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RTOs, ISOs Seeing Load Changes, Adjusting Models Due to Pandemic

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Peter Key's picture
Freelance Writer, Editor, Consultant Self-employed

I've been a business journalist since 1985 when I received an MBA from Penn State. I covered energy, technology, and venture capital for The Philadelphia Business Journal from 1998 through 2013....

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  • Apr 2, 2020

Restrictions related to the novel coronavirus are lowering the peaks and reshaping the load curves of the nation’s regional transmission organizations and independent system operators, as well as causing the organizations to tinker with their forecast models.

PJM Interconnection is a case in point. All the 13 Mid-Atlantic and Midwest states partially or completely in its territory, as well as Washington, D.C., have stay-at-home orders in place, and most have had coronavirus-related restrictions for a while.

The RTO recently put out a comparison of its five-year average load to its load this year for the period from March 14 through March 29. This year’s daily peak was always at least 3.2 percent lower than the average and was down more than 11 percent on four occasions, including March 27, when it was off 14.7 percent, although the data for that day is preliminary. The total energy used by its customers daily was always beneath the average by at least 2.3 percent and was more than 10 percent below the average on four days, including March 27, when it was down from the average by 12.3 percent.

“What we’re working on is trying to factor in the weather, because it was unseasonably warm for March, so you’re going to have a decrease in load attributable to that,” said Jeff Shields, PJM’s media relations manager.

To attempt to account for the weather, PJM compiled a data set consisting of two columns: the values in one were the actual loads for each day and the values in the other were the values that PJM’s load forecasting model would have produced had it exactly forecast the weather for the day.

In doing that, however, PJM ran into another problem: the RTO’s forecasting model had already begun to take the load changes caused by coronavirus-related restrictions into account in making its predictions. That, Shields said, is good for PJM’s actual forecasting, but throws a monkey wrench into the RTO’s attempt to isolate the effect of coronavirus-related restrictions on its load.

To get around that, PJM will have to create a version of its forecasting model that isn’t learning from the daily load values and use that version to help it better understand the coronavirus-related restrictions’ effect. Meanwhile, PJM continues to use the version of the model that is learning from its daily load values to calculate its actual forecasts.

In its effort to isolate the effect that coronavirus-related restrictions are having on its load, Shields said, PJM is having its long-term forecasters work with its short-term operations forecasters, something it doesn’t normally do. The RTO plans to post an analysis of the restrictions’ effect on load to its operating committee’s main web page every Monday and report on its analyses at the monthly meetings of its operating committee and systems operations subcommittee.

The California Independent System Operator is also working on its forecasting. Anne Gonzalez, a senior public information officer with CAISO, said the ISO has seen load forecasting errors increase due to a lack of historical data for a pandemic event and is taking steps to reduce the load forecasting errors in its day-ahead and real-time markets.

California Gov. Gavin Newsom issued a statewide stay-at-home order on March 19, but had put similar orders in place in parts of the before then. As a result of the orders, CAISO saw load reductions of 5 percent to 8 percent on weekdays and 1 percent to 4 percent on weekends from March 17 to March 28, with the greatest impact during its morning peak hours. CAISO attributed the load reductions to a shift from commercial, restaurant and retail power consumption to residential power consumption, with Gonzalez saying that although residential consumption is up, commercial customers generally consume more power, so the drop in their power use more than offsets the increased use in power by residential customers.

CAISO has seen the most significant impacts on its load from California’s stay-at-home order in San Francisco, the part of the Bay Area served by Pacific Gas & Electric and Southern California Edison’s territory, Gonzalez said.

The ISO also has seen its load decrease progressively since the state’s stay-at-home order was issued, Gonzalez said. That happened in Spain and Italy after stay-at-home orders were issued in those countries. Based on what occurred in Spain and Italy, CAISO expects its load to level off about three weeks after the order was issued, Gonzalez said.

The New York Independent System Operator said its daily peak loads are trending about 4 percent lower than usual. It said its original analysis for the week ending March 20 showed that daily energy usage was down 2 percent to 3 percent and its estimate for the week ending March 27 was that daily energy usage was down between 4 percent and 5 percent. New York issued a statewide stay-at-home order March 22, but much of the state had restrictions of some sort in place before then.

NYISO also said it’s seeing a more gradual morning ramping period, with load lagging up to 9 percent below usual in the New York City area between 6 a.m. and 10 a.m. The lag is more pronounced in New York City and Long Island, where it’s around 11 percent. New York City also is lagging throughout the day, primarily due to a reduction in commercial power use.

Midcontinent Independent System Operator, whose territory includes Louisiana, Michigan and Illinois, which contain centers of coronavirus activity, also is seeing a later morning peak. Additionally, the ISO said, its peak tends to last longer, which is expected because its many of its customers are staying home and using more electricity there.

Texas Gov. Greg Abbott issued a stay-at-home order on March 31 but had put some restrictions in place prior to then. In a study it released April 1, the Energy Reliability Council of Texas said that over the week beginning March 22, energy use in its footprint was down 2 percent from a year ago. ERCOT said its daily peaks haven’t been affected by coronavirus-related restrictions, but its load has been consistently lower between 6 a.m. and 10 a.m. Load values during that period have been decreasing over the past three weeks and are now 10 percent lower than what its model would predict after accounting for typical model error, ERCOT said.

All the states in ISO New England’s footprint have stay-at-home orders in place, although they issued them at different times. The restrictions have reduced demand across ISO-NE’s system from 3 percent to 5 percent compared to what the ISO would expect given the weather, Mike Knowland, ISO-NE’s manager of forecasting and scheduling said in a Q&A posted on its website.

Knowland said ISO-NE’s forecasters are seeing load patterns that resemble the ones typically seen on snow days, when schools are closed and many people remain home rather than go to work. The patterns include a slower than normal ramp in the morning and an increased use of power during the afternoon, he said.

Like other ISOs and RTOs, ISO-NE is altering its forecasting methods to account for the pandemic. Knowland said its forecasters are putting together forecasts based on what they would expect demand to be without the coronavirus-related restrictions, then adjusting those forecasts based on the usage patterns they’ve seen over the past few weeks. ISO-NE and other grid operators in North America and elsewhere are communicating to report on what they’re seeing as a result of the pandemic and sharing best practices, he said.


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