Outages

Each week, the AESO compiles a report of all the planned transmission outages required by transmission facility owners (TFOs) for maintenance and switching activities. The AESO System Controller studies the operation of the Alberta Interconnected Electric System under various possible contingencies, and creates an operational plan that addresses contingency plans for the coming week, with a focus on maintaining reliable operation and minimizing any disruption to market participants. The following reports provide information for market participants on generator, transmission and load outages.

1. Long Range Significant Transmission Outages

This report helps coordinate outages between transmission facility owners (TFOs) and informs participants, generally, by listing outage requests from TFOs for the period 24 months beyond the current approved outages listing. It concerns significant transmission facilities as defined in ISO Rule 306.4. The report is updated on Wednesdays but may be updated at other times, if necessary, and each posting is time-stamped. The outages are posted for awareness, but have not necessarily been approved yet by the System Controller.

2. System Coordination Plan - Approved Outages

This report sends notice of outage approvals to TFOs. It includes all transmission outages 69 kV or greater that have been approved by the System Controller for the following operating week (Saturday to Friday). The report is updated on Wednesdays but may be updated at other times, if necessary, and each posting is time-stamped.

3. 24 Month Supply and Demand Graphs

These graphs help plan generator and intertie outages by presenting the available supply compared with expected AIES demand over a rolling window of 24 months. AIES demand includes load and required reserve. The supply portion accounts for scheduled generator outages and derates, including those caused by transmission outages, and reductions to intertie capability due to transmission system conditions. Generating unit outages are aggregated so that individual unit outage information is not disclosed. The graphs are updated each weekday, sometimes more than once per day, and time-stamped. The information is available only in this graphical format.

4. Daily Outage, Monthly Outage and 7 Days Hourly Available Capability Reports

These reports illustrate generating unit outages based on pool participant submissions in the Energy Trading System. Both outage reports are based on the difference between maximum capability and available capability of generating units, whereas the 7 Days Hourly Available Capability Report illustrates the availability percentage calculated as the sum of the available capability divided by the total maximum capability.  All three reports are updated at regular intervals and are time stamped. The outage information is aggregated by fuel type to avoid identifying any particular generating unit. Additionally, a generic 350 MW unit maximum capability is used to protect the identity of coal generating units. Daily load outages are also illustrated within the Daily Outage Report and are time stamped separately as these outages are not updated as frequently as the generating unit outages. 

5. Available Transfer Capacity Report

This report presents the current and anticipated available transfer capabilities for the Saskatchewan and British Columbia interties to create market awareness of Alberta import/export conditions. The report covers a selectable period, on an hour-by-hour basis, as far out as thirteen (13) months.

To better understand the implications of outages in general, it is important for stakeholders to also view the appropriate ISO Rule or Operating Policy and Procedure (OPP), available on the AESO website. For example, the OPPs address the resulting curtailment of net generation and operating reserve for affected generators. There could also be additional remedial actions due to unexpected system conditions.