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    Grid Reliability and Operational Preparedness

    Background

    The Alberta Interconnected Electric System (AIES) has experienced significant disturbance events in 2020 and 2021.

    • Tripping of generation in Alberta and/or the tripping of the interties with British Columbia and Montana, including the most recent system disturbance on June 3, 2021; the subsequent activation of the Under-Frequency Load Shed (UFLS) impacted customers in Alberta.
    • While operating in an islanded mode in 2020 the AIES lost a generating unit, which led to the frequency dropping to 59.6 Hz before recovering.

    In response to these significant disturbance events and the challenging nature of the ever-evolving provincial interconnected electricity grid, the AESO has developed appropriate short-term and long-term mitigation plans to ensure the continued reliability of the grid and maintain operational preparedness.

    Increasing penetration levels of renewables and distributed energy resources (DER) on the system, combined with system frequency response and inertia concerns, as well as the nature of Alberta’s interconnection with the rest of the Western Electricity Coordinating Council (WECC) region, provides a unique set of challenges in operating the AIES and maintaining operational preparedness.

    The AESO will be proactive in ensuring the continued reliability of the electricity grid, given the evolving grid and resource mix, and expects these initiatives to support this objective in the long term. The AESO will continue to engage and collaborate with stakeholders as appropriate, as it progresses on these various initiatives.

    • Information Session | Oct. 7, 2021

      The AESO will be hosting a virtual information session on Oct. 7, 2021 from 9:30 a.m. to 11:30 a.m.

      Purpose

      The purpose of the session is to:

      • Provide an update on system events, including the June 3, 2021 event
      • Provide an update on the AESO’s mitigation plans including various initiatives that have been completed, are currently underway, or are planned in the near future to address system reliability needs
      • Discuss implications to the province’s Most Severe Single Contingency (MSSC) of 466 MW

      Information session materials

    • Information Session | March 9, 2021

      The AESO hosted a virtual information session on March 9, 2021 from 9 a.m.to 11 a.m.

      Purpose

      The purpose of the session is to provide an update on the 2020 and 2021 events, and to provide an overview of various initiatives that are planned or currently underway to address AESO event analysis findings and operational preparedness as the grid evolves.

      Information session materials

    • Information Session | July 28, 2020

      The AESO hosted a virtual information session on July 28, 2020 from 2:30 p.m. to 4 p.m.

      Purpose

      The purpose of the session is to provide an update regarding reasons for the trip, system performance during the event, and the mitigations implemented in order to reduce the risk of impacting customers in Alberta from such system events in the future.

      Background

      The Alberta Interconnected Electric System (AIES) experienced a significant disturbance event on June 7, 2020 at 2:50 p.m. due to the tripping of the interties with British Columbia (BC) and Montana (MT). This resulted in impacting customers within Alberta through the unexpected activation of the province’s Under-Frequency Load Shed (UFLS) program.

      At this point, the AESO has completed its initial investigations into the incident and the system’s response to the event including generation, load, load shed service for imports (LSSi), and system inertia. 

      Based on the preliminary investigation, the AESO has implemented initial mitigation measures to reduce the risk of a reoccurrence of impacting customers in Alberta through unexpected activation of the province’s UFLS program when under high import conditions. These initial mitigation measures include:

      • Arming additional volumes of LSSi;
      • Monitoring system inertia in real time and reducing BC/MT Available Transfer Capability (ATC) if the inertia falls below a certain threshold; and,
      • During inclement weather conditions along the Alberta-BC intertie corridor, reducing BC/MT ATC to as low as 550 MW if high imports are occurring.

      These mitigation measures will remain in effect until the AESO has completed its investigations and has evidence of improved response, particularly from generation and LSSi within the province, to under frequency-related system events.

      Information session materials