Back in the previous century when I was just learning to shave, I was trying an electric razor for the first time when a lightning bolt hit the power pole outside my bathroom window. There was a blinding flash, a loud crack, and all the lights (and my shaver) went out. I was a ham radio operator at the time, and as soon as I figured out what happened I went out to survey the damage. The power pole had a thick black scar twisting around it and it had split. My antenna tower, just a dozen feet or so away from it, was unscathed. Now, lightning is pernicious and unpredictable, and I’ll never know whether it was just pure luck that the lightning didn’t follow my antenna wiring straight into the house. I suspect, however, that my luck had at least something to do with the fact that I was pretty fanatic about following proper (or even excessive) grounding procedures. The tower was steel and it was attached to the ground, and most of my friends in the hobby would have considered that sufficient — especially considering that thunderstorms were downright rare where we lived. I had, however, faithfully followed the guidelines in the ARRL Handbook and had grounded the tower with an eight-foot copper ground rod at the base of the tower, and had another such ground rod and a lightning arrestor where the coaxial cable entered the house. The house, my antennas, and the radio equipment were undamaged.
I see a lot of laissez faire approaches to grounding. Shortly after we bought this house, I removed some unneeded satellite dishes. As I was removing the wiring, I noticed that the service equipment was “grounded” by being wired to a cold water pipe. Normally, in most cases, that’s considered good enough. I think it’s questionable practice, but I’m not a cable installer. In this case, however, said cold water pipe ran about six feet along the house where it transitioned to PVC without ever getting anywhere near the ground. A lightning strike anywhere near those satellite dishes would have sent a big induced current to ground directly through the satellite receivers and, probably, any connected television sets.
Here at the compound, with a completely off-grid solar plant, it’s particularly important that grounding be done right. There’s no utility-supplied grounding, and no transmission lines and towers to help bleed off big voltage differentials caused by thunderstorm activity and nearby strikes. While a direct strike is going to do damage no matter what, proper grounding can help prevent direct strikes by neutralizing big potential differentials before they become strikes. So, as you can see above, I have run heavy-gauge copper wire in a short, straight line from the service equipment enclosures to the ground rods, providing a “low impedance path” for accumulated energy to dissipate without traveling through structures and equipment.
The folks who did the solar install and the house re-wire did a great job, but they weren’t fanatics like I am when it comes to grounding. I’ve added four ground rods, one wherever any kind of wire enters or leave a structure.
I feel so, like, you know, so grounded now.
—2p