Courtesy of Farnam
An impressive natural phenomenon, lightning’s power and beauty are equaled only by its unpredictability and potential for destruction.
On average, over 20 million cloud-to-ground lightning flashes occur every year in the continental United States. Worldwide, as many as 2,000 people are killed by lightning each year. This is in addition to the livestock deaths and injuries it causes. In fact, lightning is thought to be the leading “natural” killer of livestock and is also responsible for millions of dollars in damage to farm buildings and equipment annually.
Thunder is caused directly by lightning, but you can have lightning without a thunderstorm. Lightning has even been seen in heavy snowstorms and intense forest fires. The air near a lightning flash is actually hotter than the surface of the sun. Because the air near the lightning channel heats and cools so rapidly, it builds to an extremely high pressure and causes a shock wave, which then becomes a sound wave audible as thunder.
If you can hear thunder, you’re at risk of getting hit by lightning. But just because it’s not raining doesn’t mean there is no danger of lightning. Some thunderstorms produce little rain, but can still result in potentially dangerous lightning strikes. Lightning can occur as far as 10 miles away from actual rainfall, and lightning often begins striking before the storm arrives.
Research has shown that when lightning strikes the ground, it tends to seek out any metal in the area. This explains why buried phone and electric lines are often vulnerable to lightning damage. (This is also a very good reason not to wash that pile of dirty dishes, chat on the phone or take a leisurely bath during a thunderstorm!)
By the way, it’s absolutely not true that lightning never strikes twice. Lightning can and does strike the same place more than once. Case in point, the Empire State Building, which is struck almost 100 times annually.
Lightning Protection Systems
Horse owners can help protect their animals by having lightning protection systems installed on barns, run-in sheds and even large trees. To ensure that the system is properly installed, always hire a qualified contractor.
Although many people refer to “lightning rods,” these rods are just one component of the whole system.
There are 5 basic parts to a lightning protection system: air terminals (commonly referred to as lightning rods), conductors made of copper or aluminum, grounding rods that provide contact with the earth so lightning charges can dissipate, bonding to connect metal parts and lightning/surge arrestors to guard against damage that might come through electrical lines. All materials in a lightning protection system should be UL listed.
Bob Turner, owner of Turner Lightning Protection in Columbus, Ohio, explains that a lightning protection system has two objectives: to provide a direct path for lightning to follow into the ground, rather than choosing its own path, and to minimize damage, injury or death caused by the lightning as it follows that path. It’s important to understand that lightning rods do not attract lightning, nor can they prevent lightning from hitting. The system simply provides a safe path for the lightning’s electric current to travel into the ground and dissipate.
For a typical barn, rods are installed along the roof peak approximately every 20 feet, depending on the length of the building. Conductor cable is then run from one end of building to the other and connected to the rods. Copper-clad ground rods are driven into the ground to a depth of approximately 10 feet. Ground rods are buried about 2 feet out from the building and spaced no farther than 80 feet apart, so the length and width of the structure will determine how many are needed. The conductor cable runs down the sides of the building and connects to the ground rods. Proper grounding is essential because without it, lightning rods aren’t effective.
“Lightning can travel into a building by electrical lines, which is why arrestors are needed,” says Turner. If a building, such as a run-in shed or shelter, doesn’t have electricity run to it, arrestors are not needed.
The purpose of lightning/surge arrestors is to prevent damage from lightning entering via the wiring, which can destroy appliances and injure someone using them at the time. FYI, those plug-in surge protectors sold at home improvement stores are meant to protect electronic equipment and appliances from everyday power surges, not from lightning damage.
Danger to Horses
“The problem with animals and lightning is the phenomenon known as ‘ground potential rise,’ or GPR. Lightning is a current, so when it strikes the earth, a wave of voltage emanates from that spot,” notes Ernest M. Duckworth Jr., P.E., owner and president of the Lightning Protection and Grounding Institute (LPGI & Affiliates), based in Sedalia, Colorado.
“Picture it as throwing a rock into a calm lake,” adds Duckworth, who has been an electrical protection engineer since 1974. “When the rock hits the water, ripples spread out from it. The same thing happens with lightning as the energy spreads out from where the strike occurs. Lightning tends to disperse along the surface of the ground.”
He explains that having four legs makes horses more vulnerable to lightning.
“Say there’s a thunderstorm and frightened horses huddle under a tree. If lightning strikes the tree, the energy goes down into the earth and that voltage, or GPR, then comes up into the two hooves closest to the strike. That voltage passes through his body and vital organs and exits through the other two hooves, electrocuting the horse.”
Duckworth says this type of strike is more prevalent than a direct strike. That’s a good incentive to install lightning protection systems in trees, since this can help protect horses that tend to stand under them during thunderstorms.
An air terminal, or lightning rod, is attached near the top of the tree and conductor cable is run to the ground rod, which is driven into the ground away from the base of the tree, usually at the branch line, so that tree roots aren’t damaged if lightning strikes. If you have a large number of trees and don’t want to have lightning rods installed in all of them, you should choose the trees that horses tend to gather under. Lone trees in a field are especially good targets for lightning and warrant protecting.
Contrary to some old wives’ tales, metal does not attract lightning, but it is a good conductor. This explains why horses have been injured and killed while standing near wire fencing with metal posts, which is a good reason to have such fences grounded. Horses and cattle have also been killed while standing in puddles and near water tanks, so it’s a good idea to have a qualified installer ground the tank where the water line comes in.
If in doubt about lightning safety, the National Oceanic and Atmospheric Administration National Weather Service recommends following the “30/30 Lightning Safety Rule.” Seek shelter indoors if you see lightning and hear thunder less than 30 seconds afterwards. Stay indoors for 30 minutes after the last clap of thunder.
Your local fire department can be a helpful resource when it comes to protecting your horses and buildings from lightning and fire hazards. They can often inspect the farm buildings and offer fire prevention advice and suggestions for improvements.