What do bowling balls have to do with birds sitting on power lines?
By Sean J. Vanslyke
Birds on the Wire
The electricity business – or at least the part where Team SEMO delivers electricity to homes, farms and businesses – is anything but routine and humdrum. We plan improvements to enhance our system on a regular basis – to the tune of $3-$5 million per year – to keep the lights on. We challenge ourselves to be more reliable as your expectations for reliable energy continue to grow. Plus, we seek ways to control Mother Nature and the animal kingdom to reduce power outages.
Power outages are frustrating. Power outages on a nice sunny day are really frustrating. About 99.99% of the time we keep the energy flowing and the lights on. But, there are times when Mother Nature or animals just beat us at our game. While we have installed thousands of animal guards, we have power outages due to birds attempting to eat bugs gathered in places near energized power lines or snakes curling up to warm transformers. Often, it all goes well for the animals until they make two points of contact.
When making safety presentations to kids and adults, we usually hear the question: How do birds sit on power lines without getting electrocuted? MIT School of Engineering’s Aaron Johnson posted a response to the question.
“It’s not uncommon for a character in the movies to end up with a blackened face and a headful of frizzy hair after touching a live electrical wire. What makes for a good gag in the entertainment biz, however, is likely to kill you in real life — unless you’re a bird. Birds have no problem sitting, unruffled, on the high-voltage power lines you often see lining the road.
“This ability has nothing to do with them being birds, explains Ranbel Sun, a recent grad from electrical engineering and computer science who currently teaches at Phillips Academy in Andover, Massachusetts. It’s all about the connections they’re making — or, more importantly, not making.
“Electrical current is the movement of electrons,” explains Sun. The movement of electrons through a device like your TV is what gives it the energy to display images and produce sound. Sun describes the long process these moving electrons take to get to your house. “The electrons are essentially being pulled from the ground by the power station,” she says. “They move through the power lines, through your TV, and eventually they make their way back into the ground from where they came.” This creates a closed loop, which is required for electricity to flow.
“The other thing electrons need in order to move is motivation — or, more specifically, a difference in what’s called electrical potential. “Imagine lugging a bunch of bowling balls up a mountain,” Sun explains. “If you give them a path, the balls will naturally roll down the mountain to a lower position.” At the top of the mountain, the bowling balls (which represent the electric current) have a high potential, and they will travel down any path that becomes available. When a bird is perched on a single wire, its two feet are at the same electrical potential, so the electrons in the wires have no motivation to travel through the bird’s body. No moving electrons means no electric current. Our bird is safe, for the moment anyway… If that bird stretches out a wing or a leg and touches a second wire, especially one with a different electrical potential, it will open a path for the electrons — right through the bird’s body.
“There are other perils for our feathered friends, Sun points out. “The wood pole supporting the wires is buried deep in the ground,” she says, “so it would also be dangerous for a bird to sit on the pole and touch a wire.” This is the problem that people encounter if they touch live wires — since we are almost always in contact with the ground. Our bodies turn out to be excellent conductors of electricity, and the electrical current will happily use them to complete a closed path to flow from high potential (the wire) to low potential (the ground). ZAP!
“So how do workers repair live electrical wires without getting hurt? They use insulating materials in their clothing, equipment, and bucket trucks. Insulating materials such as rubber are materials through which electricity has a hard time flowing. So instead of passing through the electrician, the electrons stay on the other side of his rubber gloves or rubber-handled tools. (Keep in mind: these aren’t everyday household gloves and tools — those are too thin to protect you from a shock and are often not made entirely of rubber) Another technique is to hang beneath a helicopter. Since neither the worker nor the helicopter is connected to the ground (like a bird), the worker just has to make sure he only touches one wire at a time. Despite continual safety improvements, being a power linesman is still one of the ten most dangerous jobs in America. So, it’s a good idea to stay away from electrical wires unless you’re a trained professional — or a bird.”
We can all learn from each other. I thought Johnson’s writing and Sun’s image of bowling balls rolling down the hill helps teach us about electricity’s goal to reach the ground. Please share the importance of not climbing poles and not touching power lines with your family and friends. Let’s be safe.
Book of the Month
“There is no substitute for the motivating power of a great cause. It is the canard of our culture that we would be happier if we weren’t so busy, if we weren’t working so hard, if we didn’t have so much homework. If only we could relax more and take more vacations. But leisure has little to do with one’s happiness. To the contrary, I’ve found that the happiest people have found some cause and they stride through life propelled by a commitment. The fact of the matter is that most people are bored. When students dislike school it is often because school expects so little of them. When people hate their jobs it is rarely because their jobs ask too much of them – it is because their jobs are routine and humdrum.” Alan Loy McGinnis – Bringing Out the Best in People
Be smart. Act safe.