On Fri, 20 May 2016 10:49:44 -0700 (PDT), westom
wrote:
On Friday, May 20, 2016 at 5:32:29 AM UTC-4, Micky wrote:
I'm going to assume you know that one story about one house, or even
100 houses, does not make a risk as great when there are many 1000's
of houses ...
Underground wires that enter telco COs get same protection as wires that are overhead.
I don't care about surge protection that is added. The topic was what
the risk was without protection.
In one venue, that protector failed at the subscriber interface. That wire from CO to subscriber was completely underground. Why did he have a surge if a threat does not exist as you only assume?
Don't put words in my mouth, especially words I said the opposite of.
I never said there a thread doesn't exist. In fact even the part at
the top here makes clear that I believe that a house with underground
wires can have lightning damage.
It was bad enough when you avoided my question, but that's about you.
Putting words in my mouth that I didn't say or imply is about me, and
that's worse.
Because the threat does exist. Because the threat has been well understood for longer than any of us have existed.
Professionals demonstrate how protection must be installed in a Tech Note. Protection is even on the incoming underground phone line because (as indicated in the picture) a lightning strike can enter via buried wires:
https://www.erico.com/catalog/literature/TNCR002.pdf
Legendary application notes from Polyphaser state same:
http://www.polyphaser.com/SiteMedia/...3.pdf?ext=.pdf
The power and telephone feeds to your house can be either aerial
or underground. Most people think underground is better from a
lightning standpoint. Buried underground, it will not be hit
directly, but if a nearby tree is hit, the amount of energy
coupled through the conductive ground medium can be almost
equal to a direct hit. By being underground, the shielding
effect to the wires is not great.
A Bell System Technical Journal paper in the late 1950s by Bodle and Gresh describe lightning strikes to underground cables over 5 month period in NJ, MI, GA, and MD. Somehow professionals have it wrong?
That quote doesn't address whether the risk is greater or not. If
you think the risk is the same underground or overhead, just say that.
You've never said that. Had you said that after my first post, we
would have been done by now.
That you go to so much effort not to say the risk is the same makes me
think you think the risk is greater for overhead.
Does not matter if wires are overhead or underground. All incoming wires - overhead or underground - must connect low impedance to properly earthed 'whole house' protection before entering a structure - assuming one wants to protect appliances.
Proper whole house protection is irrelevant to the topic.