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The Prospective Solar Tsunami

ID 100370424 © Pitris |

Different from the past, the upcoming cycle-24 solar maximum is currently surrounded by an unprecedented general expectation. Indeed the so-called solar tsunami has now come to the forefront of interest turning into a household word; what for decades was strictly a scientific matter has now transcended this dominion to fall into the popular realm; this happening follows to some extent the sets of predictions and omens reported almost on a daily basis from all kind of sources. Furthermore the sun, with its variable magnetic activity, is not the only problem of this nature, man-made electromagnetic pulse (EMP) has become another threat potentially having a similar devastating impact upon our most critical electricity-based infrastructure. There are good reasons which well warrant the perception that the risk of large damaging solar storms may be right.

Risk Analysis/Evaluation

Given the very serious social implications a major GIC/EMP episode could have, it seems imperative that a formal comprehensive risk analysis be conducted by the main stakeholders. Decision theory and behavioral research could provide a reliable analytical framework whereby a social evaluation of costs vs. different courses of action can be correlated and internalized; the probabilities of the different scenarios under consideration should lead to a set of ranked outcomes, each with a distinct price tag. The option of doing little or nothing must be incorporated into this assessment.

Traditional Industrial Stance

The electric utility is a complex multifaceted industry, which has also been undergoing structural and regulatory changes that represent a real oversight contest in almost every respect. It can be said that in general there are both institutional and jurisdictional challenges which conspire against any conceivable public policy, and its enforcement, designed to cope with the GIC/EMP perils. In addition, the utility system traditional conservative stand, with undertones of skepticism regarding this problem, likely based on the perception that its particular exposure is minimal. In any case it subsumes the belief that there is no definite liability beyond the simple loss of revenue stemming from unsupplied energy; consequently, companies are primarily reluctant to spend on mitigation ways and means.

Institutional Progress

On the other hand there has been some institutional progress recently; the House of Representatives passed on 6/1/2010 the Grid Reliability and Infrastructure Defense Act. It amended the Federal Power Act by adding a new section 215a. This would have given the Federal Energy Regulatory Commission (FERC) new charter to protect the electrical grid against cybersecurity and other threats (including solar storms and EMP). This Act did have provisions for the utilities to recover costs from ratepayers. Unfortunately the legislation did not pass the Senate but it may have been included in one of the 2010 appropriation bills.

In addition the North American Electric Reliability Corporation (NERC) is also working on this area; in its June 2010 release: High-Impact, Low-Frequency (HILF) Event Risk for the North American Bulk Power System. In this document it is stated that the participation from high-level government officials in both the U.S. and Canada will be key to help building consensus among business leaders on the appropriate level of investment in mitigating these threats when considered among the many other investment priorities facing the electric sector. A definite Proposal for Action on GIC/EMP is then outlined calling for Governmental authorities in North America to support industry efforts to address these risks. An executive order from government leaders, such as the President of the United States, would give additional weight to the importance of these issues relative to other priorities in both the public and private sectors.


There are only two basic technologies for mitigation of GIC/EMP available to the industry today; both of them hold US Patents and have been recognized by the oversight institutions; these are:

  • Blocking Device and Fault Current Grounding -- A condenser blocking device is connected from transformer neutral to ground which impedes the GIC current circulation, yet allowing the flow of the neutral AC current. A main bypass path includes switching devices or gaps which provide a low-impedance path across the capacitor under fault conditions.
  • Neutral Resistor Bypass Device -- Also known as GIC Reducer; this is a neutral grounding scheme that minimizes the geomagnetically induced current by means of a linear resistor. A protective varistor is connected in parallel with it; this component is really a non-linear resistor similar to the one found in metal-oxide surge arresters. The operating principle is simple: the resistor is sized for reducing the GIC currents to harmless while the non-linear varistor provides a bypass path to ground capable of sustaining, as per well-established guidelines, a protective level which coordinates conservatively with the transformer-neutral Basic Insulation Level (BIL). As a result the apparatus' solid neutral grounding, particularly its Ro/X1 ratio, remains essentially unchanged (

Discussion of Mitigation concepts

The blocking device was the first countermeasure available after the large solar storm of 1989 and the concern it caused; it remains a valid resource since. However, the industry has been reluctant to install it, probably due to its high cost and bulkiness, including a significant substation redesign. But the utilities may as well find inconceivable the insertion of a capacitor in series with a non-linear inductance (transformer), particularly in a very critical location. Additionally, capacitor switching can be problematic. The use of power electronics with pulse and timing controls brings about added reliability concerns.

Fortunately, the recently-emerged neutral resistor bypass device seems to overcome the pitfalls of previous concepts. First of all, transformer resistor neutral grounding has been a utility common application/practice for almost a century. Furthermore, resistors are passive elements easy to switch on and off; also the scheme layout comprises very few components of the distribution class, thus bearing a minimal footprint (the size of a small fridge). Yet the absence of ancillary components, power electronics or command-and-control hardware improves considerably the reliability picture. Finally, estimates from providers place the cost of a unit under 1 percent of transformer cost.

Moreover in a recent deposition before the House Homeland Security Subcommittee on Emerging Threats, Cybersecurity, and Science and Technology a group of experts stated: 'The analysis performed to date for the EMP Commission indicates that the conceptual design of installing neutral resistors on the transformer neutral-to-ground connections is the preferred option of protection'; 'The advantage of this design is that it will be relatively simple to develop with lower engineering trade-off risks and lower overall installed costs compared other more exotic devices'.

In turn the EMP Commission in its April 2008 report recommended Congress the installation of neutral grounding resistors throughout the North American power grid.

Looking Beyond

National Security demands to take very seriously the threats posed by solar magnetic storms and man-made electromagnetic pulse (EMP). The solar cycle 24, peaking in early 2013, has been anticipated by NASA to be a very active one and possibly of the dangerous southward polarity type. Both the US and Canada Governments shall take steps towards making sure that proper response is in place to protect the critical infrastructures of electric power delivery and communications.

Appropriate government authorities, potentially including DOE, FERC, DHS, NOAA, NASA, should work closely, in harmony with research organizations and the private sector, to consider a roadmap for long-term initiatives, development, and deployment on mitigating options for these threats. These efforts shall be coordinated with NERC and the electricity sector.

The Neutral Resistor Bypass Device appears to be a cost-effective mitigation means to cope with GIC/EMP. A full scale testing program should be established as early as possible in due anticipation of year 2013.

Co-authored with Alberto Ramirez Orquin




Vanessa Ramirez's picture

Thank Vanessa for the Post!

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Bob Meinetz's picture
Bob Meinetz on March 7, 2019

Vanessa and Alberto, thanks for your fascinating contribution.

The Neutral Resistor Bypass Device appears to be a cost-effective mitigation means to cope with GIC/EMP. A full scale testing program should be established as early as possible in due anticipation of year 2013.

Any updates?

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