The Alberta Electric System Operator (AESO) has provided more details on why there were multiple grid alerts last week.

Marie-France Samaroden, AESO Vice President, Grid Reliability said that the first grid alert was issued mid-week last week, on April 3 in the evening.

"The AESO issues a grid alert when the power system is under stress and emergency reserves are needed to demand and maintain system reliability. We [had] high renewable energy during the day on April 3, as well as high renewables forecasted. An unexpected outage of thermal generation led to tight conditions during our evening peak and prompted the grid alert."

However, she added that the grid alert ended a little over an hour after it had been declared. 

"The event was quickly resolved with the support of import from interties [transmission lines that connect separate electric grids]."

However, less than 48 hours later on Friday, another grid alert was issued just before 7 a.m.

"Although our studies, the evening prior, indicated that we would have 800 Megawatts of extra supply available, the wind generation that materialized was 900 Megawatts below forecast," Samaroden said. "At 8:49 a.m., we had a Thermal Generator trip offline, which resulted in a loss of 400 megawatts."

She specified that the thermal generator was a natural gas generator. At that point, AESO directed their transmission and distribution partners to shed 250 megawatts of load.

"The load set directive within place from 8:53 a.m. to 9:16 a.m. The load shed is a tool that we use to ensure overall grid stability. Generation increased and we returned to normal operations at 11 a.m." 

Due to the grid alert on Friday, there were several rotating outages impacting thousands of residents across the province. A few hours after AESO's grid alert on Friday, ENMAX alerted consumers in Calgary of power outages in several communities.

"AESO has issued a province-wide directive that power consumption must be reduced due to an imbalance in supply and demand. Customers in the areas of Springbank Hill, Signal Hill, West Springs, Aspen Woods, Strathcona Park, Skyline East, McCall, Deerfoot Mall, Mckenzie Lake, Mckenzie Towne, and East Shepard Industrial may see power disruptions lasting about 30 minutes," a tweet on Friday morning from ENMAX stated.

Sometime later another tweet was sent, detailing that customers in the areas of Stoney 2, Thorncliffe, Huntington Hills, Greenview, Skyline West, Alyth/Bonnybrook, Highfield, Rural West, Rural Northwest, Greenwood/Greenbriar, Canada Olympic Park, Bowness, Somerset, Shawnessy would also see power disruptions lasting about 30 minutes.

Power was restored to the impacted communities later that day. Like ENMAX, EPCOR also tweeted on Friday that AESO directed them, 'to help manage power consumption in the province.'

"Rotating outages are now in effect in [Edmonton]."

The rotating outages were stopped once AESO declared an end to the grid alert as well.

"We've worked with our transmission and distribution partners and they have programs in which they rotate [the] load; they make sure that there are no hospitals are critical infrastructure in those outages as they go forward,"  Samaroden added.

The grid alerts are not the first to happen consecutively this year. In January, during a brutal cold snap, Alberta experienced multiple grid alerts. 

AESO underlines that grid alerts can occur for several reasons, some of which include unplanned generation facility outages, time of day and wind conditions, which impact the availability of solar and wind-generated energy, extremely cold or hot weather, which drives increased use of heating or air conditioning systems, as well as other factors beyond transmission and generation facility owners’ control, such as lightning, or downed power lines.

During grid alerts, consumers are asked to reduce energy consumption which includes: 

  • Turn off unnecessary lights and electrical appliances
  • Minimize the use of air conditioning/space heaters
  • Delay the use of major power-consuming appliances such as washers, dryers and dishwashers until after peak hours
  • Use cold water for washing clothes—most of the energy used goes to heating the water (only running full loads helps too)
  • Delay charging electric vehicles and/or plugging in block heaters
  • Cook with your microwave, crockpot or toaster oven instead of the stove
  • Limit the use of kitchen or bathroom ventilation fans
  • Use motion-detector lights in storage areas, garages, and outdoors when possible
  • Work on a laptop instead of a desktop computer (laptops are more energy-efficient than desktop units)

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