Grid threats increase daily - from foreign foes, terrorists, criminals and hackers. Utilities are tasked with guarding against a rising tide of potentially disruptive intrusions into their power grid and electronic networks. What will it take to keep the power more...
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Alberto Ramirez Orquin, Associate Professor of Electrical Engineering, University of Puerto Rico at Mayaguez Vanessa Ramirez, Senior Consultant, The Structure Group
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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I followed this issue closely in the 80's for a West Coast utility following the transformer failures at a New Jersey nuke and an earlier transmission line failure in Canada. Our conclusion was that our major transmission lines (the Pacific Intertie as the major backbone for the WSCC) were both distant and perpendicular to the magnetic pole and so not likely to see geomagnetic currents.
These are low probablity events and you are correct that some changes to current design standards can be made to reduce the frequency and consequences of such events. However, the economics, to me, point to not spending much money on specific measures.
There is a similar, man-made cause that shares some remedies and defenses - electromagnetic pulse from nuclear explosions. Of course, the probablity of such an attack is unknown and by no means certain, unlike solar storms.
A core problem is who is to foot the bill for the engineering and installation of remedies?
Alberto Ramirez Orquin 2.7.09
A large number of West Coast power systems do have series compensation which acts like a blocker to GIC and that may also explain the good experience. The cost issue is crucial indeed. We believe, however, that the cost of failure may sore even more pretty soon, particularly if the grid to plug-in vehicle technology evolves as excepted. A single major blackout would bear an astronomical tab. Nevertheless current remedies, as discussed, including engineering and control/communication costs are very expensive and the challenge resides now in coming up with a simple cost/ effective solution. We believe this is attainable even before the next solar maximum. In any event a good engineering decision regarding tackling or not the problem should consider all cost and benefits in a probabilistic context. In other words, the option of doing nothing ought to be revaluated.
Alberto Ramirez Orquin 2.9.09
As stated, the trade off follows a trend: the cost of unsupplied energy escalates (actually in the EU some utilities must pay customers very dearly for it; it could reach 10,000 $/Mwh) and the cost of remedies lowers, it is bound to clear sometime. We believe with current technology a GIC countermeasure tag should lay in the vicinity of 1% of the transformer cost and not much higher, as currently stands.
Joseph Somsel 2.9.09
At 1% of transformer cost for major transmission lines, you might find a market although you'll need an analysis methodolgy to identify those lines that are sensitve and those that are not. Lines tangential to the magnetic poles (magnetic longiitudinal, if you will) would see much geomagnetic currents.
However, outages are never valued at $10,000/lost MWhr in the US. Most state regulatory bodies set an annual reliability target of about 99.95%. Having spares with a reasonable estimated MTTR might be an alternative.
Here in California, we faced a similar problem with seismic ratings for our 5000kV switchgear. We finally replaced most of the fragile breakers with seismic-rated units from Japan.
Alberto Ramirez Orquin 2.9.09
Agreed, not every transformer/reactor or phase shifter is a candidate, and efforts should take place soon in order to identify the valid cases; not a minor task. I would guess there are hundreds of those apparatus. I discussed the issue of the un-served energy cost in a previous Pulse article: ‘The Electric Grid: Society's emerging supercritical infrastructure’. Clearly the 10,000 $/Mwh is only a reference or internalized proxy price for planning purposes. The fact that most US Utilities consider outages merely as ‘loss of revenue’, in addition to some appliance damage coverage, does not trump the fact that the socio/economical cost of a blackout (as an externality), particularly in big cities is immense; probably far in excess of that proxy, even without national security considerations. The reliability standard is well intended but may become untenable or unrealistic with further deregulation/unbundling/divesting of T&D assets/services. The seismic approach for CA switchgear is a good example of right preparedness.
Vanessa Ramirez 2.18.09
Having spares with a reasonable estimated MTTR might be an alternative probably only when three-phase banks are made of three single-phase units.
Bruce Cavender 4.28.09
Excellent Article!
Protecting the Grid from GIC events might go a way to reducing vulnerability to EMP attack also.
Certainly the Grid is the greatest EMP target in the USA in terms of asymmetrical warfare for a rogue nation with only one bomb and one ICBM.
I recently researched the tech side of EMP and there are three components to EMP...two of which I was unaware of. E1 and E2 components serve to cause flashovers and are very short lived. However the E3 component, a magnetohydrodynamic phenom, can pump current into these faults for up to 8-10 MINUTES.
REF: Report of the commission to Assess the Threat to The US from Electromagnetic Pulse Attack - Critical National Infrastructures April 2008
Reading the recent book "One Second After" would help stir some discussion about the best way to protect the Grid (and our livelyhoods) from EMP AND GICs.
