42 October 2018 Components in Electronics www.cieonline.co.uk

Space

The sun has always been benigntowards the Earth, providing light andheat essential to the growth ofcivilisations. However, as our technology hasadvanced, so the sun has become a threattoo, with its constantly changing surfaceplasma creating magnetic storms. Coronalmass ejections (CMEs) are large bursts ofsolar wind plasma carrying intense magneticfields, and the biggest in modern times wasthe Carrington Event of September 1859,named after the English amateurastronomer Richard Christopher Carrington,who observed a huge solar flare on the daybefore the superstorm broke.

Near misses in recent years have causedmajor technological damage, for examplethe collapse of Quebec’s electricity grid inMarch 1989 at a total cost to the Canadiangovernment of $12.7 billion, a 1956 eventwhich was the highest recorded foratmospheric radiation, and the highestrecorded radiation events measured onspacecraft in August 1972, October 1989and October 2003.

Whilst spacecraft, satellites and aircraftwill of course lie first in the path of anygeomagnetic storm heading in ourdirection, at ground level geomagneticallyinduced currents (GICs) will arrive on allinterconnected architecture simultaneouslyat high speed. Hence protection afforded tothe critical nodes of the electricity grid – thesuper grid transformers – would not preventGIC transients from causing huge damageto equipment at local sites elsewhere.

Solar activity follows an 11-year cycle,with the most intense events occurring near

the cycle’s peak, so therefore we shouldtake the threat as seriously as possible.

The geomagnetic field will affect largeregional areas and induce transient currentsto flow in the cables of electrical distributionsystems. The amplitudes and waveshapes ofthese transients are affected by thegeography and topography of location, aswell as the electrophysical characteristics oftransmission lines. The low thresholds ofsusceptibility of modern equipment systemsto fast, high-amplitude transients makeGICs a clear and present danger to thecontinuity of critical infrastructure services.The most technologically advancedcountries should have prognostic modellingto predict which of their strategic locationsrun the highest risk of transients couplingon to exposed electrical cables.

Indeed the mitigation of solarsuperstorms necessitates a number oftechnology-specific approaches which comedown to engineering out as much risk as isreasonably possible, and then adoptingoperational strategies to deal with theresidual risk. For the former, enhanced surgeprotectors – above and beyond thoseinstalled for lightning – can harden nationalelectricity grids against GICs. For the latter,space and terrestrial sensors are required tomonitor the superstorm’s progress from itsearly stages as intensified activity on thesun’s surface through to its final impact onthe Earth.

With all this in mind, US RepublicanCongressman Trent Franks of Arizona andformer House Speaker Newt Gingrichintroduced a Bill in the House of

Representatives in June 2013 to amendthe Federal Power Act to protect the USgrid. Called the SHIELD Act, an acronym for“Secure High-voltage Infrastructure forElectricity from Lethal Damage” Act, the Billis pushing the Federal Government to installgrid-saving devices, surge protectors thatcould save the transformers and powersystem from electromagnetic pulses. The Billcentres on protecting high-voltagetransformers serving towns and cities,principally because a June 2012Department of Energy report identifiedthese as a key vulnerability in the grid, citingvolatile pricing for copper and electrical steelraw materials and a lead-time forreplacement that can stretch to 20 months.These complex voltage switching devicesnamely weigh up to 400 tons, cost millionsof dollars and are made in only a handful offacilities Stateside.

Nevertheless the provisions of the SHIELDAct, although far-sighted and economicallysound, do not address the issue of high-speed GIC transients arriving simultaneouslyen masse and wrecking the equipment inlocal assets such as computer rooms,communications hubs, base stations, datacentres, public utilities, process plant, banksand air traffic control towers.

So, to protect such engineeringinfrastructure and equipment systems at alocal level, one of the most viable solutionsis MPE’s high-reliability High-AltitudeElectroMagnetic Pulse (HEMP) filters toMIL-STD-188-125. Why? Because thistechnology is transferred from the defencearena (nuclear blasts high in theatmosphere) to extreme space weatherapplications (CMEs). Characteristicscommon to both these situations, apartfrom the dangerous levels of radiationeach creates, is that general EMP eventswill hit all electrical systems simultaneouslyand can never be constrained withinnational borders: numerous countries orregions may be unfortunate enough to beaffected and caught unawares by thesuddenness of a strike.

MPE has pioneered electrical filters forthe protection of critical defence andnational infrastructure assets from the effectof Nuclear ElectroMagnetic Pulse (NEMP)since the mid-1980s, when their hallmarkintegrated solution combining metal oxidevaristors (MOVs), capacitors and inductorsaccorded with the NATO specifications ofthe day. The same product designphilosophies which will successfullyattenuate high-speed, high-amplitudeNEMP currents may be applied to safeguardagainst the effects of GICs.

These products incorporate an integratedcombination of staged diversion and

attenuation elements, most usually in theform of surge arrestors and full frequencyspectrum filters. They incorporate MOVs asa front-end transient suppressor, giving anultra high-speed response to arrest theincoming pulse. Then the bespoke inductiveand capacitive elements of the filter givehighly effective full frequency spectrumprotection against induced pulse currents atthe cable entry points of AC mains power,telephone, data and control lines that arebased on long-line copper wire technology.

MPE’s military products are designed tobe of high reliability and to survive multipleexposures to peak NEMP currents derivedfrom the highest yield weapons. Thesefilters attenuate the ultra-fast high bulkcurrents induced in exposed cables andwires to levels below the damage thresholdsof susceptible electronic equipment systemsand far exceed the requirements forhardening commercial assets against theeffects of GICs.

A practical consideration is that thecoupled circuit design featured by MPEcreates a far more compact unit forinstallation in tight spaces – down to aquarter of the size of conventional systemsin which each line is wired up to a separatefilter – whilst supporting easy inspectionand maintenance. Those size and weightadvantages afford significant shipping,installation and space benefits to installerand user alike.

In conclusion, according to a reportproduced by Lloyd’s in co-operation withAtmospheric and Environmental Research,solar superstorms of Carringtonmagnitude will occur once every 150years, so our next one is now overdue,and the effects of the event on human lifewould be more devastating than everbefore, owing to our dependence on thetwo-edged sword of technology.

www.mpe.co.uk

Paul Currie, sales and marketing director, MPE Ltd talksabout how to protect engineering infrastructure fromsolar activity

The impact of solar superstorms onengineering infrastructureand how to protect it

CIE_October_p42_CIE 11/10/2018 08:21 Page 42