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What Could Go Wrong?

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I’ve been discussing the national electrical grid in the last 4 posts. If you’ve kept up, you now know that The Grid is a huge, extremely complex network of generating stations and transmission lines, and all the equipment needed to transmit electricity over those lines from the generating stations to consumers’ doors.

So what could go wrong? After all, isn’t it just a bunch of wires? Nope, guess again! The Grid handles massive amounts of energy at very high voltage. Every piece of it is designed to handle a certain amount of energy under certain conditions, or problems occur.

The Grid is interconnected so that if one part fails, energy can be rerouted over another. If demand surges in one region that doesn’t have enough supply to meet the demand, then additional power can be delivered from other regions. The problem is that when energy is rerouted like that, it has the potential to exceed the conditions for which the equipment was designed. If voltage goes either too high or low, then equipment can burn out or destroy itself in various other ways.

Further, if one area fails and energy is transferred to another part of The Grid, then some parts of the grid must carry the transferred electricity in addition to their standard load. As electricity moves down a wire, the wire heats it up. Being made of metal, wires expand when heated. As long as the amount of electricity stays within the design range, it is okay. But if too much electricity flows through a wire, the wire gets too hot, and it expands too much, which means it sags. Sagging wires are at risk of touching something underneath, creating a short, or of getting close enough that the electricity can arc to whatever is below. If a short or arc occurs, it is deadly to whatever it touches, it melts the wire, and it burns out equipment up and down the system.

Add to this the fact that demand for electricity is constantly changing. Typically it is higher in the summer than the winter (but just the opposite in northern climates), and typically it is higher during the day than at night. Grid operators have to constantly adjust the amount of electricity fed into The Grid to match the demand, they have to constantly route electricity so as to avoid overloading, and they have to reroute around local outages and problems.

And finally, add the fact that cities adopted different operating practices and standards as they electrified. When they interconnected into The Grid, it meant trying to integrate all of these different operating procedures and standards.

It is a tremendously complex balancing act. In Missouri, our largest power outages have occurred mostly because storms have destroyed vast portions of the local electric distribution system. (See Electrical Outages from Storms Increase.) On the other hand, the great northeast blackouts of 1965, 1977, and 2003 occurred because relatively small failures in a single spot caused underloads or overloads as energy was shunted to other parts of The Grid. These then failed, and the problem cascaded until, in 2003, 55 million people were affected.

Mostly The Grid is an amazingly reliable part of life. You flip a switch, and the electricity is just there. Almost always. But every now and then, it fails in a spectacular way!

NERC, the North American Electric Reliability Corporation, develops operating standards to ensure reliability. It has only had the legal authority to enforce them since 2005, however. In addition, they issue an annual long-term reliability assessment. The next post will look at findings from their 2013 report.

Sources:

Nersesian, Roy. 2007. Energy for the 21st Century: A Comprehensive Guide to Conventional and Alternative Sources. Armonik, NY: M.E. Sharpe.

“Northeast blackout of 2003.” Wikipedia. http://en.wikipedia.org/wiki/Northeast_blackout_of_2003.

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