From: Terry King
Subject: Re: Info on protecting UTP network / phone / AC mains so lightningon cable doesn't destroy everything (again)?
Date: Tue, 5 Nov 2002 13:23:00 -0500
Organization: Waits River Valley School
X-Newsreader: MicroPlanet Gravity v2.30.1784
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.
Regards, Terry King ...In The Woods In Vermont