Our ever-increasing dependence on technology makes the notion of bearing any long-term lack of service from our precious critical infrastructures socially unthinkable. On the other hand, there is an atypical, nature-made scenario which we have been warned may pose a severe challenge to this proposition.

Of course the industry is used to dealing with all types of meteorological inclemency, but the essence of a Geomagnetically Induced Current (GIC) from solar storms is quite different. This is a well-known phenomenon with abundant background literature and documentation, and there is a wealth of scientific work in progress that also makes use of state-of- the-art space/satellite resources designed to predict and monitor this activity. But it must be also said that there is some discrepancy regarding the assessment of current and future exposure, potential implications to the power system, and of the proper ways and means to deal with it.

Many energy companies, in particular, simply do not believe this is a real problem. However, the U.S. Department of Energy (DOE) has clearly indicated that a GIC event is a major concern and can not be downplayed or minimized; the Department has also offered detailed considerations and calculations that, for example, yield a near 0.11 probability of having a least one major storm in this upcoming solar maximum cycle. It appears no region is quite immune to it.

Precedents

This potentially hazardous process has just begun, and it is expected to peak by the year 2012. It is worth noting that research has established that a major solar storm impacted earth in 1859 with an intensity which, had it happened today, would have caused a global blackout of devastating proportions with unpredictable consequences, according to current estimates. More recent cases have seen lower, yet considerable, intensities; nevertheless, the field orientation of the storm is also a critical factor.

Furthermore it is well known that magnetic circuits of power apparatus may suffer permanent damage or at least a hidden derating or cumulative loss of life. There are many thousands of EHV transformers, reactors and phase shifters in U.S. grids and worldwide. Unfortunately there is a very limited manufacturing capacity in the world, creating an extremely problematic replacement/repair outlook. It is for this reason that a major solar storm could leave millions of customers in large cities without power for months or even years. This seems unimaginable, and has not even been modeled in order to produce a much-required comprehensive societal evaluation.

Mitigation

A general consensus exists today that there is a complete lack of a satisfactory and cost-effective GIC countermeasures. Nonetheless, some devices are available to mitigate this problem. Chiefly, these are capacitive blocking arrangements connected to the transformer neutral, which can be of the passive or active type (the active type makes use of ample power electronics components). While this approach may be effective, it is looked upon unfavorably by the utility industry due to its high cost and perceived operational risk. Moreover, if adopted, these would impose a significant prosthesis to substation equipment at very sensitive points.

Another more prevailing strategy being considered to cope with GIC relies heavily on early satellite detection, allowing the power system operator to undertake some defensive action. Unfortunately, such an action most likely comprises shutting down the power system, in a methodical fashion, to protect the different installations during a storm. A definite shortcoming to this approach can be found in the fact that the actual severity and timing of an incoming solar surge is not ascertainable with precision. Hence a self-inflicted blackout based on these premises does not seem like sound or intelligent engineering, or even a plausible response to an incoming solar surge. Besides, this course requires a high-level decision- making process which can turn extremely dicey and difficult to come by within a relatively short time framework.

Looking Beyond

While all this may be deemed as somewhat remote and unlikely, there are lessons that can be learned without having to wait for an actual disaster to happen. Looking at other disciplines such as civil and hydraulic engineering, we are reminded of the proper use of world safety standards. Particularly when earth dams are designed, a statistical 10,000-year peak river flow (called the ten-millenary flood) is applied to assure the structure withstands and survives such an incursion. We have seen enough catastrophic failures when these guidelines have been ignored or misapplied. Consequently, for GIC, looking at, say, one century, or for a storm magnitude return interval, does not appear to be an unreasonable criterion; yet there is no guideline for grid security here. In any event, some sort of GIC standard is needed and should be formulated in order to establish good engineering practice. At least the oversight institutions should explain what is diligently in place for coping with this peril.

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