As Part of Our Continual Assessment of Bulk Power System Reliability as the North American Electric Reliability Corporation (NERC), we've identified a number of challenges to reliability, notably including:

• Load is forecasted to grow by 20%, while committed supply is only expected to increase by 10% over the next 10 years

• The grid is being operated much closer to the edge than ever before

• Bulk power system reliability is becoming more dependent on natural gas availability and transportation

• The bulk power system is on the cusp of dramatic change incorporating enhancements to support climate change and carbon legislation.

Renewable energy resources, such as wind, solar and wave, are an important piece of the solution to these challenges and have recently garnered significant public support and investment. It is critical, however, to match this growing support for renewables with support for the transmission infrastructure that will deliver the energy they generate to consumers: a “clean energy superhighway.”

This transmission infrastructure includes not only the lines needed to transport power over long distances and often challenging terrain, but also the monitoring and forecasting technologies, ancillary services and operating tools needed to reliably integrate these resources into the grid. Unlike traditional generation, which is dispatchable and generally available when needed, resources like wind, solar and wave are “variable” in their output and availability.

This presents special challenges to grid planners and operators — requiring the monitoring and measurement of new reliability factors, such as wind forecasts and trends. NERC has begun to take an active role in supporting the integration of variable resources, drawing on its ability to bring together industry experts to improve reliability by creating a task force with the support of NERC's Planning and Operating Committees.

The magnitude of the integration challenge varies by target penetration levels, with some locations expecting up to 30% of annual energy to come from renewable, and therefore predominately variable, resources. Changes to traditional planning, design and operational methods are necessary to reliably integrate these resources and fully maximize their contributions to reliability.

The NERC Integration of Variable Generation Task Force (IVGTF) is made up of nearly 50 industry volunteers representing all facets of variable resource component production through to their implementation and use. The goals of the IVGTF are to:

• Raise industry awareness and understanding of variable generation's unique characteristics

• Increase understanding of reliability considerations with large-scale integration of variable generation into the bulk power system

• Investigate changes to traditional approaches used by system planners and operators required to reliably integrate variable generation

• Scan NERC standards to identify potential gaps.

The guiding principles of the IVGTF include:

• Bulk power system reliability must be maintained, regardless of the variable and traditional generation mix

• All generation must contribute to overall bulk power system reliability

• Standards and criteria relating to variable generation must be fair, transparent and performance based

• Planners and operators must have a complete understanding of the challenges presented by large-scale integration of wind and other variable generation into existing bulk power systems

• Wind and other variable generation must effectively integrate into planning and operations practices to ensure reliability of the bulk power system

• Additional technology developments should be described in terms of overall system reliability performance requirements.

Results of this work, targeted for completion in the first quarter of 2009, will be documented in a NERC report covering the characteristics of variable generation and its planning, technical and operational impacts. The report also will include the philosophical and technical reliability considerations integrating variable resources into the bulk power system.

NERC also plans to offer specific recommendations for planning, operations planning and real-time operating time frames, and to provide a high-level review of pertinent NERC standards in the report.

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Mark G. Lauby is manager, reliability assessments, with the North American Electric Reliability Corporation.
mark.lauby@nerc.net