 |  Question by Char posted 01 Aug 2003 | Protecting ethernet cables from effects of lightening | a few months ago, we had a terrific (horrible) lightning event that was so sever that, even though you couldn't see if anything was actually hit, it blew out our garage door sensors, fried the GFI outlet in the garage, took out our cable modem, network switch, WAP's ethernet port, and various other network connection points -- USB, ethernet, and parallel. This, despite the fact that we had turned off and unplugged everything but we had left all the various cables connected. If I had been using SHIELDED Cat5e cables, would that have protected them from behaving so badly in response to what must have been some atmospherically propagated EMP?
Thanks. |  |  Answer by Dmitri Abaimov posted 23 Aug 2003 | Dear Char,
It's difficult to tell for sure, but the result might be even worse with shielded cable since the shield will have to be grounded, and in a regular residential building there is usually only one point of grounding - electrical power ground. This point would surely take the hit, and some of the charge could even propagate through to your ground-bonded equipment, like your PC's metallic case, for example. So, even if you would unplug the PC's power, there will be still a path to electrical ground through the NIC's connection to the cable's shield.
So, the bottom line is: shielding a cable is not a solution to lightning problem.
Sincerely,
Dmitri Abaimov, RCDD
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