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LIGHTNING PROTECTION (Page 4)
Now, back to our discussion of lightning protection:
Before moving on to how we can protect our horses and barns from lightning strikes, I’d like to give you a few more numbers to consider, courtesy of the Lightning Protection Institute: A typical lightning flash is four-tenths of a second long, generates about 25,000 amperes (an ampere measures the rate of flow of electrons that flow past any point in a wire each second) and 30,000,000 volts (volt measures the force that makes the electrons flow), and has temperatures of from 30,000 to 50,000°F. In comparison, your house current is 110 or 220 volts and most people set their thermostats at around 70°F.
The Lightning Protection Institute did a study of 250 equine lightning deaths and found:
- 103 horses burned to death or were asphyxiated in barns that were ignited by lightning bolts (41.2%)
- 70 horses were struck directly in open fields (28.0%)
- 40 horses were standing under trees that were hit by lightning (16.0%)
- 21 horses were killed at watering troughs (8.4%)
- 10 horses were killed either standing in streams or fording them at the time of the strike (4.0%)
- 4 horses were killed by lightning current conducted through wire fences (1.6%)
- 2 horses were standing next to utility poles that were struck by lightning (0.8%)
This study shows that 64% of those deaths (in barns, under trees, at water troughs, near wire fences) could have been prevented. (continues after picture)
PROTECTING OUR BARNS AGAINST LIGHTNING STRIKES
The Lightning Protection Institute also found that nine out of ten barns struck by lightning burn to the ground and are total losses. And it happens very, very fast. One owner saw lightning strike the metal roof on his bank barn, raising it up, and flames immediately erupted in the upper level. All the horses in the lower level were found dead from the lightning strike, and a pet rabbit in a metal hutch next to the barn was also killed. It all happened too fast for him to react. In the minute or two it took him to get his wits about him and call the fire department, all the damage was done. There was nothing left for the fire department to save.
Lightning strikes a barn (or any other building) because the materials in it are better conductors than air. Lightning protection systems are designed and installed to protect all the points where a lightning bolt would most likely strike and all objects to which the current might sideflash. This is where the current jumps from one object to another, for example, a herd of cows standing under a tree that is hit could be killed by current that jumps from the tree to the cows' bodyies. It makes no difference, by the way, whether or not a horse is shod—it’s the water in his body that is the conductor—and the current will not “go around” the horse to hit his shoes, it will go straight through the horse into the ground.
The part of the system most easily recognized is the air terminal, or lightning rod. These are pointed metal rods, usually copper or aluminum, installed on a building’s high points. On a barn that’s commonly the roof ridge. How many terminals are needed depends on the length of the barn.
Down conductors, also known as main conductors, are heavy braided copper cables that connect the air terminals with each other and with the grounds. Their job is to conduct a lightning bolt from the terminal struck to the ground, and to do that, each down conductor requires its own ground.
