I’ve been discussing the national electrical grid in the last several 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 local distribution grids.
So what could go wrong? After all, isn’t it just a bunch of wires? Nope, guess again! To function properly, The Grid needs to be precisely balanced and synchronized. In addition, The Grid handles massive amounts of energy at very high voltage. Every piece of it is designed to handle certain amounts of energy under certain conditions, or problems occur. If demand surges in one region, or if supply goes offline, then the generators in that region slow down and get out of sync, or their voltage changes and goes outside the limits they were designed to operate at. But The Grid is interconnected so that additional power can be delivered into the region from other regions, or energy can be rerouted, solving the problem before it threatens the integrity of The Grid.
The problem is that when energy is rerouted like that, unless it is precisely balanced, it has the potential to cause problems of its own. If voltage goes either too high or low, then equipment can burn out or destroy itself in various ways. When energy is rerouted, then the wires over which it is routed carry extra electricity. As electricity moves down a wire, the wire heats up. 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. It might burn out. Alternatively, metal expands when it heats. Thus, if the wire gets too hot, it will sag. 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 can melt the wire or burn out equipment up and down the system.
I wasn’t able to find any copyright-free images to share with you, but if you would like to see what arcing looks like, go to YouTube and view the videos by “Blade Runner” and “Ross Tvdoctor”. They should give you a good idea.
The demand for electricity is constantly changing. In the South 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 and balance the 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, 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: in 2003, 55 million people were affected. (Figure 1)
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.
Loy, Brendan. 2003. The Empire State Building in the Dark During the Great Northeast Blackout of 2003, IMG 6514. Source: Flickr Creative Commons. https://www.flickr.com/photos/brendanloy/2669855698.
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.