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Consequences of power grid failures

Immediate consequences of these grid failure events are distinctly unpleasant. People have been trapped in elevators, or been unable to leave high-rise buildings if they are unable to walk down many flights of steps. Typically, underground and other railway systems have trapped people; loss of power has blacked out traffic control and communication systems. Water and fuel pumping systems fail without mains power, and sewage pumping and processing have equally stopped. Mobile phone systems have sometimes survived, but because modern phones need recharging relatively often, a power loss of just two days could be fairly disastrous. In most countries, criminal activities have exploited the possibilities of alarm failure and overloaded police response. Financially, the loss of industry, failure of supplies in shops, etc. have been estimated for the short-term examples I am citing, and the monetary numbers normally are quoted in billions. As a guide to the financial impact, the USA has an average of nine hours of power loss per consumer each year as a result of very minor local disruptions to power connections (i.e. unrelated to widespread events), but even this is estimated to be an economic cost of $150 billion per year.

The urban myth—that after prolonged power blackouts the results of people being trapped together in elevators and trains, or without home entertainments, has been followed nine months later by a baby boom—may have an element of truth. My examples that hit very large populations are all for relatively short-term failures of electrical power (i.e. less than a day). However, the baby boom statistics may become more obvious for power losses that last a few weeks, although up until now these long-term failures have mostly involved small communities.

For the electrical grid systems, the exposed cable networks are extensive, with high-voltage power transmission lines on pylons. Viewed in other terms, these are extremely large and efficient antennae. Many have power transmission networks over distances approaching a thousand miles in a single link (i.e. a superbly long antenna). For interconnected grid arrangements, the antennae lengths are considerably more. Aurora events can therefore induce surprisingly large additional voltages and currents in such network lines. Although mains voltages are, say, 240 volts in Europe or 110 volts in North America, transmission losses over long distances are severe at these voltages. Therefore the power grids operate at voltages above one hundred thousand (100,000) volts, as power losses can be reduced at the higher values. Actual numbers are unimportant for this disaster plot, but some systems run up to 750 kilovolts. The UK grid typically has the higher-voltage sections operating at 275,000 or 400,000 volts. These numbers are so far from 240 volts that there is a lot of complexity needed to transform the power down to the voltages we use as consumers. Even further complexity is needed to maintain a constant frequency (e.g. 50 Hertz in the UK). The equipment that does all of this is critical and expensive, so if any section is destroyed, it instantly puts further pressure on power sent via alternative pathways. It is great technology, but it has the potential to collapse under conditions of extreme electrical overload.

Despite the high-quality engineering, the voltage and power surges caused by solar events can drive the power grids into an overload mode. Damage scenarios are many and well documented. Power cables can melt or arc down to the ground, which can cause pylons to collapse. Alternatively, the power surges rip through the transformer stations, and the extra power is sufficient to burn out both the transformers and the frequency control circuitry.

During this century, power cable systems have become much longer, more complex, and more interlinked, with the result that even small flares have produced blackouts and destroyed transformers and other equipment. In the last 15 years, there have been numerous examples, particularly in high-latitude countries such as Sweden and Canada. This is to be expected, as the aurora effects are most visible there, but really major storms can be seen much farther away from the poles, and induce far greater electrical disturbances. At high latitudes some precautionary measures exist, but at lower latitudes (where aurora type interference is rare) there may be no attempt at building adequate protection against major flares. For interconnected regions and countries, the system is endangered by the weakest link of this electrical supply chain.

Damage to a single transformer in an extended network can normally be handled, whilst repairs are being made, by rerouting power via alternative paths in the grid. If more than one section of the grid is closed, then alternative power routing may not be possible. This difficulty has occurred in the USA where, as a result of overload trips cutting in, there has been a total power blackout over large regions. The serious longer-term problems occur when more than one transformer unit is destroyed (as could happen in the solar flare scenario). Replacements are far more problematic, because the electricity companies do not keep enough spares (they are too varied and too expensive). Therefore loss of a single transformer may cause problems for many months. However, multiple losses would be catastrophic and long term, as they could cause a power loss over a large region. In extreme cases, it will be an entire country: there would not be manufacturing capability to build the replacements, and the country would be totally dependent on foreign suppliers. They would also be vulnerable to exploitation or invasion.

 
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