Thanks for the pdf. Looks like an interesting read and I’ll check it out.
Like you, I also have surge protectors around the house. Low clamping voltage, fair number of joules (nothing crazy), and fire proof. And another whole house suppressor in the basement breaker panel. I tried to have a tiered approach, but with the realization in the end, there’s only so much I can reasonably do and it becomes an insurance issue.
Along with designing high power transmitters (in the KW range), I also design high power limiters. You’re correct with your comments. It’s amazing that many whole house suppressors connect to the panel via wire. Along w/your your 90 degree bend comment, the electrical length length of the wire is essentially an inductor. That’s a high Z at a high frequencies, negating the effectiveness of the suppressor. On top of that, what if the wire electrical length is 90 degrees at the transient frequency? The low impedance of the suppressor clamping will be transformed into a high Z at the other end (fail). Of course surge suppressors are designed to work at some defined waveform (i.e. pass some defined test), not sure how well that works in a ‘real life’ event…
I guess in the end, we just do what we can. Mother Nature will win if she wants too.
I’m just glad the house didn’t burn down!
P.S. I don’t know if AFCI breakers are are mandatory. Not sure if that requirement is national, or varies according to location. Electrician mentioned it was at one point, but then seemed to change. Don’t know, haven’t looked into it. We built in 2010, wasn’t a requirement back then.
Protection of electrical and electronic equipment from lightning surges arriving on power lines, communication (phone & internet etc) lines and on antenna cables can effectively be done by surge protection equipment and AFCI.
Protection of building and it’s content from a direct or nearby lightning strike cannot be done by surge protection equipment due to immense amount of voltage and current the bolt carries. The most effective method of protection is to provide a good path to this curren to ground, so that it does not pass through the building. This is what the system of Lightning Rods, connected to Earthing Rods by heavy copper wire or heavy copper strip do.
The lightning bolt, which has already jumped across miles of air between cloud and ground, will not be stopped by electronic strips or air gaps or surge protectors/divertors. It will simply pass through or jump over these.
We are lucky in Southern Cal – we’ve had steady rain for more or less the last two 2 months with no lightning. So we can get away with not having lightning protection. I can remember when I lived in the midwest, we had lightning, but no lightning protection and we seemed to survive. On the other hand, further out on the great plains (Nebraska, for example), they have incredible electrical storms, so probably need lightning protection.
Florida has more lightening than elsewhere in the US. My area has lightning 83 days a year (2nd highest). Ft. Meyers, FL has 88 days with lightning (highest). Number 3 and 4 are Tallahassee and Orlando. About 20 people are killed by lightning in Florida each year.
NFPA780 recommends that a conductor should not form an included angle of less than 90° or a bend radius of less than 8 inches.
A radius of curvature tends to cause the electric field adjacent to the conductor to increase, thus increasing the chance of flashover between the conductor and nearby grounded metallic bodies such as duct work, piping, and other systems.
Not only that, but the curvature smaller radius would raise the inductance in that conductor. It’s a quarter turn.
Keeping the radius high, it keeps a low inductance, so the transients can pass to the ground without seeing a big impedance there. “Big” impedance, at. 100kA current is not that big … Example, a 0.01 ohm impedance (in that high frequency) will create a 10000 V across it. It will flash-over.
Yes. That, and a short length of copper between the clamp and grounding rod. I connected my ground to the copper (1/4" pipe 2" long) and the pipe section to the buried rod. Trying to distract the bolt.
Nothing will stop a lighting strike. Looks like that has been covered for this “Grounding rod question”
I just put in a GOES receiver so I am testing out an SMA<>SMA surge protector but there are not a lot of choices. At least the coax shield is properly grounded. I am going to put these on my 1090 and 978 coax feeds soon.
As for grounding; Besides the NEC250 requirements here in the USA I installed an extensive ground system around the property. All of the metal things are connected to the ground system.
The gold lines are the copper ground system with the round/circles being ground rods. Some of the perimeter ground rods are only 4ft and the others 6ft and 8ft.
Personally I think that’s excessive.
Lightning strike doesn’t travel too far horizontally into ground… like 50 yards. But adding all those copper pathways might help it “reach” further, to the other buildings.
A ground ring around the tower was sufficient IMO.
Interesting lecture: Lecture 20 - Lightning protection Pt. 1 Structures (arizona.edu)
