buckeyefarmer
Epic Contributor
The fact t posts are not driven very deep, probably very little. You can test it with a megger.
Those with lightning storms, how do you protect electronics?
- Thread starter davrow
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CobyRupert
Super Member
100 T posts 2' feet in the ground is 200' of additional contact with the ground. Over a larger area. Greatly multiplying the ground grid compared to one 8' ground rod, but probably not if you're already bonded to a utility water pipe.
Funny story about wells. When we moved into our house (on top of a hill) we lost well pump twice in 5 years from lighting. Lightning hit tree in the woods behind the house (500-1000' away) and the surge current from the trees to the ground travels to the path of least resistance which happened to be the 60' ground rod which happens to be our well casing. Current surge into the well casing arced over the submerged pump insulation to get to the grid (a really good ground), killing the pump motor. After the second time, I ran a #4 wire from the main breaker panel, next to the ground rod connection, and bonded it to the well casing. 23 years later we have never had a pump problem.
Remember the current will always follow the path of least resistance.
Paul
Remember the current will always follow the path of least resistance.
Paul
k0ua
Epic Contributor
Lightning currents DO NOT follow the path of least resistance. Lightning currents follow all paths. There will be much more current flow in the paths with low resistance than in the paths with high resistance. But ALL possible paths will distribute some currents.
buckeyefarmer
Epic Contributor
The only thing predictable about lightning is it will hit something..
Fuddy1952
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I always heard as seen by slow motion video first thing is a dart tracker goes from ground up to the cloud, then lightning follows that back down. The people who survived a lightning strike it couldn't have been a direct hit but one of the secondary ones. My thought is lightning rods work because it's a ground potential up in the air, lightning will strike someplace else. If lightning were to directly hit a rod it would blow it and the wire apart.
Grateful11
Veteran Member
We had a lightning strike last year that came in through the cable line, took out the DVR, went from there through the HDMI cable to our 55" Vizio and zapped the main board. I know it sounds crazy but we like that TV so much we got the board repaired, no longer available, and fixed it. Spent about $250. It's a full-array backlight with anti glare screen and has awesome picture quality. It's about 7 years old. A guy that runs a radio and tv repair shop that been in business since 1938. Unplugging the TV or the DVR from the wall socket would not have done any good. Now we disconnect the the HDMI cable from the TV.
buckeyefarmer
Epic Contributor
The only thing we ever fried was our treadmill circuit board, from static electric.
k0ua
Epic Contributor
By the way it is not just lightning currents that don't follow the path of least resistance ALL electricity DC and AC always follows ALL paths. Think of it like this How would lightning "know" which path is the path of least resistance. It doesn't "know". Say you took a power supply of 12 volts, and you had 3 resistors across that supply of 3 different values of resistance. Current will of course flow in each resistor according to each resistance. The resistors with the lowest resistance will carry the most current, the resistors with the highest resistance will carry the least amount of current.
You are correct since ground is an omnipotential path. However my point, to have been simplistic, is that the current densities will be proportional to the resistivity of the substrate. A 60' steel rod (or pipe) has a significant surface area in contact with the ground (dirt in this context) and therefore will have a lower impedance path compared to other paths. Pictures of lightning strikes to the surface sometimes show these paths of highest current density, which implies the lowest resistance.
paul
(ee old guy and former ham operator)
