-Mar-26 10:00 18-Mar-26 16:00 6 Hours
Continuous		 715s 703 (715s Leming Lake), 7L66 (715s Leming Lake - 717s Ethel Lake) PRC-005 Trip Coil Testing, 703CT Inspection/ Testing  
ALTALINK 23-Mar-26 07:00 26-Mar-26 16:30 3.4 Days
Continuous		 AML 511s T30 (AML 511s Crossings), AML 511s SVC Plus (AML 511s Crossings) Firmware upgrades on protections that are OOS, VCS Maintenance, Annual SVC+ maintenance  
ATCO, SUNCOR 23-Mar-26 08:00 29-Mar-26 20:00 6.5 Days
Continuous		 29PL9-2 (29EDD-1 Millennium - 848s Ruth Lake) 29EDD1;29CVT-1 SYSTEM;PM 5y,10y  
ALTALINK 26-Mar-26 07:00 26-Mar-26 18:00 11 Hours
Daily		 237s T2 (237s Foothills), 237s 240kV Bus 2 (237s Foothills) Install bus support piles for new 240kV Bay.  
ALTALINK 27-Mar-26 07:00 27-Mar-26 18:00 11 Hours
Daily		 237s T1 (237s Foothills), 237s 240kV Bus 1 (237s Foothills) Install bus support piles for new 240kV Bay.  
ALTALINK 30-Mar-26 07:00 08-Apr-26 18:00 9.46 Days
Continuous		 87s 240kV East Bus (87s Gaetz), 87s T2 (87s Gaetz), 914L (86s Bigstone - 87s Gaetz) Installing new 87s1352 & 87s1552. Closing Open points 'E', 'J', 'K' & 'L'. Creating permanent bus cut between 87s27 & 87s 240kV East Bus.  
ATCO, SUNCOR 30-Mar-26 08:00 05-Apr-26 20:00 6.5 Days
Continuous		 6L32 (29EDD-1 Millennium - 737s ATC Horseshoe) 29EDD1;29CVT-6 SYSTEM;5y,10y
  
SUNCOR 01-Apr-26 08:00 10-Apr-26 20:00 9.5 Days
Continuous		 29EDD-34 29PT-341 (29EDD-34), 29EDD-34 29-952-142 (29EDD-34), 29EDD-34 29-952-143 (29EDD-34), 29EDD-34 29-652-10200T (29EDD-34), 29EDD-34 29-652-10301 (29EDD-34), 29EDD-34 29-652-10302 (29EDD-34), 29EDD-34 29-652-10303 (29EDD-34), 29EDD-34 29PS-0375 (29EDD-34), 29EDD-34 29PS-0380 (29EDD-34), 29EDD-34 29PS-0381 (29EDD-34), 29EDD-34 29PS-0383 (29EDD-34), 29EDD-34 29PS-609 (29EDD-34) 10 year PM on 29EDD34;29PT-341 system and 5 year, 10 year PM on 29EDD34;29PP-103 system
  
SUNCOR 01-Apr-26 08:00 11-Apr-26 20:00 10.5 Days
Continuous		 29EDD-34 29PT-340 (29EDD-34) 29EDD34;29PT-340 SYSTEM;PM 5y,10y; 29EDD34;29PP-102 SYSTEM;PM 5y,10y
  
ENMAX, ALTALINK 04-Apr-26 08:00 04-Apr-26 18:00 10 Hours
Continuous		 1003L (74s Janet - SS-25) Surge Arrestor Power Factor Test - 25MD240-1003  
ENMAX, ALTALINK 04-Apr-26 08:00 04-Apr-26 18:00 10 Hours
Continuous		 1003L (74s Janet - SS-25) Surge Arrestor Power Factor Test - 25MD240-1003  
ENMAX, ALTALINK 05-Apr-26 08:00 05-Apr-26 18:00 10 Hours
Continuous		 985L (74s Janet - SS-25) Surge Arrestor Power Factor Test - 25MD240-985  
ENMAX, ALTALINK 05-Apr-26 08:00 05-Apr-26 18:00 10 Hours
Continuous		 985L (74s Janet - SS-25) Surge Arrestor Power Factor Test - 25MD240-985  
SUNCOR 06-Apr-26 08:00 12-Apr-26 20:00 6.5 Days
Continuous		 29PL9-3 (29EDD-1 Millennium - 29EDD-3), 29EDD-3 29PT-6 (29EDD-3) 29EDD1;29CVT-4 SYSTEM;PM 5y,10y;
 
ENMAX 06-Apr-26 08:00 14-Apr-26 16:00 8.33 Days
Continuous		 65.2TR (SS-65) Tap Changer Inspection - 65.2-TC  
ALTALINK 13-Apr-26 07:00 20-Apr-26 18:00 7.46 Days
Continuous		 87s 240kV West Bus (87s Gaetz), 87s T1 (87s Gaetz), 914L (86s Bigstone - 87s Gaetz) Closing Open point 'I' and creating second permanent bus cut between 87s26 & 87s 240kV West Bus.  
SUNCOR 13-Apr-26 08:00 19-Apr-26 20:00 6.5 Days
Continuous		 29EDD-1 T1 (29EDD-1 Millennium), 29EDD-1 260kV South Bus 1 (29EDD-1 Millennium), 29EDD-1 72kV South Bus (29EDD-1 Millennium) 29EDD1;XFMR T1; X260B1; X72B1 SYSTEM;PM 5y  
ALTALINK, TRANSALTA 13-Apr-26 10:00 17-Apr-26 16:00 4.25 Days
Continuous		 179s T1 (179s Gleichen) 179s Oil reclaim, 25kV insulator replacements throughout 179s25,179s9,179s26 line sides & 25kV Bus / VR1 and bus side of 179s6, T1 maintenance,& VR1 maintenance.  
SUNCOR 20-Apr-26 08:00 26-Apr-26 20:00 6.5 Days
Continuous		 29EDD-1 T2 (29EDD-1 Millennium), 29EDD-1 260kV North Bus 2 (29EDD-1 Millennium), 29EDD-1 72kV North Bus (29EDD-1 Millennium) 29EDD1;XFMR T2; N260B2; N72B1 SYSTEM;PM 5y  
ATCO 21-Apr-26 09:00 26-Apr-26 17:00 5.33 Days
Continuous		 9LA93 (973s Lanes Lake - 9L93 tap) Cutover and commission 9L93 protection ccts from Bkrs 901/903 to Bkrs 904/905

  
ALTALINK 22-Apr-26 23:00 23-Apr-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 23-Apr-26 03:00 23-Apr-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ALTALINK 27-Apr-26 13:00 08-May-26 17:00 11.17 Days
Continuous		 275s T2 (275s Jenner) 275sT2 Oil Reclaim  
ATCO 04-May-26 09:00 18-May-26 17:30 14.35 Days
Continuous		 13L50 (2029s Heathfield - 2075s Newell) Kinbrook Addition to 2075s  
ATCO 04-May-26 09:00 18-May-26 17:30 14.35 Days
Continuous		 2029s T11 (2029s Heathfield) Kinbrook Addition to 2075s Newell.  
ATCO 04-May-26 09:00 18-May-26 17:30 14.35 Days
Continuous		 2075s T11 (2075s Newell) Kinbrook Addition to 2075s Newell.  
ATCO 05-May-26 09:00 07-May-26 17:00 2.33 Days
Continuous		 9L59 (801s Anderson - 9LA59 tap), 9L59 (972s Tinchebray - 9LA59 tap) Connect new 907B to 900BS1
  
ATCO 07-May-26 09:00 19-May-26 17:00 12.33 Days
Continuous		 9L16 (755s Cordel - 972s Tinchebray) GOI is required on 907B to isolate 908/909 bay and new 9L16.  
ATCO 08-May-26 09:00 09-May-26 17:00 1.33 Days
Continuous		 972s 240kV Bus 900BS2 (972s Tinchebray) Connect new 909A to 900BS2  
ATCO, ALTALINK 11-May-26 07:00 14-May-26 18:00 3.46 Days
Continuous		 7LA114 (658s Chard - 7L114 tap), 7L114 (72s Leismer - 7LA114 tap), 7L114 (907s Waddell - 7LA114 tap), 907s Waddell AltaLink outage on 72sT2 causing an outage to 7L114 at 907S  
ALTALINK, ATCO 11-May-26 07:00 14-May-26 18:00 3.46 Days
Continuous		 72s T2 (72s Leismer), 72s 144kV Bus (72s Leismer), 7L114 (72s Leismer - 7LA114 tap) Transformer maintenance, doble, install Coresense & Qualitrol  
ALTALINK, ATCO 11-May-26 07:00 14-May-26 18:00 3.46 Days
Continuous		 72s 114 (72s Leismer), 7L114 (72s Leismer - 7LA114 tap) maintenance  
SUNCOR 18-May-26 08:00 24-May-26 20:00 6.5 Days
Continuous		 29PL9-12 (29EDD-34 - 29EDD-65) 29EDD34;29PL9-12 SYSTEM;PM 5y,10y
  
ATCO 19-May-26 09:00 19-May-26 17:00 8 Hours
Continuous		 9L16 (755s Cordel - 972s Tinchebray), 755s 904 (755s Cordel), 755s 905 (755s Cordel), 972s 903 (972s Tinchebray) Disconnect 9L16 from existing A-frame deadend and 9L16D2 (to be renamed 9L86D1)
Restore bus leave renamed 9L86D1 open for future line connection.
  
ATCO 19-May-26 09:00 29-May-26 17:00 10.33 Days
Continuous		 9L16 (755s Cordel - 972s Tinchebray) Disconnect 9L16 from existing A-frame deadend and 9L16D2 (to be renamed 9L86D1)
Restore bus leave renamed 9L86D1 open for future line connection.
  
ALTALINK 19-May-26 13:00 29-May-26 18:00 10.21 Days
Continuous		 275s T1 (275s Jenner) 275sT1 Oil Reclaim  
ATCO 02-Jun-26 09:00 13-Jun-26 17:00 11.33 Days
Continuous		 972s 905B (972s Tinchebray), 972s 906A (972s Tinchebray) Connect new 9L62 to 972S and prepare to energize.
String Conductors/OPGW 9L62 from Str #3 to substation A-frame deadends and connect to 9L62D1, coordinate with AML conductor jumpers and OPGW termination at the TFO boundary 9L86 Str 409		  
ALTALINK 10-Jun-26 23:00 11-Jun-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 11-Jun-26 03:00 11-Jun-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ATCO 14-Jun-26 09:00 25-Jun-26 17:00 11.33 Days
Continuous		 9L62 (972s Tinchebray - 87s Gaetz) Work on parallel line 9L86  
ATCO, CNRL 15-Jun-26 05:00 29-Jun-26 10:00 14.21 Days
Continuous		 859s 701TD (859s Primrose), 859s 701 (859s Primrose), 859s 704 (859s Primrose), 859s Protection & Control (859s Primrose), 859s RTU/SCADA (859s Primrose), 859s 52G (859s Primrose), 859s 701T (859s Primrose) maintenance  
ATCO 16-Jun-26 09:00 25-Jun-26 17:00 9.33 Days
Continuous		 972s 240kV Bus 900BS2 (972s Tinchebray) Connect new 9L86 to 972S and prepare to energize.
String Conductors/OPGW 9L86 from Str #3 to substation A-frame deadends and connect to 9L86D1, coordinate with AML conductor jumpers and OPGW termination at the TFO boundary 9L86 Str 409
Complete protection commissioning		  
ATCO 29-Jun-26 13:00 30-Jun-26 17:00 28 Hours
Continuous		 9LA93 (973s Lanes Lake - 9L93 tap) Line to Ground Clearance Mitigation, Span 50-51. Repair deficiency on structure 57  
ATCO 06-Jul-26 10:00 27-Nov-26 16:00 144.29 Days
Continuous		 2015s 902 (2015s Yeo) Remove circuit breaker for use at 2102S Armistead. New breaker to be installed at 2015S Yeo substation once received from manufacturer.  
SUNCOR 15-Jul-26 08:00 25-Jul-26 20:00 10.5 Days
Continuous		 29EDD-2 29PT-3 (29EDD-2 Tar Island), 29PL6-22 (29EDD-1 Millennium - 29EDD-2 Tar Island) 29EDD2;29PT-3, 29PL6-22 SYSTEM;PM 5y,10y
  
ATCO 21-Jul-26 08:00 22-Jul-26 17:00 1.38 Days
Continuous		 7L65 (709s Vegreville - 7LA65 tap), 7L65 (710s Vermilion - 7LA65 tap), 7LA65 (708s Grizzly Bear - 7L65 tap) Switch Repairs, 7LA65D1  
ALTALINK 29-Jul-26 23:00 30-Jul-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 30-Jul-26 03:00 30-Jul-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ALTALINK 10-Aug-26 09:30 13-Aug-26 17:00 3.31 Days
Continuous		 702L (137s Sedgewick - 757s Battle River) Interphase spacers and pole replacements  
ATCO 10-Aug-26 10:00 13-Aug-26 16:30 3.27 Days
Continuous		 7L702 (137s Sedgewick - 757s Battle River) Interphase spacers and pole replacements  
ATCO 17-Aug-26 10:00 20-Aug-26 16:30 3.27 Days
Continuous		 7L702 (137s Sedgewick - 757s Battle River) Interphase spacers and pole replacements  
ALTALINK 17-Aug-26 10:00 20-Aug-26 16:30 3.27 Days
Continuous		 702L (137s Sedgewick - 757s Battle River) Interphase spacers and pole replacements  
ALTALINK, ATCO, FMGW 18-Aug-26 08:00 19-Aug-26 17:00 1.38 Days
Continuous		 964AL (1024s Granlea - 964L tap), 1024s PT-6001 (1024s Granlea), 1024s PT-6002 (1024s Granlea), 1024s 952-600001 (1024s Granlea), 1024s PS-6005 (1024s Granlea), 1024s PS-6006 (1024s Granlea), 1024s PS-6007 (1024s Granlea), 1024s PS-6008 (1024s Granlea), 1024s 489-600201 (1024s Granlea) maintenance activities (testing and inspection) of electrical equipment  
ALTALINK 07-Sep-26 07:00 08-Sep-26 18:00 1.46 Days
Continuous		 237s T2 (237s Foothills), 237s 240kV Bus 2 (237s Foothills) Closing Open Point 'C'  
ALTALINK 09-Sep-26 07:00 10-Sep-26 18:00 1.46 Days
Continuous		 237s T1 (237s Foothills), 237s 240kV Bus 1 (237s Foothills) Closing Open Points 'A' & 'B'  
ALTALINK 10-Sep-26 18:00 15-Sep-26 13:00 4.79 Days
Continuous		 1141L (1172s Laramide - 237s Foothills) End to end testing with Laramide 1172s  
ALTALINK 16-Sep-26 23:00 17-Sep-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 17-Sep-26 03:00 17-Sep-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ATCO 21-Sep-26 10:00 24-Sep-26 16:00 3.25 Days
Continuous		 888s 906 (888s Dover) 21B/9L74 relay replacement. Cutover breaker and CT to new protection  
ATCO 25-Sep-26 10:00 28-Sep-26 16:00 3.25 Days
Continuous		 888s 905 (888s Dover) 21B/9L74 relay replacement. Cutover breaker and CT to new protection  
ALTALINK 05-Oct-26 08:00 28-Nov-26 19:00 54.5 Days
Continuous		 62s T2 (62s Brazeau Plant) maintenance  
ATCO 05-Oct-26 10:00 08-Oct-26 16:00 3.25 Days
Continuous		 9L74 (888s Dover - 960s Birchwood Creek) 21B/9L74 relay three terminal line testing  
ATCO 12-Oct-26 10:00 15-Oct-26 16:00 3.25 Days
Continuous		 888s 906 (888s Dover) 21A/9L74 relay replacement. Cutover breaker and CT to new protection  
ATCO 16-Oct-26 10:00 19-Oct-26 16:00 3.25 Days
Continuous		 888s 905 (888s Dover) 21B/9L74 relay replacement. Cutover breaker and CT to new protection  
ATCO 26-Oct-26 10:00 29-Oct-26 16:00 3.25 Days
Continuous		 9L74 (888s Dover - 960s Birchwood Creek) 21B/9L74 relay three terminal line testing  
Syncrude 03-Nov-26 08:00 18-Nov-26 16:00 15.33 Days
Continuous		 UE-1 (D05 - UE-1 Syncrude Plant 30-2), T1 (D05 Syncrude), D05 511 (D05), D05 519 (D05), D05 71 (D05), D05 71A (D05), D05 71B (D05), D05 80 (D05), D05 80B (D05), D05 79 (D05), D05 79B (D05), D05 73 (D05), D05 73A (D05), D05 73B (D05), D05 75 (D05), D05 75A (D05), LCF (D05), ML-4 (D05), UE-1 7206 (UE-1 Syncrude Plant 30-2), UE-1 72-16 (UE-1 Syncrude Plant 30-2), D05 511A (D05), D05 519A (D05), D05 519B (D05), D05 80A (D05), D05 79A (D05), D05 75B (D05) complete 6-Year 72 kV A bus preventive maintenance in D05 substation  
ALTALINK 05-Nov-26 03:00 05-Nov-26 07:00 4 Hours
Daily		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 23-Dec-26 23:00 24-Dec-26 03:00 4 Hours
Continuous		 62s T1 (62s Brazeau Plant) maintenance  
ALTALINK 24-Dec-26 03:00 24-Dec-26 07:00 4 Hours
Daily		 62s T2 (62s Brazeau Plant) maintenance  
ATCO 09-Feb-27 09:00 11-Feb-27 17:00 2.33 Days
Continuous		 7L228 (845s Big Mountain - 7L20 tap) AESO project P2716 - Install 7L228 bypass to facilitate the installation of new line switches for the new 7LA228 T-tap line connection to the new 2103S Pakenham substation
Open 7L228, replace structures 551 and 551A, connect bypass.		  
ATCO 08-Mar-27 10:00 17-Mar-27 17:00 9.25 Days
Continuous		 9L24 (946s Oakland - 959s Lanfine), 959s 906 (959s Lanfine), 959s 905 (959s Lanfine), 946s 902 (946s Oakland), 946s 903 (946s Oakland) Replace A/B protection relays at 959S Lanfine and 946S Oakland
Cut in and reroute 9L24
Connect new 9LA24 T-tap
Commission Telecom and Protection to new 1072S Rose Lynn substation		  
ATCO 16-Mar-27 09:00 18-Mar-27 17:00 2.33 Days
Continuous		 7L228 (845s Big Mountain - 7L20 tap) AESO project P2716 - Disconnect bypass, connect new 7LA228D1 to 7LA228 Str #2, connect 7L228 to 7L228D2, connect 7L228 to 7L228D3. Renumber existing line switches 7L228D2 - D4, 7L228D3 - D5, 7L228D4 - D6
Commission DTT from Pakenham to Big Mountain		  
ATCO 22-Mar-27 09:00 25-Mar-27 17:00 3.33 Days
Continuous		 2091s 704 (2091s Thornton) AESO project P2716 - cut over new SEL 2440 wiring at 2091S, relay programming, commission DTT and LTO from 2103S Pakenham  
ATCO 26-Mar-27 09:00 29-Mar-27 17:00 3.33 Days
Continuous		 740s 704 (740s H.R. Milner), 7L20 (740s H.R. Milner - 810s Dome Cutbank) AESO project P2716 - cut over RAS #171 wiring at 740S, relay programming, commission LTO 7L20/7L228  
ATCO 12-Apr-27 10:00 19-Apr-27 17:00 7.29 Days
Continuous		 7L22 (790s Poplar Hill - 7L88 tap) Cut open 7L22, connect new line section to new 2061S Dobbs
7L22/21B relay upgrades at 790S Poplar Hill and 811S Clairmont Lake
On completion energize new 2061S Dobbs substation		  
ATCO 03-May-27 10:00 06-May-27 17:00 3.29 Days
Continuous		 7L22 (811s Clairmont Lake - 7L88 tap) 7L22/21B relay upgrade at 811S Clairmont Lake
Upon completion new 2061S Dobbs substation ready to energize		  
ATCO 10-May-27 10:00 11-May-27 17:00 31 Hours
Continuous		 7L03 (749s Flyingshot Lake - 7L09 tap) Cutover and commission RAS analogs and LTO to 790S Poplar Hill RAS Hub  
ATCO 12-May-27 10:00 13-May-27 17:00 31 Hours
Continuous		 7L03 (731s Elmworth - 7L09 tap) Cutover and commission LTO to 790S Poplar Hill RAS Hub  
ATCO 14-May-27 10:00 15-May-27 17:00 31 Hours
Continuous		 7L69 (731s Elmworth - 815s Goodfare) Cutover and commission LTO to 790S Poplar Hill RAS Hub  
ATCO 16-May-27 10:00 17-May-27 17:00 31 Hours
Continuous		 7L07 (790s Poplar Hill - 815s Goodfare) Cutover and commission LTO to 790S Poplar Hill RAS Hub  
SUNCOR 01-Jun-27 08:00 10-Jun-27 17:00 9.38 Days
Continuous		 635EDD-1000 635-752-635PT-1000 (635EDD-1000), 635EDD-1000 635PT-1000 (635EDD-1000) FH - Maintenance on Transformer, associated breakers, other equipment in isolation boundary and protection system testing.  
SUNCOR 11-Jun-27 08:00 20-Jun-27 17:00 9.38 Days
Continuous		 635EDD-1000 635-752-635PT-1001 (635EDD-1000), 635EDD-1000 635PT-1001 (635EDD-1000) FH - Maintenance on Transformer, associated breakers, other equipment in isolation boundary and protection system testing.  
ATCO 20-Jul-27 08:00 21-Jul-27 17:00 1.38 Days
Continuous		 7L53 (706s Irish Creek - 7LA53 tap), 7LA53 (969s Lindbergh - 7L53 tap), 7L53 (700s Bonnyville - 7LA53 tap) Cold Lake Area Project to connect 1064s  
ATCO 22-Jul-27 08:00 25-Jul-27 17:00 3.38 Days
Continuous		 7L91 (715s Leming Lake - 826s Marguerite Lake) Cold Lake Area Energy Centre Project
  
ALTALINK, ATCO, FMGW 17-Aug-27 08:00 18-Aug-27 17:00 1.38 Days
Continuous		 964AL (1024s Granlea - 964L tap), 1024s PT-6001 (1024s Granlea), 1024s PT-6002 (1024s Granlea), 1024s 952-600001 (1024s Granlea), 1024s PS-6005 (1024s Granlea), 1024s PS-6006 (1024s Granlea), 1024s PS-6007 (1024s Granlea), 1024s PS-6008 (1024s Granlea), 1024s 489-600201 (1024s Granlea) maintenance activities (testing and inspection) of electrical equipment  
ALTALINK 08-Nov-27 08:30 11-Nov-27 17:30 3.38 Days
Continuous		 409s 110 (409s Shell Scotford) Install new Deadend corner structure on ALC02L  
ALTALINK 08-Nov-27 08:30 11-Nov-27 17:30 3.38 Days
Continuous		 409s 107 (409s Shell Scotford) Install new Deadend corner structure on ALC02L.  
ATCO 08-Nov-27 09:00 11-Nov-27 17:00 3.33 Days
Continuous		 ALC02L (409s Shell Scotford - 879s Upgrader) Install new Deadend corner structure on ALC02L  
ATCO 08-Nov-27 09:00 11-Nov-27 17:00 3.33 Days
Continuous		 ALC01L (408s Air Liquide Scotford - 409s Shell Scotford) Install new Deadend corner structure on ALC02L.  
ATCO 06-Mar-28 10:00 22-Mar-28 16:00 16.21 Days
Continuous		 826s 903 (826s Marguerite Lake), 826s 907 (826s Marguerite Lake), 826s 901T (826s Marguerite Lake) Expand 240kV ring bus for new 9L42 line  
ALTALINK 13-Mar-28 09:30 16-Mar-28 17:30 3.33 Days
Continuous		 939L (77s Sagitawah - 809s Louise Creek) Cut over 9L939 to temp bypass structures to allow for installation of new deadend corner towers. These are required to make the final connections to the new 2105S Jackson substation.  
ATCO 13-Mar-28 10:00 16-Mar-28 17:00 3.29 Days
Continuous		 9L939 (77s Sagitawah - 809s Louise Creek) Cut over 9L939 to temp bypass structures to allow for installation of new deadend corner towers. These are required to make the final connections to the new 2105S Jackson substation  
ALTALINK 17-Mar-28 09:30 17-Apr-28 17:30 31.33 Days
Continuous		 939L (77s Sagitawah - 809s Louise Creek) Install foundations (TBD assume concrete), assemble and erect new Q-towers 9L938/9L939-155A and 9L938/9L939-156A in existing ROW centreline. Daily outage until such a time as the new towers begin to encroach on 9L938.  
ATCO 17-Mar-28 10:00 17-Apr-28 17:00 31.29 Days
Continuous		 9L938 (77s Sagitawah - 809s Louise Creek) Install foundations (TBD assume concrete), assemble and erect new Q-towers 9L938/9L939-155A and 9L938/9L939-156A in existing ROW centreline. Daily outage until such a time as the new towers begin to encroach on 9L938.  
ALTALINK 18-Apr-28 09:30 25-Apr-28 17:30 7.33 Days
Continuous		 938L (77s Sagitawah - 809s Louise Creek) Open 9L938 conductors, complete assembly and connect to the new Q-Towers 9L938/9L939-155A and 9L938/9L939-156A, string to 2105S Jackson deadend and terminate. Re-label 9L938 segment from 809S Louise Creek to 2105S Jackson to 9L140.  
ATCO 18-Apr-28 10:00 25-Apr-28 17:00 7.29 Days
Continuous		 9L938 (77s Sagitawah - 809s Louise Creek) Open 9L938 conductors, complete assembly and connect to the new Q-Towers 9L938/9L939-155A and 9L938/9L939-156A, string to 2105S Jackson deadend and terminate.
Relabel 9L938 segment from 809S Louise Creek to 2105S Jackson to 9L140.		  
ALTALINK 01-May-28 09:30 04-May-28 17:30 3.33 Days
Continuous		 939L (77s Sagitawah - 809s Louise Creek) Disconnect 9L939 conductors from temp structure  
ATCO 01-May-28 10:00 04-May-28 17:00 3.29 Days
Continuous		 9L939 (77s Sagitawah - 809s Louise Creek) Disconnect 9L939 conductors from temp structure 9L939 -155A - 155E reconnect to existing structures 9L938/9L939-156 and 9L938/9L939-155, connect to the new Q-Towers 9L938/9L939-155A and 9L938/9L939-156A, string to 2105S Jackson deadend and terminate.
Relabel 9L939 segment from 809S Louise Creek to 2		  
ATCO 08-May-28 09:00 10-Jul-28 17:00 63.33 Days
Continuous		 959s 240kV Bus 900BS2 (959s Lanfine) GOI on 9L141 until line terminated into 1162S Fair Acres and ready to energize  
ATCO 08-May-28 09:00 10-Jul-28 17:00 63.33 Days
Continuous		 959s 240kV Bus 900BS2 (959s Lanfine) GOI on 902/903 until line terminated and 1162S Fair Acres ready to energize  
ATCO 09-May-28 10:00 13-May-28 17:00 4.29 Days
Continuous		 9L02 (809s Louise Creek - 813s Little Smoky) Install concrete foundations for new structures 9L02/320A, 320H in preparation to cut into 9L02 and convert to a t-tap.  
ATCO 15-May-28 09:00 17-May-28 17:00 2.33 Days
Continuous		 959s 240kV Bus 900BS1 (959s Lanfine) Connect new bus from new 902B to existing switch 901A to add new line 9L141,
Cutover and commission 900PT1 ccts to new 9L141 relays		  
ATCO 18-May-28 09:00 20-May-28 17:00 2.33 Days
Continuous		 959s 240kV Bus 900BS2 (959s Lanfine) Connect new bus from new Bkr 903 to existing switch 903B to add new line 9L141,
Cutover and commission 900PT2 ccts to new 9L141 relays		  

AB-BC, AB-SK & AB-MATL: refer to AESO web posting: http://itc.aeso.ca/itc/public/atc
Also,
AB-BC, AB-SK & AB-MATL: refer to ISO Rule 203.6: http://www.aeso.ca/rulesprocedures/18592.html

Prepared On: 2025-11-26   15:42:17


This document and the information contained herein are based upon information and data which by their nature contain a degree of uncertainty and are subject to change. In addition, this document may contain information and data from public sources and/or third parties, which have been assumed to be accurate and complete and have not been verified. Accordingly, the Independent System Operator, operating as the Alberta Electric System Operator (the "AESO") makes no warranty, representation or guarantee, express or implied, with respect to this document or the information contained herein, including, but not limited to, any warranty, representation or guarantee of accuracy, completeness, timeliness, reliability, availability, absence of computer virus, non- infringement, merchantability or suitability for any purpose. Under no circumstances will the AESO, its members, officers, employees, contractors or agents, or any of their respective affiliates, be liable for any errors or omissions in, or any losses, damages or claims whatsoever, whether in contract, tort or otherwise, arising from use of or reliance upon, this document or any information contained herein.

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