Described by jakdedert is a building all but begging for lightning
damage. For example, a cow stands in an open field when lightning
strikes a nearby tree. The cow is killed. Killed by electromagnetic
fields? Of course not. Killed because cow was part of a path from
cloud, through tree, into earth to earth borne charges maybe miles
distant. The electrically shortest path was not under the cow. It was
up cow's hind legs and down fore legs. Cow was part of a direct
lightning strike from cloud to distant earthborne charges.

Cow could have lived is a halo ground surrounded the cow. That
buried conductor would have, instead, routed electricity around (not
through) cows. The concept is called single point earthing. Cow with
separated legs has multiple earthing connections - therefore dead. Cow
centered in a halo ground has a single point ground.

jakdedert describes here (and previously) utilities (ie mutli-line
phones) entering and earthed more like the cow. Building is even worse
because earthing points are farther apart. Destructive charge can
enter building on telephone line (overhead or underground line) either
from its grounding connection or via utility wire (from nearby struck
tree, from other struck building, or entering via ground rod). That
transient crossed building, destructively through appliances, to obtain
earth via AC electric.

Connecting phone line with a 20' plus ground wire or via pipes
accomplishes little. Wire has impedance. That means earthing from
each incoming utility to a single point earth ground MUST be less than
10 feet. Other features such as no splices, no sharp bends, no solder
joints (on wire or pipe), etc also required to lower impedance. Not
resistance - impedance.

A minimal single point ground is a grounding rod. That means even
incoming cable TV wire must make that 'less than 10 foot' earthing
connection to earthing electrode. Better earthing is a halo ground
(what saved the 'dead' cow) or even better, Ufer ground.

What does a protector do? A protector only connects from AC electric
or phone lines (that cannot be earthed directly) to an earthing
electrode. Protector is nothing more than an connection. No earth
ground means an ineffective protector - which many overpriced, plug-in
protector manufacturers hope you never learn. Plug-in protectors that
have no earthing connection, then, connect to what? They hope youj
never ask that question.

Cable TV does not need protectors which often degrade cable modem or
TV signal. Cable is earthed directly - hardwired - to earth without
any protector for superior protection. Wire does better than a
protector.

An electric utility demonstrates bad, good, and ugly earthing. Ugly
because the earthing electrode must be 'lengthened' so that all
utilities make a common earthing point:
http://www.cinergy.com/surge/ttip08.htm

Water pipe typically is not good earthing. Pipes too long, too far
away, too many sharp bends, solder joints, etc. A major difference
between earthing for human safety verses earthing for transistor
safety. A major difference between resistance and impedance means wire
distance is more critical that a low resistance ground. Worse,
jakdedert describes grounding to pipes or water faucets. That means
ineffective and multi point earthing - that also killed the cow.

Most critical component in a lightning protection system is earthing.
Earthing defines uality of that protection 'system' and effectiveness
of protectors. Ineffective plug-in protectors avoid all mention of
earthing to sell hyped products at higher profits. Such ineffective
products have no dedicated earthing connection AND avoid earthing
discussions to keep customers ignorant. Bottom line: a protector is
only as effective as its earth ground.

Effective protector manufacturers have names such as GE, Polyphaser,
Square D, Intermatic, Siemens, Cutler-Hammer, and Leviton. Their
effective products have that dedicated earthing wire.Notice that names
such as APC, Tripplite, Belkin, and Monster are specifically not
mentioned. The telephone company already installs an effective 'whole
house' protector in their NID (premise interface) box. But again, you
(the owner) define its effectiveness by providing an earthing system.

UK residents who suffer so few lightning storms also suffer frequent
and unnecessary damage. This because UK incoming phone lines don't
have that necessary earthing. BT does install effective earthed
protectors on their end. But subscribers are expected to pay for their
own protection - which is provided free in North America.

Also is a myth that underground wires are better protected. Does not
matter as demonstated by the 'dead' cow. Any utility that does not
first connect to single point ground before entering a building is an
obvious incoming path for household electronics damage. As the
'dead' cow demonstrates, single point earthing means even a nearby
lightning strike can be a direct strike into building electronics - if
building's earthing is not properly installed and connected to by every
incoming utility wire.

Damage could have been from voltage potential between different
buildings OR from buried wire carrying transient from a nearby struck
tree. Multiple sources of damage - all due to a building owner who did
not install the most critical component in a protection 'system':
single point earth ground. Why does a telco Central Office, connected
to every other building in town by copper wires, not suffer damage?
The solution has been standard for so many generations - proven
multiple generations before transistors were created. Protection is
and is defined by earthing. Even protectors are only as effective as
their earthing.

Travis Jordan wrote:
Michael Kennedy wrote:
I found out the hard way that burrying the wire doesn't help with
lightning protection when I ran a cat5 ethernet wire from my house to
a friends last year. That thing got zapped evey time we had a bad
storm..

The problem wasn't caused by the ethernet wiring; it was the difference
in ground potential between the two homes.

You should have optically isolated the two ends to avoid the problem.