ISOs send load forecasting, renewables, transmission data to FERC

The six independent system operators and regional transmission organizations operating in the United States on Oct. 30 filed a combined report to FERC, outlining their performance in various areas of operations and effectiveness for the period of 2010 to 2014.

Besides providing detailed data on transmission congestion management, coordinating transmission outages, generation dispatch behavior, load forecasting and forecasting for renewable resources, the report included market pricing measures and administrative costs for each ISO or RTO.

The report followed previous efforts updating FERC on grid operator performance for two different periods from 2005-2010. The reports were prompted by a 2008 review by the Government Accountability Office that recommended FERC work with various stakeholders to develop measures to track the performance of ISO and RTO markets and operations.

The data provided “illustrates the transparency of ISO/RTO operations and reinforces the value of ISO/RTO operation of the grid and administration of wholesale electricity markets,” according to the report (Docket No. AD14-15). The values include efficient wholesale market operations, reliability monitoring, enablement of demand response and energy efficiency, advancing public policy objectives and adapting to changing generation mixes in response to both price signals and environmental requirements.

The report provides information from the California ISO, PJM Interconnection, the Midcontinent ISO, Southwest Power Pool, ISO New England and the New York ISO.

Load forecasting accuracy was mainly higher than 95 percent for the reporting period among the ISOs, with varying levels of “mean absolute percentage error,” which is a more quantitative measure of precision. “The ISOs/RTOs are striving to improve load forecasting accuracy” since if day-ahead or morning forecasts are inaccurate, the result could be reliability problems due to lower commitment of resources or additional costs due to excess commitment of resources, the report said.

Several ISOs mentioned increased importance of forecasting renewable resources given their growth in the generation market and their intermittent nature. PJM said it began tracking wind forecasting accuracy in December 2009, and it recently sought to ensure current measures are effective.

PJM said it began a wind power forecasting request for proposals in 1Q15 to make sure that the current vendor is providing accurate, reliable and cost-effective service, and the effort concluded with the selection of the incumbent vendor.

During 3Q15, “PJM began an initiative to investigate Solar Power Forecasting services,” PJM said, without providing a schedule for the process.

The California ISO told FERC that it continues to examine how it can more accurately forecast variable resource production in the day-ahead timeframe. With current penetration levels of wind and solar photovoltaic resources, the California ISO said it “has already identified increasing need for flexibility in the existing resource fleet to meet net load ramps.”

The California ISO also is starting a high-level study on the impacts of distributed energy resources, including potential changes to the use of the transmission system with higher levels of distributed energy resources.

“We have also discovered that planning studies for transmission maintenance must consider new congestion patterns that will result from power flows created by a new low-carbon fleet,” the California ISO said in its section of the report. “While transmission providers typically have planned maintenance of transmission elements during shoulder months, this action has sometimes exacerbated over-generation conditions and negative prices within localized areas.”

ISO-NE noted that the growth of demand response and the changing nature of the generation fleet can affect the need and usage of transmission assets planned or already in service.

“Because of new resources coming on line and changes in the demand forecast, the need for some projects in New England are under review,” ISO-NE said.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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