From: "Tony (remove \"_\" from email address)"
Subject: Re: Info on protecting UTP network / phone / AC mains so lightningon cable doesn't destroy everything (again)?
Date: Wed, 06 Nov 2002 10:10:44 +1000
X-Newsreader: Forte Agent 1.92/32.572
Thank you very much for your post. Your situation is similar to mine, and you
have achieved much of what I wanted to - so all the other mechanisms you used
are relevant to me too. I will certainly need to improve the grounding. The
inductance of the breakers hadn't occurred to me before - what a bonus.
Similarly the coiled coax common mode choke trick looks useful. I hadn't been
disconnecting the cable when not in use, as the little F connectors don't look
like they'd take that forever, but now....
On Tue, 5 Nov 2002 13:23:00 -0500, Terry King
>We need to differentiate between lightning strikes on or very close to
>the house, and lightning surge voltages coming in on power /
>I agree that a direct or almost-direct hit will cause very high voltage
>fields, and magnetically-induced currents in much of typical home wiring,
>and is very difficult to protect against successfully.
>But the major occurrences of damage are conducted into the house on
>external wires. These CAN be protected against, moderately well.
>I have had a direct strike on the power/phone pole 75 feet from the
>house. (I know every strike and situation is different!) But the only
>damage I had was to my homebrew telephone line protector, and it
>blew open the first set of coils, just as it was supposed to!
>My stepdaughter was standing on the porch, with the pole in view,
>and it temporarily blinded her; we know where it hit! Of course, it
>took out the power circuit fuse on the pole...
>To the extent that this is relevant, my situation was:
>1. Power pole 75 feet away, decent ground rod on it.
>2. Buried 100 amp service cable from 100 Amp breaker at pole (has some
>3. Real Good Ground at the house: 3 10 foot ground rods, #6 copper
>bonding them together, wide copper strap from ground rod to phone
>cable entrance to Power entrance.
>4. Whole House surge protectors wired just after the main breakers
>on the electric panel busses. Main Breaker inductance a plus!
>5. Serious two-level protector on the phone line (two small 100
>microhenry inductors followed by gas discharge unit, followed by two more
>inductors, followed by Semiconductor suppressors with small bypass
>capacitors. (Surge physically opened the first set of inductors AKA
>fuses). Oh, these (now I have two lines) protectors are mounted on a
>copper strap that is 2 feet from one ground rod, with the incoming wire
>coming up thru a hole in the copper strap to the first set of inductors
>and the gas-discharge unit. Extremism in Stuff Hooked Up To My Computer
>is not a Vice. (Barry Goldwater, who was a Radio Amateur, probably said
>I don't have cable, but I DO have coax fed Ham Radio antennas coming
>in. They have their shields bonded to the perimeter ground, and gas-
>discharge units at the entrance point. That's what I'd do IF I had cable.
>And I have a small coil of coax (5 turns 6 inch diameter) just before the
>cable hits the ground. (Inductance is the enemy of fast-rising pulses.
>Your enemy's enemy is your friend).
>What you can do:
>1. Real Good Grounds
>2. Protectors at the ground perimeter where wiring comes in.
>3. Good insurance for a Direct Strike
>I still disconnect my HF transceiver when not in use, and shut off the
>computer, if there is an obvious close storm :-)
> In article , NOSPAM@rsccd.org says...
>> > Well, to be quite honest, the best suggestion I can offer is to get some
>> > decent homeowners insurance. All of the surge protectors on the market
>> > are designed for surges, not lightning strikes.