Using a huge saw, suspended beneath a helicopter:
Burying power lines (also called “undergrounding” by engineers) seems like an obvious way to improve reliability. Those of us in the industry are used to seeing interest in this idea surge at the local and state level every winter, with another bump sometimes after hurricane season! An honest study of the costs and benefits, however, reveals a more complex picture, one in which the true value of undergrounding is highly dependent on local conditions.
The assumption by most people is that burying power lines will reduce the amount of time they spend without power. And it’s true that buried lines are less likely to experience outages, though it’s probably not as much an advantage as people think. Underground lines can be affected by flooding, digging, corrosion, and tree roots. When a line is underground, it’s also much more difficult to locate and isolate a problem. Thus when there are problems with buried power lines, the lines tend to remain out-of-service for longer.
Speaking of problems, let’s address maintenance, where again the story is not so simple. Getting to underground lines requires more time, bigger crews, and heavier equipment. On the other hand, compared to overhead lines, vegetation management is a lot simpler and can be performed at significantly reduced cost. Buried lines also avoid clearance issues in commercial areas.
Construction of new underground lines is a lot more expensive than putting up overhead lines for similar reasons to the cost of maintenance. [See the video below for a walk-through of the underground construction process.]
Other significant factors affecting the cost-benefit calculation include aesthetics and safety, both of which typically support undergrounding. Simply put, people don’t like looking at poles and lines in their neighborhoods. Exactly how much of an affect there is would be difficult to say, but the analysis usually assumes that overhead lines negatively impact property values. Safety is a factor mostly because of the poles. Tens of thousands of accidents and a significant percentage of vehicle fatalities involve utility poles.
Yes, it would be nice to have those lines and poles out of the way. The question is, are we willing to pay the price?
When I explained before that animal incursions are a significant cause of power outages, I bet you weren’t thinking of snakes! This snapshot from Alabama Power, however, documents one that, climbing a pole, caused a short that blew a transformer fuse.
Sitting in a comfortable office writing reliability standards is one thing. But braving the wind and cold, not to mention the height and current, is another. Thank you to the linemen and their families.
A number of years ago, I saw a show on TV all about the work of electric linemen. Unfortunately, I forgot to write down the name of the show and for some time I’ve been trying to track it down without success. The other day, I caught part of Modern Marvels: Wiring America on The History Channel and thought it might be the one I’d been looking for. After watching the whole thing now however, I know it’s not. Still, I think it does a pretty good job of introducing a general audience to the technology of electric transmission. ip address It even mentions my favorite character in the history of electric utilities, Samuel Insull.
Wiring America is as much about telecom as electric transmission, though I found that interesting as well. Coverage of electricity really begins about the 22 minute mark and Insull makes his appearance at 28 minutes.
If anyone has any idea what that show about lineman may have been, please let me know.
With all the complex issues that go in to maintaining transmission system reliability—voltage support and coordination of protection systems, for example—there are still many simple, low-tech problems that are major headaches for system operations and maintenance. You’re probably aware of the importance of vegetation management. Trees touching power lines have been a leading cause of blackouts. But what are some of the other problems encountered?
Animal incursions are common and can lead to a variety of failures. Birds build nests on insulators. Raccoons dig under fences, climb poles, and walk the wires. seo analysis . Compromised insulation and faults can be the result. A deer on the lines is a little unusual, but you get the idea.
People aren’t innocent either. At current commodity prices, copper theft has become a significant problem for many utilities. I’ve heard more than one manager of a rural utility complain about insulators being used for target practice. And check this video out for the modern version of tilting at windmills:
Even when trying to perform proper maintenance, low-tech problems can surprise you. At one utility where I was performing a condition assessment, they told the story of how a worker driving a mower accidentally clipped a guy-wire. The cable snapped up and wrapped itself around all three phases of the transmission line.
The lesson? Don’t get so caught up with technology that you forget the basics. Also, “stuff happens.”