NERC: Loss of Reactive Power, Voltage Instability Likely Outcome from Geomagnetic Disturbance Effects

A new report released in early March by the North American Electric Reliability Corp. (NERC) found that loss of reactive power was the most likely outcome from a severe solar storm that was centered over North America. Significant losses of reactive power could lead to voltage instability, and, if not identified and managed appropriately, power system voltage collapse could occur, the report concludes. 

The report was released as media outlets widely reported that what was being described as “the biggest solar storm in five years” was hammering our planet. On March 6, two solar flares reportedly erupted from the surface of the sun, sending plasma and charged particles toward Earth.

The report, 2012 Special Reliability Assessment: Effects of Geomagnetic Disturbances on the Bulk Power System, takes a comprehensive look at multiple, complex issues to evaluate geomagnetic disturbance (GMD) effects. The report from the electric reliability organization that develops and enforces reliability standards for federal authorities in the U.S. and Canada outlines the most likely outcomes, while offering short- and long-term recommendations for industry.

GMD emanate from the sun. Scientists have determined that solar coronal holes and coronal mass ejections are the two main categories of solar activity that drive solar magnetic disturbances on Earth. For more information on solar storm monitoring and predictions, see “The Great Solar Storm of 2012?

Essentially, coronal mass ejections can create a large mass of charged solar energetic particles that escape from the sun’s halo and travel to Earth within 14 and 96 hours. Charged particles from the coronal mass ejection then interact with Earth’s magnetosphere-ionosphere and produce electrojets. "Typically millions of amperes in magnitude, electrojets perturb Earth’s geomagnetic field,” the report says. "Long man-made conducting paths, such as transmission lines … can act as ‘antennae’ (depending on impedance), that allow the quasi-DC currents to enter and exit the power system at transformer grounds, disrupt the normal operation of the power system and, in some cases, cause damage to equipment."

“The effect of GMD on the reliability of the bulk power system remains an important consideration,” said Gerry Cauley, NERC’s president and chief executive officer. “NERC’s report identifies grid vulnerabilities from GMDs and highlights solutions to mitigate risk to bulk power system reliability.”

While loss of reactive power was found to be the most likely outcome from a severe solar storm, the Geomagnetic Disturbance Task Force also assessed the vulnerability of high-voltage transformers. While some transformer types were found to be at risk from geomagnetically induced currents, they tend to have certain design characteristics that increased their vulnerability, or were transformers nearing their end-of-life.

The task force identified short-term recommendations that NERC and the industry can implement quickly, including the review of both system operating and training requirements with a focus on GMDs; an update to NERC’s GMD alert to include information from this new assessment; and a public webinar to outline the assessment and highlight next steps. The task force, which had high-level participation from experts across multiple fields in both private industry and federal government, also made long-term recommendations, which include:

  • Developing additional open source tools and models to develop GMD mitigation strategies.
  • Improving tools for system operators to manage GMD impacts.
  • Educating and sharing information between researchers and industry.
  • Reviewing the need for enhanced NERC Reliability Standards.

“NERC has mapped out short-term and mid- to long-term actions to address GMD affects” said Mark Lauby, vice president and director of Reliability Assessment and Performance Analysis at NERC. “NERC will address GMD effects through a multi-year collaboration with industry and governmental agencies.”

This effort was one of the key steps identified in the High-Impact, Low-Frequency Event Risk to the North American Bulk Power System (HILF) report completed by NERC and the Department of Energy in June 2010. That report focused on a class of rare risks to the bulk power system, including GMD, that were identified as part of NERC and the Electricity Subsector Coordinating Council roadmap for addressing these types of events.

The GMD report is the second of four ongoing efforts from the roadmap that include the spare equipment database report, which has already been released, and two upcoming reports from task forces focused on cyber attack and severe impact resilience.

—Sonal Patel is POWER’s senior writer. This material first appeared in POWERnews.

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